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Novel bactericidal surface: Catechin-loaded surface-erodible polymer prevents biofilm formation
Maeyama, R., I. K. Kwon, et al. (2005), J Biomed Mater Res A 75(1): 146-55.
Abstract: We developed a novel bactericidal surface based on a catechin-loaded surface-erodible polymer. (-)-Epigallocatechin-3-gallate (EGCg), which is the main constituent of tea catechins, showed a dose-dependent inhibitory effect on Escherichia coli biofilm formation and a dose-dependent enhanced destructive effect on biofilm. EGCg-immobilized surfaces were prepared by photopolymerization of liquid biodegradable polyesters. The releasing rate was enhanced with an increase in surface-erosion rate of photocured polymers. Polymers with high releasing capacity dose-dependently reduced biofilm formation on the surfaces. The confocal laser scanning microscopic and scanning electron microscopic observations revealed that EGCg induced biofilm-destructing activities, which include bacterial membrane damage, degradation of exopolysaccharides, and detachment of colonized cells. From these results, potential advantages of the clinical use of catechin-loaded polymer-coated implants or catheters are discussed in terms of a reduced occurrence of biomaterial-centered infections without substantial toxicity or adverse effects.

Novel biocompatible phosphorylcholine-based self-assembled nanoparticles for drug delivery
Salvage, J. P., S. F. Rose, et al. (2005), J Control Release 104(2): 259-70.
Abstract: Major challenges associated with nano-sized drug delivery systems include removal from systemic circulation by phagocytic cells and controlling appropriate drug release at target sites. 2-methacryloyloxyethyl phosphorylcholine (MPC) has been copolymerised in turn with two pH responsive comonomers (2-(diethylamino)ethyl methacrylate (DEA) and 2-(diisopropylamino)ethyl methacrylate (DPA), to develop novel biocompatible drug delivery vehicles. Micelles were prepared from a series of copolymers with varying block compositions and their colloidal stability and dimensions were assessed over a range of solution pH using photon correlation spectroscopy. The drug loading capacities of these micelles were evaluated using Orange OT dye as a model compound. The cytotoxicity of the micelles was assessed using an in vitro assay. The MPC-DEA diblock copolymers formed micelles at around pH 8 and longer DEA block lengths allowed higher drug loadings. However, these micelles were not stable at physiological pH. In contrast, MPC-DPA diblock copolymers formed micelles of circa 30 nm diameter at physiological pH. In vitro assays indicated that these MPC-DPA diblock copolymers had negligible cytotoxicities. Thus novel non-toxic biocompatible micelles of appropriate size and good colloidal stability with pH-modulated drug uptake and release can be readily produced using MPC-DPA diblock copolymers.

Novel biodegradable films and scaffolds of chitosan blended with poly(3-hydroxybutyrate)
Cao, W., A. Wang, et al. (2005), J Biomater Sci Polym Ed 16(11): 1379-94.
Abstract: In order to develop a novel biomaterial, films of chitosan blended with poly(3-hydroxybutyrate) (PHB) were prepared by an emulsion blending technique and their properties were characterized. Scanning electron microscopy (SEM) showed that PHB microspheres were formed and were entrapped in chitosan matrices, which made the film surface rough. With increasing PHB content, the roughness of the film surface increased, while the swelling capability of the films decreased. In a wet state, the blended films exhibited a lower elastic modulus, a higher elongation-at-break and a higher tensile strength compared with chitosan films. Cell-culture experiments revealed that the blended films had better cytocompatibility than chitosan films. To explore the potential application of the blended material in tissue engineering, the porous blended scaffolds were fabricated and their pore morphology was observed by SEM. The results revealed that not only pore structure but also pore wall morphology of the blended scaffolds could be controlled by selecting the parameters of the fabrication process. These advantageous properties indicate that the blended chitosan/PHB material is promising for tissue engineering applications.

