Mechanisms of polymer degradation in implantable devices

Ali, S.A.M.; Zhong, Sheng; Doherty, Patrick; Williams, David

doi:10.1016/0142-9612(93)90063-8

Cited by 168 publications

(81 citation statements)

References 26 publications

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“…O citrato será então incorporado no Ciclo de Krebs, resultando em CO 2 e H 2 O, podendo sua eliminação ser feita através da urina e da respiração. O material foi reabsorvido e metabolizado [23] .…”

Section: Suportes (Scaffolds) Suportes (Scaffolds) Suportes (Scaffoldunclassified

Polímeros bioreabsorvíveis na engenharia de tecidos

Barbanti

Zavaglia

Duek³

2005

Polímeros

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[3] , sistemas para liberação controlada de drogas [4] , stents [5] e dispositivos ortopédicos [6] . Atualmente fazem parte do cotidiano dos centros cirúrgicos no mundo inteiro.Embora muitos dispositivos protéticos artificiais estejam disponíveis, poucos podem substituir completamente todas as complexas funções biológicas. Em situações clíni-cas mais severas somente o transplante do órgão retoma as atividades orgânicas. Assim, de uma forma idealizada, a melhor alternativa seria obter um novo órgão ou tecido, substituindo aquele que não desempenha normalmente suas funções. Nos dias de hoje, a idéia da reconstrução de órgãos e tecidos criados em laboratório é amplamente difundida e investigada no mundo todo [7,8] . Resumo: A Engenharia de Tecidos consiste em um conjunto de conhecimentos e técnicas para a reconstrução de novos órgãos e tecidos. Baseada em conhecimentos das áreas de ciência e engenharia de materiais, biológica e médica, a técnica envolve a expansão in vitro de células viáveis do paciente doador sobre suportes de polímeros bioreabsorvíveis. O suporte degrada enquanto um novo órgão ou tecido é formado. Os poli(α-hidróxi ácidos) representam a principal classe de polímeros sintéticos bioreabsorvíveis e biodegradáveis utilizados na engenharia de tecidos. No desenvolvimento e na seleção desses materiais, o tempo de degradação é fundamental para o sucesso do implante. Os estudos e os desafios atuais são normalmente direcionados ao entendimento das relações entre composição química, cristalinidade, morfologia do suporte, e o processamento desses materiais. Este artigo faz uma revisão dos trabalhos recentes sobre a utilização dos polímeros sintéticos bioreabsorvíveis como suportes na engenharia de tecidos. Engenharia de tecidos Palavras-chave: Engenharia de tecidos, polímeros bioreabsorvíveis, poli(α-hidróxi ácidos). Bioresorbable Polymers in Tissue EngineeringAbstract: Tissue Engineering is based on a group of techniques for the reconstruction of new organs and tissues. Based on knowledge of materials science and engineering, biology and medicine, the technique involves the in vitro expansion of viable cells obtained from the patient on the polymeric scaffolds. The scaffold degrades while a new organ or tissue is formed. The poly(α-hydroxy acids) are the principal biodegradable and bioresorbable polymers used in tissue engineering. In developing and selecting bioresorbable scaffolds, the degradation time is fundamental for successful biocompatibility and biofuncionality. Hence, degradation studies often address variables such as the chemical composition, crystallinity, morphology of the scaffold and the processing of these materials. This paper reviews recent work in bioresorbable polymers used as scaffolds in the tissue engineering. Keywords: Tissue engineering, bioresorbable polymers, poly(α-hydroxy acids). IntroduçãoQuando a estrutura biológica de um órgão ou tecido não pode ser reparada, a alternativa viável para o restabelecimento das funções normais do paciente é repô-la com um implante feito de um b...

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Section: Suportes (Scaffolds) Suportes (Scaffolds) Suportes (Scaffoldunclassified

Polímeros bioreabsorvíveis na engenharia de tecidos

Barbanti

Zavaglia

Duek³

2005

Polímeros

View full text Add to dashboard Cite

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“…However, this approach alone may not adequately capture the aggressive chemical environment that is created by activated immune cells, which release digestive enzymes and reactive oxygen species (ROS) (Badwey and Karnovsky 1980, Halliwell 1992, Polikov et al 2005, Freinbichler et al 2011, Patrick et al 2011. In our system, we have included hydrogen peroxide to mimic the effect of ROS generation during the brain's injury response (Ali et al 1993, Zhao et al 1995, Patrick et al 2011.…”

