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Evaluation of chitosan/beta-tricalcium phosphate microspheres as a constituent to PMMA cement
Lin, L. C., S. J. Chang, et al. (2005), J Mater Sci Mater Med 16(6): 567-74.
Abstract: Two methods, a traditional emulsion technique and a high voltage electrostatically modified encapsulation system, were used to fabricate degradable chitosan/beta -tricalcium phosphate (beta-TCP) microspheres. The two distinct kinds of microspheres both exhibited good sphericity and the beta-TCP was trapped well inside the chitosan gel. The microspheres prepared by high voltage electrostatic system exhibited a rougher outer surface and narrower size distribution. These microspheres were then used as an added constituent to commercially available PMMA bone cement. Four modified cement composites that were prepared with different composition ratios of the two kinds of chitosan/beta-TCP microspheres that were made from emulsion technique (C1P1 and C2P1) and from a process by a high voltage electrostatic system (EC1P1 and EC2P1) were compared with the PMMA cement (Pure P). The characteristics of these materials indicate that with the addition of chitosan/beta-TCP microspheres as a constituent into the PMMA cement significantly decreases the curing peak temperature. Furthermore, the setting time increases from 3.5 min to 9 min, as compared to the PMMA cement. These changes could be beneficial for the handling of the bone cement paste and causing less damage to the surrounding tissues. Understandably, the presence of chitosan/beta-TCP microspheres in the prepared composites reduced the ultimate compressive strength and bending strength. From the degradation test and SEM observations, the modified chitosan/beta -TCP/PMMA composites could be degraded gradually and create rougher surfaces that would be beneficial to cell adherence and growth.

Evaluation of coated oxygenators in cardiopulmonary-bypass systems and their impact on neurocognitive function
Khosravi, A., C. A. Skrabal, et al. (2005), Perfusion 20(5): 249-54.
Abstract: INTRODUCTION: Coronary artery bypass graft surgery (CABG) using cardiopulmonary bypass (CPB) is assumed to be associated with a decline of neurocognitive functions. This study was designed to analyse the neurocognitive function of patients with coronary heart disease before and after CABG and to determine possible protective effects of oxygenator surface coating on neurological outcome. METHODS: Forty patients scheduled for selective CABG were prospectively randomized into two groups of 20 patients each according to the type of hollow-fibre membrane oxygenator used. Non-coated oxygenators (Group A) were compared to phosphorylcholine (PC)coated oxygenators (Group B). A battery of six neurological tests was administered preoperatively, 7-10 days and 4-6 months after surgery. RESULTS: One patient of Group A suffered from a perioperative stroke and died on postoperative day 3, presumably because of sudden heart failure. Two patients of Group A (10%) developed a symptomatic transitory delirious psychotic syndrome (STPT) on postoperative days 3 and 5. None of the patients of Group B had perioperative complications. The test analysis revealed a trend of declined neurocognitive function early after CABG, but did not show any difference in neurocognitive outcome between the two groups. DISCUSSION: PC coating of the oxygenators did not show any significant benefit on neurocognitive function after CABG using CPB.

Evaluation of crosslinked chitosan hydrogel beads as a carrier for prolonged delivery of diclofenac sodium: in vitro and in vivo studies
Alsarra, I. A. (2004), Boll Chim Farm 143(10): 359-64.
Abstract: Chitosan hydrogel beads containing diclofanac sodium were prepared using ionotropic gelation technique in which tripolyphosphate solution was used as a counterion. Chitosan molecular weight, tripolyphosphate concentration and crosslinking time were found to have an effect on the percentage of the drug loading. The loading efficiency of diclofenac sodium was very high (more than 90%). A longer-period of contact with the counterion ions decreased the efficiency of drug loading. The beads produced all had good spherical geometry. The beads showed a narrow size distribution in which 95% of the beads prepared were in the range of 2-3 mm. Comparison of release rate-time plots of dissolution data of marketed product with the newly developed dosage form indicated the ability of the later to sustain more diclofenac sodium release. The beads were evaluated for their bioavailability in six beagle dogs relative to the commercial enteric-coated Voltaren tablets. The in vivo availability study, reveled that the prepared beads filled in hard gelatin capsules had a 126.22% bioavailability relative to that of the commercial Voltaren tablets. The beads showed comparable pharmacokinetic parameters to that of the commercial tablets. The results suggested the possibility of producing a promising sustained drug delivery system for diclofenac sodium.

