Biomaterials (v.26, #22)
Degradable thiol-acrylate photopolymers: polymerization and degradation behavior of an in situ forming biomaterial by Amber E. Rydholm; Christopher N. Bowman; Kristi S. Anseth (4495-4506).
Degradable thiol-acrylate photopolymers are a new class of biomaterials capable of rapidly polymerizing under physiological conditions upon exposure to UV light, with or without added photoinitiators, and to depths exceeding 10 cm. These materials are formed in situ, and the versatility of their chemistry affords a high degree of control over the final material properties. For example, variations in monomer mole fractions directly affect the final network molecular structure, varying the time required to achieve complete mass loss from 25 to 100 days, the molecular weight distributions of the degradation products, and the swelling ratios and compressive moduli throughout degradation. Additionally, varying the mole fraction of multifunctional thiol monomer in the initial reaction mixture controls the concentration of reactive sites in the network available for post-polymerization modification of the polymer.
Keywords: Thiol-acrylate polymerization; In situ cross-linking; Photopolymerization; Hydrolytic degradation; Poly(ethylene glycol);
Effect of synthetic peptides on osteoblast adhesion by Monica Dettin; Maria Teresa Conconi; Roberta Gambaretto; Andrea Bagno; Carlo Di Bello; Anna Michela Menti; Claudio Grandi; Pier Paolo Parnigotto (4507-4515).
The quality of the early cell/material interactions is responsible for the long-term functional properties of any implanted device. Accordingly, “next generation” dental/orthopedic biomaterials should be able to promote osteoblast adhesion thus improving the integration process between surgically placed implants and biological tissues. Recent studies have identified a wide range of biochemical signals that can be exploited to promote adhesion, migration, proliferation and differentiation of cells. The clinical use of natural factors to promote osteoblast adhesion is complicated because those are often insoluble and unstable macromolecules and, in addition, it is difficult to obtain them in high quantities, with good purity grade and at low cost. A valid alternative could be the use of short peptides carrying the minimum active sequence of the natural macromolecular factor. This paper describes the properties of two classes of peptides, promoting different adhesion mechanisms, to enhance rat bone marrow osteoblast adhesion both to polystyrene and to acellular bone matrix.
Keywords: Peptide; Cell adhesion; Adhesion molecule; Adsorption; Bioactivity;
Influence of nanoporous alumina membranes on long-term osteoblast response by Ketul C. Popat; Erin E. Leary Swan; Vivek Mukhatyar; Kwan-Isara Chatvanichkul; Gopal K. Mor; Craig A. Grimes; Tejal A. Desai (4516-4522).
A major goal of bone tissue engineering is to design better scaffold configuration and materials to better control osteoblast behavior. Nanoporous architecture has been shown to significantly affect cellular response. In this work, nanoporous alumina membranes were fabricated by a two-step anodization method to investigate bone cell response. Osteoblasts were seeded on nanoporous alumina membranes to investigate both short-term adhesion and proliferation and long-term functionality and matrix production. Cell adhesion and proliferation were characterized using a standard MTT assay and cell counting. The total protein content was measured after cell lysis using the BCA assay. Matrix production was characterized in terms of surface concentrations of calcium and phosphorous, components of bone matrix, using X-ray photoelectron spectroscopy (XPS). The results from nanoporous alumina membranes were compared with those of amorphous alumina, aluminum, commercially available ANOPORETM and glass. Results indicate improved osteoblast adhesion and proliferation and increased matrix production after 4 weeks of study.
Keywords: Bone tissue engineering; Nanoporous alumina; Matrix production; Osteoblast adhesion;
Myoblast proliferation and differentiation on fibronectin-coated self assembled monolayers presenting different surface chemistries by Michael A. Lan; Charles A. Gersbach; Kristin E. Michael; Benjamin G. Keselowsky; Andrés J. García (4523-4531).
