Materials Science & Engineering C (v.31, #5)

Electrochemical impedance-based DNA sensor using a modified single walled carbon nanotube electrode by Jessica E. Weber; Shreekumar Pillai; Manoj Kumar Ram; Ashok Kumar; Shree R. Singh (821-825).
Carbon nanotubes have become promising functional materials for the development of advanced electrochemical biosensors with novel features which could promote electron-transfer with various redox active biomolecules. This paper presents the detection of Salmonella enterica serovar Typhimurium using chemically modified single walled carbon nanotubes (SWNTs) with single stranded DNA (ssDNA) on a polished glassy carbon electrode. Hybridization with the corresponding complementary ssDNA has shown a shift in the impedance studies due to a higher charge transfer in ssDNA. The developed biosensor has revealed an excellent specificity for the appropriate targeted DNA strand. The methodologies to prepare and functionalize the electrode could be adopted in the development of DNA hybridization biosensor.
Keywords: Carbon nanotube; DNA; Impedance; Cyclic voltammetry; Biosensor; Salmonella;

In-vivo study of adhesion and bone growth around implanted laser groove/RGD-functionalized Ti-6Al-4V pins in rabbit femurs by J. Chen; R.A. Bly; M.M. Saad; M.A. AlKhodary; R.M. El-Backly; D.J. Cohen; N. Kattamis; M.M. Fatta; W.A. Moore; C.B. Arnold; M.K. Marei; W.O. Soboyejo (826-832).
Titanium surfaces were designed, produced, and evaluated for levels of osseointegration into the femurs of rabbits. A total of 36 Ti-6Al-4V pins (15 mm length, 1.64 mm diameter) were prepared into three experimental groups. These were designed to test the effects of osseointegration on laser grooved, RGD coated, and polished control surfaces, as well as combined effects. Circumferential laser grooves were introduced onto pin surfaces (40 μm spacing) using a UV laser (λ = 355 nm). The tripeptide sequence, Arginine-Glycine-Aspartic acid (RGD), was functionalized onto laser grooved surfaces. Of the prepared samples, surface morphology and chemistry were analyzed using scanning electron microscopy (SEM) and Immunoflourescence (IF) spectroscopy, respectively. The experimental pin surfaces were surgically implanted into rabbit femurs. The samples were then harvested and evaluated histologically. Sections of the sample were preserved in a methylmethacralate mold, sliced via a hard microtome, and polished systematically. In the case of the RGD coated and laser grooved surfaces, histological results showed accelerated bone growth into the implant, pull-out tests were also used to compare the adhesion between bone and the titanium pins with/without laser textures and/or RGD coatings.► Circumferential laser grooves were introduced onto pin surfaces using a UV laser. ► The tripeptide sequence, RGD, was functionalized onto laser grooved surfaces. ► The experimental pin surfaces were surgically implanted into rabbit femurs. ► RGD coated laser groove surfaces accelerated bone growth into the implant. ► RGD coated laser grooved surfaces enhanced the adhesion between the bone and implant.
Keywords: RGD peptide; Laser groove; Adhesion; Titanium; Implants;

Effects of alloying elements on the cytotoxic response of titanium alloys by Alessandra Cremasco; André Dutra Messias; Andrea Rodrigues Esposito; Eliana Aparecida de Rezende Duek; Rubens Caram (833-839).
Titanium alloys, especially β-type alloys containing β-stabilizing elements, constitute a highly versatile category of metallic materials that have been under constant development for application in orthopedics and dentistry. This type of alloy generally presents a high mechanical strength-to-weight ratio, excellent corrosion resistance and low elastic modulus. The purpose of this study is to evaluate the cytotoxicity and adhesion of fibroblast cells on titanium alloy substrates containing Nb, Ta, Zr, Cu, Sn and Mo alloying elements. Cells cultured on polystyrene were used as controls. In vitro results with Vero cells demonstrated that the tested materials, except Cu-based alloy, presented high viability in short-term testing. Adhesion of cells cultured on disks showed no differences between the materials and reference except for the Ti–Cu alloy, which showed reduced adhesion attributed to poor metabolic activity. Titanium alloys with the addition of Nb, Ta, Zr, Sn and Mo elements show a promising potential for biomedical applications.
Keywords: Titanium alloys; Biocompatibility; In vitro; Biomaterials; Fibroblast;

Tin oxide hexagonal-shaped nanodiscs (SnO) and spherical nanoparticles (SnO2) have been prepared by using a simple household microwave irradiation method with an operating frequency of 2.45 GHz. This technique permits us to produce gram quantity of homogeneous nanoparticles in just 10 min. The crystallite size was evaluated from powder X-ray diffraction (XRD) studies and was in the 20 to 25 nm range. Transmission electron microscopy (TEM) analysis showed that the as prepared SnO form as hexagonal-shaped nanodiscs and upon subsequent annealing at 500 °C for 5 h in air, the SnO gets converted to spherical-shaped nanoparticles of SnO2. The SnO2 sample shows good sensitivity towards the relative humidity. The calculated response and recovery time were found to be 32 s and 25 s respectively. These results indicate promising applications of SnO2 nanoparticles in a highly sensitive environmental monitoring and humidity controlled electronic devices. The samples were further subjected to thermal analyses (TG–DTA) and UV–VIS diffusion reflectance spectroscopy (DRS) studies.
Keywords: SnO2; Microwave irradiation; Nanomaterials; Thermal properties; Humidity sensor;

Porous β-NaCaPO4 containing borate glass-ceramic scaffolds by Yifan Tu; Wen Liang; Huanjun Zhou; Christian Rűssel (845-850).
A novel β-NaCaPO4 containing borate glass-ceramic is prepared. Two porous glass-ceramic scaffolds are prepared by binding particles with the size of 200–300 μm by 5 wt.% sodium silicate solution and 2 wt.% chitosan solutions, respectively. The reaction of the scaffolds in the SBF solution is characterized by weight loss analysis, XRD, FTIR, and SEM. The same is done to the 45S5 glass scaffolds as comparison. XRD and FTIR indicate that the carbonate hydroxyapatite has formed more rapidly on the borate glass-ceramic scaffolds. The carbonated hydroxyapatite depositing on chitosan binding scaffolds has lower crystallization degree than that on sodium silicate binding scaffolds and is similar to that of the human bone, which makes the chitosan binding scaffolds a good potential prospect in the field of tissue engineering.
Keywords: Glass-ceramic; Scaffolds; Binding; Tissue engineering;

Mg–Al-layered double hydroxide intercalated with a model drug, salicylate, was deposited on laboratory-made magnesium ferrite and commercial magnetite nanoparticles. The obtained core–shell nanocomposites have been characterized by a variety of methods. The combined information from X-ray diffraction patterns, electron diffraction patterns, FTIR spectra, X-ray photoelectron spectra, electron microscopy images, thermogravimetric analysis and microchemical analysis has indicated a similar nature and composition for the two samples. Magnetic measurements have revealed that although the inherent magnetization of magnetite was significantly higher, the nanocomposites displayed nearly similar magnetic properties.
Keywords: Nanocomposites; Core–shell structures; Organic–inorganic hybrids; Layered double hydroxides; Intercalations;

Comparative study of fluoride conversion coatings formed on biodegradable powder metallurgy Mg: The effect of chlorides at physiological level by M.D. Pereda; C. Alonso; M. Gamero; J.A. del Valle; M. Fernández Lorenzo de Mele (858-865).
The development of a biodegradable metallic implant demands a precisely defined degradation profile and adequate mechanical properties. Mg has been proposed for this purpose but it has an excessively high corrosion rate and insufficient yield strength. In the present work pure Mg mechanically reinforced by a powder metallurgy (Mg(PM)) route and treated with KF was used. The effect of chlorides, at the physiological level, on four fluoride conversion coatings (F-CC) formed on Mg(PM) was evaluated comparatively. The behavior of Mg(PM) during fluoride treatments (0.01 M–0.3 M fluoride-containing solutions) before and after the addition of chlorides (8 g L− 1 NaCl) was investigated by conventional corrosion techniques and by scanning electrochemical microscopy (SECM) complemented with SEM observations and EDX analysis. Results showed that the composition and the microstructural characteristics of the F-CCs as well as their corrosion behavior change with KF concentration and immersion time. Treatments in the 0.01 M–0.1 M KF range prove to be effective to protect Mg(PM) against corrosion in the absence of chlorides while higher KF solution concentration (0.3 M) adversely affects the corrosion resistance of this metal. In the presence of chloride ions the F-CCs progressively lose their fluoride content and their corrosion resistance at a rate that depends on the treatment conditions. Such temporary corrosion protection is appropriate for biodegradable implants.
Keywords: Magnesium; Fluoride conversion coating; Chloride; Biodegradable; Powder metallurgy; Biomaterial;

