Biomaterials (v.26, #24)
An analytical model for the dissolution of different particle size samples of Bioglass® in TRIS-buffered solution by Marta Giulia Cerruti; David Greenspan; Kevin Powers (4903-4911).
We analyzed the early stages of reactivity of three different particle size samples of Bioglass® 45S5 and a bulk sample in TRIS-buffered solution at pH 8. Ion release, measured with ion-coupled plasma emission spectroscopy, and pH variations are reported. It was demonstrated that differences in the initial surface area influence the increase in pH, the rate of elemental release, and the rate of calcium phosphate reprecipitation. In particular, a thicker Ca/P layer was obtained on larger particles. The equilibrium value of Si in solution was independent of sample form and amount of sample dissolved, and was always close to the value observed when bulk silica is dissolved at pH 8. An analytical model is proposed for cation release, based on a two-step mechanism. It was found that the early stage of dissolution was nearly diffusion controlled for larger particles and bulk samples. The second stage was similar to a first-order homogeneous dissolution. The influence of sample surface area/solution volume ratio seemed to be more complex than that proposed in the early works presented in the literature. It is suggested that variation of surface area has a significant impact on the course of the dissolution.
Keywords: Bioactive glass; Small particles; TRIS buffer; Dissolution model; ICP; FTIR;
Microstructure and corrosion behaviour in biological environments of the new forged low-Ni Co–Cr–Mo alloys by Sachiko Hiromoto; Emi Onodera; Akihiko Chiba; Katsuhiko Asami; Takao Hanawa (4912-4923).
Corrosion behaviour and microstructure of developed low-Ni Co–29Cr–(6, 8)Mo (mass%) alloys and a conventional Co–29Cr–6Mo–1Ni alloy (ASTM F75-92) were investigated in saline solution (saline), Hanks’ solution (Hanks), and cell culture medium (E-MEM+FBS). The forging ratios of the Co–29Cr–6Mo alloy were 50% and 88% and that of the Co–29Cr–8Mo alloy was 88%. Ni content in the air-formed surface oxide film of the low-Ni alloys was under the detection limit of XPS. The passive current densities of the low-Ni alloys were of the same order of magnitude as that of the ASTM alloy in all the solutions. The passive current densities of all the alloys did not significantly change with the inorganic ions and the biomolecules. The anodic current densities in the secondary passive region of the low-Ni alloys were lower than that of the ASTM alloy in the E-MEM+FBS. Consequently, the low-Ni alloys are expected to show as high corrosion resistance as the ASTM alloy. On the other hand, the passive current density of the Co–29Cr–6Mo alloy with a forging ratio of 50% was slightly lower than that with a forging ratio of 88% in the saline. The refining of grains by further forging causes the increase in the passive current density of the low-Ni alloy.
Keywords: Forged low-Ni Co–Cr–Mo alloy; Corrosion; Surface composition; Microstructure; Biological solution;
Structure, microstructure, and magnetism in ferrimagnetic bioceramics by Th. Leventouri; A.C. Kis; J.R. Thompson; I.M. Anderson (4924-4931).
The structural and magnetic properties of ferrimagnetic bioglass ceramics in the system [0.45(CaO,P2O5)(0.52−x)SiO2 xFe2O3 0.03Na2O], x=0.05, 0.10, 0.15, 0.20 and heat-treated at the temperature range 600–1100 °C are assessed. The structure and microstructure of the samples are characterized with X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Calcium phosphate and magnetite develop as the two major crystalline phases. For x = 0.10 and 0.20, calcium phosphate undergoes a gradual transition from the monoclinic to the rhombohedral crystal system (SG P21/a→R3c) as the heat-treatment temperature increases from 800 to 1100 °C. Dendrites of iron oxide with crystallites of various sizes are observed to form within a glassy matrix enriched in calcium, phosphorous, and silicon. Saturation magnetization, remanence, and coercivity are found from dc magnetic measurements. They vary with the specific processing parameters of the composites, and these are correlated with the observed structure and microstructure of the materials.
