摘要:

AbstractThe effects of microstructure and wettability of porous high density polyethylene (HDPE) substrates on chondrocyte collagen synthesisin vitrowere assayed. Three size grades of hydrophilic and hydrophobic HDPE substrates with ranges of pore volumes of 40–60%, pore sizes of 115–335 μm, and surface areas per unit volumes of 7–20 mm2/mm3were seeded with fetal bovine chondrocytes. After 7 days of incubation, the cells within all substrates remained spherical, and contained mainly type II collagen (as verified by type I and II collagen I‐ELISAs). After 21 days, the majority of cells had spread; however, the matrices still contained mainly type II collagen. The hydrophilic matrices contained significantly more type II collagen than the hydrophobic matrices at both 7 and 21 days, whereas the amount of type II collagen was not influenced by the pore attributes. A significantly higher percentage of type II collagen was also observed in all seeded porous substrates as compared with seeded polystyrene culture dishes, perhaps indicating that the three‐dimensional particular nature of the HDPE matrices enhanced the maintenance of phenotypically differentiated chondrocytes and entrapment of their extracellular matrix products. © 1994 John Wile

ISSN:0021-9304    

DOI:10.1002/jbm.820280802

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe aim of this study was to investigate the effects of ultrasound irradiation on a biodegradable drug delivery system. Microporous, disk‐shaped specimens of a 50‐50% copolymer of polylactic and polyglycolic acids were gel cast from an acetone solution. A protein was incorporated in these specimens, which were then immersed in phosphate buffered saline and subjected to ultrasound irradiation every second day. The investigation was performed in two phases: in the first, a study was performed for 58 days to determine if ultrasonic irradiation affected the kinetics of protein release from the specimens. In the second phase, effects of frequency and duration of the ultrasound signal on the degradation of the implant were studied for 40 days. The results indicate that ultrasound irradiation resulted in almost a threefold increase in protein elution from the specimens. Both the ultrasound frequency and signal duration affected the molecular weight loss and mass loss, and changed the overall degradation kinetics of the polymer. © 1994 John Wiley&Sons,

ISSN:0021-9304    

DOI:10.1002/jbm.820280803

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractMucopolysaccharides such as hyaluronic acid and its salts are essential components of new hydrophilic bilaminar coatings being developed in these laboratories. The polysaccharide top‐coat is covalently bonded by periodic urethane links to a substrate copolymer which in this study has been coated on polymethyl methacrylate slabs. Such coated slabs were exposed for up to 28 months to three levels of hyaluronidase in phosphate buffered saline at 37°C, the enzyme concentration ranging from that normally present in human serum to 60 times that level. The coating survived without damage. The rationale proposed is that the enzyme is unable to position its active site with the immobilized hyaluronate molecule and is therefore unable to catalyze the hydrolysis. © 1994 John Wiley&Sons,

ISSN:0021-9304    

DOI:10.1002/jbm.820280804

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA series ofin vitroexperiments demonstrated a clear effect of additive hyaluronic acid (HA) on animal joints with experimentally reduced lubricating ability. Eleven canine hip joints were utilized and the experimental conditions tested were: (i) intact joints, (ii) after washing the joint surfaces, and (iii) after adding 1% HA to them. The frictional coefficient of every joint increased after washing and subsequently decreased after adding HA. The mean values were 0.007 (SD 0.004) on the intact joints, 0.020 (SD 0.009) after washing, and 0.013 (SD 0.005) after the addition of HA. The differences between the three values of frictional coefficients were shown to be statistically significant (p<0.01). © 1994 John Wiley&Sons, Inc

ISSN:0021-9304    

DOI:10.1002/jbm.820280805

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

Abstract3‐Mercaptopropionic acid (MPA),L‐cysteine (L‐cys), and glutathione (GSH) monolayers were immobilized onto gold and used inin vitroprotein tests. The surfaces were characterized with ellipsometry, static contact angle measurements, atomic force microscopy, and Fourier transform in frared reflection absorption spectroscopy (FT‐IRAS). After incubations in human plasma and antibody solutions, the surface antisera binding patterns were determined with ellipsometry. Using serum instead of plasma, complement activation was studied in the same fashion. Activated coagulation Factor XII and Kallikrein formation on the surfaces and in the plasma were studied using a kallikreinspecific colorimetric assay. 3‐Mercaptopropionic acid indicated contact activation of coagulation butL‐cysteine did not. Glutathione displayed low deposition of plasma proteins, large deposition of proteins from serum, and did not promote kallikrein formation. None of the surfaces could be attributed complement activating properties, as determined by antibody deposition. The present study demonstrates that surface biology in complex model systems can be conveniently studiedin vitrothrough systematic and well defined surface modifications. © 1994 John Wil

ISSN:0021-9304    

DOI:10.1002/jbm.820280806

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractIn vivoand electron microscopy were used to study the hepatocellular responses of rat livers to intravenously injected polymeric microspheres. Two microsphere preparation with different surface characteristics and degradability were used in this study.In vivomicroscopy revealed that both poly(benzylL‐glutamate) (PBLG) and poly(hydroxypropylL‐glutamine) (PHPG) microspheres caused disturbance in the microcirculation of rat liver up to 2 months after injection. The observed changes included stagnant flow and adherence of white blood cells to the endothelial lining of venules and sinusoids. Kupffer cell (KC) activation following phagocytosis of microspheres was evidenced by the enlargement of KCs and increased number of KCs taking up fluorescent latex particles. Electron microscopy of rat livers revealed a wide range of hepatocellular injury associated with the administration of PBLG and PHPG microspheres. These results indicate that a small amount of remaining microspheres is sufficient to induce continuous disturbance to hepatic microcirculation and that particulate drug carriers should be designed to be rapidly degraded so that the return to normal liver function is possible. © 1994 John Wiley&Sons,

