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Results for “Biocompatible Materials”

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PubMed1994

Formation, derivatization and applications of bacterial cellulose.

Acetobacter xylinum produces highly crystalline cellulose extracellularly using glucose as a carbon source. The polymer formed is free of other biogenic compounds, separable in a simple way and characterized by its high water-absorption capacity. Stepwise solvent exchange from water to unpolar solvents leads to a drastic decrease of the water content of the bacterial cellulose without decrease of the highly swollen and activated state. Heterogeneous as well as homogeneous derivatizations, e.g. carboxymethylation, silylation and acetylation, were performed on the wet or dried biopolymer. Furthermore, different methods for formation of hollow fibres during biosynthesis were investigated. Such tubes may have applications as biocompatible material in medicine.

Absorption↗

PubMed2002

Effects of systematic variation of amino acid sequence on the mechanical properties of a self-assembling, oligopeptide biomaterial.

In order to elucidate design principles for biocompatible materials that can be created by in situ transformation from self-assembling oligopeptides, we investigate a class of oligopeptides that can self-assemble in salt solutions to form three-dimensional matrices. This class of peptides possesses a repeated sequence of amino acid residues with the type: hydrophobic/negatively-charged/hydrophobic/positively-charged. We systematically vary three chief aspects of this sequence type: (1) the hydrophobic side chains; (2) the charged side chains; and (3) the number of repeats. Each of these has been previously shown to influence the self-assembly properties of these materials. Employing a rheometric assay we measure the shear modulus of gels created from variants of each of these aspects. First, we observe order-of-magnitude changes in shear moduli when we vary oligopeptide length, with biphasic dependence on length. This result may be due to competition between, in short oligopeptides, additional repeats either increasing the diameter of the filaments or increasing the area of interaction between individual molecules and, in large oligopeptides, additional repeats allowing the oligopeptides to fold back upon themselves and decrease their effective length. Second, no statistically significant difference is observed among the hydrophobic variants, suggesting that hydrophobicity and steric overlap are unlikely to play a significant role in filament mechanical properties. Finally, in variation of the charged side chains we observe a small difference in the shear moduli that, if significant, may mean that decreasing the energetic penalty for dehydrating the charged side chains can lead to a stiffer matrix. Overall, we demonstrate that it is possible to achieve order-of-magnitude changes in shear modulus by simple variations of oligopeptide length, while the residue substitutions affect only self-assembly properties. Thus, diverse aspects of these molecules can be designed rationally to yield desirable materials properties of different types.

Amino Acid Sequence↗

PubMed1997

Evaluation of the frictional properties of an elastomer with enhanced lipid-adsorbing ability.

Wear particle production in load-bearing orthopaedic implants is one of the major factors currently limiting the service life of the implant. Most of the research carried out to date in attempting to solve this problem has used the approach of finding more wear-resistant biocompatible material pairs. In contrast, other researchers have attempted to reduce wear by encouraging elastohydrodynamic film formation through the use of elastomeric bearing surfaces. Unfortunately, these elastomeric bearing surfaces have poor tribological properties when a fluid film is not present. Boundary lubrication of an elastomeric orthopaedic bearing may alleviate some of these difficulties. The purpose of this research was to fabricate and characterize an elastomeric material that had a surface capable of specifically adsorbing a naturally occurring boundary lubricant. Dipalmitoyl phosphatidylcholine (DPPC) has been previously shown to be able to act as a boundary lubricant at stresses that occur in human load-bearing joints such as the hip and knee; therefore, DPPC was chosen for use in this study. It was expected that in an aqueous liposome suspension the static coefficient of friction microseconds of such a material would be lower, and increase less quickly over time, than a similar material without an ability to adsorb specifically DPPC when articulated against a polished chrome steel ball bearing. The lipid-adsorbing elastomer did not possess the desired tribological properties. This result was attributed to the polymer adsorbing the DPPC in the liposome phase and not in the bilayer phase, and interaction among the polymeric surface, DPPC and water. This approach to lubricating orthopaedic bearings was shown to have some merit, but a great deal of work needs to be done before such an approach can be used on a clinically available material.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2000

Advances in ureteral stent technology.