Effect of 60Co irradiation on the properties of chitosan rod by Kai Shen; Qiaoling Hu; Zhengke Wang; Jian Qu (866-872).
Three dimensional layered chitosan rod with high bending strength and potential application as internal fixation of bone fracture was prepared by in-situ precipitation method. To evaluate the effect of 60Co irradiation on the properties of it, chitosan rod was irradiated at doses from 10 kGy to 200 kGy. FT-IR, Ubbelohde viscometer, conductometric titration, GPC, XRD, SEM and universal materials testing machine were used to monitor the changes in structure, morphology and mechanical performance. Results indicated that the chain scission effect obviously dominated in the radiation degradation of chitosan rod. With the increase of irradiation dose, the amount of C═O groups clearly increased, the deacetylation degree (DD), intrinsic viscosity and weight-average molecular weight (Mw) kept decreasing, and the crystallization peak and bending strength reached their maxima at the dose of 20 kGy. Chitosan rod irradiated at 20 kGy had a relatively higher and more stable bending strength of 132.3 ± 1.6 MPa. So it was selected as the model to study the lysozyme degradation of irradiated chitosan rod, showing a weaker hydrophilicity than the unirradiated chitosan rod, and almost the same degradation rate.
Keywords: Chitosan; 60Co irradiation; Chain scission effect; Lysozyme degradation; Color change; In-situ precipitation;

Influence of sterilization methods on cell behavior and functionality of osteoblasts cultured on TiO2 nanotubes by Seunghan Oh; Karla S. Brammer; Kyung-Suk Moon; Ji-Myung Bae; Sungho Jin (873-879).
We investigated the adhesion, proliferation and osteogenic functionality of osteoblasts cultured on titanium dioxide (TiO2) nanotubes in response to different sterilization methods (dry autoclaving vs. wet autoclaving). We prepared various sizes (30–100 nm diameter) of TiO2 nanotubes on titanium substrates by anodization, sterilized nanotubes by different conditions, and seeded osteoblast cells onto the nanotube surfaces with two different cell seeding densities (10,000 vs. 50,000 cells/well in 12-culture well). The result of this study indicates that the adhesion, proliferation and alkaline phosphatase activity of osteoblasts cultured on only the larger 70 and 100 nm TiO2 nanotube arrays were dramatically changed by the different sterilization conditions at a low cell seeding density. However, with a higher cell seeding density (50,000 cells/well in 12-cell culture well), the results revealed no significant difference among altered nanotube geometry, 30–100 nm diameters, nor sterilization methods. Next, it was revealed that the nanofeatures of proteins adhered on nanotubular TiO2 morphology are altered by the sterilization method. It was determined that this protein adhesion effect, in combination with the cell density of osteoblasts seeded onto such TiO2 nanotube surfaces, has profound effects on cell behavior. This study clearly shows that these are some of the important in vitro culture factors that need to be taken into consideration, as well as TiO2 nanotube diameters which play an important role in the improvement of cell behavior and functionality.
Keywords: TiO2 nanotubes; Sterilization method; Osteoblast; Cell seeding density; Alkaline phosphatase activity;

Morphology-tuning by changing the composition of a binary hydrogel comprising thymidine and melamine by Zhixin Yu; Binglian Bai; Haitao Wang; Xia Ran; Guibao Jin; Ji Sun; Chengxiao Zhao; Min Li (880-884).
We report on the self-assembly of a new two-component hydrogel of thymidine (T) and melamine (M) which formed supramolecular complex (≥ 0.1%, w/v) based on intermolecular hydrogen-bonding. The 3D morphologies were tuned by changing the molar ratio of T and M in aqueous medium from 3/1 to 1/3. The xerogels respectively showed rod, sheet and flower structures as observed under SEM. Fourier transform infrared (FT-IR) spectroscopy and wide angle X-ray scattering (WAXD) patterns confirmed that thymidine and melamine form supramolecular complexes through intermolecular hydrogen-bonding. The different structures of the complexes are proposed for the different compositions of the components.
Keywords: Hydrogel; Morphology-tuning; Self-assembly; H-bonding; Thymidine;

Corrosion behavior of β titanium alloys for biomedical applications by M. Atapour; A.L. Pilchak; G.S. Frankel; J.C. Williams (885-891).
The corrosion behavior of biocompatible β titanium alloys Ti–13Mo–7Zr–3Fe (TMZF) and Ti–35Nb–7Zr–5Ta (TiOsteum) was investigated in 0.9% NaCl and 5 M HCl solutions. Extra-low-interstitial Ti–6Al–4V, which is also a candidate material for biomedical applications, was studied for comparison. The as-received TiOsteum and TMZF alloys exhibited single-phase β and α + β microstructures, respectively, so the latter was also investigated in the solutionized and quenched condition. In 0.9% NaCl solution, all three alloys exhibited spontaneous passivity and very low corrosion rates. Ti–6Al–4V and the as-received TMZF exhibited active-passive transitions in 5 M HCl whereas TiOsteum and TMZF in the metastable β condition showed spontaneous passivity. Potentiodynamic polarization tests, weight loss and immersion tests revealed that TiOsteum exhibited the best corrosion resistance in 5 M HCl. Analysis of surfaces of the corroded specimens indicated that the α/β phase boundaries were preferential sites for corrosion in Ti–6Al–4V while the β phase was preferentially attacked in the two-phase TMZF. The performance of the alloys in corrosive environment was discussed in terms of the volume fraction of the constituent phases and partitioning of alloying elements between these phases.
Keywords: Ti alloys; Corrosion;

Rapid prototyping of nano- and micro-patterned substrates for the control of cell neuritogenesis by topographic and chemical cues by Ajay V. Singh; Lasma Gailite; Varun Vyas; Cristina Lenardi; Stefania Forti; Michela Matteoli; Paolo Milani (892-899).
Rapid prototyping of titania substrates with micro and nanofeatures is obtained by combining nanosphere lithography with supersonic cluster beam deposition on protein-functionalized glass supports. The proliferation and differentiation of PC12 cells were studied on these substrates. The facile control and modification of the substrate structure at the micro- and nanoscale allowed us to characterize the role of functional and structural features on neuritogenesis and to control this phenomenon by identifying the optimal topography.
Keywords: Micropatterning; Nanotopography; Cell culture; Neural network; Titanium oxide;

The effects of Pt and Pd addition to a Zr-20Nb alloy on its microstructure and mechanical property, as well as the elution of metals from the alloys in lactic acid solution, were investigated. The microstructure was characterized with an X-ray diffractometer (XRD), an optical microscope (OM), and a transmission electron microscope (TEM). The mechanical properties were evaluated by a tensile test. The β phase is dominantly observed in the Zr-20Nb as well as in the Pt-added and Pd-added Zr-20Nb alloys. Needle-like microstructures are observed in equiaxed grains in all alloys. Pd addition to the Zr-20Nb alloy suppresses ω phase formation more than Pt addition does. The 0.2% offset yield strength and the ultimate tensile strength of the Pt-added and Pd-added Zr-20Nb alloys increase with the Pt and Pd concentrations. XRD analysis revealed that the lattice parameter of β-Zr in the Pt-added and Pd-added Zr-20Nb alloys decreases with the Pt and Pd concentrations. Pt and Pd solute in β-Zr as a substitutional element and contribute to the increase in the strength by solid solution hardening. The addition of 2Pt and 2Pd to the Zr-20Nb alloy also improves metal elution from the alloys in lactic acid solution.
Keywords: Zirconium–niobium–platinum alloy; Zirconium–niobium–palladium alloy microstructure; Mechanical properties; Metal release;