Evaluation of cryopreserved bone and synthetic biomaterials in promoting spinal fusion
Nasca, R. J., J. E. Lemons, et al. (1991), Spine 16(8 Suppl): S330-3.
Abstract: The purpose of the study was to evaluate the use of cryopreserved allograft bone and tricalcium phosphate in promoting spinal fusion. Nine 20-30 lb swine underwent posterior spinal fusion at T5-T6, T13-T14, and L2-L3. Autogenous bone, cryopreserved allograft bone, or equal parts of allograft bone and tricalcium phosphate were added to the decorticated posterior elements. A total of 27 sites were prepared for fusion. The spines were retrieved at 6 months and evaluated for integrity and stability of the fusion sites by clinical examination, three-point bending tests, multiplanar radiographs, and undecalcified tetracycline-labeled and decalcified histologic sections. The nine sites that received autogenous bone were solidly fused. There were one clinical and two radiographic nonunions in the nine sites that received cryopreserved allograft bone. Sites that received a mixture of allograft bone and tricalcium phosphate demonstrated slight motion at two locations and radiographic evidence of fusion at all levels. The extent and degree of fusion was not site-specific. Three-point bending analysis did not demonstrate a significant trend as to site or materials specificity. No adverse histologic response was noted. Histologic sections and tetracycline labels confirmed abundant new bone formation at all sites at 6 months. Although autogenous bone remains the gold standard for use in spinal arthrodesis, this study demonstrates the value of cryopreserved allograft bone alone and in combination with tricalcium phosphate in promoting spinal fusion.

Evaluation of demineralized bone matrix paste and putty in periodontal intraosseous defects
Bender, S. A., J. B. Rogalski, et al. (2005), J Periodontol 76(5): 768-77.
Abstract: BACKGROUND: Demineralized bone matrix (DBX) paste and putty are particulate demineralized bone matrices in a 2% or 4% hyaluronate carrier, respectively. The purpose of this study was to determine the effectiveness of DBX paste and putty compared to demineralized freeze-dried bone allograft (DFDBA) in the treatment of human intraosseous periodontal defects. METHODS: Sixty systemically healthy individuals between the ages of 31 and 71 years with at least one intraosseous periodontal defect of > or = 3 mm in depth and radiographic evidence of at least 40% to 50% vertical bone loss were accrued. Following initial non-surgical periodontal therapy, sites were randomly selected to receive either DBX paste, DBX putty, or DFDBA (control). Baseline and 6-month reentry soft and hard tissue parameter measurements were made by calibrated examiners. Data were analyzed within and between groups utilizing analysis of variance (ANOVA) and paired and unpaired Student t tests. RESULTS: Probing depth reductions were significantly improved in all treatment groups with DFDBA, DBX paste, and putty patients demonstrating 2.8 mm, 3.6 mm, and 2.3 mm, respectively. Attachment level gains were significantly improved from baseline for all treatment groups with DFDBA, DBX paste, and putty, respectively, demonstrating 2.4 mm, 2.9 mm, and 1.6 mm. Bone fill was similar between all groups with DBX paste, putty, and DFDBA control groups demonstrating 2.0 mm, 2.4 mm, and 2.2 mm, respectively. All groups yielded significant improvements in percent bone fill with DFDBA, DBX paste and putty, respectively, achieving 37%, 42.1%, and 50% with no significant differences between the groups. CONCLUSION: In summary, demineralized bone matrix paste, demineralized bone matrix putty, and demineralized freeze-dried bone allograft all demonstrated similar favorable improvements in soft and hard tissue parameters in the treatment of human intraosseous defects.