This review focuses on technological advances and relevant research related to ureteral stents. The importance of physical and chemical biomaterial type, biocompatibility, material coatings such as hydrogels, and infection related to indwelling ureteral stents are discussed. Recent in vitro and in vivo research has focused on materials that will reduce encrustation and bacterial biofilm formation. The adsorption of antimicrobials onto devices holds promise of reducing infection rates, but multidrug resistant bacteria, short leaching times and adverse side effects make it essential that alternative strategies be investigated. Just so, encrustation limits the long-term use of urinary materials, and a better understanding of factors involved in encrustation are needed to reduce the problem.

Biocompatible Materials↗

PubMed1997

Evaluation of the biocompatibility of a nonceramic hydroxyapatite.

In this study, the biocompatibility of calcium phosphate cement (CPC) was systematically investigated, which included systemic injection acute toxicity assay, cell culture cytotoxicity assay, gene mutation assay (Ames test), chromosome aberration assay (micronucleus test), DNA damage assay (unscheduled DNA synthesis test) and implant histological evaluation. The results showed that the CPC had no toxicity and all tests for mutagenicity and potential carcinogenicity of CPC extracts are negative. CPC was implanted into the femurs of rabbits under no-load condition and the histology of specimens revealed that the implant tightly joined with the surrounding bone, only a very slight histological inflammatory reaction occurred. Thus, CPC is a highly biocompatible material and seems to be safe for application in humans.

Animals↗

PubMed2004

Biofabrication: using biological materials and biocatalysts to construct nanostructured assemblies.

Emerging opportunities are placing greater demands on device fabrication: next-generation microelectronics will need minimum features of less than 100 nm, high-throughput drug screening will require facile methods to incorporate sensitive biological components into microelectromechanical systems (MEMS), and implantable devices will need to be built from biocompatible materials. Increasingly, these emerging demands are being addressed by combining traditional microfabrication methods with 'biofabrication': namely, the use of biologically derived materials and biocatalysts. Recent fabrication techniques are using biological construction materials as process aids or structural components, and enzymes are being considered for their potential to fabricate devices with high selectivity under mild conditions. If incompatibilities between biology and microfabrication can be eliminated, then biofabrication will be poised to emerge as the standard for nanoscale construction.

Animals↗

PubMed2006

A knitted, fibrin-covered polycaprolactone scaffold for tissue engineering of the aortic valve.

State-of-the-art tissue engineered heart valves are not strong enough to withstand aortic blood pressure levels. When a strong and slowly degrading scaffold is used, the starting position of valvular tissue engineering is a stronger valve and seeded cells are allowed more time to create a strong extracellular matrix. A polycaprolactone knitted patch with leaflets was developed as a valvular scaffold. It was sutured into a tube and covered with fibrin gel. The opening and closing behavior and leakage of knitted scaffolds without cells were studied and compared to those of stentless porcine valves. An MTT test was performed on polycaprolactone and fibrin. A loading device was developed to study the durability of the knitted scaffold. The scaffold showed proper opening and it showed coaptation upon closing, but a 39 +/- 3% (n = 3) leakage, compared to a 8 +/- 1% (n = 3) leakage of tested porcine valves. MTT tests showed that polycaprolactone and fibrin are biocompatible materials. Durability testing of the knitted scaffold (n = 1) did not show rupture after ten million loading cycles. A tissue engineering process that includes cell culture will have to show whether this scaffold, besides mechanically reliable and biocompatible, is suitable to lead to a functional, nonregurgitant, durable aortic valve.

Aortic Valve↗

PubMed2003

Investigation of the bone tissue response to glass-ionomer microimplants in the canine maxillary alveolar ridge.