Biomaterial surface properties modulate protein adsorption and cell adhesion to elicit diverse cellular responses in biomedical and biotechnological applications. We used alkanethiol self-assembled monolayers presenting well-defined chemistries (OH, CH3, NH2, and COOH) to analyze the effects of surface chemistry on myoblast proliferation and differentiation. Surfaces were pre-coated with equivalent densities of fibronectin. C2C12 skeletal myoblasts exhibited surface-dependent differences in cell proliferation (COOH=NH2>CH3=OH). Myogenin and troponin T gene expression levels were up-regulated on CH3 and OH surfaces compared to other chemistries. Furthermore, immunostaining for sarcomeric myosin revealed surface chemistry-dependent differences in myogenic differentiation following the pattern OH>CH3>NH2=COOH. Immunostaining analyses of integrin subunits demonstrated surface chemistry-dependent differences in integrin binding to adsorbed fibronectin. OH and CH3 surfaces supported selective binding of α 5 β 1 integrin while the COOH and NH2 functionalities displayed binding of both α 5 β 1 and α V β 3 ⋅ Myogenic differentiation correlated with differences in integrin binding; surface chemistries that supported selective binding of α 5 β 1 displayed enhanced differentiation. Finally, blocking β 1 , but not β 3 , integrins inhibited differentiation, implicating specific integrins in the differentiation process. These results demonstrate that surface chemistry modulates myoblast proliferation and differentiation via differences in integrin binding to adsorbed fibronectin.
Keywords: Cell adhesion; Integrin; Self-assembled monolayers; Fibronectin; Differentiation; Myoblast;
Cytotoxicity of three-dimensionally ordered macroporous sol–gel bioactive glass (3DOM-BG) by Kai Zhang; Newell R. Washburn; Carl G. Simon (4532-4539).
In this study, 80% SiO2–20% CaO (mole fraction) three-dimensionally ordered macroporous sol–gel bioactive glass (3DOM-BG, average pore size: 345 nm) particles were prepared and characterized. Since the 3DOM-BGs have a novel microstructure and ion-releasing profile, the cytotoxicity of 3DOM-BG particles was tested. The cytotoxicity tests were performed using MC3T3-E1 osteoblast-like cells: (1) Wst-1 assay for cell viability after culture in extracts from 3DOM-BG particles; (2) phase contrast microscopy for cell morphology after culture with 3DOM-BG particles; and (3) fluorescence microscopy for imaging cells cultured directly on 3DOM-BG particles. The results showed that 3DOM-BG particles were not cytotoxic, and that cells attached, spread and proliferated on and around 3DOM-BG particles.
Keywords: Porosity; Sol–gel; Bioactive glass; Apatite; Cell culture;
Long-term maintenance of human articular cartilage in culture for biomaterial testing by Raimund Strehl; Tommi Tallheden; Eva Sjögren-Jansson; Will W. Minuth; Anders Lindahl (4540-4549).
Cartilage is a tissue that derives its unique mechanical and biological properties from the combination of relatively few cells and a large amount of a complex extracellular matrix. Furthermore, cartilage tissue is comparatively slow to respond to changes or harmful influences. To date, the optimal generation and long-term maintenance of cultured human articular cartilage for in vitro testing of biomaterials, poses an experimental difficulty. Experiments using cultured isolated chondrocytes in combination with scaffolds often fail to yield results comparable to the in-vivo situation. Consequently, our aim was to develop a culture method that allows in vitro maintenance of human hyaline cartilage explants in an optimal quality over an extended period of time. Such a culture could, for example, be used to determine the long-term effect of a new scaffold on intact cartilage, as an in vitro model for repair processes and to investigate biomaterial integration.In this study we compared conventional static cultures with and without serum supplementation to a serum-free perfusion culture for the ability to maintain human articular cartilage explants in a morphologically intact and differentiated state over an extended period of time of up to 56 days. Results were evaluated and compared by morphological, histochemical and immunohistochemical methods.The experiments showed that short-term maintenance of cartilage in a differentiated state for up to 14 days is possible under all culture conditions tested. However, best long-term culture results for up to 56 days were obtained with perfusion culture under serum-free conditions. Such a perfusion culture system can be used to perform biocompatabilty tests in vitro by long-term coculture of biomaterial and intact human articular cartilage.