Keywords: Calcium phosphate; Ferrimagnetic materials; XRD; Quantitative Rietveld refinement;
Filler features and their effects on wear and degree of conversion of particulate dental resin composites by C.P. Turssi; J.L. Ferracane; K. Vogel (4932-4937).
Based on the incomplete understanding on how filler features influence the wear resistance and monomer conversion of resin composites, this study sought to evaluate whether materials containing different shapes and combinations of size of filler particles would perform similarly in terms of three-body abrasion and degree of conversion. Twelve experimental monomodal, bimodal or trimodal composites containing either spherical or irregular shaped fillers ranging from 100 to 1500 nm were examined. Wear testings were conducted in the OHSU wear machine ( n = 6 ) and quantified after 105 cycles using a profilometer. Degree of conversion (DC) was measured by FTIR spectrometry at the surface of the composites ( n = 6 ). Data sets were analyzed using one-way Anova and Tukey's test at a significance level of 0.05. Filler size and geometry was found to have a significant effect on wear resistance and DC of composites. At specific sizes and combinations, the presence of small filler particles, either spherical or irregular, may aid in enhancing the wear resistance of composites, whithout compromising the percentage of reacted carbon double bonds.
Keywords: Composite; Microstructure; Abrasion; FTIR;
Growth of nano-scale hydroxyapatite using chemically treated titanium oxide nanotubes by Seung-Han Oh; Rita R. Finõnes; Chiara Daraio; Li-Han Chen; Sungho Jin (4938-4943).
A vertically aligned nanotube array of titanium oxide was fabricated on the surface of titanium substrate by anodization. The nanotubes were then treated with NaOH solution to make them bioactive, and to induce growth of hydroxyapatite (bone-like calcium phosphate) in a simulated body fluid. It is shown that the presence of TiO2 nanotubes induces the growth of a “nano-inspired nanostructure”, i.e., extremely fine-scale (∼8 nm feature) nanofibers of bioactive sodium titanate structure on the top edge of the ∼15 nm thick nanotube wall. During the subsequent in-vitro immersion in a simulated body fluid, the nano-scale sodium titanate, in turn, induced the nucleation and growth nano-dimensioned hydroxyapatite (HAp) phase. The kinetics of HAp formation is significantly accelerated by the presence of the nanostructures. Such TiO2 nanotube arrays and associated nanostructures can be useful as a well-adhered bioactive surface layer on Ti implant metals for orthopaedic and dental implants, as well as for photocatalysts and other sensor applications.
Keywords: Nanostructure; Hydroxyapatite; TiO2; Nanotubes; Implant; Bone;
Protein layer coating method on metal surface by electrochemical process through genetical introduced tag by Tetsuya Haruyama; Tsutomu Sakai; Kouhei Matsuno (4944-4947).
The technology of mercaptide self-assembly has previously been used to coat proteins onto metals, but is not practical for many surfaces. In this study, a short peptidic tag was employed for the electrochemical immobilization of proteins on metals (ECtag). A 6-mer histidine (α-amino-1H-imidazole-4-propionic acid) homopeptide was employed as an ECtag ligand, which forms coordinate bonds with Ni2+ and other divalent metal ions. Protein A was chosen as a model protein for the immobilization, and was genetically tagged with an ECtag for immobilization onto a Pt electrode surface through the reduction of ECtag:Ni2+ to ECtag:Ni by the electrode potential.
Keywords: Protein immobilization; Biofilm; Surface modification; Biosensor; Electrode;
Comparative in vitro study on a ultra-high roughness and dense titanium coating by Veronica Borsari; Gianluca Giavaresi; Milena Fini; Paola Torricelli; Matilde Tschon; Roberto Chiesa; Loris Chiusoli; Armando Salito; Andreas Volpert; Roberto Giardino (4948-4955).