This paper reports the results of experimental use of glass-ionomer microimplants in the augmentation of the maxillary alveolar ridge in dogs. The study included ten adult mongrel dogs 5 years of age, weighing between 50 and 70 pounds (25-30 kg), divided into 2 groups of 5 dogs each. In both groups, the maxillary 4th premolar and 1st molar were removed after the elevation of a buccal mucoperiosteal flap. The alveolar bone adjacent to the extracted teeth was also removed. In the experimental group (5 dogs), Ionogran a glass-ionomer microimplants (GIMIs) (Ionogran particle size of 0.5-1.0 mm, IONOS Medizinische Produkte GmbH & Co. KG, D-8031 Seefeld, Gemany) were used for augmentation and were inserted in the created defects. The extraction sockets and bone defects were augmented with an average amount of 2 g of GIMIs. In the control group, the bone defects were left unfilled as a control for bone healing. Histological examination showed that the glass-ionomer microimplants were extremely osteoconductive and inert materials. Stimulation of growth of new bone tissue in contact with the glass-ionomer microimplants was evident. No inflammatory cells were detected on or adjacent to the GIMIs. In the control group, incomplete bone healing with fibrous scar tissue and inflammatory cells was noted. These results indicate that glass-ionomer microimplants represent highly osteoconductive and biocompatible materials for use in bone surgery.

Aluminum Silicates↗

PubMed2006

[Role of conditioning medium cytotoxicity. An example with an intraocular lens preloaded in injector].

INTRODUCTION: Following material vigilance cases encountered with the hydrophilic acrylic intraocular lens, ACR6D SE preloaded in the Premier shooter, we studied the cytotoxicity of the intraocular lens and its conditioning to identify the cytotoxic element. We proposed medical device modification to improve its biocompatibility. MATERIALS AND METHODS: Biocompatibility-cytotoxicity assays were carried out according to ISO 10993-5 recommendations. Tests were performed on the SRA 01/04 human lens epithelial cell line. Neutral red, Hoechst 33342, and YO-PRO-1 fluorescent probes were used to assess membrane integrity, total DNA, and membrane fluidity, respectively. Materials samples were prepared in culture medium according to the ISO 10993-5 elution procedure. Pure saline solutions and conditioning liquids were tested directly on cells. RESULTS: The intraocular lens and injector were not cytotoxic. Conditioning liquids induced membrane fluidity perturbation characteristic of apoptosis. Tests performed on new versions of the medical device identified a better adapted conditioning liquid. CONCLUSION: The results suggest that the cytotoxicity of the conditioning liquid could explain the postoperative complication rate. When we changed the conditioning liquid with sterile irrigating solution (i.e., rich divalent cation marine solution), we eliminated cellular stress. Fluorescent probes are well adapted to assess medical device biocompatibility-cytotoxicity.

Biocompatible Materials↗

PubMed2002

[Progress in research and application of the tissue engineering blood vessels].

Vascular tissue engineering is a novel approach by which an ideal vascualr graft constructed in vitro that will not be obstructed for a long time without immunological reaction after implantation. This article reviewed the definition of the tissue engineering blood vessel (TEBV), cellular resourses, the selection of biocompatible materials, the devising methods and the research achievements. Furthermore, it also discussed the current problems of TEBV and looked forward to future clinical application.

Biocompatible Materials↗

PubMed1983

[Selected light microscopy and polarization optical studies of implant-bone interfaces].

Implant bone specimen of inert materials and of the material BVK Ap 40 mended histologically. The bone specimen were both decalcified and carried to the polish technique after plastics embedding. The experiments were carried out in miniature swines (type Mini-Lewe) and rabbits. Microscopical and polarisation optical investigations were carried out. A connective-tissue membrane was provable at the interface implant-bone in all cases with use of the biocompatible material titanium. With BVK Ap 40 was observed a direct compound with the bone.

Animals↗

PubMed2000

The impact of advances in dental sciences on primary dental care.

The next century will see phenomenal changes especially and, most importantly, in patient empowerment, in the improvement of health in the disadvantaged, and in the harmonisation of standards of healthcare throughout the world. Advances in the dental sciences will facilitate these improvements but the major changes surely will be largely stimulated and motivated by the information revolution and the advances in molecular and materials sciences. The identification, and protection against disease, of patients who, because of a genetic predisposition, are at particular risk of disease is likely to become possible. Simple, sensitive, effective, non-invasive and safe diagnostic procedures will become available, as will chairside diagnostic test kits that would identify specific microorganisms causal of oral disease. The advances in digital imaging will be taken further and linked to record-keeping. Specific safe agents targeted at responsible microorganisms will be devised, and systems to deliver therapeutic agents effectively and prevent tissue damage simply will be perfected. Painless, minimally-invasive techniques for the removal of diseased oral tissues will become available, as will biocompatible materials for replacement of lost oral tissues.