Novel biomaterial from reinforced salmon collagen gel prepared by fibril formation and cross-linking
Yunoki, S., N. Nagai, et al. (2004), J Biosci Bioeng 98(1): 40-7.
Abstract: The improvement of the thermal stability of gel prepared from salmon atelocollagen (SC) was studied. The denaturation temperature (Td) of the SC solution was found to be 18.6 degrees C. Neutral buffer including 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) was mixed with acidic SC solution at 4 degrees C, resulting in the introduction of EDC cross-linking during fibril formation. The mechanical strength and thermal stability of the resultant cross-linked SC fibrillar gels reached maximum values at an EDC concentration of 50 mM (f-50 gel). In particular, the melting temperature of the f-50 gel was 47 degrees C, much higher than that of the EDC cross-linked SC gel without fibril formation at the same EDC concentration. The proliferation rate of human periodontal ligament cells on the f-50 gel was higher than that of a porcine atelocollagen fibrillar gel. These results suggest that the gel employed for biomaterials can be fabricated from low Td fish collagen by EDC cross-linking during fibril formation.

Novel biomaterials for bisphosphonate delivery
Josse, S., C. Faucheux, et al. (2005), Biomaterials 26(14): 2073-80.
Abstract: One type of gem-bisphosphonate (Zoledronate) has been chemically associated onto calcium phosphate (CaP) compounds of various compositions. For that purpose, CaP powders of controlled granulometry have been suspended in aqueous Zoledronate solutions of variable concentrations. Using mainly (31)P NMR spectroscopy, two different association modes have been observed, according to the nature of the CaP support and/or the initial concentration of the Zoledronate solution. beta-tricalcium phosphate (beta-TCP) and mixtures of hydroxyapatite and beta-TCP (BCPs) appear to promote Zoledronate-containing crystals formation. On the other hand, at concentrations <0.05 mol l(-1) CDAs (calcium deficients apatites) seem to undergo chemisorption of the drug through a surface adsorption process, due to PO(3) for PO(4) exchange, that is well described by Freundlich equations. At concentrations >0.05 mol l(-1), crystalline needles of a Zoledronate complex form onto the CDAs surface. The ability of such materials to release Zoledronate, resulting in the inhibition of osteoclastic activity, was shown using a specific in vitro bone resorption model.

Novel biomaterials. International Conference on Biomedical Materials--basic and applied studies. 24-28 May 1997. Portonovo, Ancona, Italy
Haris, P. I. (1997), Mol Med Today 3(12): 522-3.

Novel chitosan-based hyaluronan hybrid polymer fibers as a scaffold in ligament tissue engineering
Funakoshi, T., T. Majima, et al. (2005), J Biomed Mater Res A 74(3): 338-46.
Abstract: To clarify the feasibility of using novel chitosan-based hyaluronan hybrid polymer fibers as a scaffold in ligament tissue engineering, their mechanical properties and ability to promote cellular adhesion, proliferation, and extracellular matrix production were studied in vitro. Chitosan fibers and chitosan-based 0.05% and 0.1% hyaluronan hybrid fibers were developed by the wet spinning method. Hyaluronan coating significantly increased mechanical properties, compared to the chitosan fibers. Rabbit fibroblasts adhesion onto hybrid fibers was significantly greater than for the control and chitosan fibers. For analysis of cell proliferation and extracellular matrix production, a three-dimensional scaffold was created by simply piling up each fiber. At 1 day after cultivation, the DNA content in the hybrid scaffolds was higher than that in the chitosan scaffold. Scanning electron microscopy showed that the fibroblasts had produced collagen fibers after 14 days of culture. Immunostaining for type I collagen was clearly predominant in the hybrid scaffolds, and the mRNA level of type I collagen in the hybrid scaffolds were significantly greater than that in the chitosan scaffold. The present study revealed that hyaluronan hybridization with chitosan fibers enhanced fiber mechanical properties and in vitro biological effects on the cultured fibroblasts.