Characterization of a calcium phosphate–TiO2 nanotube composite layer for biomedical applications by A. Roguska; M. Pisarek; M. Andrzejczuk; M. Dolata; M. Lewandowska; M. Janik-Czachor (906-914).
Well-ordered nanotube arrays of titania ~ 0.7 μm high and about 40 or 110 nm in diameter were prepared via electrochemical oxidation at constant voltage (10, 15, 20 or 25 V) in a mixture of 0.86 wt.% of NH4F, glycerol and deionized water. The effect of annealing the nanotubes at 600 °C on their morphology and structure was examined using SEM and TEM techniques. These substrates are suitable supports for a calcium phosphate coating deposited by a simple immersion in Hank solution.The nucleation and growth of a calcium phosphate (Ca–P) coating deposited on TiO2 nanotubes (NT) from Hanks' solution was investigated using SEM. XPS and FTIR surface analytical techniques were used to characterize the self-organized porous TiO2 layers covered with calcium phosphate coatings before and after protein adsorption. Our results confirm that the nanotubular titania layer became stable after annealing at 600 °C, while its internal structure changed from amorphous to crystalline anatase, and eventually, a mixture of anatase and rutile. These thermally stabilized TiO2 nanotubes significantly enhance apatite formation in Hanks' Balanced Salt Solution as compared to pure Ti covered with a native oxide layer. The Ca–P/TiO2 NT/Ti surface adsorbs a higher amount of protein (bovine serum albumin, BSA) for a geometric surface area than does the Ti surface. The above difference in protein adsorption suggests a more promising initial cellular response for a Ca–P/TiO2 NT/Ti composite than for a typical Ti implant surface.
Keywords: TiO2 nanotubes (TiO2 NT); Calcium phosphate coatings (Ca–P); Scanning electron microscopy (SEM); Transmission electron microscopy (TEM); X-ray photoelectron spectroscopy (XPS); Serum albumin (SA);

PHEMA cryogel for in-vitro removal of anti-dsDNA antibodies from SLE plasma by Erdoğan Özgür; Nilay Bereli; Deniz Türkmen; Serhat Ünal; Adil Denizli (915-920).
Supermacroporous poly(2-hydroxyethyl methacrylate) (PHEMA) cryogel carrying DNA was used in the removal of anti-dsDNA antibodies from systemic lupus erythematosus (SLE) patient plasma. The PHEMA cryogel was prepared by bulk polymerization which proceeds in an aqueous solution of monomer frozen inside a plastic syringe. After thawing, the PHEMA cryogel contains a continuous matrix having interconnected macropores of 10–200 μm size. Pore volume in the PHEMA cryogel was 67.5%. Ester groups in the PHEMA structure were converted to imine groups by reacting with poly(ethyleneimine) (PEI) in the presence of NaHCO3. Amino (− NH2) content of PEI-modified PHEMA cryogel was determined as 82 mg PEI/g. Then, DNA was attached onto the PHEMA cryogel via amino groups (53.4 mg DNA/g cryogel). Anti-dsDNA-antibody concentration declined significantly from 780 IU/ml to 80 IU/ml with the time. The maximum anti-dsDNA-antibody adsorption amount was 70 × 103  IU/g. Anti-dsDNA-antibodies could be repeatedly adsorbed and eluted without noticeable loss in the anti-dsDNA-antibody adsorption amount.
Keywords: Antibody removal; Anti-dsDNA; PHEMA; Cryogels; DNA; SLE;

The structural characteristics of biomedical porous materials are crucial for bone tissue to grow into a porous structure and can also influence the fixation and remodeling between the implant and the human tissues. The current study has been investigating the effect of the ball-milling variable of time on the structural characteristics and pore morphology of a biomedical porous Ti–16Sn–4Nb (wt.%) alloy. The alloy was synthesized using high-energy ball milling for different periods of time, and the porous Ti–16Sn–4Nb alloy was fabricated by using a space holder sintering process. The resultant powder particles, bulk, and porous samples were characterized using a scanning electron microscope (SEM), laser particle-size analyzer, chemical analysis, X-ray diffraction analysis (XRD), and the Vickers hardness test. The results indicated that the inner pore surface, pore wall architecture, degree of porosity, pore size and the inter-pore connectivity of the sintered porous alloy are all considerably affected by ball-milling time.
Keywords: Mechanical alloying; Titanium alloys; Porous materials; Powder metallurgy; Biomaterials;

Interaction of chitosan capped ZnO nanorods with Escherichia coli by P. Bhadra; M.K. Mitra; G.C. Das; R. Dey; S. Mukherjee (929-937).
ZnO nanorods of around 80 nm length and 30–60 nm diameter, encapsulated in chitosan were synthesized through co-precipitation technique and was characterized by XRD, UV–VIS, SEM, HRTEM, AFM and FTIR. The aim of the study was to investigate the attachment of chitosan capped zinc oxide nanoparticles (ZnO NP) with Escherichia coli bacterial outermost cell membrane and their mode of action against these bacteria. The detailed characterization studies were carried out to develop insight into the process of influence of these nanostructures on bacterial cells. Antibiotic characteristics of chitosan capped ZnO nanoparticles have been compared with Amoxicillin by zone of inhibition through cup plate method.
Keywords: ZnO nanorod; Chitosan; Co-precipitation; E. coli; Mode of interaction;

Controlled radical polymerization based on 1, 1-diphenylethylene (DPE method) was used to prepare pH-responsive magnetic composite microspheres. By this method, Fe3O4/Poly (acrylic acid-stat-methyl methacrylate-block-(2-dimethylamino) ethyl methacrylate) (Fe3O4/P(AA-MMA-DMA)) microspheres were prepared via emulsifier free emulsion polymerization of acrylic acid (AA), methyl methacrylate (MMA) and (2-dimethylamino) ethyl methacrylate (DMA) using 1, 1-diphenylethylene (DPE) as radical control agent in the presence of Fe3O4 nanoparticles. The structure and properties of Fe3O4/P (AA-MMA-DMA) microspheres were characterized by IR, 1H NMR, SEC-MALLS, TEM, TGA, VSM and DLS. The application of Fe3O4/P (AA-MMA-DMA) microspheres in controlled release of drug was also investigated. It was found that the DPE method allowed the preparation of pH-responsive magnetic composite microspheres, and Fe3O4/P (AA-MMA-DMA) microspheres obtained were pH-responsive, perfect sphere-shaped morphologies, superparamagnetism with a saturation magnetization of 14.36 emu/g, and high magnetic content with a value of 29%. Moreover, Fe3O4/P (AA-MMA-DMA) microspheres could control the release of phenolphthalein in a buffer solution by adjusting the pH value.
Keywords: Preparation; Magnetic composite microsphere; pH-responsive; DPE method; Controlled release;

Quasi-static torsional deformation behavior of porous Ti6Al4V alloy by Vamsi Krishna Balla; Shantel Martinez; Ben Tunberg Rogoza; Chase Livingston; Deepak Venkateswaran; Susmita Bose; Amit Bandyopadhyay (945-949).
Laser processed Ti6Al4V alloy samples with total porosities of 0%, 10% and 20% have been subjected to torsional loading to determine mechanical properties and to understand the deformation behavior. The torsional yield strength and modulus of porous Ti alloy samples was found to be in the range of 185–332 MPa and 5.7–11 GPa, respectively. With an increase in the porosity both the strength and the modulus decreased, and at 20% porosity the torsional modulus of Ti6Al4V alloy was found to be very close to that of human cortical bone. Further, the experiments revealed clear strain hardening and ductile deformation in all the samples, which suggests that the inherent brittleness associated solid-state sintered porous materials can be completely eliminated via laser processing for load bearing metal implant applications.
Keywords: Laser deposition; Torsion test; Porous material; Titanium alloy; Deformation;