Evaluation of diffusion in gel entrapment cell culture within hollow fibers
Wu, D. Q., G. L. Zhang, et al. (2005), World J Gastroenterol 11(11): 1599-604.
Abstract: AIM: To investigate diffusion in mammalian cell culture by gel entrapment within hollow fibers. METHODS: Freshly isolated rat hepatocytes or human oral epidermoid carcinoma (KB) cells were entrapped in type I collagen solutions and statically cultured inside microporous and ultrafiltration hollow fibers. During the culture time collagen gel contraction, cell viability and specific function were assessed. Effective diffusion coefficients of glucose in cell-matrix gels were determined by lag time analysis in a diffusion cell. RESULTS: Significant gel contractions occurred in the collagen gels by entrapment of either viable hepatocytes or KB cells. And the gel contraction caused a significant reduction on effective diffusion coefficient of glucose. The cell viability assay of both hepatocytes and KB cells statically cultured in hollow fibers by collagen entrapment further confirmed the existence of the inhibited mass transfer by diffusion. Urea was secreted about 50% more by hepatocytes entrapped in hollow fibers with pore size of 0.1 mum than that in hollow fibers with MWCO of 100 ku. CONCLUSION: Cell-matrix gel and membrane pore size are the two factors relevant to the limited mass transfer by diffusion in such gel entrapment of mammalian cell culture.

Evaluation of Eudragit-coated chitosan microparticles as an oral immune delivery system
Hori, M., H. Onishi, et al. (2005), Int J Pharm 297(1-2): 223-34.
Abstract: Chitosan microparticles containing ovalbumin (OVA), OVA-containing chitosan microparticles (Chi-OVA), were prepared, coated with Eudragit L100 (ER), and evaluated as oral vaccine. Chi-OVA with an OVA content of 34.4% (w/w) and a mean particle size of 2.3 microm were used for experiments in vitro and in vivo. ER-coated Chi-OVA (ER-Chi-OVA) contained 3.6-20.5% (w/w) OVA and had a particle size of 47.9-161.1 microm. Chi-OVA dissolved readily in JP 14 first fluid, but not in JP 14 second fluid. The release of OVA from Chi-OVA was suppressed extensively in JP 14 second fluid. ER-Chi-OVA did not dissolve in JP 14 first fluid, and the release of OVA was suppressed greatly in JP 14 first and second fluids. OVA solution, Chi-OVA and ER-Chi-OVA (200 and 800 microg OVA/mouse) were administered to Balb/C mice twice at a 1-week interval. At 7 d after the second administration, plasma OVA-specific IgG and fecal OVA-specific IgA levels were measured. OVA-specific IgG tended to be enhanced in Chi-OVA and ER-Chi-OVA, but was the highest in OVA solution. OVA-specific IgA was induced significantly more efficiently by ER-Chi-OVA than the others. These suggested that ER-Chi-OVA should be possibly useful to induce an intestinal mucosal immune response.

Evaluation of homologous bone graft versus biomaterials in the aesthetic restoration of the middle third of the face
Carboni, A., G. Gasparini, et al. (2002), Minerva Chir 57(3): 283-7.
Abstract: BACKGROUND: Bone deficits of the midface can be observed following tumor surgery, facial traumas or malformations, and can determine aesthetic deformities requiring surgical corrections. The goal of this study is to illustrate the 23 years experience of the Maxillo-Facial Department of the "La Sapienza" University of Rome, in surgical correction of middle third bone loss for aesthetic improvement, and to compare postsurgical results from the use of biomaterials and homologous bone grafts. METHODS: From January 1977 to January 2000, 18 patients were surgically treated with bone grafts for bone deficit of the midface requiring aesthetic improvements, and 23 received biomaterial placement in the same district. A retrospective analysis regarding aesthetic improvements following corrective (reconstructive) surgery was carried out in order to compare long-term results obtained with bone grafts and biomaterials. RESULTS: Of the 19 implants of the zygomatic bone, 1 patient suffered from infection, observ-ed on the 8th day, following iliac bone graft in the maxillary area. Of the 32 prostheses, 7 became infected and in 1 case the material became exposed: Proplast(R) became infected 2 times, Gore-tex(R) 3 times and 1 time became exposed; 2 of the 24 Medpor(R) implants resulted in infection. The employment of bone graft obtained a good short term aesthetic result. Medpor(R) employment, was evaluated as an optimal aesthetic improvement. We cannot evaluate the results obtained with Gore-tex(R) and Proplast(R) because of the few cases treated. Anyway we consider unsatisfactory the corrections obtained with these 2 materials. CONCLUSIONS: Homologous bone grafts are still considered as the best choice when a further fixture positioning is planned for prosthetic rehabilitation of the alveolar ridge of the upper jaw or mandible. At the present time, some biomaterials are the definitive solution for restoring facial harmony in the 3 spatial dimensions.