A new implant surface has been developed with the purpose of avoiding as much stress shielding as possible, and thus prolong the prosthesis lifespan. The aim of this study was to investigate the in vitro effect of this new ultra-high roughness and dense Titanium (Ti) surface (PG60, R a = 74 μ m ) in comparison with medium (TI01, R a = 18 μ m ) and high (TI60, R a = 40 μ m ) roughness and open porous coatings; all the coatings were obtained by vacuum plasma spraying. MG63 osteoblast-like cells were seeded on the tested materials and polystyrene, as control, for 3 and 7 days. Cells proliferated on the material surfaces similarly to the control. Alkaline phosphatase activity had lower values for TI60 than TI01 (p<0.0005) and PG60 (p<0.005). Osteocalcin levels measured on TI60 were significantly (p<0.0005) lower in comparison with TI01 and PG60 at 7 days. Procollagen-I synthesis reduced with increasing roughness and the lowest data was found for PG60. While at 3 days Transforming Growth Factor β1 levels augmented with increasing roughness, at 7 days TI60, the high roughness surface, was significantly lower than PG60 (p<0.005) and TI01 (p<0.001). All tested materials showed significantly higher Interleukin-6 levels than those of polystyrene at both experimental times. Nitric Oxide activity on TI01 was significantly (p<0.05) higher than on TI60 and polystyrene.In conclusion, the new ultra-high roughness and dense coating PG60 provided a good biological response, even though, at least in vitro, it behaved similarly to the coatings already used in orthopaedics.
Keywords: Osteoblast; Titanium; Plasma spraying; Surface roughness; Cell proliferation; Cytokines;
Influence of carboxyl group density on neuron cell attachment and differentiation behavior: Gradient-guided neurite outgrowth by Bin Li; Yuexia Ma; Shu Wang; Peter M. Moran (4956-4963).
A UV pre-irradiation step followed by a UV grafting step was used to graft poly(acrylic acid) (PAA) on polymeric substrates. These substrates were then used to investigate the influence of carboxyl groups (–COOH) on cell behavior. Both the attachment and differentiation behaviors of C17.2 cells showed a –COOH group density-dependent response. In order to achieve an even distribution of cells on a –COOH gradient surface for neuron differentiation studies, an Ar plasma post-treatment was applied to the PAA-grafted surfaces. It greatly improved the cell adhesion properties with little damage to –COOH groups. This allows uniform distributions of seeded cells even on substrates with –COOH gradients. A linear or stepped –COOH gradient was found to be capable of serving as a repelling cue to guide the outgrowth of neurites from C17.2 cells. Up to 3.7 times more cells developed neurites growing down the –COOH gradient than growing up it.
Keywords: Carboxyl groups; Grafting; Gradient; C17.2 cells; Neurite outgrowth guidance;
Calcification as an indicator of osteoinductive capacity of biomaterials in osteoblastic cell cultures by Heidi A. Declercq; Ronald M.H. Verbeeck; Leo I.F.J.M. De Ridder; Etienne H. Schacht; Maria J. Cornelissen (4964-4974).
Mineralized extracellular matrix formation is representative for the osteoinductive capacity of biomaterials and is often tested in vitro. Characteristics of in vitro mineralization of primary rat osteoblastic cells (bone marrow, calvaria, periosteum, fetal and adult long bone) and UMR-106 cells were compared by von Kossa staining, FTIR, X-ray diffractometry, TEM and related to parameters of early (ALP and collagen I formation) and late (osteocalcin secretion) osteoblast expression. All cultures expressed high alkaline phosphatase activity and were able to form bone apatite. However, a nodular versus diffuse mineralization pattern was observed. Bone marrow, calvaria and periosteum (early passage) derived cells mineralized restrictively on the three-dimensional area of a nodule. The extracellular matrix consisted of collagen I fibers, among matrix vesicles loaded with needle-like crystals. Long bone, late passage periosteum derived and UMR-106 cells exhibited a diffuse mineralization pattern. Needle-like crystals were observed between the cells but collagen fibers and matrix vesicles could not be detected. Secretion of osteocalcin was detected in cultures derived from bone marrow and absent in UMR-106 and long bone derived cell cultures. The present study demonstrates that dystrophic calcification can not be distinguished from cell-mediated calcification with von Kossa, FTIR and X-ray diffractometry. Primary osteoblastic cells capable of forming nodules are recommended to evaluate the osteoinductive properties of biomaterials.