Novel functional biodegradable polymer. III. The construction of poly(gamma-glutamic acid)-sulfonate hydrogel with fibroblast growth factor-2 activity
Matsusaki, M., T. Serizawa, et al. (2005), J Biomed Mater Res A 73(4): 485-91.
Abstract: Poly(gamma-glutamic acid)-sulfonate (gamma-PGA-S) hydrogel, with fibroblast growth factor (FGF)-2 activity was investigated as a novel, next-generation tissue-engineering material. gamma-PGA-net-gamma-PGA-S72 (S72-netgel) was prepared with gamma-PGA-S and gamma-PGA-S72 (72% sulfonated gamma-PGA) to provide the high mobility of gamma-PGA-S72 for FGF-2 activity. Cell adhesion and proliferation activities were evaluated on gamma-PGA and gamma-PGA-S hydrogels along with S72-netgels. Both cell adhesion and proliferation activities of gamma-PGA and gamma-PGA-S hydrogels were low. In contrast, S72-netgels had high cell adhesion and proliferation activities, because of their low swelling ratios and high sulfonic acid group concentrations. Furthermore, S72-netgels had high FGF-2 activity, because gamma-PGA-S72 retained FGF-2 activity when incorporated into S72-netgels. S72-netgels should be useful as next-generation tissue-engineering material containing FGF-2 activity.

Novel human endothelial cell-engineered polyurethane biomaterials for cardiovascular biomedical applications
Wang, D. A., L. X. Feng, et al. (2003), J Biomed Mater Res A 65(4): 498-510.
Abstract: A tri-block coupling-polymer composed of 4,4'-methylenediphenyl diisocyanate and poly (ethylene oxide) (PEO), abbreviated MPEO, was used as the template surface-modifying additive (SMA), based on which selected amino acids (lysine, arginine, glycin, and aspartic acid) and RGD peptide were respectively conjugated as functional endgroups of the PEO spacer-arms through sulfonyl chloride-activation routes. After the immobilization of biofunctional factors, the SMA-MPEO derivatives were noncovalently introduced onto the biomedical poly(ether urethane) (PEU) surfaces by physical blending methods. The SMA synthesis and PEU surface modification were monitored and analyzed by nuclear magnetic resonance spectroscopy, attenuated total reflection-infrared spectroscopy, and X-ray photoelectron spectroscopy. The human umbilical vein endothelial cells (HUVECs) were collected and harvested manually by collagenase digestion. The cell culture was performed respectively on the MPEO derivative-modified PEU surfaces and also on the surfaces of the commercially available polystyrene cell-culture plates (TCPS) for control. The cell adhesion rates and cell proliferation rates of the in vitro cultivated HUVEC were measured using flow cytometry. The individual cell viability rates were determined with MTT assay. The cell morphologies of the living HUVECs were investigated by optical inverted microscopy, and more detailed information was acquired from scanning electrical microscopy. The results indicated that the efficacy of SMA functional endgroups was the dominant factor for HUVEC compatibility; the proper-sized PEO spacers (M(w) 2 k) could support and mobilize the functional endgroups, optimizing the surface (interface) environment for the cell growth. As the endgroups of the SMA-MPEO derivatives and the bio-functional factors, the basic amino acids (lysine and arginine) demonstrated similar performances to that of the widely acknowledged cell growth-promoter, RGD peptide, which were superior to TCPS. Therefore, these MPEO derivative-modified PEU materials are promising to serve as novel polymeric permanent implants or interventional devices for cardiovascular biomedical applications.

