摘要:

AbstractThe ultra‐high‐strength, self‐reinforced (SR) absorbable polymeric composites, consisting of reinforcement elements, like fibers, and of matrix polymer which have the same chemical element composition as reinforcement, were defined. A method to manufacture self‐reinforced, absorbable polyglycolide (SR‐PGA) rods of polyglycolide sutures (Dexon) by sintering them partially together at elevated temperature and pressure was presented. The rods with nominal diameters of 1.5 mm, 2.0 mm, 3.2 mm, and 4.5 mm showed initial bending modulus and strength values of 8–15 GPa and 220–405 MPa, respectively. Their initial shear strengths were 165–255 MPa. The smallest rods (diam. 1.5 mm) lost their mechanical strength after implantation in the subcutis of rabbits in 4–5 weeks while the thickest rods retained their strength over 8 weeks. The ultra‐high‐strength SR‐PGA rods were concluded to be suitable for fixation of cancellous bone fractures, osteotomies, and epiphyseal plate fractures where the fixation is not exposed to excessive mechanical stresses and where the loads are predomin

ISSN:0021-9304    

DOI:10.1002/jbm.820250102

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractVariable alumina quantities were added to two types of calcium phosphate materials–hydroxyapatite ceramics with Ca/P = 1.67 and calcium metaphosphate glass with Ca/P = 1–in order to increase their mechanical properties. Raman spectroscopy shows that alumina interacts with the phosphate group of these materials, while thermomechanical analysis shows that their elastic modulus has a value similar to that of bone. Histological sections demonstrate that the surface in close contact with ceramic materials shows a good integration between bone and biomaterial. All ceramic specimens are penetrated by well‐stained, presumably glycoprotein, matrix, that consistently forms a thin network in close contact with the implant. After 6 weeks bone growing on both ceramic and glass shows signs of maturation with a lamellar structure and an apparently normal mineralization. In the case of the glass, inside this newly formed bone, were often observed two layers, the internal one showing a well defined lamellar stru

ISSN:0021-9304    

DOI:10.1002/jbm.820250103

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractAnin vitrostudy assessing the kinetics of drug release from antibiotic–fibrin seal compounds and the antibacterial efficacy of the delivered drug has been performed. Antibiotic sensitivity and the amount of drug released was measured by means of agar diffusion test. Standard and experimental curves were established for each antibiotic and each bacterial test in order to evaluate the quantities of the drug released during each 24 h period. The reconstitution of lyophilized human fibrin with an aqueous solution containing an antibiotic resulted in only minor modification of the clotting process, with the exception of those solutions containing cefotaxim and mezlocillin which failed to clot altogether and were excluded from further study. The evaluation of the kinetics of elution of the antibiotics from the fibrin clots showed that all of the antibiotics had been almost completely released by 96 h. The delivered amount of each drug was enough to maintain the Minimal Inhibitory Concentration (MIC) until the 4th day of culture for the most of antibiotics, resulting in a prolonged release of the dru

ISSN:0021-9304    

DOI:10.1002/jbm.820250104

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractIn order to study the interaction of calcium phosphate coatings with bone tissue, coated titanium cylinders with a standard size were implanted in dog femora. Coatings were made by plasma spraying powders of hydroxylapatite, β‐whitlockite, and tetracalciumphosphate particles. The plasma spraying process tuns β‐whitlockite into α‐TCP. Bone bonding and bone formation were evaluated by mechanical push‐out tests and histological observations. Hydroxylapatite and tetracalciumphosphate coatings show an interface strength after 3 months of implantation of 34.3 ± 6.5 MPa and 26.8 ± 3.9 MPa, respectively, while α‐TCP and blanco titanium lead to an interface strength of 10.0 ± 3.5 MPa and 9.7 ± 1.3 MPa, respectively. Histological examinations revealed that hydroxylapatite and tetracalciumphosphate give rise to an excellent bone formation, while α‐TCP and blanco titanium evoked remodeling a

ISSN:0021-9304    

DOI:10.1002/jbm.820250105

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractInvestigations are reported on the composition of protein layers adsorbed from plasma to various modified polystyrene resins. As well as polystyrene itself, polystyrene bearing sulfonate groups in the benzene rings, and polystyrene sulfonate in which the sulfonate groups were converted to amino acid sulfamide, were investigated. Some of these resins were shown in previous work to have anticoagulant properties. To study the adsorption of proteins from plasma, the resins were exposed to citrate anticoagulated human plasma for 3 h. Adsorbed proteins were then eluted sequentially by 1M Tris buffer and 4% SDS solution, and examined by SDS‐PAGE. The gel patterns were similar on all resins except polystyrene. From the MWs of the gel bands, the major protein component appeared to be fibrinogen. Smaller amounts of plasminogen, transferrin, albumin, and IgG were also present. In addition, Ouchterlony immunoassay of the eluates from one resin gave positive identification of complement C3, fibronectin, IgG, and IgM. Many other minor gel bands remain unidentified. A consistent finding for all resins was the presence of plasmin‐type fibrinogen degradation products though the amounts varied with resin type. It is concluded from this (and from experiments showing FDP formation when fibrinogen was adsorbed to the resins, from buffer containing a trace of plasminogen) that the functional groups in these materials promote the adsorption of plasminogen and its activation to a plasmin‐like molecule. It appears from the substantial quantities of fibrinogen adsorbed to these materials after 3 h exposure to plasma that the Vroman effect (giving transient adsorption of fibrinogen) is not operative on these materials. It is hypothesized that specific interactions occur between fibrinogen and sulfonate g

ISSN:0021-9304    

DOI:10.1002/jbm.820250106

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractCalcification is the principal cause of the clinical failure of bioprosthetic heart valves (BHV). Calcification occurs through an interaction of host and implant factors, mainly younger age and glutaraldehyde pretreatment, respectively. The hypothesis of this work was that an impaired balance between positively and negatively charged amino acids, due to the reaction with Lys and Hyl tissue‐collagen residues, expose affinity sites to Ca++. We further hypothesized that regardless of the cause(s) of BHV calcification, positive charge modification of the tissues will prevent their propensity to calcify. Modification of BHV tissue was obtained by covalently binding protamine sulfate, a polybasic peptide, via formaldehyde and subsequent glutaraldehyde tissue crosslinking. Protamine‐bound tissue exhibited stability properties (shrinkage temperature and resistance to collagenase digestion) similar to BHV tissue. Protamine‐treated tissue was less permeable to Ca++, and reduced staining was observed with positively charged dyes, indicating the presence of positively charged functional groups in the modified tissue. Significant prevention of calcification was exhibited by the p‐bound tissue in comparison to BHV tissue, 30.9 and 109 μg/mg calcium, respectively, after 30 days of subdermal implants in rats. The modification procedure resulted in stable, covalent links of approximately 10% w/w protamine with undiminished anticalcification properties, even after 1 year storage. The results support our hypotheses, and orthotopical heart valve replacements are required in order to completely evaluate the treatment efficacy and bio‐com

ISSN:0021-9304    

DOI:10.1002/jbm.820250107

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractPoly(sodium vinyl sulfonate) (PVS) was found to be 1/14 times as active as heparin in inducing the conformational change and activation of antithrombin III. The conformational change of antithrombin III was investigated in terms of the intrinsic fluorescence of tryptophan residue, the extrinsic fluorescence using 1,6‐diphenyl‐1,3,5‐hexatriene as fluorescent probe, and Fourier‐transform infrared spectroscopy. It was evident in the experiment using 2,4,6‐trinitrobenzene sulfonate that PVS elicited the activity of antithrombin III by interacting with amino groups of the protein as does heparin.Sodium vinyl sulfonate was graft‐polymerized onto polyetherurethane (PEU) film that was treated with glow discharge in advance. PVS‐grafted PEU film adsorbed antithrombin III easily and, like ungrafted PVS, induced conformational change and activation of antithrombin III. However, the mechanism of interaction of the PVS graft with antithrombin III did not seem to be completely the same as that of ungrafted PV

ISSN:0021-9304    

DOI:10.1002/jbm.820250108

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe effects of massive administration of bioactive ceramic powder (Bioglass (45S5), Ceravital (KGS), apatite‐wollastnite containing glass ceramics (A‐W GC), and hydroxyapatite (HA)), by intraperitoneal (IP), intramuscular (IM), or subcutaneous (SC) injection in Balb/c mice were examined in this investigation. Alumina, Silica Glass (SG), and A‐W‐A1 (containing the same amount of crystal as A‐W GC and 6.3% Alumina) were used as nonbioactive controls. The particle size of each material injected was smaller than 44 μm. In addition to the above, two more sizes (smaller than 105 μm and smaller than 255 μm) of A‐W GC powder, and a 1 × 1 × 0.2 cm plate of the A‐W GC were also evaluated. When the particle size was smaller than 44 μm, intraperitoneal injections of 5 mg per g of body weight of BG, KGS, A‐W GC, and A‐W‐A1 were lethal to the mice. Ceramics in fine powder form, which are generally believed to have higher bioactivity, are associated with higher mortality except A‐W‐A1. On the other hand, when the particle size of the ceramic was increased, the fatal effects of ceramic powders in mice decreased. Plate form of ceramics implanted I.P. had no systemic effects. Intramuscular or SC injections of bioactive ceramic powder with a particle size smaller than 44 μm had almost no systemic effects. Both the particle size of the ceramic powder and the route of administration influenced the reactivity of the bioactive ceramics in the mice. In conclusion, regardless of particle size, neither SC nor IM injection of large doses of highly bioactive ceramics had an adve

ISSN:0021-9304    

DOI:10.1002/jbm.820250109

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThree types of brominated methacrylates, SBPPM, BPylM, and BNEM, were synthesized. The distribution of Br, Ca, and Fe at the interface between dentin treated with the 10‐3 solution and resin containing these monomers was analyzed using an electron‐probe microanalyzer (EPMA) in order to predict the composition and thickness of the interface layer on dentin for the corresponding unbrominated methacrylates. There was no significant difference between the brominated and unbrominated methacrylates in either the bond strength to the treated dentin or in the thickness of the interface layer on dentin observed with a scanning electron microscope (SEM). The thickness determined with EPMA was equivalent to that observed with SEM. The concentration of each brominated methacrylate in the interface layer was higher than the original concentration in the resin monomers, and BNEM showed higher concentration than the others. The presence of Fe in the layer was confirmed by E

ISSN:0021-9304    

DOI:10.1002/jbm.820250110

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY

ISSN:0021-9304    

DOI:10.1002/jbm.820250101

出版商:John Wiley&Sons, Inc.    

年代:1991

数据来源: WILEY