Keywords: Osteoblast differentiation; Extracellular matrix; Calcification; Bone apatite; Biomaterial;
The role of Galectin-1 in the interaction between chondrocytes and a lactose-modified chitosan by Patrizia Marcon; Eleonora Marsich; Amedeo Vetere; Pamela Mozetic; Cristiana Campa; Ivan Donati; Franco Vittur; Amelia Gamini; Sergio Paoletti (4975-4984).
Evidences for the involvement of the Galectin-1 in the interaction of pig chondrocytes with a lactose-modified chitosan, namely Chitlac, are reported. The Chitlac glycopolymer has been shown to promote pig chondrocyte aggregation and to induce extracellular matrix production. Highly pure Galectin-1 was obtained from pig spleen by affinity chromatography and its identity was determined by ion spray mass spectrometry analysis of tryptic peptide fragments obtained after in-gel digestion. The complete sequence of pig Galectin-1 CDS was obtained by screening a pig EST database using human Galectin-1 sequence as template. The Galectin-1 cDNA was cloned into a pGEX-4T-1 expression vector and the recombinant protein was purified, characterized and used to produce a rabbit anti-serum. Recombinant Galectin-1 interacts in a dose-dependent manner with Chitlac as determined with ELISA assay. Expression level of galectin-1 gene, quantified by real-time PCR, was significantly higher in chondrocytes cultivated on Chitlac. In the same way, the presence of Chitlac stimulates secretion of Galectin-1 in culture medium that, by immunohistochemical analysis, revealed to be clustered on the surface of Chitlac-induced aggregates. These data indicate the role of Galectin-1 as a bridging agent between Chitlac and chondrocyte aggregates.
Keywords: Galectin-1; Glycopolymer; Biomaterial; Chondrocyte; Cartilage;
The fibroblast response to tubes exhibiting internal nanotopography by Catherine Cecilia Berry; Matthew J Dalby; David McCloy; Stanley Affrossman (4985-4992).
The use of three-dimensional scaffolds in cell and tissue engineering is widespread; however, the use of such scaffolds, which bear additional cellular cues such as nanotopography, is as yet in its infancy. This paper details the novel fabrication of nylon tubes bearing nanotopography via polymer demixing, and reports that the topography greatly influenced fibroblast adhesion, spreading, morphology and cytoskeletal organisation. The use of such frameworks that convey both the correct mechanical support for tissue formation and stimulate cells through topographical cues may pave the way for future production of intelligent materials and scaffolds.
Keywords: Actin; Cell adhesion; Cell morphology; Cell spreading; Nanotopography; Vinculin;
The effect of patient gait on the material properties of UHMWPE in hip replacements by Shirley M. Davey; John F. Orr; Fraser J. Buchanan; James R. Nixon; Damien Bennett (4993-5001).
The wear of ultra-high molecular weight polyethylene (UHMWPE) acetabular components in total hip replacements (THRs) has been shown to be highly dependent on the direction of shear. Greatly reduced wear rates have been reported for unidirectional, compared to multidirectional, articulation in vitro. This work for the first time enables investigation of a relationship between clinical wear conditions, as determined by patient gait path, and the mechanical and structural changes that occur within the UHMWPE acetabular component. Individual patients’ wear paths were determined prior to revision operation from hip joint kinematics measured by clinical gait analysis. The material properties of the acetabular components removed during the revision operation were subsequently analysed. A technique using Fourier transform infra- red analysis (FTIR) was developed to quantify the orientation of the individual UHMWPE lamellae. This study shows that there is a direct relationship between a patient's clinical gait path and the molecular properties of their UHMWPE acetabular socket. Patient kinematics are an important factor affecting the wear and long-term biocompatibility of UHMWPE used as a bearing surface in THR.