Novel hydrogel membrane based on copoly(hydroxyethyl methacrylate/p-vinylbenzyl-poly(ethylene oxide)) for biomedical applications: properties and drug release characteristics
Arica, M. Y., G. Bayramoglu, et al. (2005), Macromol Biosci 5(10): 983-92.
Abstract: The aim of this study was to synthesize and characterize a novel biocompatible polymeric membrane system and demonstrate its potential use in various biomedical applications. Synthetic hydrogels based on poly(hydroxyethyl methacrylate), poly(HEMA), have been widely studied and used in biomedical fields. A novel copolymer hydrogel was prepared in the membrane form using 2-hydroxyethyl methacrylate monomer (HEMA) and a macromonomer p-vinylbenzyl-poly(ethylene oxide) (V-PEO) via photoinitiated polymerization. A series of poly(HEMA/V-PEO) copolymer membranes with different compositions was prepared. The membranes were characterized using infrared, thermal and SEM analysis. The thermal stabilities of the copolymer membranes were found to be lowered by an increase in the ratio of macromonomer (V-PEO) in the membrane structure. Because of the incorporation of PEO segments, the copolymers exhibited significantly higher hydrophilic surface properties than pure poly(HEMA), as demonstrated by contact angle measurements. Equilibrium swelling studies were conducted to investigate the swelling behavior of the membranes. The equilibrium water uptake was reached in about 4 h. Moreover, the blood protein adsorption and platelet adhesion were significantly reduced on the surface of the PEO containing copolymer membranes compared to control pure poly(HEMA). Drug release experiments were performed in a continuous release system using model drug (vancomycin) loaded copoly(HEMA/V-PEO) membranes. A specific poly(HEMA/V-PEO) membrane formulation possessing the highest PEO content (with a HEMA:V-PEO (mmol:mmol) feed ratio of 112:1 and loaded with 40 mg antibiotic/g polymer) released about 81% of the total loaded drug in 24 h at pH 7.4. This membrane composition provided the best results and can be considered as a potential candidate for a transdermal antibiotic carrier and various biomedical and biotechnological applications.

Novel in vivo murine model to study islet potency: engraftment and function
Bharat, A., N. Benshoff, et al. (2005), Transplantation 79(11): 1627-30.
Abstract: Standard islet potency testing uses transplantation of islets under the kidney capsule in diabetic severe combined immunodeficient (d-SCID) mice. Even though it is possible to achieve normoglycemia in the majority of recipients by this method, the surgical procedure, by itself, is technically difficult and associated with an appreciable mortality of animals. In addition, the spatially limited renal subcapsular site restricts the mass of islet tissue that can be transplanted. Matrigel basement membrane matrix (MATRIGEL), extracted from a mouse sarcoma, is rich in angiogenic growth factors and has been shown to support the growth of mammalian cells using murine models. In this report we demonstrate that subcutaneous islet transplantation with MATRIGEL can effectively achieve normoglycemia and that this is a simple and reproducible model for in vivo islet potency testing in d-SCID mice that overcomes many drawbacks of the conventional method of kidney subcapsular islet transplantation.

Novel intramedullary plug with sliding mechanism used in revision total knee arthroplasty
Fujita, H., T. Kitaori, et al. (2005), J Biomed Mater Res B Appl Biomater 74(1): 419-22.
Abstract: A novel intramedullary plug with sliding mechanism has been developed and evaluated clinically in the settings of revision total knee arthroplasty (TKA). The new plug consists of a pair of specially designed components. Each component is shaped like an obliquely cut cylinder. Postoperative plain radiographs of 8 arthroplasties that include 7 stemmed femoral components and 6 stemmed tibial components (total 13 regions) were examined. No radiolucent line between the cement and the cortical bone was observed. Plugging was complete in 11 regions. No migration of the plug was observed. Slight leak of the cement was observed in 2 of 7 femoral components, but not found in tibial components. Our study demonstrated the efficacy of the plug in occluding the femoral and tibial canal completely in 11 out of 13 regions in revision TKAs.

