Cytological evaluation of the tissue-implant reaction associated with subcutaneous implantation of polymers coated with titaniumcarboxonitride in vivo

The aim of the present study was to evaluate the influence of titanium-coated polymers on the inflammatory response and remodeling of connective tissue during wound-healing processes. Discs of polyethyleneterephthalate (PET) and silicone as well as high-weight meshes of polypropylene (PP) were coated with a titaniumcarboxonitride (Ti(C,N,O)) layer by a plasma-assisted chemical vapor deposition process (PACVD) and implanted subcutaneously in the dorsal lumbar region of Wistar rats. Light microscopic and histological evaluation of capsule thickness, capsule quality, implant-tissue interface and collagen composition was performed 7, 14, 21 and 28 days post-operatively. All implants were surrounded by a fibrous capsule with decreasing thickness after 2-4 weeks post-implantation. Titaniumcarboxonitride-coated polymers showed no significant differences in capsule thickness and inflammatory cellular response. An increased collagen type III/I ratio, especially for titaniumcarboxonitride-coated materials, was found in week one after implantation remaining elevated up to week 4. This might be associated with disordered collagen metabolism and immature scar reaction. In contrast to previous in vitro experiments, Ti-coating of polymers did not improve biocompatibility after subcutaneous implantation in rats. Material reduction to low-weight meshes and enlargement of pore size may demonstrate a benefit of Ti-coated meshes with an increased biocompatibility.     

In vivo biodegradability and biocompatibility evaluation of novel alanine ester based polyphosphazenes in a rat model

Amino acid ester substituted polyphosphazenes are attractive candidates for various biomedical applications because of their biocompatibility, controllable hydrolytic degradation rates, and nontoxic degradation products. In this study, the biocompatibility of three L-alanine ethyl ester functionalized polyphosphazenes was evaluated in a subcutaneous rat model. The polymers used in the study were poly[bis(ethylalanato)phosphazene] (PNEA), poly[(50% ethylalanato) (50% methylphenoxy) phosphazene] (PNEA(50)mPh(50)), and poly[(50% ethylalanato)(50% phenyl phenoxy) phosphazene] (PNEA(50)PhPh(50)). Polymer disks of diameter 7.5 mm were prepared by a solvent evaporation technique and were implanted subcutaneously in rats. After 2, 4, and 12 weeks, the polymer along with the surrounding tissues were excised, prepared, and viewed by light microscopy to evaluate the tissue responses of the implanted polymers. The tissue responses were classified as minimal, mild, or moderate, based on a biocompatibility scheme developed in our laboratory. Minimal inflammation was characterized by the presence of few neutrophils, erythrocytes, and lymphocytes; mild response was characterized by the predominant presence of macrophages, fibroblasts, or giant cells; and moderate inflammation was characterized by the abundance of macrophages, giant cells, and by the presence of tissue exudates. The in vivo degradation profiles of the polymers at various time points were evaluated by gel permeation chromatography (GPC). PNEA and PNEA(50)mPh(50) matrices elicited varying levels of tissue responses during the 12-week implantation period. At 2 weeks both polymers evoked a moderate response, and by 12 weeks the response was found to be mild. However, PNEA(50)PhPh(50) elicited a mild response at the end of 2 weeks and demonstrated a further decreased inflammatory response after 12 weeks. The in vivo degradation of the polymers was followed by determining the molecular weights of the explanted polymer disks. PNEA and PNEA(50)mPh(50) disks showed significant decrease in molecular weight after 2 weeks of implantation. The molecular weights of PNEA and PNEA(50)mPh(50) residues could not be determined by GPC after 12 weeks of implantation because of almost complete degradation. On the other hand the in vivo degradation of PNEA(50)PhPh(50) was found to be slow, with a 63% loss in molecular weight in 12 weeks. Furthermore, this polymer maintained its shape and structure during the entire study. Thus, these polymers demonstrated excellent tissue compatibility and in vivo biodegradability and can be potential candidates for various biomedical applications.     

Bioerodible polyanhydrides as drug-carrier matrices. II. Biocompatibility and chemical reactivity

The biocompatibility of bioerodible polyanhydrides and toxicology of the polymer breakdown products were assessed. Poly-[bis (p-carboxy-phenoxy) propane anhydride] (PCPP), Poly(terephthalic acid anhydride) (PTA), and their copolymers with sebacic acid were tested. The polymers did not provoke inflammatory responses in the corneas of rabbits over a six week implantation period. Subcutaneous implantation studies of PCPP in rats over a six month period showed no evidence of inflammatory cells and only slight tissue encapsulation by layers of fibroblastic cells. The degradation products of the polymers were nonmutagenic, noncytotoxic, and had a low teratogenic potential. The in vitro growth of mammalian cells on the polymers was unaffected as measured by cell morphology and cell growth rate. The chemical reactivity of the polyanhydrides with reactive model drugs, para substituted anilines, was also examined. Amides were formed when the drugs were injection molded with the polyanhydrides at 120 degrees C. However, no reaction was observed using compression molding at room temperature. No reaction occurred between the polymer and the drug during the hydrolytic degradation of the matrix at 37 degrees C.     

Biocompatibility studies on plasma polymerized interface materials encompassing both hydrophobic and hydrophilic surfaces.

The biocompatibility of radiofrequency plasma polymerized films (less than 100 nm thick) deposited on biomedical polymer supports has been characterized by in vitro and in vivo methods. The polymer interface materials covered a wide range of elemental composition and surface properties, and were prepared from N-vinyl-2-pyrrolidone, gamma-butyrolactone, n-hexane, and hexamethyldisilazane (PPHMDSZ). The biocompatibility studies showed that the interface materials were noncytotoxic to mouse and human fibroblasts, as shown by morphologic evaluation, and by determination of extracellular LDH; and they did not stimulate interleukin-1-like production from human monocytes, as indicated by a thymocyte proliferation assay. The human fibroblast proliferation assay showed that three of the polymers supported cell growth at levels comparable to, or greater than, polymer controls, while the hydrophobic PPHMDSZ inhibited both cell attachment and proliferation. The response to subcutaneous implantation for all test materials was indicative of biocompatibility, with rapid resolution of the acute phase response and normal wound healing. The wide range of composition and surface properties for the plasma polymerized films evaluated in this study suggest that this general class of materials is likely to exhibit excellent biocompatibility.     

聚-(3-羟丙基)-DL-天冬酰胺组织相容性的初步观察

药物控释高分子材料要求有良好的生物相容性。我们对聚－（３－羟丙基）－ＤＬ－天冬酶胺（ＰＨＰＡ）材料进行了皮下埋植实验、组织病理学观察、血生化和微核等检测,早期,在埋植部位出现了异物反应,第１３天部分小鼠肝组织小血管边出现轻度炎症反应,３４ｄ上述反应逐渐减轻或消失,肝肾组织细胞形态和功能基本正常,实验表明,ＰＨＰＡ具有良好的生物相容性。     

Surface characteristics, mechanical properties, and cytocompatibility of oxygen plasma-implanted porous nickel titanium shape memory alloy

Good surface properties and biocompatibility are crucial to porous NiTi shape memory alloys (SMA) used in medical implants, as possible nickel release from porous NiTi may cause deleterious effects in the human body. In this work, oxygen plasma immersion ion implantation (O-PIII) was used to reduce the amount of nickel leached from porous NiTi alloys with a porosity of 42% prepared by capsule-free hot isostatic pressing. The mechanical properties, surface properties, and biocompatibility were studied by compression tests, X-ray photoelectron spectroscopy (XPS), and cell culturing. The O-PIII porous NiTi SMAs have good mechanical properties and excellent superelasticity, and the amount of nickel leached from the O-PIII porous NiTi is much less than that from the untreated samples. XPS results indicate that a nickel-depleted surface layer predominantly composed of TiO(2) is produced by O-PIII and acts as a barrier against out-diffusion of nickel. The cell culturing tests reveal that both the O-PIII and untreated porous NiTi alloys have good biocompatibility.     

In vivo biocompatibility and biodegradation of 3D-printed porous scaffolds based on a hydroxyl-functionalized poly(ε-caprolactone)

The aim of this study was to evaluate the in vivo biodegradation and biocompatibility of three-dimensional (3D) scaffolds based on a hydroxyl-functionalized polyester (poly(hydroxymethylglycolide-co-ε-caprolactone), PHMGCL), which has enhanced hydrophilicity, increased degradation rate, and improved cell-material interactions as compared to its counterpart poly(ε-caprolactone), PCL. In this study, 3D scaffolds based on this polymer (PHMGCL, HMG:CL 8:92) were prepared by means of fiber deposition (melt-plotting). The biodegradation and tissue biocompatibility of PHMGCL and PCL scaffolds after subcutaneous implantation in Balb/c mice were investigated. At 4 and 12 weeks post implantation, the scaffolds were retrieved and evaluated for extent of degradation by measuring the residual weight of the scaffolds, thermal properties (DSC), and morphology (SEM) whereas the polymer was analyzed for both its composition ((1)H NMR) and molecular weight (GPC). The scaffolds with infiltrated tissues were harvested, fixed, stained and histologically analyzed. The in vitro enzymatic degradation of these scaffolds was also investigated in lipase solutions. It was shown that PHMGCL 3D-scaffolds lost more than 60% of their weight within 3 months of implantation while PCL scaffolds showed no weight loss in this time frame. The molecular weight (M(w)) of PHMGCL decreased from 46.9 kDa before implantation to 23.2 kDa after 3 months of implantation, while the molecular weight of PCL was unchanged in this period. (1)H NMR analysis showed that the degradation of PHMGCL was characterized by a loss of HMG units. In vitro enzymatic degradation showed that PHMGCL scaffolds were degraded within 50 h, while the degradation time for PCL scaffolds of similar structure was 72 h. A normal foreign body response to both scaffold types characterized by the presence of macrophages, lymphocytes, and fibrosis was observed with a more rapid onset in PHMGCL scaffolds. The extent of tissue-scaffold interactions as well as vascularization was shown to be higher for PHMGCL scaffolds compared to PCL ones. Therefore, the fast degradable PHMGCL which showed good biocompatibility is a promising biomaterial for tissue engineering applications.     

Biostability and blood-contacting properties of sulfonate grafted polyurethane and Biomer.

Sulfonate-containing polyurethanes were evaluated for in vivo biodegradation using subcutaneously implanted tensile bars. In addition, these anionically charged polyurethanes were evaluated for in vivo activation of human complement C3a and ex vivo platelet deposition in arteriovenously-shunted canines. The sulfonate derivatized polymers included laboratory synthesized polyurethane and Biomer. Other polymers used for references included Intramedic polyethylene, Silastic and a poly(ethylene oxide) based polyurethane. The biodegradation results indicated that Biomer and the laboratory sulfonated Biomer (both manufactured with stabilizers), remained mechanically stable, retaining both tensile strength and elasticity after 4 weeks of subcutaneous implantation. The unstabilized polyurethanes (with or without sulfonation), however, showed marked cracking and a loss of mechanical properties after the same period of subcutaneous implantation. Sulfonated polyurethanes depressed human complement C3a activation in plasma, as indicated by decreased levels of anaphylatoxin production. The results of canine ex vivo blood contacting experiments were conducted in both an acute and chronic model and demonstrated decreased platelet deposition and activation for the sulfonated polyurethanes.     

Biocompatibility of supercritical CO2-treated titanium implants in a rat model

Supercritical phase CO2 is a promising method for sterilizing implantable devices and tissue grafts. The goal of this study is to evaluate the biocompatibility of titanium implants sterilized by supercritical phase CO2 in a rat subcutaneous implantation model. At 5 weeks post implantation titanium implants sterilized by supercritical phase CO2 produce a soft tissue reaction that is comparable to other methods of sterilization (steam autoclave, ultraviolet light radiation, ethylene oxide gas, and radio-frequency glow-discharge), as indicated by the thickness and density of the foreign body capsule, although there were some differences on the capillary density. Overall the soft tissue response to the implants was similar among all methods of sterilization, indicating supercritical phase CO2 treatment did not compromise the biocompatibility of the titanium implant.     

Biostability and blood-contacting properties of sulfonate grafted polyurethane and Biomer

Sulfonate-containing polyurethanes were evaluated for in vivo biodegradation using subcutaneously implanted tensile bars. In addition, these anionically charged polyurethanes were evaluated for in vivo activation of human complement C3a and ex vivo platelet deposition in arteriovenouslyshunted canines. The sulfonate derivatized polymers included laboratory synthesized polyurethane and Biomer. Other polymers used for references included Intramedic^TM polyethylene, Silastic^TM and a poly(ethylene oxide) based polyurethane. The biodegradation results indicated that Biomer and the laboratory sulfonated Biomer (both manufactured with stabilizers), remained mechanically stable, retaining both tensile strength and elasticity after 4 weeks of subcutaneous implantation. The unstabilized polyurethanes (with or without sulfonation), however, showed marked cracking and a loss of mechanical properties after the same period of subcutaneous implantation. Sulfonated polyurethanes depressed human complement C3a activation in plasma, as indicated by decreased levels of anaphylatoxin production. The results of canine ex vivo blood contacting experiments were conducted in both an acute and chronic model and demonstrated decreased platelet deposition and activation for the sulfonated polyurethanes.     

Development and evaluation of biocompatible inks for the local measurement of oxygen using in vivo EPR

In vivo EPR oximetry is a powerful minimally invasive method that allows the measurement of oxygen in tissues through the use of a paramagnetic probe. In the present study, we investigated new strategies for preparing biocompatible inks containing carbon black particles (Printex U), which could be used as oxygen sensors. The carbon black particles were dispersed in solutions of biocompatible polymers of carboxy methyl cellulose (CMC), hydroxypropyl methyl cellulose (HPMC) or polyvinyl pyrrolidone (PVP). A total of 12 polymers with different molecular weights were tested. A physico-chemical characterization of the inks was carried out to assess the sedimentation of the particles, the rheological behavior of these inks, and the relative diffusion of the inks. The preparations with CMC and PVP had the highest viscosity and stability. The presence of the polymers did not modify the calibration curves (EPR linewidth as a function of the pO2) of the carbon black. In vivo, the oxygen sensors were stable for at least one month in muscles as the EPR linewidth remained fully sensitive to induced ischemia or carbogen challenge. The calibration curve was not modified after this period of implantation. A first study of biocompatibility was carried out in vitro (hemolysis and cytotoxicity assay) and in vivo (histological examination). No sign of toxicity was observed using these inks. These preparations are good candidates for future in vivo studies including clinical trials.     

Effect of calcium and phosphorus ion implantation on the corrosion resistance and biocompatibility of titanium

This paper is concerned with the corrosion resistance and biocompatibility of titanium after surface modification by the ion implantation of calcium or phosphorus or calcium + phosphorus. Calcium and phosphorus ions were implanted in a dose of 10(17) ions/cm(2). The ion beam energy was 25 keV. The microstructure of the implanted layers was examined by TEM. The chemical composition of the surface layers was determined by XPS and SIMS. The corrosion resistance was examined by electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 degrees C. The biocompatibility was evaluated in vitro. As shown by TEM results, the surface layers formed during calcium, phosphorus and calcium + phosphorus implantation were amorphous. The results of the electrochemical examinations (Stern's method) indicate that the calcium, phosphorus and calcium + phosphorus implantation into the surface of titanium increases its corrosion resistance in stationary conditions after short- and long-term exposures in SBF. Potentiodynamic tests show that the calcium-implanted samples undergo pitting corrosion during anodic polarisation. The breakdown potentials measured are high (2.5 to 3 V). The good biocompatibility of all the investigated materials was confirmed under the specific conditions of the applied examination, although, in the case of calcium implanted titanium it was not as good as that of non-implanted titanium.     

The influence of implantation site on the biocompatibility and survival of alginate encapsulated pig islets in rats