Keywords: Wear mechanism; Polyethylene; Hip replacement prosthesis; FTIR; Crystallinity;
Premixed rapid-setting calcium phosphate composites for bone repair by Lisa E. Carey; Hockin H.K. Xu; Carl G. Simon; Shozo Takagi; Laurence C. Chow (5002-5014).
Although calcium phosphate cement (CPC) is promising for bone repair, its clinical use requires on site powder–liquid mixing. To shorten surgical time and improve graft properties, it is desirable to develop premixed CPC in which the paste remains stable during storage and hardens only after placement into the defect. The objective of this study was to develop premixed CPC with rapid setting when immersed in a physiological solution. Premixed CPCs were formulated using the following approach: Premixed CPC=CPC powder+nonaqueous liquid+gelling agent+hardening accelerator. Three premixed CPCs were developed: CPC–monocalcium phosphate monohydrate (MCPM), CPC–chitosan, and CPC–tartaric. Setting time for these new premixed CPCs ranged from 5.3 to 7.9 min, significantly faster than 61.7 min for a premixed control CPC reported previously ( p < 0.05 ). SEM revealed the formation of nano-sized needle-like hydroxyapatite crystals after 1 d immersion and crystal growth after 7 d. Diametral tensile strength for premixed CPCs at 7 d ranged from 2.8 to 6.4 MPa, comparable to reported strengths for cancellous bone and sintered porous hydroxyapatite implants. Osteoblast cells attained a normal polygonal morphology on CPC–MCPM and CPC–chitosan with cytoplasmic extensions adhering to the nano-hydroxyapatite crystals. In summary, fast-setting premixed CPCs were developed to avoid the powder–liquid mixing in surgery. The pastes hardened rapidly once immersed in physiological solution and formed hydroxyapatite. The cements had strengths matching those of cancellous bone and sintered porous hydroxyapatite and non-cytotoxicity similar to conventional non-premixed CPC.
Keywords: Premixed calcium phosphate cement; Rapid setting; Hydroxyapatite; Strength; Cell culture cytotoxicity; Bone repair;
Shrinkage strain-rates of dental resin-monomer and composite systems by Mohammad Atai; David C. Watts; Zahra Atai (5015-5020).
The purpose of this study was to investigate the shrinkage strain rate of different monomers, which are commonly used in dental composites and the effect of monomer functionality and molecular mass on the rate.Bis-GMA, TEGDMA, UDMA, MMA, HEMA, HPMA and different ratios of Bis-GMA/TEGDMA were mixed with Camphorquinone and Dimethyl aminoethyle methacrylate as initiator system. The shrinkage strain of the samples photopolymerised at Ca. 550 mW/cm2 and 23 °C was measured using the bonded-disk technique of Watts and Cash (Meas. Sci. Technol. 2 (1991) 788–794), and initial shrinkage-strain rates were obtained by numerical differentiation.Shrinkage-strain rates rose rapidly to a maximum, and then fell rapidly upon vitrification. Strain and initial strain rate were dependent upon monomer functionality, molecular mass and viscosity. Strain rates were correlated with Bis-GMA in Bis-GMA/TEGDMA mixtures up to 75–80w/w%, due to the higher molecular mass of Bis-GMA affecting termination reactions, and then decreased due to its higher viscosity affecting propagation reactions. Monofunctional monomers exhibited lower rates. UDMA, a difunctional monomer of medium viscosity, showed the highest shrinkage strain rate ( P < 0.05 ).Shrinkage strain rate, related to polymerization rate, is an important factor affecting the biomechanics and marginal integrity of composites cured in dental cavities. This study shows how this is related to monomer molecular structure and viscosity. The results are significant for the production, optimization and clinical application of dental composite restoratives.
Keywords: Dental composites; Monomer system; Shrinkage strain; Shrinkage strain rate; Conversion; Viscosity;
Effect of structural change of collagen fibrils on the durability of dentin bonding by Bin Yang; Rainer Adelung; Klaus Ludwig; Klaus Bößmann; David H. Pashley; Matthias Kern (5021-5031).