Novel microwave technology for cryopreservation of biomaterials by suppression of apparent ice formation
Jackson, T. H., A. Ungan, et al. (1997), Cryobiology 34(4): 363-72.
Abstract: Ice formation inside or outside cells has been proposed to be a factor causing cryoinjury to cells/tissues during cryopreservation. How to control, reduce, or eliminate the ice formation has been an important research topic in fundamental cryobiology. The objective of this study was to test a hypothesis that the coupled interaction of microwave radiation and cryoprotectant concentration could significantly influence ice formation and enhance potential vitrification in cryopreservation media at a relative slow cooling rate. Test samples consisted of a series of solutions with ethylene glycol (a cryoprotectant) concentration ranging from 3 to 5.5 M. A specific microwave resonant cavity was built and utilized to provide an intense oscillating electric field. Solutions were simultaneously exposed to this electric field and cooled to -196 degrees C by rapid immersion in liquid nitrogen. Control samples were similarly submerged in liquid nitrogen but without the microwave field. The amount of ice formation was determined by analysis of digital images of the samples. The morphology of the solidified samples was observed by cryomicroscopy. It was found that ice formation was greatly influenced by microwave irradiation. For example, ice formation could be reduced by roughly 56% in 3.5 M ethylene glycol solutions. An average reduction of 66% was observed in 4.5 M solutions. Statistical analysis indicated that the main effects of microwave and ethylene glycol concentration as well as the interaction between these two factors significantly (P < 0.01) influenced ice formation amount, confirming the hypothesis. This preliminary study suggests that a combined use of microwave irradiation and cryoprotectant might be a potential approach to control ice formation in cells/tissues during the cooling process and to enhance vitrification of these biomaterials for long-term cryopreservation.

Novel modulation of drug delivery using binary zinc-alginate-pectinate polyspheres for zero-order kinetics over several days: experimental design strategy to elucidate the crosslinking mechanism
Pillay, V., M. P. Danckwerts, et al. (2005), Drug Dev Ind Pharm 31(2): 191-207.
Abstract: A Box-Behnken design was applied to mathematically establish whether different degrees of crosslinking were induced by Zn2+ and Ca2+ ions in polyspheres composed of alginate and/or pectin, and the model drug ibuprofen. Based on their different crystal structures and coordination numbers, a theoretical model was proposed demonstrating that Zn2+ ions preferentially crosslink alginate and pectin. In addition, the lower coordination number of Zn2+ (4-6) would significantly retard hydration of both polymers, as opposed to Ca2+ (7-9). The responses studied for 28 statistically derived polyspheres included drug encapsulation efficiency, physicomechanical behavior, and in vitro drug release potential. Single-tailed Student's t-tests on data generated for the encapsulation efficiencies, primary facture values, and rupture energies indicated that Zn2+ was statistically superior (p<0.05) in crosslinking alginate and pectin. Further textural analysis revealed a good correlation between the Brinell hardness number and fracture load, while an inverse relationship was found for matrix tensile strength. Viscosity studies demonstrated different in situ crosslinking thresholds for Zn2+. The Durbin-Watson statistic and correlation coefficient revealed that the quadratic regression function was highly accurate in predicting the responses. Using a generalized reduced gradient algorithm on dissolution values obtained after 2 hours (t2h) provided optimized solutions for achieving zero-order release extending from 2 hours to 7 days. Mathematical simulations projected drug release from 25 to 50 days.