Keywords: Biocompatability; Bioreactor; In vitro test; Cell culture; Human articular cartilage; Tissue Culture; Perfusion; Differentiation;
Neovascularization and bone regeneration by implantation of autologous bone marrow mononuclear cells by Takashi Hisatome; Yuji Yasunaga; Shinobu Yanada; Yasuhiko Tabata; Yoshito Ikada; Mitsuo Ochi (4550-4556).
We examined whether transplantation of autologous bone marrow mononuclear cells (BM-MNCs) can augment neovascularization and bone regeneration of bone marrow in femoral bone defects of rabbits. Gelatin microspheres containing basic fibroblast growth factor (bFGF) were prepared for the controlled release of bFGF. To evaluate the in vivo effect of implanted BM-MNCs, we created bone defects in the rabbit medial femoral condyle, and implanted into them 5×106 fluorescent-labeled autologous BM-MNCs together with gelatin microspheres containing 10 μg bFGF on an atelocollagen gel scaffold. The four experimental groups, which were Atelocollagen gel (Col), Col+5×106 BM-MNCs, Col+10 μg bFGF, and Col+5×106 BM-MNCs+10 μg bFGF, were implanted into the sites of the prepared defects using Atelocollagen gel as a scaffold. The autologous BM-MNCs expressed CD31, an endothelial lineage cell marker, and induced efficient neovascularization at the implanted site 2 weeks after implantation. Capillary density in Col+BM-MNCs+bFGF was significantly large compared with other groups. This combination also enhanced regeneration of the bone defect after 8 weeks to a significantly greater extent than either BM-MNCs or bFGF on their own. In summary, these findings demonstrate that a combination of BM-MNCs and bFGF gelatin hydrogel enhance the neovascularization and the osteoinductive ability, resulting in bone regeneration.
Keywords: Neovascularization; bFGF; Bone regeneration; Bone marrow mononuclear cells; Gelatin microsphere bFGF;
The use of temperature–composition combinatorial libraries to study the effects of biodegradable polymer blend surfaces on vascular cells by Hak-Joon Sung; Jing Su; Joseph D. Berglund; Bianca V. Russ; J. Carson Meredith; Zorina S. Galis (4557-4567).
Controlling cellular and physiological responses such as adhesion, proliferation and migration is a highly desirable feature of engineered scaffolds. One important application would be the design of tissue engineered vascular grafts that regulate cell adhesion and growth. We utilized temperature–composition combinatorial polymer libraries to investigate the effects of surfaces of blended poly(d,l-lactic-co-glycolic acid) (PLGA) and poly(ε-caprolactone) (PCL) on murine vascular smooth muscle cells (SMC). In this manner, SMCs were exposed to ∼1000 distinguishable surfaces in a single experiment, allowing the discovery of optimal polymer compositions and processing conditions. SMC adhesion, aggregation, proliferation, and protein production were highest in regions with mid- to high-PCL concentrations and high annealing temperatures. These regions exhibited increased surface roughness, increased microscale PLGA-rich matrix stiffness, and significant change of bulk PCL-rich crystallinity relative to other library regions. This study revealed a previously unknown processing temperature and blending composition for two well-known polymers that optimized SMC interactions.
Keywords: Surface modification; Surface analysis; Cell adhesion; Cell proliferation; Cell activation; Protein adsorption;
Endothelial cell—interactions with polyelectrolyte multilayer films by Cédric Boura; Sylvaine Muller; Dominique Vautier; Dominique Dumas; Pierre Schaaf; Jean Claude Voegel; Jean François Stoltz; Patrick Menu (4568-4575).
The seeding of endothelial cells (ECs) on biomaterial surfaces became a major challenge, allowing to improve the non-thrombogenic properties of these surfaces. Recently, the use of polyelectrolyte films has been suggested as a new versatile technique of surface modification aimed at tissue engineering. In this study, we evaluate the adhesion properties of ECs on two types of polyelectrolyte films ending either by poly(d-lysine) (PDL), or poly(allylamine hydrochloride) (PAH), and compared them to data obtained on PDL or PAH monolayers, glass and fibronectin (Fn)-coated glass. ECs seeded on polyelectrolyte films showed a good morphology, allowing ECs to resist physiological shear stress better compared to ECs seeded on glass or Fn. The expression of β 1 integrins was slightly lower on polyelectrolyte films than on control surfaces. However, the phosphorylation of focal adhesion kinase, involved in the transduction of adhesion signal, was not modified on PAH ending films compared to control surfaces; whereas it became lower on PDL ending films. Finally, PAH ending films improve strongly ECs adhesion without disturbing the adhesion mechanism, necessary for the development of a new endothelium. These types of films or similar build-ups could thus be used in the future as a way to modify surfaces for vascular tissue engineering.