Section: Introductionmentioning

confidence: 99%

Rapid evaluation of the durability of cortical neural implants using accelerated aging with reactive oxygen species

et al. 2015

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Objective-A challenge for implementing high bandwidth cortical brain-machine interface devices in patients is the limited functional lifespan of implanted recording electrodes. Development of implant technology currently requires extensive non-clinical testing to demonstrate device performance. However, testing the durability of the implants in vivo is timeconsuming and expensive. Validated in vitro methodologies may reduce the need for extensive testing in animal models.Approach-Here we describe an in vitro platform for rapid evaluation of implant stability. We designed a reactive accelerated aging (RAA) protocol that employs elevated temperature and reactive oxygen species (ROS) to create a harsh aging environment. Commercially available microelectrode arrays (MEAs) were placed in a solution of hydrogen peroxide at 87 °C for a period of 7 days. We monitored changes to the implants with scanning electron microscopy and broad spectrum electrochemical impedance spectroscopy (1 Hz-1 MHz) and correlated the physical changes with impedance data to identify markers associated with implant failure.Main results-RAA produced a diverse range of effects on the structural integrity and electrochemical properties of electrodes. Temperature and ROS appeared to have different effects on structural elements, with increased temperature causing insulation loss from the electrode microwires, and ROS concentration correlating with tungsten metal dissolution. All array types experienced impedance declines, consistent with published literature showing chronic (>30 days) declines in array impedance in vivo. Impedance change was greatest at frequencies <10 Hz, and smallest at frequencies 1 kHz and above. Though electrode performance is traditionally characterized by impedance at 1 kHz, our results indicate that an impedance change at 1 kHz is not a reliable predictive marker of implant degradation or failure.Significance-ROS, which are known to be present in vivo, can create structural damage and change electrical properties of MEAs. Broad-spectrum electrical impedance spectroscopy

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“…In this study, MTX release rate was not expected to be influenced by polymer degradation owing to the known slow hydrolysis rate of PCL. While the polymers were designed to be ultimately biodegradable, as PCL itself is broken down by esterolytic cleavage, 46,47 we also intended for the polymer main Paper chains to be stable enough over the time period of cell culture experiments such that any drug release resulting from disulfide cleavage would be immediately detectable above any drug liberated by 'background degradation' of PCL components. Prior reports have shown that PEG-PCL co-polymer micelles similar to those prepared in this study decreased in molar mass by ~ 6% over a 12 week period in PBS.…”

Section: Discussionmentioning

confidence: 99%

Bioreducible cross-linked core polymer micelles enhance in vitro activity of methotrexate in breast cancer cells

et al. 2017

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Polymer micelles have emerged as promising carriers for controlled release applications, however, several limitations of micelle-based drug delivery have also been reported. To address these issues, we have synthesized a functional biodegradable and cytocompatible block copolymer based on methoxypoly(ethyleneglycol)-b-poly(ε-caprolactone-co-α-azido-ε-caprolactone) (mPEG-b-poly(εCL-co-αN3εCL)) as a precursor of reduction sensitive core-crosslinked micelles. The synthesized polymer was formulated as micelles using a dialysis method and loaded with the anti-inflammatory and anticancer drug methotrexate (MTX). The micellar cores were subsequently crosslinked at their pendant azides by a redoxresponsive bis(alkyne). The size distributions and morphology of the polymer micelles were assessed using dynamic light scattering (DLS) and transmission electron microscopy, and drug release assays were performed under simplified (serum free) physiological and reductive conditions. Cellular uptake studies in human breast cancer cells were performed using Oregon-green loaded core-crosslinked micelles. The MTX-loaded core-crosslinked micelles were assessed for their effects on metabolic activity in human breast cancer (MCF-7) cells by evaluating the reduction of the dye MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. The apoptosis inducing potential of MTX-loaded core-crosslinked micelles was analysed using Hoechst/propidium iodide (PI) and annexin-V/PI assays. The data from these experiments indicated that drug release from these cross-linked micelles can be controlled and that the redox-responsive micelles are more effective carriers for MTX than non-crosslinked analogues and the free drug in the cell-lines tested.

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Mechanisms of polymer degradation in implantable devices

Cited by 168 publications

References 26 publications

Polímeros bioreabsorvíveis na engenharia de tecidos

Polímeros bioreabsorvíveis na engenharia de tecidos

Rapid evaluation of the durability of cortical neural implants using accelerated aging with reactive oxygen species

Bioreducible cross-linked core polymer micelles enhance in vitro activity of methotrexate in breast cancer cells

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