Interfacial assembly of sandwich mixed (Phthalocyaninato)(Porphyrinato) rare earth triple-decker complexes by Qingyun Liu; Yong Li; Hongguo Liu; Jianzhuang Jiang; Yongzhong Bian (950-953).
Interfacial assembly of sandwich mixed (phthalocyaninato)(porphyrinato) rare earth triple-decker complexes [(Pc)Eu(Pc)Eu(TPyP)] (1) and [(TPyP)Sm(Pc)Sm(TPyP)] (2) (Pc = phthalocyaninate, TPyP = meso-tetrakis(4-pyridyl)porphyrinate) has been comparatively studied at the air/pure water and the air/CdCl2 aqueous solution subphase interfaces. Surface pressure-area isotherms revealed the remarkable increase of limiting mean molecular area of the triple-deckers with the presence of Cd2+, suggesting the occurrence of in situ interfacial coordination. The formation of coordination bonds between the pyridyl groups of TPyP macrocycles in the triple-deckers and Cd2+ ions from the subphase was further supported by FT-IR spectroscopic data. Electronic absorption measurements showed the formation of J-aggregates of the triple-decker molecules in the interfacial assembled films.
Keywords: Phthalocyanine; Porphyrin; Rare earth metals; Interfacial assembly; Coordination;

This study aims to synthesize and characterize a biodegradable scaffold with a cellulose/nano-hydroxyapatite base for bone tissue engineering. At first, nano particles of hydroxyapatite were synthesized via precipitation method; furthermore scaffolds were fabricated by solvent casting/particulate leaching technique, where poly(methyl methacrylate) were utilized as porogen. The 1-n-allyl-3-methylimidazolium chloride ionic liquid was used for dissolution of cellulose as well. Scaffolds with 3 different compositions (5, 15, and 30 wt.% of nano-hydroxyapatite) had 85–90% porosity. Also, the morphology of the samples was studied employing SEM. Images showed that pore sizes of the scaffolds were nearly 250–450 μm. Meanwhile, sample bioactivity was determined via MTT assay and ALP test. Bioactivity and compatibility of the samples were confirmed; in addition, no toxicity was observed after 14 days. SEM studies demonstrated that the cells can attach to the surface of the nanocomposite samples. This behavior revealed osteoconductivity of the composite surface.
Keywords: Cellulose; Nanohydroxyapatite; Composite; Scaffold;

Evaluation of oral carvedilol microparticles prepared by simple emulsion technique using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and polycaprolactone as polymers by Manoela Klüppel Riekes; Fernanda Malaquias Barboza; Débora Dalla Vecchia; Milton Bohatch; Paulo Vitor Farago; Daniel Fernandes; Marcos Antonio Segatto Silva; Hellen Karine Stulzer (962-968).
Polymeric microparticles containing carvedilol (CRV) were obtained successfully using a simple emulsion/organic evaporating method. Three different formulations were developed using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polycaprolactone (PCL) as polymers; the resulting samples were submitted to physical–chemical characterization and in vivo evaluation. The physical–chemical analysis indicated that the PHBV promoted a porous aspect in the microparticle's surface, while PCL a smooth aspect. The PCL-CRV microparticles showed a higher loading efficiency and a longer drug release time, being selected for in vivo evaluation. The in vivo assays indicated that PCL-CRV polymeric microparticles has a pharmacological antihypertensive effect for a longer period of time, representing a good alternative to improved the life quality of the patient that uses this drug.
Keywords: Microparticles; Carvedilol; PCL; PHBV; Controlled release;

Charge injection in an LED with a hybrid composite as the emissive layer by G. Gozzi; D.L. Chinaglia; T.F. Schmidt; O.N. Oliveira (969-974).
Understanding and controlling charge transport are crucial to achieve optimized organic devices, including light emitting diodes. In this study, we investigate the charge injection in devices made with a hybrid composite (HC) containing Zn2SiO4:Mn (ZSP:Mn) in a polymeric blend consisting of poly(o-methoxyaniline) (POMA) and poly(vinylidene co-trifluorethylene) P(VDFTrFE), with the architecture ITO/HC/metallic electrode (ME). Charge injection was found to depend mainly on the POMA semiconducting phase. For ITO/HC/Au, an Ohmic junction was observed because the work function of ITO is close to that of Au, which also matches the energy levels of HC. Holes are injected through the HC/Au junction, as the highest occupied molecular orbital (HOMO) level of POMA matches the Fermi level of Au. The impedance spectroscopy data for the ITO/HC/ME devices were analyzed with a theoretical model where charge injection was assumed to occur via hopping with a distribution of potential energy barriers. The average hopping distance was estimated as 5.5 Å and only the device with the Al electrode had the current limited by the interface mechanism (charge injection). For ITO/HC/Cu and ITO/HC/Au devices the limiting factor for the charge transport was the bulk resistance of the samples, in spite of the existence of a small interface energy barrier. The disorder parameter was 0.18 and 0.19 for the HC/Cu and HC/Al interfaces, respectively, which arises from the disordered nature of the hybrid material. The combination of the Cole–Cole model and the Miller–Abrahams function are a good approach to describe charge a.c. injection processes in disordered materials.
Keywords: Hybrid composite; Electroluminescent device; Charge injection; Hopping mechanisms; Impedance spectroscopy;

Electrochemical characteristics of an electrodeposited chlorogenic acid film on multi-wall carbon nanotubes glassy carbon electrode (CGA–MWCNT–GCE) and its role as a sensor for electrocatalytic oxidation of hydroxylamine are described. Cyclic voltammograms of the CGA–MWCNT–GCE indicate a pair of well-defined and nearly reversible redox couple with the surface confined characteristics at a wide pH range of 2.0–12.0. The charge transfer coefficient, α, and the charge transfer rate constant, ks, of CGA adsorbed on MWCNT were calculated 0.48 and 44 ± 2 s−1 respectively. The CGA–MWCNT–GCE shows a dramatic increase in the peak current and/or a decrease in the overvoltage of hydroxylamine electrooxidation in comparison with that seen at a CGA modified GCE, MWCNT modified GCE and activated GCE. The kinetic parameters of electron transfer coefficient, α, the heterogeneous electron transfer rate constant, k′, and exchange current, i0, for oxidation of hydroxylamine at the modified electrode surface were determined using cyclic voltammetry. Four linear calibration ranges and high repeatability with relative standard deviation of 4.6%, for a series of four successive measurements in 17.7 μM hydroxylamine, are obtained at the CGA–MWCNT–GCE using an amperometric method. Finally, the modified electrode was successfully used for determination of spiked hydroxylamine in two water samples.
Keywords: Hydroxylamine; Chlorogenic acid; Multi-wall carbon nanotubes; Electrocatalytic oxidation; Rate constant; Sensor;

Gel-derived SiO2–CaO–Na2O–P2O5 bioactive powders: Synthesis and in vitro bioactivity by Renato Luiz Siqueira; Oscar Peitl; Edgar Dutra Zanotto (983-991).
In the present work, bioactive powders of the quaternary SiO2–CaO–Na2O–P2O5 system were synthesized by means of a sol–gel route. In their synthesis, tetraethoxysilane (Si(OC2H5)4), calcium nitrate tetrahydrate (Ca(NO3)2∙ 4H2O) and sodium nitrate (NaNO3) were chosen as precursors of SiO2, CaO and Na2O, respectively. For P2O5, two different precursors were tested: triethylphosphate (OP(OC2H5)3) and phosphoric acid (H3PO4). The gels were then converted into ceramic powders by heat treatments in the temperature range 700–1000 °C. The resulting materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) and in vitro bioactivity in acellular simulated body fluid (SBF). During the conversion of the gels into ceramics the mineralization behavior of the two sets of samples was different, but all the resulting materials were bioactive. The samples prepared using phosphoric acid exhibited the best in vitro bioactivity. This result was attributed to the preferential formation of bioactive sodium calcium silicate Na2Ca2Si3O9 crystals, especially in the samples submitted to heat treatments at 700 and 800 °C, which could not be observed in the samples prepared using triethylphosphate.
Keywords: Sol–gel; Bioactive glass-ceramics; SiO2–CaO–Na2O–P2O5; In vitro tests;