Keywords: Polyelectrolyte multilayers; Endothelial cells; Cell adhesion; β1 integrins; Focal adhesion kinase;
Cell adhesive PET membranes by surface grafting of RGD peptidomimetics by Stéphane Biltresse; Mireille Attolini; Jacqueline Marchand-Brynaert (4576-4587).
A non-peptide mimic of the Arg-Gly Asp (RGD) active sequence of adhesive proteins (such as vitronectin) has been equipped with two different spacer-arms for surface anchorage. The covalent grafting on poly(ethylene terephthalate) (PET) membrane was realized via the activation of the hydroxyl polymer chain-ends by tosylation followed by nucleophilic substitution. The surface density of peptidomimetics was determined by X-ray photoelectron spectroscopy (XPS), on the basis of F/C atomic ratios since a fluorine tag was incorporated into the RGD-like compounds. The biological activity of soluble peptidomimetics was evaluated versus isolated human integrin α v β 3 (vitronectin receptor), and versus CaCo2 cells. Inhibition of cellular adhesion was observed after pre-incubation of CaCo2 cells with soluble peptidomimetics. On the other hand a significant promotion of cellular adhesion resulted from the surface grafting of peptidomimetics on the PET culture substrate. The best performance was obtained with the RGD-like integrin ligand bearing a triethylene glycol spacer-arm.
Keywords: RGD peptidomimetics; Poly(ethylene terephthalate) membrane (PET); In vitro cell culture; CaCo2 cells; Vitronectin; Polymer surface modification; XPS analysis; Biocompatibility;
Cultivation of endothelial cells on adhesive protein-free synthetic polymer gels by Yong Mei Chen; Nozomi Shiraishi; Hideo Satokawa; Akira Kakugo; Tetsuharu Narita; Jian Ping Gong; Yoshihito Osada; Kimiko Yamamoto; Joji Ando (4588-4596).
Various hydrogels without modification by any cell adhesive proteins have been investigated as cell scaffolds. The present study shows that bovine fetal aorta endothelial cells can adhere, spread, proliferate, and reach confluence on poly(acrylic acid), poly(sodium p-styrene sulfonate), and poly(2-acrylamido-2- methyl-1-propanesulfonic sodium) gels, whereas cells reach subconfluence on poly(vinyl alcohol) and poly(methacrylic acid) gels. The proliferation behavior was sensitive to both hydrogel charge density and crosslinker concentration. The relationship between cell proliferation and zeta potential of gels was discussed. It was found that hydrogels with a negative zeta potential higher than about 20 mV facilitates cell proliferation.
Keywords: Hydrogel; Biocompatibility; Cell proliferation; Cell culture; Tissue engineering; Polymer;
3D femtosecond laser patterning of collagen for directed cell attachment by Yaoming Liu; Shan Sun; Sima Singha; Michael R. Cho; Robert J. Gordon (4597-4605).
Three-dimensional micropatterned collagen scaffolds were fabricated by femtosecond laser ablation. An 800 nm, 45 fs Ti:Sapphire laser was used to create various 3D patterns in a collagen gel, including holes, lines and grids. An optimal collagen concentration was found for both substrate patterning and cell compatibility. The threshold fluence for ablation of the scaffold was found to be 0.06 J/cm2, and the morphology of the ablation craters was measured as a function of fluence. Mesenchymal stem cells from rat bone marrow and human fibroblasts were seeded within the ablated patterns and were shown to be viable for at least 10 days.
