Journal of biomedical materials research最新文献

Poly (2-hydroxyethyl methacrylate) (PHEMA) particles of cylindrical and spherical shape were developed as a preparation for tumor treatment or control of hemorrhage by blocking their blood supply. In this report, PHEMA particles were used for the management of hemobilia, that is, bleeding into biliary passages. The origin of hemobilia in 31 patients was localized by selective angiography. With the objective of prophylaxy of hemorrhage, selective embolization with PHEMA particles of the branches of the hepatic artery responsible for the supply of blood to the focus of damage was used in 18 patients. This low-trauma method allowed either a complete control of bleeding or, at least, intraoperative blood loss was reduced more than twice. Histological investigation of the occluded blood vessels showed that the thrombus was attached to the particles and was reinforced by the porous structure of the polymer. A hypercoagulation reaction was observed in the postembolization period. This allowed correction of the hypocoagulation in the hemostasis system.

Previously, small phagocytosable particles of high density polyethylene (HDPE) but not Ti6-Al4-V alloy, at a concentration of 10(8) particles/mL inhibited net bone formation in vivo after 3 weeks in the bone harvest chamber (BHC). These findings reflected the effects of particles during the phase of bone ingrowth. In this study, we tested whether these effects persisted or were different during the phase of bone maturation and remodeling. BHCs were bilaterally implanted in mature male NZW rabbits. After a 6-week period for osseointegration, the contents of the chamber were harvested and discarded. One percent sodium hyaluronate, the carrier, was then placed within the canal of the chambers bilaterally and the tissue within the chambers was harvested 3 weeks later. HDPE particles were then inserted unilaterally for a 3-week period, followed by Ti6-Al4-V for 3 weeks, HDPE for 6 weeks, and Ti6-Al4-V for 6 weeks. The side chosen for each treatment was switched consecutively; the nonimplanted, contralateral chamber served as a control. At 3 weeks the control treatments yielded trabeculae of woven bone in a fibrovascular stroma. By 6 weeks, the peripheral trabeculae were thicker, and a central marrow cavity was developing. Bone ingrowth was less with HDPE particles at 3 and 6 weeks compared to controls. Ti6-Al4-V particles did not inhibit bone ingrowth at 3 weeks but showed a trend at 6 weeks. The characteristics of particles affect the differentiation, maturation, and remodeling of mesenchymal tissue differently.

The aim of this study was to compare the bone-bonding rates of eight calcium phosphate ceramic (CPC) coatings attached to strain gauges, alone and in conjunction with an OP1 device (Creative BioMolecules, Hopkinton, MA) and autologous concentrated pericyte cells. These coatings were studied to develop faster bone bonding to long-term in vivo strain sensors. Characterization of the CPC powders using electron microscopy and X-ray diffraction showed that they had shapes ranging from spherical to rocklike and properties ranging from highly crystalline to amorphous. CPC coated gauges were placed on the femora of young male dogs during aseptic surgery and were initially held in place using resorbable sutures. Test groups were euthanized after 3, 9, and 12 weeks. Both femora of the dogs were explanted and cantilever loaded. Response of the implanted hydroxyapatite (HA) coated gauges were compared to the response of bench-top glued sets of gauges (controls) attached to the contralateral femur and reported as a percentage of the control values. One CPC coating type showed an average response of 30% of controls after 3 weeks, four showed average responses higher than 75% after 9 weeks, and three showed averages higher than 82% after 12 weeks in vivo. Amorphous CPC coatings bonded more quickly than crystalline ones and particle shape had less effect than crystal structure on bonding rates. When either OP1 or autologous concentrated pericyte cells were placed on selected CPC coated gauge surfaces, the CPC5 coated gauges bonded best after 3 weeks with a response of 59%. After the same time period in vivo, CPC3 and CPC7 provided responses of 40 and 16%, respectively. Comparison of a soluble calcium-coated CPC with an uncoated one that had identical crystal structure and similar particle shape indicated that the calcium coating slowed bone bonding substantially in the young dog model. Optical microscopy of stained undecalcified bone sections and backscattered electron imaging indicated bone formation at all bone-HA interfaces and an increase in the number of areas of bone remodeling adjacent to the gauge at all time periods. Gross bone remodeling due to strain gauge placement was only observed near the distalmost cell-seeded strain gauges. Selection of the type of coating and enhancement system can accelerate bone bonding to strain sensors but must be tailored to the bone of the model in which it is being used. Augmentation of CPC coatings with cells or OP1 resulted in variable enhancement of the bonding rate and depended on the CPC and the enhancement system.

Bioprostheses derived from collagenous tissues have to be fixed and subsequently sterilized before they can be implanted in humans. Clinically, the most commonly used fixative is glutaraldehyde. However, the tendency for glutaraldehyde to markedly alter tissue stiffness and promote tissue calcification are well-recognized drawbacks of this fixative. To address the deficiencies with the glutaraldehyde-fixed tissue, a new fixative, epoxy compound, was used to fix biological prostheses. The study was undertaken to investigate the fixation rates and crosslinking densities of biological tissues fixed with various epoxy compounds. These epoxy compounds are different in their chemical structures. Glutaraldehyde was used as a control. The fixation rates and crosslinking densities of the fixed tissues were determined by measuring their fixation indices and denaturation temperatures, respectively. Generally, the epoxy-fixed tissues were more pliable than the glutaraldehyde-fixed one. Furthermore, the tissues fixed with monofunctional epoxy compound were more pliable than those fixed with multifunctional epoxy compounds. With increasing pH or temperature, the fixation rate of epoxy compound increased. However, the number of epoxide functional groups did not seem to affect the fixation rate of the epoxy compound. The fixation rate of glutaraldehyde was faster than that of epoxy compounds. Additionally, the crosslinking density of the glutaraldehyde-fixed tissue was greater than that of the epoxy-fixed counterparts. Moreover, it was noted that the denaturation temperatures of the tissues fixed with glutaraldehyde or multifunctional epoxy compounds were significantly higher than the fresh ones (p < 0.05), while that fixed with monofunctional epoxy compound stayed roughly the same throughout the entire fixation process (p > 0.05). The results obtained in this study may be used to optimize the fixation process for developing bioprostheses fixed with epoxy compounds.