Spectrophotometric and chemometric studies on the simultaneous determination of two benzodiazepines in human plasma by Siavash Riahi; Kowsar Bagherzadeh; Nazila Davarkhah; Mohammad Reza Ganjali; Parviz Norouzi (992-996).
A numerical simple, accurate and precise method based on spectrophotometric data coupled with multivariate calibration methods, PLS and MLR, combined with GA was developed for the simultaneous determination of two benzodiazepines, Clobazam and Flurazepam. A data set of absorption spectra obtained from a calibration set of mixtures containing the compounds was used to build GA-PLS and GA-MLR models. The models were tested using a dataset constructed from the compound synthetic solutions. The better model was also applied to plasma samples. The proposed method requires no preliminary separation steps and can be used for these drugs analysis in quality control laboratories.
Keywords: Benzodiazepines; Spectrophotometry; Partial least squares; Multivariate linear regression; Chemometrics; Simultaneous determination;

Hydrogels from silk fibroin metastable solution: Formation and characterization from a biomaterial perspective by Grinia Michelle Nogueira; Mariana Agostini de Moraes; Andrea Cecília Dorión Rodas; Olga Zazuco Higa; Marisa Masumi Beppu (997-1001).
Silk fibroin (SF) hydrogels were obtained from the dialysis of a SF metastable solution. Temperature and calcium concentration in SF solution/hydrogel were measured, as critical variables for SF gelation phenomenon. Gelation time of SF solution was increased by decreasing the dialysis temperature, whereas the residual calcium concentration was higher when higher dialysis temperatures were applied. Hydrogels obtained at 20 °C were characterized after freeze-drying. SEM micrographs showed porous structures, of ca. 20 μm (in cross-sectional area) and 5 μm (on surface). XRD indicated the presence of a β-sheet structure that is formed during SF gelation. In hydrogel formation, SF molecules in solution are dehydrated and interact by intra and intermolecular hydrogen bonds, forming a stable hydrogel. DSC measurements showed the decomposition peak for SF at 290 °C, characteristic of SF β-sheet structure, which is in accordance with the XRD results and demonstrate its high thermal resistance. SF hydrogels were found not to be toxic to cells using in vitro cytotoxicity tests. Results indicate that silk fibroin hydrogels hold promise for use in the biomaterial field.
Keywords: Biomaterials; Biopolymers; Silk fibroin; Hydrogels;

Four kinds of chitosan membranes, (Ch, C-G, C-N, and C-GN), were prepared in this study. Ch system of chitosan membranes were prepared by solution casting method without any treatment. C-G system of chitosan membranes were prepared by solution casting method with adding glutaraldehyde as crosslinking agent. C-N system of chitosan membranes were prepared by solution casting method with the treatment of NaOH solution. C-GN system of chitosan membranes were crosslinked with glutaraldehyde and treated with 1 M NaOH solution. Infrared spectroscopy and differential scanning calorimetry (DSC) were conducted to characterize the structure and thermal properties of chitosan membrane. To evaluate the usage of chitosan for the carrier of drug, water content and degradation of the chitosan membrane were determined. It was found that the values of equilibrated water content in chitosan membranes increased with the chitosan content in the stock chitosan solution. The assessment of 5-FU permeability through the chitosan membranes was determined. The linear relationship between the permeability of 5-FU through the membrane and the wt.% of chitosan content in stock chitosan solution was found. Both values of intercept and slope were determined. The value of intercept means that the permeability of 5-FU through the chitosan membrane, which is assumed to be prepared from stock chitosan solution containing infinite dilute chitosan content. The value of slope indicates that the effect of the treatment method on the permeability of 5-FU through the chitosan membrane. From the evaluation of normalized flux, diffusivity and saturation concentration of 5-FU in various chitosan membrane, it was found that more number of 5-FU molecules were trapped in the chitosan membrane of C-GN system than that in C-N system and resulted in the decrease of diffusivity of 5-FU molecules through the chitosan membrane.
Keywords: Chitosan; 5-fluorouracil; Permeability coefficients; Normalized flux; Diffusivity; Saturation concentration;

The magnetic and heat generating properties of the ferrimagnetic zinc-ferrite containing bioactive glass ceramics have been enhanced by aligning magnetic field, without any compositional or micro-structural changes in the material. The glass ceramics were heated to 600 °C and cooled in an aligning magnetic field of 1 T. Magnetically aligned samples were compared with the non-aligned samples. VSM measurements taken at 500 Oe showed that coercive force, remanance magnetization and hysteresis area increased for the aligned samples. This occurred because the aligning magnetic field setup an easy axis for the magnetic domains. After cooling, the domains were trapped and became stable along the direction of aligning field. Now stronger magnetic field was required to turn the domains away from their aligned positions. Thus magnetic properties were enhanced by the aligning magnetic field and it led to enhance the heat generation under magnetic induction furnace operating at 500 Oe and 60 kHz for 2 min. Data showed that maximum specific power loss and temperature increase after 2 min were 4.4 W/g and 6.3 °C respectively for the aligned sample of maximum zinc-ferrite crystalline content having pseudo single domain crystalline structure. The glass ceramics were immersed in simulated body fluid over weeks. FTIR, SEM and EDX results indicated the growth of precipitated Hydroxyapatite suggesting the bioactivity of the materials.
Keywords: Magnetic properties; Thermomagnetic effects; Specific heat; Biomaterials; Hydroxyapatite;

In situ mineralized hydroxyapatite on amino acid modified nanoclays as novel bone biomaterials by Avinash Ambre; Kalpana S. Katti; Dinesh R. Katti (1017-1029).
A novel biomineralization route to synthesis of hydroxyapatite (HAP) in montmorillonite (MMT) clay galleries modified with 5-aminovaleric acid is presented. The oraganomodified MMT clay with mineralized HAP (in situ HAPclay) was characterized by transmission Fourier Transform infrared (FTIR) spectroscopy to evaluate molecular interactions between clay-modifier-HAP. FTIR spectroscopy studies indicated the formation of HAP within the modified MMT clay galleries. X-ray diffraction (XRD) studies indicated the formation of apatite in modified MMT clay and also showed shifts in peak positions corresponding to the apatite in in situ HAPclay. This indicated that the apatite formed in in situ HAPclay exhibits differences in its lattice structure as compared to ex situ hydroxyapatite (HAP). The in situ HAPclay was further used for the preparation of nanocomposite chitosan/polygalacturonic acid (ChiPgA) composite films. Human osteoblast cells were cultured on these ChiPgA composite films containing in situ HAPclay. Human osteoblasts form clusters and exhibit good biocompatibility with these films. This work demonstrated the potential to design biomineralized HAP in nanocomposites as new bone biomaterials.► Biomineralization of hydroxyapatite in amino acid modified montmorillonite clay galleries. ► Biomineralized HAPclay is used in combination with biopolymers for bone tissue engineering. ► A combination of mechanical property as well as biocompatibility is tailored using this nano HAP-Clay.
Keywords: Organoclay; Biomaterials; Bone; Nanocomposite; Chitosan; Polygalactouronic acid;

A study of the dynamic compressive behavior of Elk antler by Robb M. Kulin; Po-Yu Chen; Fengchun Jiang; Kenneth S. Vecchio (1030-1041).
Large mammalian antler is extremely tough and fracture resistant compared to other more brittle forms of skeletal bone. The ability of antler to resist fracture is associated with a decrease in material stiffness and yield strength and increased non-linear response, due in part to antler being fast growing, since they are typically shed and regrown annually. Since male Elk commonly engage in antler sparring as a means of making dominance displays, the ability to withstand large impacts suggest that antler may exhibit strain-rate dependent behavior even greater than skeletal bone. To evaluate this hypothesis, specimens of antler were tested in compression over a range of strain rates. Specimens were loaded either along or transversely to the osteonal growth direction, in wet and dry conditions. Results showed that antler exhibits higher compressive strengths at increased strain rates, and that strain rate and hydration are greater determinants of compressive strength than osteonal orientation. In addition, antler can sustain compressive strains a full order-of-magnitude greater than in mammalian long bone. Failed specimens showed that a hierarchical chain of deformation mechanisms sustains the large bulk strains supported by antler. These mechanisms appear to be less brittle and more fibrous than those seen previously in skeletal bone.► Antlers show strong strain rate effects, much greater than human or equine bone. ► Strain rate and hydration have a greater effect on strength than osteon orientation. ► A hierarchical chain of deformation mechanisms sustain large strains in antler.
Keywords: Antler; Bone; Compressive strength; Hopkinson bar; Strain rate;