Evaluation of hot-pressed hydroxyapatite/poly-L-lactide composite biomaterial characteristics
Ignjatovic, N., E. Suljovrujic, et al. (2004), J Biomed Mater Res B Appl Biomater 71(2): 284-94.
Abstract: Hydroxyapatite/poly-L-lactide (HAp/PLLA) is a ceramic/polymer composite, whose application as a resorbable biomaterial for the substitution and repair of hard bone tissue is widely promising in orthopedic, oral, maxillofacial, and reconstructive surgery. Hot processing is a necessary step for obtaining HAp/PLLA composite blocks with mechanical properties similar to those of bones. In this article, the changes in structure and physicochemical properties of HAp/PLLA composite, hot pressed for different pressing times (5, 15, 30, 45, and 60 min), were studied. Because the morphology of HAp/PLLA composite biomaterial is very sensitive to this procedure, its surface microstructure was analyzed by scanning electron microscopy (SEM) coupled with an energy-dispersive X-ray (EDX) detector system. Structural changes occurring in the material, mostly changes in crystallinity of PLLA, were studied by wide-angle X-ray structural analyses (WAXS) and infrared (FTIR) spectroscopy. Using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC), the influence of hot pressing on the properties, crystallization kinetics, and decomposition of HAp/PLLA composite biomaterial was analyzed.

Evaluation of human collagen biomaterials in the healing of colonic anastomoses in dogs
Mutter, D., M. Aprahamian, et al. (1997), Eur J Surg 163(4): 287-95.
Abstract: OBJECTIVE: To investigate the ability of human collagen biomaterials to secure colonic anastomoses in dogs and to evaluate the biocompatibility of anastomotic protection patches (APP). DESIGN: Experimental open study. SETTING: Experimental research centre, France. MATERIAL: 21 mongrel dogs randomised into three groups of 7 each. INTERVENTION: Standard transverse colonic end-to-end anastomoses were secured with two-layer oxidised collagen I + III sponge covered with thin crosslinked collagen IV film (APP 1) glued around the suture (n = 7); two-layer oxidised collagen I + III sponge covered with thin non-crosslinked collagen I + III film patch (APP 2) (n = 7); or sealed by fibrin sealant (n = 7), which acted as a controls. MAIN OUTCOME MEASURES: Gross examination, radiological control (barium enemas), and microscopic examination on day 35 postoperatively. RESULTS: Gross clinical and radiological examinations on day 35 showed normal wound healing in all but one dog in which the anastomoses had occluded by day 16. There was significantly less stricturing with the APP 2 patch (p < 0.05 compared with the controls). Microscopic examination showed complete absorption of the APP 2 patches as well as quicker mucosal and extracellular matrix repair than controls. The APP 1 patch gave the best healing of the muscular layer but did not reduce anastomosis stricturing, and was not totally absorbed. CONCLUSIONS: Collagen supporting devices do not alter healing of the large bowel. Encircling patches do not increase the number of adhesions or the rate of anastomotic stricturing and a thin fibrillar collagen I + III dense layer may even improve it. The speed of absorption of the patch depends on the type of dense collagen film. These results argue for a prospective clinical evaluation in humans.