Keywords: Cell adhesion; Collagen; Laser ablation; Micropatterning; Tissue engineering;
Electrospun degradable polyesterurethane membranes: potential scaffolds for skeletal muscle tissue engineering by Stefania A. Riboldi; Maurilio Sampaolesi; Peter Neuenschwander; Giulio Cossu; Sara Mantero (4606-4615).
Skeletal muscle tissue engineering represents an attractive approach to overcome problems associated with autologous transfer of muscle tissue and provides a valid alternative in muscle regeneration enhancement. The aim of this study was to investigate the suitability, as scaffold for skeletal muscle tissue engineering, of a known biodegradable block copolymer (DegraPol®) processed by electrospinning in the novel form of microfibrous membranes. Scaffolds were characterized with reference to their morphological, degradative and mechanical properties. Subsequently, cell viability, adhesion and differentiation on coated and uncoated DegraPol® slides were investigated using line cells (C2C12 and L6) and primary human satellite cells (HSCs). The membranes exhibited absence of toxic residuals and satisfactory mechanical properties (linear elastic behavior up to 10% deformation, E modulus in the order of magnitude of MPa). A promising cellular response was also found in preliminary experiments: both line cells and HSCs adhered, proliferated and fused on differently coated electrospun membranes. Positive staining for myosin heavy chain expression indicated that differentiation of C2C12 multinucleated cells occurred within the porous elastomeric substrate. Together the results of this study provide significant evidence of the suitability of electrospun DegraPol® membranes as scaffolds for skeletal muscle tissue engineering and that they represent a promising alternative to scaffolds currently used in this field.
Keywords: Block polyesterurethane; Electrospinning; Skeletal muscle tissue engineering; Satellite cell; Myoblast; Myotube;
In vivo degradation of porous poly(propylene fumarate)/poly(DL-lactic-co-glycolic acid) composite scaffolds by Elizabeth L. Hedberg; Henriette C. Kroese-Deutman; Charles K. Shih; Roger S. Crowther; Darrell H. Carney; Antonios G. Mikos; John A. Jansen (4616-4623).
This study investigated the in vivo degradation of poly(propylene fumarate) (PPF)/poly(DL-lactic-co-glycolic acid) (PLGA) composite scaffolds designed for controlled release of osteogenic factors. PPF/PLGA composites were implanted into 15.0 mm segmental defects in the rabbit radius, harvested after 12 and 18 weeks, and analyzed using histological techniques to assess the extent of polymer degradation as well as the tissue response within the pores of the scaffolds. Polymer degradation was limited to micro-fragmentation of the scaffold at the ends and edges of the implant at both 12 and 18 weeks. The tissue within the pores of the scaffold consisted of fibrous tissue, blood vessels and some inflammatory cells. In areas where polymer breakdown was evident, an increased inflammatory response was observed. In contrast, areas of bone ingrowth into the polymer scaffold were characterized by minimal inflammatory response and polymer degradation. Our results show that minimal degradation of porous PPF occurs within 18 weeks of implantation in a rabbit model. Further, the in vivo degradation data of porous PPF/PLGA scaffolds are comparable with earlier obtained in vitro data.
Keywords: In vivo test; Scaffold; Composite; Degradation; Bone tissue engineering;
Chitin-based tubes for tissue engineering in the nervous system by Thomas Freier; Rivelino Montenegro; Hui Shan Koh; Molly S. Shoichet (4624-4632).
The purpose of this study was to investigate chitin and chitosan as potential materials for biodegradable nerve guides. Transparent chitin hydrogel tubes were synthesized, for the first time, from chitosan solutions using acylation chemistry and mold casting techniques. Alkaline hydrolysis of chitin tubes resulted in chitosan tubes, with the extent of hydrolysis controlling the resulting amine content. This, in turn, impacted compressive strength and cell adhesion. Chitosan tubes were mechanically stronger than their chitin origins, as measured by the transverse compressive test, where tubes having degrees of acetylation of 1%, 3%, 18% (i.e. chitosan) and 94% (i.e. chitin) supported loads at a 30% displacement of 40.6±4.3, 25.3±4.5, 10.6±0.8, and 8.7±0.4 g, respectively. However, the chitin processing methodology could be optimized for compressive strength, by either incorporating reinforcing coils in the tube wall, or air-drying the hydrogel tubes. Chitin and chitosan supported adhesion and differentiation of primary chick dorsal root ganglion neurons in vitro. Chitosan films showed significantly enhanced neurite outgrowth relative to chitin films, reflecting the dependence of nerve cell affinity on the amine content in the polysaccharide: neurites extended 1794.7±392.0 μm/mm2 on chitosan films vs. 140.5±41.6 μm/mm2 on chitin films after 2 days of culture. This implies that cell adhesion and neurite extension can be adjusted by amine content, which is important for tissue engineering in the nervous system. The methods for easy processing and modification of chitin and chitosan described herein, allow the mechanical properties and cyto-compatibility to be controlled and provide a means for a broader investigation into their use in biomedical applications.
Keywords: Chitosan; Nerve guidance channels; Nerve regeneration; Hollow fiber membranes;
Effects of growth regulation on conditionally-transformed alginate-entrapped insulin secreting cell lines in vitro by Nicholas E. Simpson; Nata Khokhlova; Jose A. Oca-Cossio; Scott S. McFarlane; Chiab P. Simpson; Ioannis Constantinidis (4633-4641).
The ability to control cell growth is an issue of critical importance for the use of transformed β -cell lines within a bioartificial pancreas. Such control can be achieved either by entrapping the cells in a biomaterial that can inhibit cell proliferation or by genetically modifying the cells to regulate growth. Integrating tetracycline-off or -on operon systems into murine insulinoma cell lines ( β TC -tet and R7T1, respectively) allows cell growth regulation upon exposure to tetracycline (TC) or its derivative doxycycline (Dox), respectively. However, the effects of this regulatory approach on the long-term phenotypic metabolic and secretory stability of alginate-entrapped cells have yet to be thoroughly investigated. In this study, cultures of β TC -tet and R7T1 cells entrapped in alginate beads were allowed to grow freely, or were growth-regulated, either at the onset, or after 20 days of growth. The data show that growth regulation of alginate-entrapped cells is achievable with chronic administration of the regulatory compound in a concentration-dependent manner. However, as these cultures age, the amount of insulin released does not always reflect the metabolic and histological characteristics of the cultures. This change, coupled with a loss of glucose stimulated insulin secretion in the Dox treated R7T1 cell line, indicate a phenotypic shift of cells with an activated tet-operon. These observations have implications on the selection and long-term function of three-dimensional bioartificial pancreatic constructs that include conditionally transformed β -cell lines.
Keywords: Alginate; Insulinoma cells; Bioartificial pancreas; Tetracycline; Doxycycline;
A system for the direct co-culture of endothelium on smooth muscle cells by Mark D. Lavender; Zhengyu Pang; Charles S. Wallace; Laura E. Niklason; George A. Truskey (4642-4653).
The development of a functional, adherent endothelium is one of the major factors limiting the successful development of tissue engineered vascular grafts (TEVGs). The adhesion and function of endothelial cells (ECs) on smooth muscle cells (SMCs) are poorly understood. The goal of this research was to optimize conditions for the direct culture of endothelium on SMCs, and to develop an initial assessment of co-culture on EC function. The co-culture consisted of a culture substrate, a basal adhesion protein, a layer of porcine SMCs, a medial adhesion protein, and a layer of porcine ECs. Conditions that led to successful co-culture were: a polystyrene culture substrate, a quiescent state for SMCs, subconfluent density for SMC seeding and confluent density for EC seeding, and fibronectin (FN) for the basal adhesion protein. EC adhesion was not enhanced by addition of FN, collagen I, collagen IV or laminin (LN) to the medial layer. 3-D image reconstruction by confocal microscopy indicated that SMCs did not migrate over ECs and the cells were present in two distinct layers. Co-cultures could be consistently maintained for as long as 10 days. After exposure to 5 dyne/cm2 for 7.5 h, ECs remained adherent to SMCs. PECAM staining indicated junction formation between ECs, but at a lower level than that observed with EC monocultures. Co-culturing ECs with SMCs did not change the growth rate of ECs, but EC DiI-Ac-LDL uptake was increased. Thus, a confluent and adherent layer of endothelium can be directly cultured on quiescent SMCs.
Keywords: Co-culture; Smooth muscle cells; Endothelial cells;
Tissue engineered ceramic artificial joint—ex vivo osteogenic differentiation of patient mesenchymal cells on total ankle joints for treatment of osteoarthritis by Hajime Ohgushi; Noriko Kotobuki; Hiroyuki Funaoka; Hiroko Machida; Motohiro Hirose; Yasuhito Tanaka; Yoshinori Takakura (4654-4661).
Total joint arthroplasty is the common treatment of severe cases of osteoarthritis. However, complications involving failure of the bone–prosthesis interface are significant, especially in ankle arthroplasty. To prevent this complication, we attempted a tissue engineering approach using the mesenchymal cells of the patient. We collected a small amount of fresh bone marrow cells from the patient's iliac crest and expanded the number of mesenchymal cells. We then applied the mesenchymal cells to a ceramic ankle prosthesis and cultured them to form an osteoblasts/bone matrix on the prosthesis. We used tissue engineered prostheses on three patients suffering from ankle arthritis and followed their progress for at least 2 years. Follow-up X-ray examinations revealed early radiodense appearance (bone formation) around the cell-seeded areas of the prostheses about 2 months after the operation after which a stable host bone–prosthesis interface was established. All patients showed high clinical scores after the operation and did not exhibit inflammatory reactions. These preliminary results indicate that the tissue engineering approach using autologous cultured marrow mesenchymal cells might prevent aseptic loosening of the total ankle arthroplasty.
Keywords: Arthroplasty; Arthritis; Alumina ceramics; Mesenchymal cells; Osteogenesis;
A novel solvent-free method for the manufacture of biodegradable antibiotic-capsules for a long-term drug release using compression sintering and ultrasonic welding techniques by Shih-Jung Liu; Ying-E Tsai; Steve Wen-Neng Ueng; Err-Cheng Chan (4662-4669).
This report was to develop a novel solvent-free method for the manufacture of biodegradable capsules for a long-term drug delivery. To manufacture an antibiotic capsule, polylactide–polyglycolide copolymers were pre-mixed with vancomycin. The mixture was then injection compression molded to form a cylinder with a cover of 8 mm in diameter. After the addition of gentamicin sulfate into the core, an ultrasonic welder was used to seal the capsule. An elution method and an high-performance liquid chromatography assay were employed to characterize the in vitro release rates of the antibiotics over a 30-day period. It was found that biodegradable capsules released high concentration of vancomycin and gentamicin (well above the minimum inhibition concentration) in vitro for the period of time needed to treat bone infection; i.e., 2–4 weeks. A bacterial inhibition test was carried out to determine the relative activity of the released antibiotics. The diameter of the sample inhibition zone ranged from 3 to 18 mm, which is equivalent to 16.7–100% of relative activity. By adopting this novel technique, we will be able to manufacture biodegradable capsules of various medicines for long-term drug delivery.
Keywords: Antibiotic capsules; PLGA; Compression sintering; Ultrasonic welding; In vitro elution; Bacterial inhibition;
Reversal of silver sulfadiazine-impaired wound healing by epidermal growth factor by Ae-Ri Cho Lee; Hyunju Leem; Jaegwan Lee; Kyung Chan Park (4670-4676).
Silver sulfadiazine (Ag-SD) is a useful antibacterial agent for wound treatment. However, recent findings indicate that the compound delays the wound-healing process. That delay may be reversed by treatment with growth factors. The purpose of this study, was to evaluate the cyto-protective effect of epidermal growth factor (EGF) against Ag-SD treated keratinocytes and to investigate the reversibility of the impaired wound-healing process by the co-supplementation of EGF. Four types of drug-loaded collagen sponge dressings with different concentrations of Ag-SD, EGF and Ag-SD+EGF were prepared. An immortalized keratinocyte, HaCaT cells, were cultured in 35-mm Petri-dish using Dulbecco's Modified Eagle's Minimal Essential Medium (DMEM) with 10% FBS. Cultures were treated with the samples submerged, and viabilities of cultures were evaluated using MTT assay. The wound heal efficacy was evaluated in a partial thickness burn mouse model. Cells treated with EGF showed a cyto-protective effect on 1% Ag-SD treated cells with significant increase in viable cell numbers at concentrations ranging from 1 to 50 μg/ml. The cytotoxicity of Ag-SD impaired wound healing, while the addition of EGF could reverse the impairment. This evidence suggests that EGF is a useful agent in the retardation of wound healing caused by Ag-SD. Therefore, a drug delivery system containing both EGF and Ag-SD, such as that used in the study, may be clinically relevant.