Chemistry between crosslinks affects the properties of peptide hydrogels by Naresh K. Budhavaram; Matthew Stauffer; Justin R. Barone (1042-1049).
Protein hydrogels were prepared by substituting ovalbumin with different concentrations of ethyl vinyl sulfone (EVS) or acrylic acid (AA) and crosslinking with divinyl sulfone (DVS). Fourier transform-infrared (FT-IR) spectroscopic studies confirmed the addition of EVS, AA, and DVS onto the protein. Swelling was assessed as a function of pH in the range of 2.5 to 9.4 and ionic strength. The elastic modulus of the gels was determined in shear and compression. Stress relaxation was assessed in compression. The substituent highly affected swelling and modulus with both hydrogels displaying non-Gaussian behavior in the range of hydrogel environments studied. Acrylic acid substituted ovalbumin exhibited a decreasing modulus with increasing swelling behaving as a polyelectrolyte with low added salt content. Ethyl vinyl sulfone substituted ovalbumin displayed an increasing modulus with swelling originating in the finite extensibility of the highly swollen chains. AA-substituted ovalbumin showed higher modulus and reduced swelling compared to EVS-substituted ovalbumin because of its ability to hydrogen and ionic bond to other molecules.► Substituted proteins as hydrogels. ► Substituent determines intermolecular interactions and therefore mechanical properties. ► EVS allows very high swelling. ► AA allows increased crosslink density from hydrogen bonding with decreased swelling.
Keywords: Hydrogel; Protein; Addition reaction; Swelling;

The variation in the longitudinal and radial direction of the R/T ratio which is the ratio of the radially maximum length (R) to the tangentially maximum width (T) of a vascular bundle and area ratio of vascular bundles, which are cross-sectional image features of bamboo, and the relationships between the R/T ratio or area ratio and relaxation behavior were investigated. These image features varied characteristically in the longitudinal and radial directions. Relationships between these image features and relaxation behavior were evaluated using the instantaneous creep compliance ln[J (0)] and the creep intensity ln [J(3 × 104) − J (0)]. Although both instantaneous compliance and creep intensity decreased as density increased, their dependence properties were remarkably different. Instantaneous compliance was strongly correlated with R/T ratio and density, which was related to the area ratio, whereas creep intensity was weakly correlated with density in a given range. The results indicate a difference between the two relaxation properties, because creep intensity depends more on microstructures, such as the conformation of molecular chains in the substance, or interactions among cells than on R/T ratio and area ratio image features.
Keywords: Bamboo; Vascular bundle; Shape factor; Cross-section; Creep; Image analysis;

Evaluation of the attachment, proliferation, and differentiation of osteoblast on a calcium carbonate coating on titanium surface by Yi Liu; Tao Jiang; Yi Zhou; Zhen Zhang; Zhejun Wang; Hua Tong; Xinyu Shen; Yining Wang (1055-1061).
Titanium has been reported to have some limitations in dental and orthopaedic clinical application. This study described a coating process using a simple chemical method to prepare calcium carbonate coatings on smooth titanium (STi) and sandblasted and acid-etched titanium (SATi), and evaluated the biological response of the materials in vitro. The surfaces of STi, SATi, calcium carbonate coated STi (CC-STi) and calcium carbonate coated SATi (CC-SATi) were characterized for surface roughness, contact angles, surface morphology and surface chemistry. The morphology of MG63 cells cultured on the surfaces was observed by SEM and Immuno-fluorescence staining. Cell attachment/proliferation was assessed by MTT assay, and cell differentiation was evaluated by alkaline phosphatase (ALP) activity. MG63 was found to attach favorably to calcium carbonate crystals with longer cytoplasmic extensions on CC-STi and CC-SATi, resulting in lower cell proliferation but higher ALP activity when compared to STi and SATi respectively. Moreover, CC-SATi is more favorable than CC-STi in terms of biological response. In conclusion, the calcium carbonate coatings on titanium were supposed to improve the osteointegration process and stimulate osteoblast differentiation, especially in early stage. And this method could possibly be a feasible alternative option for future clinical application.► Calcium carbonate coatings were prepared on titanium substrates. ► The coating process is simple and cost-effective. ► Calcium carbonate coating could induce differentiation toward an osteoblastic phenotype. ► Calcium carbonate coating could enhance the osteointegration process especially in early stage.
Keywords: Calcium carbonate; Coating; Surface topography; In vitro; Osteointegration;

Removal of the hazardous dye—Tartrazine by photodegradation on titanium dioxide surface by Vinod K. Gupta; Rajeev Jain; Arunima Nayak; Shilpi Agarwal; Meenakshi Shrivastava (1062-1067).
The removal of the dye—tartrazine by photodegradation has been investigated using titanium dioxide surface as photocatalyst under UV light. The process was carried out at different pH, catalyst dose, dye concentration and effects of the electron acceptor H2O2. It was found that under the influence of TiO2 as catalyst, the colored solution of the dye became colorless and the process followed a pseudo first order kinetics. The optimum conditions for the degradation of dye were 6 × 10− 5  M dye concentration, pH of 11, and 0.18 mg/L of catalyst dose. In order to evaluate the effect of electron acceptor, the effect of H2O2 on the degradation process was also monitored and it was found that the hydroxyl radical formation and retardation of electron–hole recombination took place simultaneously. The adsorption studies of tartrazine at various dose of TiO2 followed the Langmuir isotherm trend. In order to determine the quality of waste water, Chemical Oxygen Demand (COD) measurements were carried out both before and after the treatment and a significant decrease in the values was observed, implying good potential of this technique to remove tartrazine dye from aqueous solutions.Display Omitted►Degradation efficiency increases with increase in catalyst concentration. ►Adsorption of tartrazine on TiO2 followed the Langmuir isotherm. ►The photocatalytic kinetics follows first order.
Keywords: Photo catalytic degradation; Titanium dioxide; Tartrazine; UV light;

Cross-linking of collagen with laccases and tyrosinases by S. Jus; I. Stachel; W. Schloegl; M. Pretzler; W. Friess; M. Meyer; R. Birner-Gruenberger; G.M. Guebitz (1068-1077).
Oxidation of acid soluble collagen (ASC), collagen suspension and BrCN-peptides (BrCN-P) with tyrosinases from B. obtusa (BoT1, BoT2) and A. bisporus (AbT) and laccases from T. versicolor (TvL) and T. hirsuta (ThL) resulted in UV/VIS peaks at 475 nm and 305 nm indicating formation of reactive o-quinones and cross-linked components. Concomitant oxygen consumption was higher for the low molecular weight enzymes (TvL and BoT2) indicating limited accessibility. SDS-PAGE and SEC bands at higher MW demonstrated the formation of cross-linked material. LC-MS/MS analysis suggested the involvement of tyrosine residues in cross-linking without major changes of sequence similarities to untreated collagen. However, an increase of the SEC α-peak together with a decrease of β-peak and the 1235/1450 cm− 1 ratio (FTIR) indicated partial degradation. Crosslinking was enhanced by phenolic molecules such as catechine which lead to increased denaturation temperature and reduced degradation by microbial collagenase. The tensile strength was increased whereas resistance to compressive forces was not influenced.Display Omitted► Enzymatic cross-linking of collagen with oxidoreductases demonstrated. ► Oxidation of collagen by laccase and tyrosinase proven. ► Applications potential of enzymatic collagen cross-linking in medical applications shown.
Keywords: Collagen; Tyrosinase; Laccase; Crosslinking;

Low density lipoprotein (LDL) cholesterol is a major ingredient of the plaque that collects in the coronary arteries and causes coronary heart diseases. Among the methods used for the extracorporeal elimination of LDL from intravasal volume, immunoaffinity technique using anti-LDL antibody as a ligand offers superior selectivity and specificity. Proper orientation of the immobilized antibody is the main issue in immunoaffinity techniques. In this study, anti-human β-lipoprotein antibody (anti-LDL antibody) molecules were immobilized and oriented through protein A onto poly(2-hydroxyethyl methacrylate) (PHEMA) cryogel in order to remove LDL from hypercholesterolemic human plasma. PHEMA cryogel was prepared by free radical polymerization initiated with N,N,N′,N′-tetramethylene diamine (TEMED). PHEMA cryogel with a swelling degree of 8.89 g H2O/g and 67% macro-porosity was characterized by swelling studies, scanning electron microscope (SEM) and blood compatibility tests. All the clotting times were increased when compared with control plasma. The maximum immobilized anti-LDL antibody amount was 63.2 mg/g in the case of random antibody immobilization and 19.6 mg/g in the case of oriented antibody immobilization (protein A loading was 57.0 mg/g). Random and oriented anti-LDL antibody immobilized PHEMA cryogels adsorbed 111 and 129 mg LDL/g cryogel from hypercholesterolemic human plasma, respectively. Up to 80% of the adsorbed LDL was desorbed. The adsorption–desorption cycle was repeated 6 times using the same cryogel. There was no significant loss of LDL adsorption capacity.► LDL cholesterol is a risk factor in the development of coronary heart diseases. ► Antibodies against LDL are used for the selective extracorporeal removal of LDL. ► Protein A is used for the oriented immobilization of anti LDL onto PHEMA cryogel. ► PHEMA cryogels are biocompatible, exhibit a low pressure drop, lack diffusion resistance and viscous samples can be easily applied on them. ► Anti-LDL antibody immobilized through protein A was more efficient than randomly immobilized anti-LDL antibody in removing LDL.
Keywords: Cholesterol removal; Cryogels; Oriented immobilization; Protein A;

The thermo-sensitive properties of poly (N-isopropylacrylamide) (PNIPA) hydrogels are modified by the addition of hydrophilic acrylamide comonomers and an interpenetrating network of sodium alginate for drug delivery applications near 37 °C. A mathematical model is presented to describe the mass transport kinetics during the hydrogel drug delivery process, which is accompanied by a volume change during phase transition. In this model, the transport in the polymer matrix is described by Fick's second law in cylindrical coordinates, with concentration dependent diffusion coefficients. The moving boundary problems caused by the polymer matrix swelling are also solved by numerical simulation. The models show that the Trypan blue release from the modified PNIPA-based hydrogels is strongly concentration dependent. The sodium alginate component is also shown to effectively facilitate the diffusion process. The results from the simulation are in good agreement with the measurements of diffusion and swelling observed from in vitro experiments. The implications of this work are also discussed for practical drug delivery systems.► Measured and modeled modified poly (N-isopropylacrylamide) hydrogels. ► Improved phase transition temperature and diffusion properties near 37 °C. ► Modeled drug release by concentration dependent diffusion and moving boundary. ► Models match well with the release profile from PNIPA-based hydrogels.
Keywords: Poly (N-isopropylacrylamide) hydrogel; Diffusion; Swelling; Modeling; Controllable drug delivery;

Polysulfone based amphiphilic graft copolymers by click chemistry as bioinert membranes by Gorkem Yilmaz; Hojjat Toiserkani; Dilek Odaci Demirkol; Serhan Sakarya; Suna Timur; Lokman Torun; Yusuf Yagci (1091-1097).
A series of well-defined amphiphilic graft copolymers with hydrophobic polysulfone (PSU) as backbones and hydrophilic poly(ethylene glycol) (PEG) as side chains were synthesized and characterized. For this purpose, PSUs were converted to azido-functionalized polymers by successive chloromethylation and azidation processes to give clickable PSUs. Then, the ω-hydroxyl function of the commercially available PEG-OH was converted into propargyl functionality by simple esterification process. Ultimately, the alkyne functionalized PEO was successfully grafted onto the PSUs by click chemistry. The final polymers and intermediates at various stages were characterized by 1H NMR, FT-IR, and GPC techniques. The bioinert character of PEG grafted PSU was confirmed by static protein adsorption and prokaryotic and eukaryotic cell adhesion studies, and compared to that of unmodified PSU.Display Omitted► Amphiphilic graft copolymers with polysulfone (PSU) backbone and poly(ethylene glycol) (PEG) side chains. ► Modification of PSU by PEG chains via click chemistry. ► Fabrication of bioinert membranes. ► A practical surface modification strategy for the manufacture of semipermeable membranes used in medical devices.
Keywords: Amphiphilic graft copolymer; Click chemistry; Polysulfone; Hydrophilic segments; Poly(ethylene glycol); Bio-inertness;

Biodegradable wound-closing devices for gastrointestinal interventions: Degradation performance of the magnesium tip by Anja C. Hänzi; Andrej Metlar; Michael Schinhammer; Heba Aguib; Tim C. Lüth; Jörg F. Löffler; Peter J. Uggowitzer (1098-1103).
The aim of this study was to investigate the degradation performance of the magnesium tip of a biodegradable rivet intended for tissue joining and fixing via endoscopic surgery. The in vitro degradation performance was assessed by immersion tests in simulated gastric fluid. The influence of the chemical composition of the alloy, salt concentration, temperature and pH value was investigated. Among the parameters varied, the pH value exhibits the most significant influence on the degradation performance. It represents a potentially useful tool for controlling the tip degradation, allowing the greatest amount of flexibility during the surgical intervention. The biodegradable Mg alloy WZ21 is shown to be a suitable material for the short-term component (the tip) of the rivet. It allows precise tip fabrication with adequate sharpness and degrades homogeneously and sufficiently fast in simulated gastric fluid at low pH values. Due to a suitable surface-to-volume ratio and its rotationally symmetrical geometry, the Trocar tip design is considered the most promising tip shape among the various designs investigated. The results of this study confirm the feasibility of this new concept of completely degradable wound-closing devices and provide a solid basis for further product development.► Description of the bio-degradation of Mg alloys in acidic environments with pH < 3. ► Evaluation of the influence of the environment on the degradation rate. ► Discussion of the applicability for endoscopic surgery procedures.
Keywords: Magnesium; Biodegradation; In vitro test; Wound closure; Gastrointestinal intervention; Endoscopic surgery;

Superhydrophilic ZrO2 nanotube layer was prepared by anodic oxidation of commercial pure Zr in aqueous solutions containing 1 M (NH4)2SO4 and 0.15 M NH4F. The effect of annealing and ultraviolet (UV) irradiation treatment on the microstructure, water contact angle and bioactivity of the ZrO2 nanotube layer was investigated. The as-anodized nanotube layer consists of cubic and amorphous ZrO2, no apatite crystals are deposited on its surface even after immersion in simulated body fluids (SBF) for 30 days, exhibiting weak apatite-inducing ability. After annealing at 450 °C for 3 h, the nanotube layer is composed of cubic and monoclinic ZrO2, and its apatite-forming ability is significantly enhanced because of its lattice structure matching that of apatite, apatite can be induced after immersion in SBF for 15 days. UV irradiation of the ZrO2 nanotube layers does not alter their surface morphologies and phase components, however, can improve the bioactivity only when the ZrO2 nanotube layer is well crystallized. The enhanced bioactivity by UV irradiation is thought to result from the abundant basic Zr―OH groups on the crystallized ZrO2 nanotube layer. Annealing and UV irradiation treatment do not alter the superhydrophilic nature of the ZrO2 nanotubes.► Annealing treatment of the nanotube layer can significantly enhance its bioactivity. ► UV irradiation immproves the bioactivity when ZrO2 nanotubes are well crystallized. ► Annealing and UV treatment don't alter the superhydrophilicity of ZrO2 nanotubes.
Keywords: Crystallinity; UV irradiation; ZrO2 nanotube; Bioactivity;

A nematogenic Schiff's base, N,N′-di-4-(4′-pentyloxybenzoate)salicylidene-l″, 3″-diamino-2″-propanol, (abbreviated as H2L6), was synthesized and its structure studied by elemental analyses, mass, NMR and IR spectra. The Schiff's base behaves as a dinegative hexa/tetradentate species in its metal complexes of the general formula, [ML6]n where MII═Mn, Co, Ni, Cu and Zn. Their structural characterizations were made by various spectroscopic techniques.► The work reveals the synthesis and spectral Studies of some 3d metal complexes. ► The mesogenic ligand yielded the metallomesogenic CuII complex. ► We have included the non-mesogenic MnII, CoII, NiII and ZnII complexes. ► The spectral studies for investigating the bonding nature of the ligand. ► Besides the physical characteristics and geometry of the complexes.
Keywords: Nematogenic; Schiff's base; Metallomesogens; Square-pyramidal; NMR and IR spectra;

GOX-functionalized nanodiamond films for electrochemical biosensor by Pedro Villalba; Manoj K. Ram; Humberto Gomez; Amrita Kumar; Venkat Bhethanabotla; Ashok Kumar (1115-1120).
The importance of nanodiamond in biological and technological applications has been recognized recently, and applied in drug delivery, biochip, sensors and biosensors. Under this investigation, nanodiamond (ND) and nitrogen doped nanodiamond (NND) were deposited on n-type silicon films, and later functionalized with enzyme Glucose oxidase (GOX). The GOX functionalized doped and undoped ND films were characterized using combination of several techniques; i.e. FTIR spectroscopy, Raman spectroscopy, atomic force microscopy (AFM) and electrochemical techniques. ND/GOX and NND/GOX thin films on n-type silicon have been found to provide sensitive glucose sensor. GOX has been chosen as a model enzyme system to functionalize with ND at molecular level to understand the glucose biosensor.► Nanodiamond (ND) films were used as an enzyme electrode for glucose quantification. ► Electrochemical behavior of doped and intrinsic films was analyzed. ► Electrode demonstrates sensitivity to glucose concentration in dynamic condition. ► Linear behavior was observed upto 8mM before saturation condition.
Keywords: Glucose oxidase; Biosensor; GOX; Nanodiamond; Amperometric current; Immobilization; Electrochemistry;

Biomimetic sensors of molecularly-imprinted polymers for chlorpromazine determination by Felismina T.C. Moreira; M. Goreti F. Sales (1121-1128).
A new man-tailored biomimetic sensor for Chlorpromazine host-guest interactions and potentiometric transduction is presented. The artificial host was imprinted within methacrylic acid, 2-vinyl pyridine and 2-acrylamido-2-methyl-1-propanesulfonic acid based polymers. Molecularly imprinted particles were dispersed in 2-nitrophenyloctyl ether and entrapped in a poly(vinyl chloride) matrix. Slopes and detection limits ranged 51–67 mV/decade and 0.46–3.9 μg/mL, respectively, in steady state conditions. Sensors were independent from the pH of test solutions within 2.0–5.5. Good selectivity was observed towards oxytetracycline, doxytetracycline, ciprofloxacin, enrofloxacin, nalidixic acid, sulfadiazine, trimethoprim, glycine, hydroxylamine, cysteine and creatinine. Analytical features in flowing media were evaluated on a double-channel manifold, with a carrier solution of 5.0 × 10−2  mol/L phosphate buffer. Near-Nernstian response was observed over the concentration range 1.0 × 10−4 to 1.0 × 10−2  mol/L. Average slopes were about 48 mV/decade. The sensors were successfully applied to field monitoring of CPZ in fish samples, offering the advantages of simplicity, accuracy, automation feasibility and applicability to complex samples.► Chlorpromazine screening by electrical sensors. ► Molecularly-imprinted materials as ionophores. ► Potentiometric detection with PVC membranes.
Keywords: Chlorpromazine; Molecularly-imprinted sensors; Potentiometry; FIA; Fish;

In-vitro release of anti-proliferative paclitaxel from novel balloon-expandable polycaprolactone stents by Shih-Jung Liu; Chao-Ying Hsiao; Jan-Kan Chen; Kuo-Sheng Liu; Cheng-Hung Lee (1129-1135).
This report investigated the in-vitro release characteristics of paclitaxel from novel balloon-expandable polycaprolactone stents. Polycaprolactone stents were first manufactured by a lab-made micro-injection molding machine. Paclitaxel and polylactide–polyglycolide (PLGA) copolymer were dissolved in acetonitrile and were coated onto the surface of the stents by a spray coating device, which was designed and built especially for this study. An elution method was utilized to characterize the in-vitro release characteristics of paclitaxel. The high performance liquid chromatography (HPLC) analysis showed that biodegradable stents could provide sustained release of paclitaxel for more than 70 days. Various process parameters that controlled the release rate of paclitaxel were studied. The experimental results suggested that the total period of drug release could be prolonged by adopting 75:25 PLGA copolymers, employing multi-layer coatings, and increasing the drug loading. In addition, the effectiveness of eluted paclitaxel on cell behavior was examined. The results showed that the eluted drug could effectively inhibit the proliferation of smooth muscle cells.► We investigate the in-vitro release characteristics of paclitaxel from polycaprolactone stents. ► Biodegradable stents provide sustained release of paclitaxel for more than 70 days. ► The eluted drug effectively inhibits the proliferation of smooth muscle cells.
Keywords: Biodegradable polycaprolactone stents; Paclitaxel; Drug delivery; In-vitro release characteristics;

This study investigated the hydrothermal transformation of brushite (dicalcium phosphate dihydrate, DCPD, CaHPO4·2H2O) into octacalcium phosphate (OCP, Ca8(HPO4)2(PO4)4·5H2O) in seven different newly developed biomineralization media, all inspired from the commercial DMEM solutions, over the temperature range of 36.5 °C to 90 °C with aging times varying between 1 h and 6 days. DCPD powders used in this study were synthesized in our laboratory by using a wet-chemical technique. DCPD was found to transform into OCP in the Ca2+, Mg2+, Na+, K+, HCO3 , Cl and H2PO4 containing aqueous biomineralization media in less than 72 h at 36.5 °C, without stirring. The same medium was able to convert DCPD into OCP in about 2 h at 75–80 °C, again without a need for stirring. Samples were characterized by using powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM).► New biomineralization solutions developed to convert DCPD into OCP at 36.5 °C to 80 °C. ► DCPD powder was the starting material. ► OCP was synthesized under static conditions (no need for stirring). ► OCP was synthesized in sealed glass media bottles in solutions free of Hepes or Tris. ► OCP can be synthesized at 75–80 °C in only 2 hours in the above solutions without stirring.
Keywords: Calcium phosphate; Brushite; Transformation; Biomineralization;

A mesogenic (nematic) Schiff's base, N-(4′′′-n-butylphenyl)-4-(4′-hexyloxy benzoate)salicylaldimine, Hbphbsal, (abbreviated as HL1), was synthesized and its structure studied by elemental analyses, mass, NMR and IR spectra. A series of mesogenic/non-mesogenic 3d metal complexes of the general formula, [M(L1)2]n where MII  = Mn, Co, Ni, Cu and Zn has been prepared and structures were studied by various spectroscopic techniques. Spectral studies imply coordination of the ligand (HL1) as uni-negative bi/tri-dentate species to the metal ions, rendering overall geometry to distorted square planar (in case of CuII complex) and octahedral geometry. The ESR spectra confirmed the presence of mixed copper–nitrogen and oxygen bonds in the chelate based on the g ׀׀ value. The CuII, CoII and NiII complexes were found to be mesogenic (nematic) and their transition, melting and clearing points deviated from the ligand upon complexation.► The work reveals the synthesis and spectral Studies of some 3d metal complexes. ► The mesogenic ligand yielded the metallomesogenic CoII, NiII and CuII complexes. ► We have included the non-mesogenic MnII, and ZnII complexes. ► The spectral studies for investigating the bonding nature of the ligand. ► Besides the physical characteristics and geometry of the complexes.
Keywords: Mesogenic salicylaldimine Schiff's base; Metallomesogens; NMR and IR spectra;

Interaction of N-fluorescein-5-isothiocyanate pyrrolidine-C60 with a bimolecular lipid model membrane by C. Schuetze; U. Ritter; P. Scharff; U. Fernekorn; S. Prylutska; A. Bychko; V. Rybalchenko; Yu. Prylutskyy (1148-1150).
In this letter we report the first synthesis of a fluorescein-functionalized fullerene, N-fluorescein-5-isothiocyanate pyrrolidine-C60, and its influence on the electrical properties of a bimolecular lipid model membrane.
Keywords: Model membrane; Fullerene; Electrical properties; Fluorescence;