This study investigates the effect of structural changes of collagen fibrils on the bonding durability of a total etch luting resin (Super-Bond C&B) and a self-etching luting resin (Panavia F 2.0) to dentin. An atomic force microscope (AFM) was used to observe structural changes of intact dentin collagen fibrils after acidic conditionings of two bonding systems. After 90 d water storage and 15,000 thermal cycles (TC) as artificial aging, micro-tensile bond strength (μTBS) was utilized to evaluate the bonding durability of the two bonding systems to dentin. μTBS after 1 d or 90 d water storage without TC were separately measured in control groups.A cross-banding periodicity of about 67 nm along collagen fibrils was seen on demineralized intertubular dentin surfaces in AFM images. For both luting resins, thermal cycling decreased ( p < 0.05 ) μTBS of 1 d and 90 d, compared to controls. Scanning electron microscope and transmission electron microscopic examinations revealed that the top and bottom of hybrid layer (HL) were weak links in the bonding interface over time. The results suggest that the top of HL contains disorganized collagen fibrils from the smear layer which degrade over time. AFM results indicate that the demineralized intact collagen fibrils beneath the smear layer were not denatured during acidic conditioning. However, these collagen fibrils may be structurally unstable due to poor infiltration by resin or loss of resin protection within the HL over time, reducing the long-term μTBS. This process was accelerated by thermal fatigue cycling.
Keywords: Collagen fibrils; Dentin bonding; Durability; AFM; SEM; TEM;
Design of functional hollow fiber membranes modified with phospholipid polymers for application in total hemopurification system by Sang Ho Ye; Junji Watanabe; Madoka Takai; Yasuhiko Iwasaki; Kazuhiko Ishihara (5032-5041).
In this study, we prepared cellulose acetate (CA) hollow fiber membranes (HFMs) modified with poly (2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate)(PMB30 and PMB80) by the dry-jet wet spinning process. The physical and chemical structures of the HFMs were controlled in order to design highly functional HFMs that had suitable performance to each targeting HFM device used in a total hemopurification system. The CA HFMs modified with the MPC polymer, such as CA/PMB30, CA/PMB80, and CA/PMB30-80 HFMs, were successfully prepared by controlling the spinning conditions. The modified HFMs showed an improved performance in solute and water permeability, due to the modification by the hydrophilic MPC polymers. The CA/PMB30 and CA/PMB80 showed a high potential in an application for a high performance hemocompatible plasmapheresis and hemofilter device. Furthermore, CA/PMB30-80 HFM, modified asymmetrically with PMB30 and PMB80, showed a potential for application in an advanced total hemopurification system as a highly functional scaffold for a biohybrid renal tubule, or a liver assist bioreactor device, because of their enhanced permeability, hemocompatibility, and cytocompatibility.
Keywords: Hollow fiber membranes (HFMs); Surface modification; MPC polymers; Hemocompatibility; Cytocompatibility; Total hemopurification system;
Quality control assessment of ePTFE precoating procedure for in vitro endothelial cell seeding by Philippe Fernandez; Audrey Deguette; Laurent Pothuaud; Geneviève Belleannée; Pierre Coste; Laurence Bordenave (5042-5047).
Over the past two decades, in vitro autologous endothelial cell (EC) coverage of expanded polytetrafluoroethylene (ePTFE) graft has been developed and clinically applied with success in infrainguinal bypasses. Before endothelialization, the luminal surface of the graft has to be coated with a currently used fibrinolytically inhibited fibrin glue. The aim of this work is to validate the precoating of the ePTFE (4 mm ID) ringed graft with fibrin. Twenty cm-long grafts were precoated with fibrin glue (2 operators) then fixed for microscopy investigations. Grafts were sliced into 3 regions. Thickness analysis was evaluated by image processing. Three grafts have been tested for endothelialization and observed at days 3, 8. Cell-free coated ePTFE were imaged using high-frequency ultrasound modality. Whatever the examined segment an overall homogeneous covering protein is shown. Fibrin thickness after image processing is 8.5±0.25 and 4.1±0.4 μm for two operators (P<.001). We have evaluated reproducibility and inter- and intra-variability of the operator, assessed quality controls and quality assurance all along the prosthesis and finally endothelialization and subsequent behaviour under shear stress conditions.