Evaluation of in vitro drug release, pH change, and molecular weight degradation of poly(L-lactic acid) and poly(D,L-lactide-co-glycolide) fibers
Crow, B. B., A. F. Borneman, et al. (2005), Tissue Eng 11(7-8): 1077-84.
Abstract: Biodegradable fibers of poly(L-lactic acid) (PLLA) and poly(D,L-lactide-co-glycolide) (PLGA) that encapsulated a water-soluble drug were created by a patented technique consisting of wet-spinning a water-in-oil emulsion. These fibers are 2.4% by mass drug, which is slowly released, making these fibers potential candidates for implantation as drug delivery devices and/or tissue-engineering substrates. Drug release kinetics and changes in molecular weight were investigated over time. This study demonstrated that drug release rates and molecular weight degradation are a function of the amount of aqueous phase added as an emulsion during fabrication. The type of polymer used (PLLA or PLGA) determines the molecular weight degradation rates, but has little effect on drug release kinetics.

Evaluation of injection augmentation treatment of hyaluronic acid based materials on rabbit vocal folds viscoelasticity
Borzacchiello, A., L. Mayol, et al. (2005), J Mater Sci Mater Med 16(6): 553-7.
Abstract: The viscoelastic properties of vocal folds after injection of hyaluronic acid (hyaluronan, HA) based materials have been studied in an animal model (rabbit) six months after injection. The results indicate that the viscoelastic properties of the vocal folds injected with the HA based materials are similar to the healthy vocal folds (non-injected samples) used as control. Histological analysis has been also performed to investigate on the fate of the injected materials after six months from the implant. The HA based materials remain up to six months and they recruited fibroblasts that induce the ingrowth of new connective tissue resulting in an endogenous soft tissue augmentation. The HA based compounds are good candidate for further studies aimed at restoring/preserving the vibratory capacity of the vocal folds with injection treatment in glottal insufficiency.

Evaluation of mesenchymal stem cells following implantation in alveolar sockets: a canine safety study
De Kok, I. J., S. J. Drapeau, et al. (2005), Int J Oral Maxillofac Implants 20(4): 511-8.
Abstract: PURPOSE: The overall goal of this project was to evaluate culture-expanded bone-marrow-derived mesenchymal stem cells (MSCs) for alveolar bone repair in terms of safety and potential efficacy. MATERIALS AND METHODS: MSCs isolated from bone marrow aspirations were culture-expanded and cryopreserved. Thawed cells were incubated with 3.2 x 5-mm hydroxyapatite/tricalcium phosphate (HA/TCP) cylinders in a closed system containing 5 x 10(7) cells/mL. Cells alone, cell-free constructs, or cell-loaded constructs were rinsed in saline and implanted in extraction sockets in the mandibular second and fourth premolar sites of 14 beagle dogs. Acute reactions were evaluated histologically after 7 or 21 days, and bone formation was examined after 49 days. RESULTS: Neither implanted MSC-related inflammation nor ectopic osteogenesis was observed. At 7 and 21 days, dil-labeled canine MSCs were found in more than 80% of the implant sites. Few canine MSCs were found in neighboring tissue. Mild inflammation present at 7 days diminished by 21 days. After 49 days, measured bone formation was 34%, 25%, and 35% for cell-loaded, cell-free, and untreated sockets, respectively (P <.05). At 21 days, bone formation was evident in all sites. Wound dehiscence was a complication associated with cell exclusionary membranes and resulted in local inflammation. DISCUSSION: The extraction model indicates the safety of MSCs implanted adherent to HA/TCP. Local bone repair occurred in the absence of nonspecific differentiation or migration with distant osteogenesis. CONCLUSIONS: An alveolar socket model may be an appropriate model for initial clinical investigation of MSC-mediated bone repair.

Evaluation of metal implants coated with several types of ceramics as biomaterials
Hayashi, K., N. Matsuguchi, et al. (1989), J Biomed Mater Res 23(11): 1247-59.
Abstract: The in vivo biocompatibility of metals coated with several different types of ceramics [alumina (alpha-Al2O3), titanium oxide (TiO2), titanium nitride (TiN), and hydroxyapatite (HAP)] was investigated. These composites had been devised for the purpose of incorporation into the stem of a total hip prosthesis. The materials were inserted into the mid-diaphyseal region of the femurs of adult dogs, and follow-up quantitative histological comparisons were performed for a period of up to 96 weeks. HAP-coated composites showed the best biocompatibility.

