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PubMed1997

Concepts in biocompatibility testing of dental restorative materials.

Due to the diversity of adverse biological effects which might be caused by dental restorative materials, biocompatibility assessment cannot rely on a single test but has to be based on a planned and structured approach (concept). First, the possible harm evoked by the material, the known data, and suitable biological and other test methods available must be taken into consideration. Modern regulatory concepts require for this purpose the services of experts to propose the appropriate set of required tests for a given material. The use of standards is generally emphasized because of better comparability of the data. Other tests may be chosen if more appropriate. Modern scientific concepts of biocompatibility testing are based on the need for rapid and cost-effective test methods, avoiding animal tests whenever possible. While formerly in vitro experiments did not take into account the special clinical situation in which the material would be used, modern concepts try to simulate important parameters of the in vivo situation as closely as possible. This may be achieved, for example, by including suitable barriers between the material and the target cells, by constructing appropriate target cells, and by choosing clinically relevant markers for measuring the biological effects caused by the material. There are indications so far that through this approach the number of animal tests can be reduced. The use of these methods may also lead to a better understanding of the mechanisms behind the biological reactions (mechanistic approach) in describing the biocompatibility of dental restorative materials.

Animals↗

PubMed2006

Currently available biomaterials for use in cardiopulmonary bypass.

Cardiopulmonary bypass (CPB) represents one of the most important technical innovations in healthcare history, yet the systemic responses to CPB remain a fundamentally unresolved problem. Study of the blood-biomaterial interaction and development of biocompatible materials is intimately related to efforts to optimize patient outcome following CPB. This article reviews the design innovations in biomaterial surfaces that have been introduced into clinical practice in an attempt to ameliorate the detrimental consequences of CPB, contrasting the actual clinical improvements and patient benefits achieved against those predicted on the basis of theory and in vitro testing. Some discussion of the underlying mechanisms of action as presently understood is provided and the current limitations of biomaterial-dependent strategies to improve outcome following CPB are addressed.

Cardiopulmonary Bypass↗

PubMed1976

Preparation and characterization of wear debris of orthopedic materials for biocompatibility studies.

In order to test the biocompatibility of wear debris of orthopedic materials, a method has been developed to produce artificial debris of stainless steel, cobalt-chromium alloy, and high-density polyethylene. In this process, called the accelerated rubbing process, two cylindrical blocks of the same alloy were held under normal pressure in triply distilled water. One block remained stationary while the other rotated at approximately 4000 rpm. The water with the metal debris was recirculated between the rubbing surfaces. To prepare debris from polyethylene, a stainless steel block was rubbed over a polyethylene block submersed in liquid nitrogen. The shape of the metal debris was granular, whereas the polyethylene debris had a shred-like shape. The size distributions were determined from scanning electron micrographs, and it was found that the particles of the metal debris (stainless steel or cobalt-chrome alloy) ranged in sizes from 0.1-10 mu with 75% of all particles less than 2 mu in diameter. The size of polyethylene debris, expressed as the volume of an ellipsoid, ranged from 10-20,000 mu3 with 45% of all particles in the range of 400-2500 mu3. The x-ray diffraction pattern revealed that the debris of stainless steel consisted primarily of the face-centered cubic (fcc) alloy with small amounts of body-centered cubic (bcc) alloy and Fe3O4, whereas the cobalt-chrome debris consisted of the fcc alloy with a small amount of Cr2O3. The structure of the polyethylene debris was quite similar to that of the solid sample used in its preparation. The percent crystallinity Pc and the size of the crystalline regions D were slightly smaller in the debris than in the solid sample, i.e., Pc = 52 and 55%, D = 90 and 130 A, in the debris and the solid, respectively. To test the suitability of the artificial debris for biocompatibility studies, stainless steel debris was implanted into knees of adult female New Zealand rabbits. Bacterial challenge studies indicated prolongation, but not increased susceptibility to infection.

Animals↗

PubMed2003

Nano-structured polymers enhance bladder smooth muscle cell function.

It is the hypothesis of the present study that a biocompatible material which mimics the nanometer topography of native bladder tissue will enhance cellular responses and lead to better tissue integration in vivo. Previous in vitro studies have verified the ability to successfully reduce the surface feature dimensions of poly(lactic-co-glycolic acid) (PLGA) and poly(ether urethane) (PU) films into the nanometer regime via chemical etching procedures. Results from these studies also provided the first evidence that bladder smooth muscle cell adhesion was enhanced on chemically treated nano-structured polymeric surfaces compared to their conventional counterparts. Although cell adhesion is necessary for a biomaterial's success, subsequent cell functions (such as long-term cell growth and proliferation) are also critical for tissue ingrowth and long-term implant survival. The present in vitro study, therefore, investigated the function of bladder smooth muscle cells on these novel, nano-structured polymers over the expanded periods of 1, 3 and 5 days. Results indicated that cell number was influenced by both surface roughness and surface chemistry changes; the important contributor, however, was increased nanometer surface roughness. This claim is supported by the fact that cell number was enhanced on nano-structured compared to conventional PLGA and PU once chemistry changes were eliminated using casting techniques.

Animals↗

PubMed1984

[The fibronectin binding test: proposal of an experimental model for the evaluation of the biocompatibility of materials of orthopedic interest].

The Authors expose their experience about a new model for testing the biocompatibility of materials of possible use as implants in surgery. This model uses a glycoprotein, Fibronectin (FN) involved in cellular adhesion; FN was purified from human plasma by affinity chromatography on denatured collagen; the protein obtained by this procedure is about 95% pure. The best value of FN binding was found to be on bioglass B5 whereas in the case of Titanium Alloy and B6 an intermediate value was measured. Results may be discussed considering other preliminary results about cell adhesion.

Biocompatible Materials↗

PubMed2005

Electronic nose screening of ethanol release during sol-gel encapsulation. A novel non-invasive method to test silica polymerisation.

Porous silica matrices prepared by sol-gel process yield biocompatible materials adequate for encapsulation of biomolecules or drugs. The procedure is simple and fast, but when alkoxyde precursors like tetraethoxysilane (TEOS) are used the polymerisation reaction leads to the formation of alcohol as a by-product, which can produce undesirable effects on the activity of entrapped enzymes or modify a drug release kinetic. Therefore, it is critical to determine that no remnant ethanol is left prior using or storing the obtained biomaterial. In this regard, the technique used in the alcohol determination should be non-invasive and non-destructive to preserve the encapsulation device intact and ready to use. In this work we have successfully used a portable electronic nose (e-nose) for the screening of silica polymerisation process during theophylline encapsulation. TEOS reaction was "smelt" since precursor pre-hydrolysis until the end of ethanol release, sensed directly at the headspace of matrices slabs. Measurements showed that ethanol was negligible since 10th day in polymeric slabs of 10 mm width and 2 cm diameter. This first use of e-nose following a polymerisation reaction opens a wide number of putative applications in pharmaceutical and biochemical fields.

Biomimetics↗

PubMed2001

Production of different morphologies of biocompatible polymeric materials by supercritical CO(2) antisolvent techniques.

High-value biocompatible-polymers have been processed with supercritical antisolvent techniques to produce solid structures of different shape and size. In particular, a class of hyaluronic acid-derived polymers (Hyaff11-p100, Hyaff11-p80, Hyaff11-p75, Hyaff 302) have been used to obtain various morphologies such as microspheres, threads, fibers, networks, and sponges. The effect of thermodynamic variables on precipitation were highlighted in some preliminary batch experiments. Then, different products were obtained by tuning the values of operating parameters. Threads and fibers were the result of a continuous supercritical antisolvent (SAS) process where a concentrated polymer solution was pumped through a micrometric nozzle: The threads showed a reticular internal structure with an adjustable type of cavity. For production of networks and sponges, the concentration of polymer plays the key role. Below a critical value it was not possible to obtain a continuous network, while above it, a structure similar to that of the natural bone with three types of internal microporosity were obtained. Again, by tuning pressure and polymer concentration, the internal porosity could be controlled. Microparticles were also produced by the SAS process, and a control of their morphology was achieved by varying the concentration of the polymer in the starting solution and the density of organic solvent-CO(2) mixtures. All the products obtained by SAS have negligible content of residual solvent. A qualitative interpretation of experimental results is presented.

Biocompatible Materials↗

PubMed1996

Material properties, biocompatibility, and wear resistance of the Medtronic pyrolytic carbon.

Pyrolytic carbon is the material of choice for components in the majority of heart valves available today. Many manufacturers have vertically integrated their manufacturing capabilities to include their own carbon manufacturing facilities. Medtronic is no exception. Because of the critical nature of pyrolytic carbon to the success of a valve design, a series of in vitro tests were conducted to determine the relative equivalence of Medtronic and CarboMedics, Inc. (CMI) pyrolytic carbon based on the Medtronic HallTM design. Correlation between in vivo and in vitro pyrolytic carbon wear is provided based on an analysis of explanted Medtronic Hall discs manufactured by CMI. Material, physical, chemical, and biocompatibility proprieties for Medtronic carbon were determined using standardized techniques. Structural integrity of the discs was evaluated by accelerated cyclic testing to determine depth of wear characteristics. Explanted valves were subjected to identical depth of wear analysis. No statistical difference was found between CMI and Medtronic pyrolytic carbon discs based on mechanical and physical properties and depth of wear on both inflow and outflow disc surfaces. Furthermore, evaluation of CMI discs after explant from human subjects confirms similar wear characteristics with a half life in excess of the 570 years projected from the in vitro experiments. In summary, material properties, structural integrity and biocompatibility testing conducted on heart valve discs made by Medtronic showed results virtually identical to those from testing of discs made by CMI.

Biocompatible Materials↗

PubMed1976

Biocompatibility of materials for total joint replacement.

The clinical use of total joint prostheses demands absolute biocompatibility of the materials employed. The purpose of this experiment was the bioassay of some materials considered as possible candidates for use in total joint prostheses as load-bearing members or as wear-resistant surfaces. Some materials already in use were also tested. 316L stainless steel was used as a control. The materials were implanted as a standardized rod and in particulate form. An average of 12 samples per material were implanted in soft tissue for six months and a total of 145 rabbits were used in this study. Twenty-five materials including metals, polymers, and ceramics were tested in solid and powdered form. A semiquantitative evaluation of local tissue reaction and a study of organs was performed. Polymers and metallic materials showed in general a mild tissue reaction. Ceramics, which some authors describe as the best tolerated materials, elicited variable tissue responses. Some of these (glass-ceramics) presented very poor tissue tolerance. The least reactive, titanium oxide, titanium aluminate, and aluminum oxide, presented a degree of tissue reaction comparable to that of corrosion resistant metals, but not superior to them. Moderate reactivity was the general rule for particulate materials except for the Pyroceram glass-ceramics, polymides, and Teflon. Ultrahigh molecular weight polyethylene in particulate form elicited a rather cellular tissue response, a fact to be considered when projecting long-term results in total joint arthroplasty. No pathological changes compatible with systemic toxicity by materials tested were observed in the study of the organs.

Animals↗

PubMed1998

Comparative study of tissue reactions to calcium phosphate ceramics among cancellous, cortical, and medullar bone sites in rabbits.

In order to understand the influence of the implantation site on bone biomaterial evaluation, we implanted cylinders of HA and beta-TCP ceramics in the femoral diaphysis and condyle of rabbits. After 3, 8, 12, and 24 weeks of implantation, histological investigation and histomorphometry were performed on undecalcified samples. Our results show that spontaneous bone healing in the empty cavities is significantly different (p < 0.05) between cortical (SBH > 80%) and cancellous bone sites (SBH < 31%) and that no new bone is formed in marrow tissue. For both porous ceramics, the highest osteogenesis was obtained in the cortical site. Osteogenesis was intermediate in the cancellous site and weak in the medullar site. The material biodegradation was the strongest in the medullar site and higher in the cancellous site than in the cortical site. Both activities were better in the beta-TCP than in the HA (p > 0.05). The marrow tissue presents a foreign-body reaction more reliable, sensitive, and durable than other bone tissues. Therefore, the cancellous bone site is a good site for evaluation of the biofunctionality of biomaterials because of the equilibrium of the osteogenesis and the biodegradation activities, but marrow tissue seems to be better for testing material biocompatibility in vivo.

Animals↗

PubMed2006

A floating metal microelectrode array for chronic implantation.

Implantation of multi-electrode arrays is becoming increasingly more prevalent within the neuroscience research community and has become important for clinical applications. Many of these studies have been directed towards the development of sensory and motor prosthesis. Here, we present a multi-electrode system made from biocompatible material that is electrically and mechanically stable, and employs design features allowing flexibility in the geometric layout and length of the individual electrodes within the array. We also employ recent advances in laser machining of thin ceramic substrates, application of ultra-fine line gold conductors to ceramic, fabrication of extremely flexible cables, and fine wire management techniques associated with juxtaposing metal microelectrodes within a few hundred microns of each other in the development of a floating multi-electrode array (FMA). We implanted the FMA in rats and show that the FMA is capable of recording both spikes and local field potentials.

Animals↗

PubMed2000

The science of tissue engineering.

This article reviews the development of tissue engineering during the last decade. The science began to fully develop in association with efforts to combine viable cells with biocompatible material. The history and scope of this new field are presented. Basic principles of cell biology, materials, and technologies are discussed. Future challenges in the field are presented.

Coated Materials, Biocompatible↗

PubMed2003

In vitro corrosion behaviour and osteoblast response of thermally oxidised Ti6Al4V alloy.

In this work, the influence of thermal oxidation treatments of Ti6Al4V at 500 degrees C and 700 degrees C for 1 h on the in vitro corrosion behaviour and osteoblast response is studied. The potential of these treatments, aimed to improve the wear surface performance as biomaterial, relies in the formation of an outer "ceramic" layer of rutile. The corrosion behaviour was evaluated in simulated human fluids by electrochemical impedance spectroscopy and anodic polarisation tests. The effect of these thermal oxidation treatments on osteoblastic behaviour was studied in primary cultures of human osteoblastic cells. Results show that thermal oxidation treatments do not decrease the high in vitro corrosion resistance of the Ti6Al4V alloy. Osteoblast adhesion studies indicate that thermal oxidation treatments do not impair the material biocompatibility. Moreover, the thermal oxidation at 700 degrees C enhances the in vitro osteoblastic cell attachment compared to the thermal oxidation at 500 degrees C.

Alloys↗

PubMed2000

Development of catheters with low fiber background signals for Raman spectroscopic diagnosis applications.

Utilization of optical-fiber catheters can turn the Raman spectroscopy system into a powerful remote biomedical diagnostic probe. An in vivo (a qualitative and a quantitative) biochemical diagnosis of biotissues is possible by developing the Raman-fiber probes with a good flexibility and less background signals generated in the probes themselves. Considering the isotropic nature of Raman scattering, the amount of Raman signal guided through the fiber is expected to depend on the numerical aperture (NA) of the fiber. To study the dependence for catheter probes experimentally, various flexible probes (with small diameter fibers) with different combinations of numerical apertures and with different assembling materials (biocompatible) have been developed. The catheter probes have been characterized by collecting the near infrared excited Raman scattered light from cholesterol powder. The results demonstrate that the catheters with a combination of lower NA (0.12) fibers used for laser excitation and relatively higher NA (0.22) fibers for Raman signal collection will have lower background signals generated in the probes. Furthermore, the catheters with a black Teflon tubing cover and black epoxy resin adhesives were found to give better results.

Adhesives↗

PubMed2006

Hydroxyapatite dip coated and uncoated titanium poly-axial pedicle screws: an in vivo bovine model.

STUDY DESIGN: A 1-year-old calf was implanted with titanium pedicle screws either uncoated (n = 7) or coated with hydroxyapatite (n = 7) by the dipping method on the pedicles of vertebrae (t10-l3). OBJECTIVE: To evaluate biomechanical and histomorphologic responses to titanium pedicle screws uncoated and coated with hydroxyapatite. SUMMARY OF BACKGROUND DATA: Failure of fixation caused by loosening of pedicle screws is a problem in spinal surgery. Enhancement of the fixation ability of screws by coating with biocompatible materials may improve prognosis of surgery. METHODS: The calf was euthanized 4 months after implantation for determination of insertion and extraction torques for screws, and histologic and scanning electron microscopic examinations of areas screw embedded. RESULTS: Insertion torques did not differ by the kind of screws (99 +/- 5.7 Ncm). However, extraction torques for screws coated with hydroxyapatite were higher than for screws uncoated (249 vs. 133 Ncm, P < 0.01). As compared with uncoated screws, implanted areas for hydroxyapatite-coated screws were denser, had more cracks, and provided better bonding. Fibrous tissue and new bone formation were observed around the areas of uncoated and hydroxyapatite-coated screws embedded, respectively. CONCLUSIONS: Hydroxyapatite coating of titanium pedicle screws by the dipping method improved fixation and vertebral bone-implant interface, suggesting a decreased risk of a screw-loosening problem.

Animals↗

PubMed2001

Utilization of MO6-G3 immortalized odontoblast cells in studies regarding dentinogenesis.

Tooth formation is the result of reciprocal instructive interactions between oral epithelium and cranial neural-crest-derived ectomesenchymal tissues. These interactions lead to the cytodifferentiation of highly specialized matrix-forming cell types, the ameloblast, odontoblast, and cementoblast, that produce the mineralized tissues enamel, dentin, and cementum, respectively. Our laboratory has been developing immortalized dental cell lines representative of these various cell types to facilitate studies on gene regulation, cell differentiation, matrix formation, and mineralization. Odontoblasts are solely responsible for the synthesis and secretion of the dentin extracellular matrix bilayer that consists of non-mineralized predentin and mineralized dentin. The mouse immortalized MO6-G3 cell line expresses the major matrix proteins associated with the odontoblast phenotype, producing a matrix that is capable of mineralization. This cell line serves as a useful tool in studies designed to explore the various processes of dentinogenesis. In this paper, we present studies using the mouse odontoblast cell line MO6-G3 as examples of the various research applications. Studies highlighted are: in vitro promoter studies investigating the tooth-specific gene regulation of the major non-collagenous dentin matrix protein, dentin sialophosphoprotein; regulation of tertiary dentin formation by cytokines, such as transforming growth factor-Beta 1; and the utilization of dentally relevant cells in dental material biocompatibility testing.

Ameloblasts↗

PubMed2002

An in vitro method for comparing biocompatibility of materials for extracorporeal circulation.

UNLABELLED: We measured the response of fresh heparinized human blood to recirculation through circuits made of LVA (Portex Industries, Hythe, Kent, UK), SRT (Rehau UK, Langley, Slough, UK) and Tygon S-65-HL (Norton Performance Plastics, Corby, Northants, UK), as control. Circuit construction: 1/2 in. tubing, heat exchanger (Dideco D-720P), Stockert roller pump, just underoccluded, Cincinnati Sub Zero heater, circuit volume of 500 ml. Flow 3.45 l/min, 37 degrees C. SAMPLES: at 10 min, 1, 2, 4 and 6 h. n=5 in each group; 2/5 SRT experiments were stopped at 45 and 60 min due to overpressurization. RESULTS: Baseline activated clotting time (ACT) of 300 s, increasing in all groups as fibrinogen fell to zero with SRT and LVA. Minimum fibrinogen was 1 g/l for Tygon. Absolute thrombocytopenia occurred (SRT and LVA 60 min and Tygon 240 min). International normalized ratio (INR) in both the SRT and LVA circuits increased, but mean increase for Tygon (0.56) was smaller than the other two materials. Plasma free haemoglobin increased in all three materials; the increase was greater in the LVA circuits compared to the control. C5b9 levels increased equally in all groups. Lactoferrin levels rose equally in all groups to a maximum at 150 min. The neutrophil counts fell, mirroring the lactoferrin. The total white cell counts also fell in all groups; in the LVA circuits, the fall was significantly lower than in the control. Rapid disappearance of platelets and fibrinogen from the blood in the SRT and LVA circuits excludes them both from extracorporeal use. Paradoxically, SRT caused the least complement activation of the three materials. This method can be used to compare biocompatibility.

Adolescent↗

PubMed1999

Human osteoblast in contact with various biomaterials in vitro.

OBJECTIVES: The aim of the study was to investigate changes in osteoblast number and viability in contact with biomaterials and to compare both tests. METHODS: Human primary culture osteoblasts were seeded on the polished surfaces of hydroxyapatite, alumina, titanium and surgical steel. After 4, 9, 14, 24 and 48h cultures were subjected to XTT viability assay. Subsequently Hoechst staining of nuclei was performed. Number of cells on each sample was counted. RESULTS: There were no differences in cell viability measured by means of XTT assay between osteoblasts cultured on hydroxyapatite and alumina during 48 hours of experiment. However on titanium as well as on surgical steel cell viability was significantly lower than on bioceramics. The lowest viability was noticed on surgical steel. Cell number on titanium was significantly higher than on steel. There were no differences between cell numbers on hydroxyapatite and alumina as well as between investigated bioceramics and metals. Nucleus number and the results of viability assay were compared. There was no correlation found between number and viability of cells. CONCLUSION: the results of a single test may not provide sufficient information on the interaction between cells and implant. Application of a battery of tests is necessary in material biocompatibility investigation in vitro.

Biocompatible Materials↗