This work investigated the impact of implantation sites on the biocompatibility of alginate encapsulated pig islets. Non-diabetic rats were implanted with adult pig islets encapsulated in alginate either intraperitoneally (IP; n=25), subcutaneously (SC; n=37) or under the kidney capsule (KC; n=34). Capsule biocompatibility (retrieval rate, capsule diameter, degree of capsule broken and cellular overgrowth, CD68/CD3 staining) as well as islets viability and functionality were assessed until 30 days after transplantation. Implantation site did not significantly influence the biocompatibility of empty alginate capsules after transplantation (n=48). Most of the empty capsules (>90%) were retrieved after harvesting and were free of cellular overgrowth until day 30 post-transplantation. Three days after implantation, no significant difference for encapsulated pig islets was observed in terms of capsule biocompatibility and islet functionality in peritoneum, KC or subcutaneously. However, between days 5 and 30 after transplantation, explanted capsules from IP demonstrated a higher degree of broken capsules (>13%) and capsules with severe cellular overgrowth (>50%, CD68+ infiltration) than capsules removed from SC and KC (p<0.05). This was associated with a significant reduction of islet viability, insulin content and insulin secretion. In rats, the peritoneum site seems not appropriate for promoting the engraftment of encapsulated pig islets. Kidney subcapsular and subcutaneous spaces represent an interesting alternative.     

In vivo biocompatibility studies. VII. Inflammatory response to polyethylene and to a cytotoxic polyvinylchloride

The cellular biocompatibility of low-density polyethylene and a cytotoxic polyvinylchloride were investigated using an in vivo cage implant system. Components of the inflammatory response (white cells, extra-cellular alkaline and acid phosphatase, the complement component C3, and total protein content) were monitored over a 21-day implantation period. Scanning electron microscopy was used to evaluate the morphologic condition of leukocytes adherent to the implanted polymers. Prior to implantation, each polymer was evaluated using an established primary acute toxicity screen. The results showed that the cytotoxic polyvinylchloride stimulated an intense acute phase inflammatory response, and at later observation periods, an intense and increasing chronic inflammatory response. In contrast, the polyethylene promoted relatively small increases in the acute and chronic phases of inflammation; the overall cellular response being essentially resolved by the third week after implantation. The initial toxicity screen of each polymer suggested that the observed differences in inflammation were primarily caused by the release from the polyvinylchloride of the added cytotoxic agent (dioctyltinbisoctylmercaptoacetate).     

Biocompatibility of chemoenzymatically derived dextran-acrylate hydrogels

The biocompatibility of chemoenzymatically generated dextran-acrylate hydrogels has been evaluated in vitro, using human foreskin fibroblasts, and in vivo, by subcutaneous and intramuscular implantation in Wistar rats for up to 40 days. In vitro tests show that hydrogel extracts only minimally reduced (<10%) the mitochondrial metabolic activity of fibroblasts. Direct contact of the hydrogels with cells induced a cellular proliferation inhibition index (CPII) of 50-80%, compared with a control, whereas through indirect contact, the CPII values were <16%, suggesting that the high CPII values achieved in the direct assay test were likely due to mechanical stress or limitations in oxygen diffusion. Hence, the hydrogels were noncytotoxic. Moreover, cell-material interaction studies show that these hydrogels were nonadhesive. Finally, histologic evaluation of tissue response to subcutaneous and intramuscular implants showed acceptable levels of biocompatibility, as characterized by a normal cellular response and the absence of necrosis of the surrounding tissues of the implant. In the first 10 days, the foreign-body reaction in the intramuscular implantation was more severe than in subcutaneous implantation, becoming identical after 30 days. In both cases, dextran hydrogels did not show signs of degradation 6 weeks postimplantation and were surrounded by a thin fibrous capsule and some macrophages and giant cells. This response is typical with a number of nondegradable biocompatible materials. These results indicate that dextran hydrogels are biocompatible, and may have suitable applications as implantable long-term peptide/protein delivery systems or scaffolds for tissue engineering.     

Effect of dual ion implantation of calcium and phosphorus on the properties of titanium

This study is concerned with the effect of dual implantation of calcium and phosphorus upon the structure, corrosion resistance and biocompatibility of titanium. The ions were implanted in sequence, first Ca and then P, both at a dose of 10(17) ions/cm2 at a beam energy of 25 keV. Transmission electron microscopy was used to investigate the microstructure of the implanted layer. The chemical composition of the implanted layer was examined by XPS and SIMS. The corrosion resistance was determined by electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 degrees C. The biocompatibility tests were performed in vitro in a culture of human-derived bone cells (HDBC) in contact with the tested materials. The viability of the cells was determined by an XTT assay and their activity by the measurements of the alkaline phosphatase activity in contact with implanted and non-implanted titanium samples. The in vitro examinations confirmed that, under the conditions prevailing during the experiments, the biocompatibility of Ca + P ion-implanted titanium was satisfactory. TEM results show that the surface layer formed by the Ca + P implantation is amorphous. The corrosion resistance of titanium, examined by the electrochemical methods, appeared to be increased after the Ca + P ion implantation.     