Evaluation of metallic and polymeric biomaterial surface energy and surface roughness characteristics for directed cell adhesion
Hallab, N. J., K. J. Bundy, et al. (2001), Tissue Eng 7(1): 55-71.
Abstract: Directed cell adhesion remains an important goal of implant and tissue engineering technology. In this study, surface energy and surface roughness were investigated to ascertain which of these properties show more overall influence on biomaterial-cell adhesion and colonization. Jet impingement was used to quantify cellular adhesion strength. Cellular proliferation and extracellular matrix secretion were used to characterize colonization of 3T3MC fibroblasts on: HS25 (a cobalt based implant alloy, ASTM F75), 316L stainless steel, Ti-6Al4V (a titanium implant alloy), commercially pure tantalum (Ta), polytetrafluoroethylene (PTFE), silicone rubber (SR), and high-density polyethylene (HDPE). The metals exhibited a nearly five-fold greater adhesion strength than the polymeric materials tested. Generally, surface energy was proportional to cellular adhesion strength. Only polymeric materials demonstrated significant increased adhesion strength associated with increased surface roughness. Cellular adhesion on metals demonstrated a linear correlation with surface energy. Less than half as much cellular proliferation was detected on polymeric materials compared to the metals. However the polymers tested demonstrated greater than twice the amount of secreted extracellular matrix (ECM) proteins on a per cell basis than the metallic materials. Thus, surface energy may be a more important determinant of cell adhesion and proliferation, and may be more useful than surface roughness for directing cell adhesion and cell colonization onto engineered tissue scaffoldings.

Evaluation of modifying collagen matrix with RGD peptide through periodate oxidation
Zhang, L., M. Hum, et al. (2005), J Biomed Mater Res A 73(4): 468-75.
Abstract: The aim of the study is to evaluate the effect of modifying collagen matrices with Arg-Gly-Asp (RGD) peptide through periodate oxidation. The collagen matrices were modified with RGD peptide, by periodate activation. The modified collagen matrices and unmodified matrices were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and electron spectroscopy for chemical analysis (ESCA). Mesenchymal stem cells (MSCs) were used to evaluate the cell compatibility of collagen matrices. In terms of cell growth, the MSCs attached much better on the modified matrix than on the unmodified one. But there was no significant difference between two groups regarding the MSC proliferation. Compared to the unmodified matrices, the mechanical strength of the modified matrix decreased sharply, and its 3D structure was destroyed. Introducing specific RGD receptor-mediated adhesion sites on matrices obviously enhanced the MSC adhesion on collagen matrices, but the coupled method of periodate oxidation would likely result in the declination of the mechanical strength of the matrix, as well as the destruction of the matrix structure. This would affect the cell growth on the matrix, and decrease the histocompatibility of the matrices.

Evaluation of plasma polymerized hexamethylcyclotrisiloxane biomaterials towards adhesion of canine platelets and leucocytes
Chawla, A. S. (1981), Biomaterials 2(2): 83-8.
Abstract: Silicone coated Celgard-2400 and Silastic membranes were prepared by plasma polymerization of hexamethylcyclotrisiloxane. The adhesion of canine platelets and leucocytes was tested by passing whole blood from the anaesthetized mongrel dog in an ex-vivo shunt system. The silicone control Celgard and silicone coated Silastic membranes had fewer platelets and fewer leucocytes compared to those on the control Silastic membranes. Furthermore, these blood cells underwent fewer morphological changes on the silicone coated Celgard and Silastic compared to those on the control Silastic. From these observations the silicone coated biomaterials were judged to be better than the Silastic as far as the adhesion of platelets and leucocytes are concerned.

