In Vitro Degradation and Release Characteristics of Biodegradable Implants Containing Trypsin Inhibitor

Athanasiou, Kyriacos A.; Singhal, A. R.; Agrawal, C. Mauli; Boyan, Barbara D.

doi:10.1097/00003086-199506000-00033

Cited by 11 publications

(19 citation statements)

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“…However, by 6 porous at 0 and 3 weeks, turning into amorphous masses with few pores by 6 weeks, and essentially disappearing weeks CC specimens exhibited the formation of needle 524B / 8h0d$$524B 04-25-97 22:55:11 jbma W-JBM ences between the groups. Earlier studies 17,19 on specimens similar to the controls in this study also demonstrated the rapid degradation in MW between 4 and 6 weeks. It is noteworthy that in the present study the pH of the media in the vicinity of the control specimens also decreased precipitously, starting at approximately the 4-week time point.…”

Section: Introductionsupporting

confidence: 78%

“…17 techniques to maintain the pH at nontoxic levels in the vicinity of degrading PLA-PGA implants. Methods to incorporate various buffering agents in PLA-PGA implants RESULTS were developed and their efficacy in controlling the local pH was examined in vitro.…”

Section: Introductionmentioning

confidence: 99%

“…implant production were previously reported elsewhere. 16,17 A measured quantity (30% by volume of the dry polymer) Figure 2 shows differences in mass loss as a function of time among the four groups. Mass changes were normalof the appropriate buffering compound was then added to the gummy precipitate and mixed thoroughly to ensure a ized with respect to each specimen's mass at 0 days.…”

Section: Introductionmentioning

confidence: 99%

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Technique to control pH in vicinity of biodegrading PLA-PGA implants

Agrawal

Athanasiou

1997

J. Biomed. Mater. Res.

427

291

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This in vitro study was performed to examine if the pH decrease in the vicinity of degrading polylactic acid (PLA) and polyglycolic acid (PGA) polymers can be offset by incorporation of basic salts within PLA-PGA implants. It has been suggested that such pH lowering results in adverse effects, which may be responsible for biocompatibility concerns raised recently about PLA and PGA polymers. The results indicated that all three salts investigated in this study were successful in controlling the decrease in pH due to the acidic degradation products of the copolymer. The pH of the test media for the control group fell to a value of 3.0 at 9 weeks. Implants containing calcium carbonate maintained the pH value between 7.4 and 6.3 throughout the degradation process. Implants with calcium hydroxyapatite and sodium bicarbonate controlled the pH values between 6.9 and 4.3 and 8.2 and 4.5, respectively. At 3 weeks, marked swelling of implants containing calcium carbonate or sodium bicarbonate was observed relative to the control implants. The molecular weight and mass changes in the implants did not show any significant differences at 9 weeks. Thus, results from this in vitro model show that a significant decrease in pH in the vicinity of PLA-PGA implants can be avoided by incorporating basic salts.

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Section: Introductionsupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Technique to control pH in vicinity of biodegrading PLA-PGA implants

Agrawal

Athanasiou

1997

J. Biomed. Mater. Res.

427

291

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“…Early tissue engineering work focused on understanding relevant in vitro characteristics of PLGA scaffolds. For example, studying release kinetics of a trypsin inhibitor from a PLGA implant showed sigmoidal kinetics with increased release between 3 and 7 weeks [26]. Results also demonstrated that cyclic compressive loading significantly slowed the decrease of molecular chain size during the first week, significantly increased protein release for the first 2-3 weeks, and significantly stiffened the implant for the first 3 weeks.…”

Section: Biodegradable Scaffoldsmentioning

confidence: 94%

Harnessing Biomechanics to Develop Cartilage Regeneration Strategies

Athanasiou

Responte²,

Brown

et al. 2015

Journal of Biomechanical Engineering

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laboratory over the past 25 years. The prevalence and severity of degeneration of articular cartilage, a tissue whose main function is largely biomechanical, have motivated the development of cartilage tissue engineering approaches informed by biomechanics. This article provides a review of important steps toward regeneration of articular cartilage with suitable biomechanical properties. As a first step, biomechanical and biochemical characterization studies at the tissue level were used to provide design criteria for engineering neotissues. Extending this work to the single cell and subcellular levels has helped to develop biochemical and mechanical stimuli for tissue engineering studies. This strong mechanobiological foundation guided studies on regenerating hyaline articular cartilage, the knee meniscus, and temporomandibular joint (TMJ) fibrocartilage. Initial tissue engineering efforts centered on developing biodegradable scaffolds for cartilage regeneration. After many years of studying scaffold-based cartilage engineering, scaffoldless approaches were developed to address deficiencies of scaffold-based systems, resulting in the self-assembling process. This process was further improved by employing exogenous stimuli, such as hydrostatic pressure, growth factors, and matrix-modifying and catabolic agents, both singly and in synergistic combination to enhance neocartilage functional properties. Due to the high cell needs for tissue engineering and the limited supply of native articular chondrocytes, costochondral cells are emerging as a suitable cell source. Looking forward, additional cell sources are investigated to render these technologies more translatable. For example, dermis isolated adult stem (DIAS) cells show potential as a source of chondrogenic cells. The challenging problem of enhanced integration of engineered cartilage with native cartilage is approached with both familiar and novel methods, such as lysyl oxidase (LOX). These diverse tissue engineering strategies all aim to build upon thorough biomechanical characterizations to produce functional neotissue that ultimately will help combat the pressing problem of cartilage degeneration. As our prior research is reviewed, we look to establish new pathways to comprehensively and effectively address the complex problems of musculoskeletal cartilage regeneration.

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“…In a series of reports published by Athanasiou et al 36 ' 51 ' 52 the fabrication and use of solution cast implants for treating cartilage defects have been described. These implants were fabricated from a 50:50 copolymer of PLA-PGA, which was dissolved in acetone and precipitated in ethanol.…”

Section: Solution Castingmentioning

confidence: 99%

Fabrication and Characterization of PLA-PGA Orthopedic Implants

1995

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Fabrication methods and property characterization of polyglycolic acid (PGA), polylactic acid (PLA), and their copolymers are reviewed. Both of these aliphatic polyesters belong to the a-hydroxy group and biodegrade in a physiological environment to monomeric acids, which are readily processed and excreted from the body. The physical and mechanical characteristics discussed include molecular weight, crystallinity, stress-strain behavior, permeability, and melting/glass transition temperatures. The most common methods of fabricating PLA-PGA materials into medical devices are described.

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In Vitro Degradation and Release Characteristics of Biodegradable Implants Containing Trypsin Inhibitor

Cited by 11 publications

References 0 publications

Technique to control pH in vicinity of biodegrading PLA-PGA implants

Technique to control pH in vicinity of biodegrading PLA-PGA implants

Harnessing Biomechanics to Develop Cartilage Regeneration Strategies

Fabrication and Characterization of PLA-PGA Orthopedic Implants

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