Keywords: Vascular grafts; Polytetrafluoroethylene; Fibrin; Endothelialisation; Autologous cells; Shear;
Directed cell migration via chemoattractants released from degradable microspheres by Xiaojun Zhao; Siddhartha Jain; H. Benjamin Larman; Sandra Gonzalez; Darrell John Irvine (5048-5063).
Chemotaxis, cell migration directed by spatial concentration gradients of chemoattractant molecules, is critical for proper function of the immune system. Materials capable of generating defined chemoattractant gradients via controlled release may be useful for the design of improved vaccines and immunotherapies that draw specific cells to an immunization site. To this end, we encapsulated formyl-Nle-Leu-Phe-Nle-Tyr-Lys (fN’LFN’YK) peptides or macrophage inflammatory protein-3α (MIP-3α or CCL20) in degradable poly(lactide-co-glycolide) microspheres that provided sustained release for more than 2 weeks in vitro. fN’LFN’YK and MIP-3α chemoattract dendritic cells (DCs), the key antigen-presenting cells involved in generation of primary immune responses, and their precursors, monocytes. Using an in vitro videomicroscopy migration assay, we detected strong chemotaxis of human monocytes and monocyte-derived DCs through 3D collagen gels toward microspheres releasing fN’LFN’YK. Similarly, microparticles releasing MIP-3α were able to attract mouse bone marrow-derived dendritic cells. Strikingly, prolonged attraction of DCs from distances up to 500 μm from the source to the point of contact with individual microspheres was observed. Such microspheres could be of general interest for the design of vaccines that promote adaptive immunity and as a platform for studying the biology of chemotaxis in vitro and in vivo.
Keywords: Chemotaxis; Controlled; Drug release; Microspheres; Immune response;
Incorporation and in vitro release of doxorubicin in thermally sensitive micelles made from poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide)-b-poly(d,l-lactide-co-glycolide) with varying compositions by S.Q. Liu; Y.W. Tong; Yi-Yan Yang (5064-5074).
Thermally sensitive block copolymers, poly(N-isopropylacrylamide-co-N, N-dimethylacrylamide)-b-poly(d,l-lactide-co-glycolide) [P(NIPAAm-co-DMAAm)-b-poly(d,l-lactide-co-glycolide) (PLGA)] with different compositions and lengths of PLGA block are synthesized and utilized to fabricate micelles containing doxorubicin (DOX), a model anticancer drug, by a membrane dialysis method for targeted anticancer drug delivery. The critical association concentration (CAC) of the polymers ranges from 4.0 to 25.0 mg/L. An increased length of core-forming block PLGA leads to a decrease in the CAC. The clearly defined core–shell structure of micelles is proved by 1H-NMR analyses of the micelles in CDCl3 and D2O. The morphology of the micelles is analyzed by transmission electron microscopy, showing a spherical structure of both blank and drug-loaded micelles. The results obtained from dynamic light scattering show that the blank and drug-loaded micelles have an average size below 200 nm. The lower critical solution temperature (LCST) of the micelles made from the various polymers is similar, around 39 °C in phophate-buffered solution (PBS). The presence of serum in PBS does not alter the LCST significantly. The drug loading capacity varies depending on the PLGA block. The polymers are degradable, and the degradation of PLGA-based polymers is faster than that of poly(lactide) (PLA)-based polymer. The DOX-loaded micelles are stable in PBS containing serum at 37 °C but deform at 39.5 °C above the normal body temperature, thus triggering DOX release. It is revealed by confocal laser scanning microscopy that free DOX molecules enter cell nuclei very fast and DOX-loaded micelles accumulate mostly in cytoplasm after endocytosis. At a temperature above the LCST, more DOX molecules release from the micelles and enter the nuclei as compared to the temperature below the LCST. DOX-loaded micelles show greater cytotoxicity at a temperature above the LCST. The P(NIPAAm-co-DMAAm)-b-PLGA micelles developed may be a good carrier for anticancer drug delivery.
Keywords: Thermally sensitive micelles; P(NIPAAm-co-DMAAm); PLGA; Doxorubicin; Drug release;
Interactions of blood proteins with poly(isobutylcyanoacrylate) nanoparticles decorated with a polysaccharidic brush by Denis Labarre; Christine Vauthier; Cédric Chauvierre; Boris Petri; Rainer Müller; Mohamed M. Chehimi (5075-5084).
The aim of this work was to examine the in vitro interactions of core-shell poly(isobutylcyanoacrylate)-polysaccharide nanoparticles (NP) with blood proteins. The particles were prepared by initiating the emulsion polymerization of isobutylcyanoacrylate (IBCA) in the presence of dextran 71 or 15 kDa, heparin, a blend of dextran 71 and heparin, or dextran sulphate in aqueous medium at pH 1. The mechanisms of polymerisation were redox radical (Rad) or anionic (An), resulting in differences in the spatial arrangement of the polysaccharide chains at the NP surface, i.e. “loops” and “trains” by anionic polymerization, “brush” by radical polymerization. Surface composition of NPs was determined by X-ray photo-electron spectroscopy (XPS) and surface charge by zeta potential measurements. In the presence of citrated blood plasma, efficacy of the steric repulsive effect of the NP dextran shell towards protein adsorption decreased in the order: Dex71-Rad>Dex15-Rad>Dex71-An⪢Dex15-An. Dextran-coated NPs adsorbed ApoA-I and fibrinogen from plasma. Concerning activation of complement in serum, the effect was sharp: Dex71-Rad was a very low activator whereas Dex15-An, Dex15-Rad and Dex71-An were strong activators. In citrated plasma, the steric repulsive effects of Hep-Rad and Dex-Hep-Rad NPs were similar to Dex71-An, and Dex-Sulph-Rad NPs adsorbed twice more proteins than Hep-Rad. Hep-Rad, Dex-Hep-Rad and Dex-Sulph-Rad NPs adsorbed IgG and fibrinogen. Complement was not activated in serum in the presence of Hep-Rad and Dex-Hep-Rad and a slight adsorption of C3 was noted. C3 was completely adsorbed on Dex-Sulph-Rad. The exquisite sensitivity of blood proteins to differences in the nature and outermost structure of the polysaccharides-coated NPs is highlighted by the present results.
Keywords: Core-shell nanoparticles; Poly(isobutylcyanoacrylate); Dextran; Heparin; Dextran sulphate; Surface properties; XPS; Blood plasma proteins adsorption; Complement activation;
Bovine BMP osteoinductive potential enhanced by functionalized dextran-derived hydrogels by Marion Maire; Frederic Chaubet; Pierrer Mary; Cinderella Blanchat; Alain Meunier; Delphine Logeart-Avramoglou (5085-5092).
This study evaluated functionalized dextran-derived hydrogels as BMP carriers using both in vitro and in vivo models. In vitro release kinetics indicated that dextran-derived hydrogels could retain rhBMP-2 growth factor in a variable manner depending on their functionalization ratio. The potential of these hydrogels when combined with extracted bovine BMP to enhance the bone formation was evaluated in a rat ectopic model. The largest osteoinduction was found when using hydrogels exhibiting the highest growth factor retention capacity. In addition, some implanted hydrogels demonstrated a capacity to induce an in-vivo calcification certainly related to their chemical composition. These properties make these materials interesting osteoconductive BMP carriers, allowing to decrease the amount of implanted factor required for bone regeneration.
Keywords: Hydrogel; Functionalized dextran; Bmp delivery system; Osteoinduction; Ectopic site;
by D.F. Williams (5093).