It has been shown that the prerequisite for glasses and glass-ceramics to bond to living bone is the formation of a layer of biologically active bonelike apatite on their surfaces. The hydrated silica formed on the surfaces of glasses and glass-ceramics plays an important role in nucleating the apatite. In the present study, the structure of the hydrated silica responsible for the apatite nucleation was investigated in an accellular simulated body fluid with ion concentrations nearly equal to those of human blood plasma. Three kinds of porous silica gels were prepared by hydrolysis and polycondensation of tetraethoxysilane in pure water or in aqueous solution containing polyethylene glycol or polyacrylic acid. The silica gels prepared in aqueous solution containing polyethylene glycol or polyacrylic acid had micron-size interconnected pores, whereas the gel prepared in pure water did not. All the gels contained a large volume of nanometer-size pores, almost the same amounts of silanol groups and D2 defect, and showed a high dissolution rate of the silica. Despite this, only the gel prepared in the solution containing polyethylene glycol formed the apatite on its surface in the simulated body fluid. This indicates that only a certain type of structural unit of the silanol group is responsible for the apatite nucleation.

Several biologic-biomaterial combinations are currently under development in an attempt to modulate tissue or organ function in patients. The FDA regulations on combination products and the intercenter agreements among the Center for Biologics Evaluation and Research (CBER), the Center for Devices and Radiological Health (CDRH), and the Center for Drugs Evaluation and Research (CDER) provide further guidance on center jurisdiction of combination products and other products where there are jurisdictional concerns. The biological component of biologic-biomaterial combinations raises a number of issues that relate to the safety and bioactivity of the final product. For example, transmission of adventitious agents to patients via somatic cells, tissue, or cell-derived products is a major safety concern as are in vivo inflammatory responses elicited by the biomaterial component. CBER has drafted a number of "Points to Consider" documents to provide further guidance in the development of biological products. The intent of this article is to provide the highlights of the FDA regulations for combination products and the intercenter agreement between CBER and CDRH delineating the responsibilities of each center for medical device activities. In addition, the article focuses on the CBER's concerns related to the development of somatic cell-biomaterial combinations for therapeutic use.

Vancomycin (VCM), a methiciline-cefem resistant Staphylococcus aureus (MRSA)-specific antibiotic, was incorporated in a self-setting tetracalcium phosphate (TTCP)-dicalcium phosphate dihydrate (DCPD) apatite cement that hardened isothermally into a hydroxyapatite (HAP) phase with crystallinity similar to that of host bone. Effective release of VCM into PBS lasted for 2 weeks from cements containing 1% VCM and for longer than 9 weeks from cements containing 5% VCM. The rate of release of VCM differed between cements with different crystallinities as well as between the two dissolution media, PBS and simulated body fluid. Mean concentration of VCM in the bone marrow tissue released from cements containing 5% VCM was 20 times the minimum inhibitory concentration 3 weeks after implantation in bone. Direct contact with new bone was observed with the cements containing 1% VCM. Slow delivery of VCM from a self-setting TTCP-DCPD apatite cement with low crystallinity could be used to treat MRSA osteomyelitis.

A simple wear test was investigated for evaluating the wear and damage of material pairs when used in total knee replacement. The test consisted of an axially loaded metallic femoral indentor and a reciprocating ultrahigh molecular weight polyethylene (UHMWPE) flat disk that represented the tibial component. A number of variables were studied including the effect of conformity by varying the radii of the femoral surface, distilled water or serum as a lubricant, different femoral materials, and different types of UHMWPE. In general, the different morphologies of the surface wear of the UHMWPE were similar to those seen on retrieved total knee replacements. Increased conformity with a cylindrical indentor gave a reduced wear rate initially, compared with that of the lower conformity spherical indentor. However, the wear rates were similar subsequent to this initial wearing in phase. Transfer films of UHMWPE were observed on the cobalt-chrome indentors for both serum and distilled water lubrication, although this film was more extensive for distilled water. The lowest wear rate was observed when oxidized zirconium was used on the femoral side, which was attributed to greater wettability, surface hardness, and immunity to oxidative wear. Tests using cobalt-chrome femoral cylinders and different grades of UHMWPE showed different wear rates. Of these PEs, GUR 415 showed less wear than both RCH 1000 and UHMWPE containing numerous fusion defects. For the latter, wear was attributed to a fatigue mechanism, although in most cases it was associated with surface phenomena rather than subsurface cracking. However, in some specimens of UHMWPE subsurface crack propagations occurred with defects. The test method is discussed in relation to its applicability to the evaluation and comparison of bearing materials and surfaces, with particular application to total knee replacements.