Anti-Infective Agents↗

PubMed2005

Epitope tagging for tracking elastin-like polypeptides.

Elastin-like polypeptides (ELPs) are a class of biocompatible, non-immunogenic and crosslinkable biomaterials that offer promise for use as an injectable scaffold for cartilage repair. In this study, an oligohistidine (His(6)) epitope tag was incorporated at the N-terminus of an ELP using recombinant DNA techniques to permit tracking without compromising on material biocompatibility. His(6)-tagged ELPs were successfully detected by Western blot analysis and quantified by ELISAs following digestion with trypsin. The mass of His(6) tagged ELP fragments freed from a crosslinked ELP hydrogel after digestion with trypsin correlated highly with hydrogel weight loss, providing evidence of the tag's capability to enable tracking of enzymatic degradation of the ELP hydrogel. The His(6) tag also facilitated recognition of crosslinked ELPs from background staining of articular cartilage. These results suggest that the His(6) epitope tag has the potential to track ELP scaffold loss independently of newly formed tissue mass for evaluating matrix remodeling in vivo.

Amino Acid Sequence↗

PubMed1999

Haemocompatibility of paediatric membrane oxygenators with heparin-coated surfaces.

Extracorporeal circulation (ECC) in paediatric patients with heparin-coated oxygenation systems is rarely investigated. The objective of this study was to evaluate, preclinically, the haemocompatibility of paediatric membrane oxygenators with heparin-coated surfaces. We compared 16 paediatric membrane oxygenators (Minimax, Medtronic) in an in vitro heart-lung machine model with fresh human blood. Eight of these oxygenation systems had a covalent heparin coating (Carmeda bioactive surface). After 90 min simulated ECC, the heparin-coated systems showed significantly higher platelet count, lower platelet-factor 4 release, reduced contact activation (factor XIIa and kallikrein), and lower neutrophil elastase levels (p < 0.05), compared to the noncoated oxygenator group. More biocompatible materials for paediatric operations may ameliorate the various postperfusion syndromes arising from ECC procedures, particularly unspecific inflammation, hyperfibrinolysis and blood loss.

Biocompatible Materials↗

PubMed1999

Effect of collagen implants in the reduction of high astigmatism induced by penetrating keratoplasty.

PURPOSE: To evaluate the insertion of EagleVision collagen plugs as spacers between corneal relaxing incisions to correct significant residual astigmatism after penetrating keratoplasty (PKP). SETTING: Ambulatory Clinic of the Department of Ophthalmology, Rhode Island Hospital, and Rhode Island Eye Institute, Providence, Rhode Island, USA. METHODS: This study comprised 8 patients meeting the following criteria: had previous PKP, had at least 5.0 diopters of residual keratometric astigmatism with all the sutures removed, were free from eye infection, and were at least 21 years old. All 8 patients had unilateral high astigmatism after PKP. Four eyes were randomly assigned to the control group of astigmatic keratectomy (AK) incisions without the collagen implants and 4 eyes to the experimental group of AK incisions with collagen implants. RESULTS: Best corrected visual acuity 1 day, 3 weeks, and 1, 2, and 6 months after AK showed decreased astigmatism in all the patients who had the relaxing incisions. The amount of astigmatism was lower in patients who received AK incisions with collagen implants (P < .28). Minimal adverse effects were noted. CONCLUSION: Implanting a biocompatible material into AK incisions to correct post-PKP astigmatism appears to be safe and may enhance astigmatic correction.

Adult↗

PubMed1990

Preliminary characterization of bioresorbable and nonresorbable synthetic fibers for the repair of soft tissue injuries.