Novel mouse model of chronic Pseudomonas aeruginosa lung infection mimicking cystic fibrosis
Hoffmann, N., T. B. Rasmussen, et al. (2005), Infect Immun 73(4): 2504-14.
Abstract: Pseudomonas aeruginosa causes a chronic infection in the lungs of cystic fibrosis (CF) patients by establishing an alginate-containing biofilm. The infection has been studied in several animal models; however, most of the models required artificial embedding of the bacteria. We present here a new pulmonary mouse model without artificial embedding. The model is based on a stable mucoid CF sputum isolate (NH57388A) with hyperproduction of alginate due to a deletion in mucA and functional N-acylhomoserine lactone (AHL)-based quorum-sensing systems. Chronic lung infection could be established in both CF mice (Cftr(tmlUnc-/-)) and BALB/c mice, as reflected by the detection of a high number of P. aeruginosa organisms in the lung homogenates at 7 days postinfection and alginate biofilms, surrounded by polymorphonuclear leukocytes in the alveoli. In comparison, both an AHL-producing nonmucoid revertant (NH57388C) from the mucoid isolate (NH57388A) and a nonmucoid isolate (NH57388B) deficient in AHL were almost cleared from the lungs of the mice. This model, in which P. aeruginosa is protected against the defense system of the lung by alginate, is similar to the clinical situation. Therefore, the mouse model provides an improved method for evaluating the interaction between mucoid P. aeruginosa, the host, and antibacterial therapy.

Novel mucoadhesion tests for polymers and polymer-coated particles to design optimal mucoadhesive drug delivery systems
Takeuchi, H., J. Thongborisute, et al. (2005), Adv Drug Deliv Rev 57(11): 1583-94.
Abstract: To design an effective particulate drug delivery system having mucoadhesive function, several mucoadhesion tests for polymers and the resultant particulate systems were developed. Mucin particle method is a simple mucoadhesion test for polymers, in which the commercial mucin particles are used. By measuring the change in particle size or zeta potential of the mucin particle in a certain concentration of polymer solution, we could estimate the extent of their mucoadhesive property. BIACORE method is also a novel mucoadhesion test for polymers. On passing through the mucin suspension on the polymer-immobilized chip of BIACORE instrument, the interaction was quantitatively evaluated with the change in its response diagram. By using these mucoadhesion tests, we detected a strong mucoadhesive property of several types of chitosan and Carbopol. Evaluation of mucoadhesive property of polymer-coated particulate systems was demonstrated with the particle counting method developed by us. To detect the mucoadhesive phenomena in the intestinal tract, we observed the rat intestine with the confocal laser scanning microscope (CLSM) after oral administration of the particulate systems. The resultant photographs clearly showed a longer retention of submicron-sized chitosan-coated liposomes (ssCS-Lip) in the intestinal tract than other liposomal particles tested such as non-coated liposomes and chitosan-coated multilamellar one. These observations explained well the superiority of the ssCS-Lip as drug carrier in oral administration of calcitonin in rats than other liposomal particles.

Novel nanoparticulate carrier system based on carnauba wax and decyl oleate for the dispersion of inorganic sunscreens in aqueous media
Villalobos-Hernandez, J. R. and C. C. Muller-Goymann (2005), Eur J Pharm Biopharm 60(1): 113-22.
Abstract: The purpose of this study was to characterize carrier systems for inorganic sunscreens based on a matrix composed of carnauba wax and decyl oleate. Ultraviolet radiation attenuators like barium sulfate, strontium carbonate and titanium dioxide were tested. The lipid matrices were used either as capsules or as accompanying vehicles for the pigments in aqueous dispersions. Manufacturing was performed using high pressure homogenization at 300bar and a temperature of 75 degrees C. To evaluate the effect of the pigments on the crystalline structure of the wax-oil mixture, X-ray diffraction and differential scanning calorimetry were used. Further parameters determined were particle size, polydispersity index, z-potential, viscosity and sun protection factor (SPF). Transmission electron microscopy was also applied for visualization of nanoparticles. The X-ray diffraction patterns and the melting points of the lipid mixtures remained unchanged after the pigments were added. The particle sizes of the encapsulated species ranged from 239 to 749.9nm showing polydispersity values between 0.100 and 0.425. Surface charge measurements comprising values up to -40.8mV denoted the presence of stable dispersions. The formulations could be described as ideal viscous presenting viscosities in a range of 1.40-20.5mPas. Significant increases in SPF up to about 50 were reported after the encapsulation of titanium dioxide. Freeze fracture micrographs confirmed the presence of encapsulated inorganic crystals.