Keywords: Antibacterial; Growth factors; Keratinocyte; Cytotoxicity; Wound healing; Collagen;
A novel pH- and ionic-strength-sensitive carboxy methyl dextran hydrogel by Rhongsheng Zhang; Mingguo Tang; Adrian Bowyer; Robert Eisenthal; John Hubble (4677-4683).
A fast and simple method for the preparation of pH-sensitive hydrogel membranes for drug delivery and tissue engineering applications has been developed using carbodiimide chemistry. The hydrogels were formed by the intermolecular cross-linking of carboxymethyl dextran (CM-dextran) using 1-ethyl-(3-3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Infrared spectra of the hydrogels suggest the formation of ester bonds between the hydroxyl and carboxyl groups in the CM-dextran. The porosity of the hydrogels produced, as shown by protein diffusion, increases in response to changes in the pH and the ionic strength of the external medium. The results show pH-dependent swelling behaviour arising from the acidic pedant groups in the polymer network. The diffusion of the protein lysozyme through the hydrogel membranes increased with increases in both pH (5.0–9.0) and ionic strength. The effect of changes of pH and ionic strength on the hydrogel's permeability was shown to be reversible. Scanning electron microscopy of these hydrogels showed that pH-dependent changes in permeability are mirrored by morphological changes in gel structure.
Keywords: Dextran; Drug delivery; Hydrogel; Membrane; Responsive;
Binding specificity of α-bilirubin-imprinted poly(methacrylic acid-co-ethylene glycol dimethylacrylate) toward α-bilirubin by Mei-Jywan Syu; Jing-Hong Deng; You-Ming Nian; Tsung-Chieh Chiu; An-Hua Wu (4684-4692).
α-Bilirubin is an important index to determine the liver's functions. Poly(methacrylic acid-co-ethylene glycol dimethylacrylate) (poly(MAA-co-EGDMA)) imprinted with α-bilirubin was proposed and shown to be able to bind α-bilirubin specifically. The extraction condition was also discussed. Polymers prepared by imprinting bilirubin in poly(MAA-co-EGDMA) and in poly(β-cyclodextrin-co-EGDMA) were compared. In this work, binding specificity of molecularly imprinted polymer (MIP) toward the target template, α-bilirubin, is discussed. Adsorption profile of α-bilirubin by bilirubin-imprinted poly(MAA-co-EGDMA) was measured as a function of time, from where the equilibrium could be determined. Two hours was determined to be the proper time for adsorption. Biliverdin as a rather similar analog compound of bilirubin was chosen for comparison of binding specificity in this study. Progesterone as well as testosterone was also chosen for study because they both co-exist in serum with bilirubin and might interfere with binding capacity of imprinted poly(MAA-co-EGDMA) toward α -bilirubin. Specificity of this polymer for bilirubin was thus confirmed by tasks carried out in mixture solutions comprised of compounds above. It is true that biliverdin contained in the binary mixture did affect the binding capacity of bilirubin. Nevertheless, polymer's binding specificity for bilirubin was essentially sufficient for recognition of α-bilirubin in the presence of other compounds. How MIP identified the target template molecule, α-bilirubin, is also elucidated.
Keywords: α-Bilirubin; Binding specificity; Imprinted poly(MAA-co-EGDMA); Biliverdin; Progesterone; Testosterone; Binary mixture; Recognition; MIP;
Erratum to ‘Evaluation of three-dimensional scaffolds made of blends of hydroxyapatite and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) for bone reconstruction’ [Biomaterials 26 (2005) 899–904] by Ya-Wu Wang; Qiong Wu; Jinchun Chen; Guo-Qiang Chen (4693).