The biocompatibility of a dental Ag-Pd-Cu-Au-based casting alloy and its structural components

The biocompatibility of type III casting gold alloy, an Ag-Pd-Cu-Au-based dental casting alloy and its two main structural components, a CuPd-rich and an Ag-rich phase, was studied after subcutaneous implantation for 7 weeks in 20 guinea pigs. The Ag-Pd-Cu-Au alloy was surrounded by a capsule of immature collagen with fibroblasts and an increased vascular supply. The CuPd-rich component induced and maintained an acute inflammation with highly vascularized granulation tissue. The tissue reaction to the Ag-rich component and the Au-based alloy was slight. Ten of the guinea pigs were sensitized to PdCl2 prior to the implantation period, but this caused no enhanced tissue reaction, except for an increase in the number of mast cells around three of the alloys.     

聚乳酸共混聚三亚甲基碳酸酯生物膜的生物性能表征及动物实验研究

聚乳酸是一种很好的生物材料，具有很好的生物相容性及可降解性。在第一代聚乳酸膜的基础上我们研制了聚乳酸共混聚三亚甲基碳酸酯（PTMC）生物软膜，并对该复合材料进行了一系列的生物性能表征，包括细胞毒性实验、急性毒性实验、皮肤刺激实验、致敏实验、溶血实验、微核实验及皮下植入实验。结果表明，共混膜无毒，无刺激，无致敏作用，不引起溶血，试验材料组微核率为1．3％士1．0％，小于3％，骨髓微核实验呈阴性。皮下植入后各个时期伤口无红肿、化脓、坏死等现象。在应用于家兔术后预防肠黏连的实验研究中，生物软膜表现出很好的实验效果。结论：聚乳酸共混聚三亚甲基碳酸酯软膜具有很好的生物相容性。     

An in vivo Biocompatibility Assessment of MEMS Materials for Spinal Fusion Monitoring

The site-specific biocompatibility of silicon chips and commercially available silicon pressure sensor die were evaluated after implantation in caprine (goat) spine. Surgical procedures were developed to insert silicon chips into the nucleus pulposus regions of the lumbar discs and pressure sensors into autologous bone grafts for cervical spine fusion. After a six-month implantation period, the animal was sacrificed and the spinal segments were meticulously harvested and analyzed for local tissue response via gross examination and histological techniques. Gross examination of cervical and lumbar spinal segments after harvest and dissection did not reveal any visible signs of adverse reactions to the MEMS materials. Furthermore, the surrounding tissues and musculature for both spinal regions were devoid of necrosis. Histological analysis of compromised spinal segments did not reveal evidence of any adverse foreign body response by the caprine spinal tissue to the implanted MEMS materials. These preliminary results support the further development of a spinal fusion monitoring system based on implantable MEMS sensors.     

Influence of polysaccharide composition on the biocompatibility of pullulan/dextran-based hydrogels

The implantation of a biomaterial for tissue engineering requires the presence of a suitable scaffold on which the tissue repair and regeneration will take place. Polymers have been frequently used for that purpose because they show similar properties to that of the natural extracellular matrix. Scaffold properties and biocompatibility are modulated by the composition of the polymers used. In this work four polysaccharide-based hydrogels (PSH) made of dextran and pullulan were synthesized. Their in vitro properties were determined and then tested in vivo in a rat model. As pullulan concentration increased in dextran hydrogels, the glass transition temperature and the maximum modulus decreased. In vitro degradation studies for 30 days demonstrated no significant degradation of PSH except for 100% pullulan hydrogel. In vivo tissue response evaluated 30 days after PSH subcutaneous implantation in rats indicated that all PSH were surrounded by a fibrous capsule. Adding pullulan to dextran induced an increased inflammatory reaction compared to PSH-D(100% dextran) or PSH-D(75)P(25)(75% dextran). This in vitro and in vivo data can be used in the design of hydrogels appropriate for tissue engineering applications.