Novel osteoblast-adhesive peptides for dental/orthopedic biomaterials
Dettin, M., M. T. Conconi, et al. (2002), J Biomed Mater Res 60(3): 466-71.
Abstract: Next generation dental/orthopedic biomaterials must be designed to enhance and support osteoblast adhesion. The osteoblasts use different ways to adhere, that is, integrin- and proteoglycan-mediated mechanisms. The present study reports on the synthesis and osteoblast-adhesive properties of peptides carrying RGD motifs and of sequences mapped on human vitronectin. Our data suggest that osteoblast adhesion on polystyrene plates modified with a linear peptide, in which the GRGDSP sequence is repeated four times, was significantly higher when compared to the adhesion obtained using branched peptides, interestingly containing the same motif. Osteoblast adhesion assays on acellular bone matrix using this active peptide gave very promising results. We also demonstrated that a novel peptide, carrying the X-B-B-B-X-B-B-X motif (where B is a basic amino acid and X is a nonbasic residue), promotes proteoglycan-mediated osteoblast adhesion more efficiently with respect to the KRSR sequence that was recently proposed as heparan-sulfate binding peptide.

Novel peptide-based biomaterial scaffolds for tissue engineering
Holmes, T. C. (2002), Trends Biotechnol 20(1): 16-21.
Abstract: Biomaterial scaffolds are components of cell-laden artificial tissues and transplantable biosensors. Some of the most promising new synthetic biomaterial scaffolds are composed of self-assembling peptides that can be modified to contain biologically active motifs. Peptide-based biomaterials can be fabricated to form two- and three-dimensional structures. Recent studies show that biomaterial promotion of multi-dimensional cell-cell interactions and cell density are crucial for proper cellular differentiation and for subsequent tissue formation. Other refinements in tissue engineering include the use of stem cells, cell pre-selection and growth factor pre-treatment of cells that are used for seeding scaffolds. These cell-culture technologies, combined with improved processes for defining the dimensions of peptide-based scaffolds, might lead to further improvements in tissue engineering. Novel peptide-based biomaterial scaffolds seeded with cells show promise for tissue repair and for other medical applications.

Novel poly(amido-amine)-based hydrogels as scaffolds for tissue engineering
Ferruti, P., S. Bianchi, et al. (2005), Macromol Biosci 5(7): 613-22.
Abstract: Biodegradable and biocompatible amphoteric poly(amido-amine) (PAA)-based hydrogels, containing carboxyl groups along with amino groups in their repeating unit, were considered as scaffolds for tissue engineering applications. These hydrogels were obtained by co-polymerising 2,2-bisacrylamidoacetic acid with 2-methylpiperazine with or without the addition of different mono-acrylamides as modifiers, and in the presence of primary bis-amines as crosslinking agents. Hybrid PAA/albumin hydrogels were also prepared. The polymerisation reaction was a Michael-type polyaddition carried out in aqueous media. The PAA hydrogels were soft and swellable materials. Cytotoxicity tests were carried out by the direct contact method with fibroblast cell lines on the hydrogels both in their native state (that is, as free bases) and as salts with acids of different strength, namely hydrochloric, sulfuric, acetic and lactic acid. This was done in order to ascertain whether counterion-specific differences in cytotoxicity existed. It was found that all the amphoteric PAA hydrogels considered were cytobiocompatible both as free bases and salts. Selected hydrogels samples underwent degradation tests under controlled conditions simulating biological environments, i.e. Dulbecco medium at pH 7.4 and 37 degrees C. All samples degraded completely and dissolved within 10 d, with the exception of hybrid PAA/albumin hydrogels that did not dissolve even after eight months. The degradation products of all samples turned to be non-cytotoxic. All these results led us to conclude that PAA-based hydrogels have a definite potential as degradable matrices for biomedical applications.

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