Preliminary characterizations of two new synthetic fibers were performed to determine their potentials for use in soft tissue scaffolding devices. A slowly bioresorbing random copolymer of dimethyltrimethylene carbonate (DMTMC) and trimethylene carbonate (TMC) was the first fiber evaluated. The second was a nonresorbable high-strength synthetic fiber of highly oriented polyethylene. Their in vitro mechanical behavior was evaluated by loading fibers in uniaxial tension to determine mechanical properties in dry and wet (saline) environments. The polyethylene fiber had a dry strength of approximately 2.0 GPa, an ultimate strain of 3 to 4%, a tangent modulus of 57 GPa, and was not affected by the saline environment. The bioresorbable fiber had a dry strength of approximately 500 MPa, an ultimate strain of 35%, and tangent modulus of 5.4 GPa. The in vitro resorption of the bioresorbable fibers produced a 15% loss in strength over a 10-week period. In vitro cell-fiber compatibility studies were conducted to assay material biocompatibility and fiber substrate efficacy. Fibroblasts proliferated and migrated on both the polyethylene and bioresorbable fibers at rates similar to those previously found for other compatible fibers, thus demonstrating the new materials to be similar in their in vitro biocompatibility profiles. Morphological assessment with SEM also confirmed that these materials were suitable substrates for cell attachment. A rabbit Achilles tendon repair model using oriented polyethylene or bioresorbable fiber tows was evaluated after 12 and 26 weeks of implantation. The mechanical performances of both types of tendon repairs were similar to those found in previous studies using carbon or PET fibers. The polyethylene fibers elicited a low-grade chronic inflammatory tissue response. The bioresorbable fibers were still intact at 26 weeks and remained relatively inert in the host tissue, eliciting a minimal foreign body response.

Animals↗

PubMed1984

A histologic comparison of Hydron and zinc oxide-eugenol as endodontic filling materials in the primary teeth of dogs.

Currently available endodontic filling materials for primary teeth demonstrate several inadequacies. Therefore, this study histologically evaluates Hydron (2-hydroxyethylmethacrylate) and zinc oxide and eugenol (ZOE) as primary tooth endodontic filling materials in dogs to compare the materials' biocompatibility and to determine whether they undergo resorption in a physiologic manner. Primary molars of six mongrel dogs, 2 to 3 months old, received one-step endodontic therapy. By random selection, two thirds of the molars were filled with either Hydron or ZOE and the remainder were used as unoperated controls. Block sections taken during physiologic root resorption were used to obtain serial hematoxylin and eosin sections of periapical regions. Hydron was phagocytosed by mononuclear macrophages in a physiologic manner and at a rate comparable to that of root tissues. In contrast, ZOE demonstrated delayed resorption and transitory inflammation. Neither material showed cytotoxicity. Hydron may therefore be a suitable endodontic material for human primary teeth.

Animals↗

PubMed2001

Novel adhesion prevention membrane based on a bioresorbable copoly(ester-ether) comprised of poly-L-lactide and Pluronic: in vitro and in vivo evaluations.

Block copolymers consisting of poly(L-lactide) (PLLA) and poly(oxyethylene-co-oxypropylene), with various compositions, were synthesized and characterized in vitro and in vivo for their application as postoperative adhesion prevention membranes. It was found that the flexibility and degradability of the cast films of the block copolymers grew with increasing Pluronic F68 [PN; poly(oxyethylene-co-oxypropylene] composition. The receding contact angle of the copolymer films against water became lower than that of the PLLA film, because the surface was predominantly covered with more hydrophilic PN segments in a wet state. This surface property significantly affects the cell attachment property of the copolymer films, and the fibroblasts cultured on the films exhibit a spheroid-like morphology. The copolymer films subcutaneously implanted in the back of rats induced milder tissue responses compared with PLLA homopolymers, because of the increased surface hydrophilicity in the former. In vivo evaluation using a uterus horn model in rats revealed that the performance of these copolymer films as an adhesion-prevention membrane is comparable to that of a conventionally utilized membrane of oxidized regenerated cellulose. These results indicate that the copolymer films are biocompatible materials with controllable mechanical properties and biodegradability as adhesion-prevention membranes.

3T3 Cells↗