Evaluation of platelet-rich plasma in combination with freeze-dried bone in the rabbit cranium. A pilot study
Aghaloo, T. L., P. K. Moy, et al. (2005), Clin Oral Implants Res 16(2): 250-7.
Abstract: Platelet-rich plasma (PRP) offers a new and potentially useful adjunct to allograft materials in oral and maxillofacial bone and implant reconstructive surgery. This study compares bone healing in four cranial defects in the rabbit grafted with freeze-dried mineralized bone (FMB) alone, FMB+PRP, freeze-dried demineralized bone (FDDB) alone, and FDDB+PRP. Fifteen New Zealand white rabbits were included in this randomized, blind, prospective pilot study. Four equal 8 mm diameter defects were created in each rabbit cranium and immediately grafted with the above materials. Five rabbits were evaluated at 1, 2, and 4 months. Radiographically, FMB+PRP showed a tendency toward increased bone density over FMB alone, but was not statistically significant (P>0.05), and FDDB+PRP showed a tendency toward increased bone density over FDDB alone, but was not statistically significant (P>0.05). Histomorphometrically, FMB+PRP showed a tendency toward increased bone area over FMB alone at 1 and 4 months, but was not statistically significant (P>0.05), and FDDB+PRP showed a tendency toward increased bone area over FDDB alone, at 1 and 2 months, but was not statistically significant (P>0.05). This study failed to show a radiographic or histomorphometric increase in bone formation with the addition of PRP to either FMB or FDDB in non-critical-sized defects in the rabbit cranium.

Evaluation of polyphosphates and polyphosphonates as degradable biomaterials
Richards, M., B. I. Dahiyat, et al. (1991), J Biomed Mater Res 25(9): 1151-67.
Abstract: A series of polymers, bisphenol A-based poly(phosphoesters), were evaluated as degradable biomaterials. Degradation was observed for the four polymers studied under both in vitro and in vivo conditions. The rate of degradation was affected by polymer side-chain structure and correlated with the swelling behavior. The ethyl side-chain polymers absorbed more water than their phenyl counterparts. Among the sterilization methods, UV irradiation followed by antibiotic treatment was the most suitable, as steam autoclave and ethylene oxide treatments altered the properties of several of the poly (phosphoesters). Tissue response to the poly(phosphoesters) in rabbits was characterized by minor encapsulation and slight or no lymphocyte, giant cell, or macrophage activity. No evidence of edema or necrosis was found. The elastic moduli of these materials varied from 488 MPa for poly(bisphenol A-ethylphosphate) (BPA/EOP) to 627 MPa for the more rigid poly(bisphenol A-phenylphosphonate) (BPA/PP). The ultimate strength, modulus, and energy to failure of BPA/PP were lower than those of similarly compression molded high-molecular-weight poly(L-lactic acid) (PLLA).

Evaluation of proliferation and functional differentiation of LLC-PK1 cells on porous polymer membranes for the development of a bioartificial renal tubule device
Sato, Y., M. Terashima, et al. (2005), Tissue Eng 11(9-10): 1506-15.
Abstract: To develop a bioartificial renal tubule system using renal tubular cells and porous polymer membrane hollow fibers, long-term maintenance of a confluent monolayer and the functionally differentiated condition of cells is essential. We examined the proliferation and functional differentiation of LLC-PK1 (Lewis-lung cancer porcine kidney 1) cells on two types of membranes: polysulfone and cellulose acetate. Cell proliferation was significantly higher on the polysulfone membrane than on the cellulose acetate membrane, and was enhanced by coating the membranes with various extracellular matrices. Confluent monolayer formation of cells was observed on matrix-coated polysulfone membrane but not on matrix-coated cellulose acetate membrane within 1 week. Cell proliferation continued for 3 weeks after confluent monolayer formation. Messenger RNA (mRNA) expression of glucose transporters, indicators of the functional differentiation of the LLC-PK1 cells, was observed in the polysulfone and cellulose acetate membrane groups, but was not observed in the nonporous polystyrene plate group under subconfluent conditions. Expression of glucose transporters mRNA was maintained for 3 weeks after confluent monolayer formation. Polysulfone membrane is more suitable than cellulose acetate membrane for a bioartificial renal tubule system with regard to LLC-PK1 cell proliferation. Extracellular matrix coating of the membrane further improves cell proliferation.

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