ISSN:0021-9304    

DOI:10.1002/jbm.820280807

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractCartilage implants which could potentially be used to resurface damaged joints were created using rabbit articular chondrocytes and synthetic, biodegradable polymer scaffolds. Cells were serially passaged and then culturedin vivoon fibrous polyglycolic acid (PGA) scaffolds. Cell‐PGA constructs were implantedin vivoas allografts to repair 3‐mm diameter, full thickness defects in the knee joints of adult rabbits, and cartilage repair was assessed histologically over 6 months.In vitro, chondrocytes proliferated on PGA and regenerated cartilaginous matrix. Collagen and glycosaminoglycan (GAG) represented 20 to 8% of the implant dry weight (dw), respectively, at the time ofin vivoimplantation; the remainder was PGA and unspecified components. Implants based on passaged chondrocytes had 1.7‐times as much GAG and 2.6‐times as much collagen as those based on primary chondrocytes.In vivo, cartilaginous repair tissue was observed after implantation of PGA both with and without cultured chondrocytes. Six month repair was qualitatively better for cell‐PGA allografts than for PGA alone, with respect to: (1) surface smoothness, (2) columnar alignment of chondrocytes, (3) spatially uniform GAG distribution, (4) reconstitution of the subchondral plate, and (5) bonding of the repair tissue to the underlying bone. These pilot studies demonstrate that it is feasible to use cell‐polymer allografts for joint resurfacingin vivo. © 1994 John Wil

ISSN:0021-9304    

DOI:10.1002/jbm.820280808

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractHigh energy β‐emitting radioisotopes like Yttrium‐90 have a radiotoxic range of about one centimeter. For cancer treatment they must be brought near the tumor cells and kept there for as long as they are radioactive. We developed as carriers for the ionic form of90Y a matrix‐type polymeric drug delivery system, poly(lactic acid) (PLA) microspheres. This radiopharmaceutical could be selectively delivered to the target site after incorporating 10% Fe3O4(magnetite) which made the magnetic microspheres (MMS) responsive to an external magnetic field. Furthermore, MMS are biodegradable and slowly hydrolyze into physiologic lactic acid after the radioactivity is completely decayed. Previously prepared 10–40 μm MMS were radiochemically loaded to high specific activity with90Y at a pH of 5.7. Stability studies showed that approximately 95% of added90Y is retained within the PLA matrix after 28 days (>10 half‐lives) at 37°C in serum, and electron microscopy showed that the microspheres retained their characteristic morphologic appearance for the same time period. Cytotoxicity studies with SK‐N‐SH neuroblastoma cells growing in monolayer showed that the radiocytotoxicity of the microspheres could be directed magnetically to either kill or spare specific cell populations, thus making them of great interest for targeted intracavitary tumor therapy. We are currently optimizing this system for use in the treatment of neoplastic meningitis. © 1994 Joh

ISSN:0021-9304    

DOI:10.1002/jbm.820280809

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractSeveral factors playing a possible role in determining coating stability and bone tissue response were studied inin vivoexperiments. These factors involving the plasmaspray coating procedure were as follows: (1) plasmaspray powder port 2 or 6; (2) particle size distribution; (3) hydroxylapatite versus fluorapatite coatings; and (4) the effect of post‐heat treatment. Coating stability and bone tissue response were examined by measuring coating thickness, coating thickness, coating length, and bone apposition against the coatings. The result was that heat treatment influenced coating stability significantly. Also, bone formation was more intense. Fluorapatite proved to be more stable than hydroxylapatite, which was in agreement with our previous reports. © 1994 John Wiley&Sons, I

ISSN:0021-9304    

DOI:10.1002/jbm.820280810

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA series of four polycarbonates derived from the ethyl, butyl, hexyl, and octyl esters of desaminotyrosyl‐tyrosine was prepared by condensation polymerization. The resulting polymers had weight average molecular weights ranging from 120,000–450,000, and their chemical structure was confirmed by elemental analysis, nuclear magnetic resonance, and Fourier transform infrared spectroscopy. The polycarbonates were evaluated as degradable biomaterials. Their surface properties were determined by electron spectroscopy for chemical analysis, attenuated total reflectance‐Fourier transformed infrared spectroscopy, and contact angle measurement. The degree of surface hydrophobicity was related to the length of the alkyl ester pendent chain. The tensile properties were dependent on the chemical structure of the polymers: For thin, solvent cast film specimens, the tensile modulus varied from 1.2–1.6 GPa, and the strength at break from 60–220 MPa. The degradation of polymeric films was followedin vitroby measuring changes in mechanical strength for up to 40 weeks, and the decrease in molecular weight and changes in surface chemistry for up to 80 weeks. The length of the pendent chain affected the degradation behavior and strength retention; the polymers with short pendent chains were more readily hydrolyzable. For sterilization, ethylene oxide treatment was less destructive, as judged by molecular weight retention, than γ‐irradiation. Spin‐cast films of all tested polycarbonates were not cytotoxic toward cultured rat lung fibroblasts. The cell response was influenced by the chemical structure of the polymer. The least hydrophobic polycarbonate (having a short ethyl ester pendent chain) was a more stimulating substrate for cell growth than the more hydrophobic polymers (carrying longer alkyl ester p

ISSN:0021-9304    

DOI:10.1002/jbm.820280811

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY