Influence of artificial body fluids and medical sterilization procedures on chemical stability of Parylene C

Beshchasna, Natalia; Adolphi, B.; Granovsky, S.A.; Braunschweig, Markus; Schneider, W.; Uhlemann, J.; Wolter, K.-J.

doi:10.1109/ectc.2010.5490711

Cited by 15 publications

(15 citation statements)

References 8 publications

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“…For brevity, detailed ethylene oxide sterilization (EtO) and EtO+ENZOL (a common enzymatic cleaner) reference sample results are omitted from this report. No indication was found using EDS, XPS, and FTIR that such processing altered film properties versus untreated references, in agreement with previous work [54]. Since the ideal accelerated aging test system will mimic material damage mechanisms observed in vivo, explant results were considered a benchmark for comparison of in vitro accelerated aging methods.…”

Section: Resultssupporting

confidence: 84%

Analytical characterization of Parylene-C degradation mechanisms on Utah arrays: evaluation of in vitro Reactive Accelerated Aging model compared to multiyearin vivoimplantation

Caldwell

Street

Sharma

et al. 2019

Preprint

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Implantable neural microelectrodes are integral components of neuroprosthetic technologies and can transform treatments for many neural-mediated disorders. However, dielectric material degradation during long-term (> 1 year) indwelling periods restricts device functional lifetimes to a few years. This comprehensive work carefully investigates in vivo material degradation and also explores the ability of in vitro Reactive Accelerated Aging (RAA) to evaluate implant stability. Parylene C-coated Utah electrode arrays (UEAs) implanted in feline peripheral nerve for 3.25 years were explanted and compared to RAA-processed devices, aged in phosphate buffered saline (PBS) + 20 mM H 2 O 2 at either 67 or 87 °C (28 or 7 days, respectively). Electron microscopy revealed similar physical damage characteristics between explants and RAA (87° C) devices. Parylene C degradation was overwhelmingly apparent for UEAs from both RAA cohorts. Controls aged in PBS alone displayed almost no damage. Spectroscopic characterization (EDX, XPS, FTIR) found clear indications of oxidation and chlorine abstraction for parylene C aged in vivo. While in vitro aging was also accompanied by signs of oxidation, changes in the chemistry in vivo and in vitro were statistically different. Analysis of RAAaged devices identified UEA fabrication approaches that may greatly improve device resistance to degradation. This work underscores the need for an improved understanding of in vivo damage mechanisms, to facilitate the critical need for representative in vitro accelerated testing paradigms for long-term implants.

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Section: Resultssupporting

confidence: 84%

Analytical characterization of Parylene-C degradation mechanisms on Utah arrays: evaluation of in vitro Reactive Accelerated Aging model compared to multiyearin vivoimplantation

Caldwell

Street

Sharma

et al. 2019

Preprint

View full text Add to dashboard Cite

show abstract

“…It has been reported that parylene C does not change the chemical and crystalline properties when exposed to H 2 O 2 -plasma whereas gamma radiation decreases the crystallinity and ethylene oxide changes Cl-nature. 24 The increased stiffness, however, caused by the addition of parylene C coating might slightly inhibit the flap valve motion, specifically degrading the reduction of a backward flow both for the distal portion of stents and whole stents.…”

Section: Discussionmentioning

confidence: 99%

Anti-Reflux Ureteral Stent with Polymeric Flap Valve Using Three-Dimensional Printing: An In Vitro Study

Park

Kim

Jeong

et al. 2015

Journal of Endourology

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“…Exposure of parylene-C to artificial blood plasma and cerebrospinal fluid for 2 months has also been shown to increase the crystallinity of the polymer, making it more brittle. Body fluids in contact with parylene may also lead to the recruitment of inflammatory or fibrogenic agents [77]. The notion that parylene-C is a suitable, biocompatible material for long-term neuroprosthetics no longer seems valid.…”

Section: Discussionmentioning

confidence: 99%

Scanning electron microscopy of chronically implanted intracortical microelectrode arrays in non-human primates

2016

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Objective Signal attenuation is a major problem facing intracortical sensors for chronic neuroprosthetic applications. Many studies suggest that failure is due to gliosis around the electrode tips, however, mechanical and material causes of failure are often overlooked. The purpose of this study was to investigate the factors contributing to progressive signal decline by using scanning electron microscopy (SEM) to visualize structural changes in chronically implanted arrays and histology to examine the tissue response at corresponding implant sites. Approach We examined eight chronically implanted intracortical microelectrode arrays (MEAs) explanted from non-human primates at times ranging from 37 to 1051 days post-implant. We used SEM, in vivo neural recordings, and histology (GFAP, Iba-1, NeuN). Three MEAs that were never implanted were also imaged as controls. Main results SEM revealed progressive corrosion of the platinum electrode tips and changes to the underlying silicon. The parylene insulation was prone to cracking and delamination, and in some instances the silicone elastomer also delaminated from the edges of the MEA. Substantial tissue encapsulation was observed and was often seen growing into defects in the platinum and parylene. These material defects became more common as the time in vivo increased. Histology at 37 and 1051 days post-implant showed gliosis, disruption of normal cortical architecture with minimal neuronal loss, and high Iba-1 reactivity, especially within the arachnoid and dura. Electrode tracts were either absent or barely visible in the cortex at 1051 days, but were seen in the fibrotic encapsulation material suggesting that the MEAs were lifted out of the brain. Neural recordings showed a progressive drop in impedance, signal amplitude, and viable channels over time. Significance These results provide evidence that signal loss in MEAs is truly multifactorial. Gliosis occurs in the first few months after implantation but does not prevent useful recordings for several years. Progressive meningeal fibrosis encapsulates and lifts MEAs out of the cortex while ongoing foreign body reactions lead to progressive degradation of the materials. Long-term impedance drops are due to the corrosion of platinum, cracking and delamination of parylene, and delamination of silicone elastomer. Oxygen radicals released by cells of the immune system likely mediate the degradation of these materials. Future MEA designs must address these problems through more durable insulation materials, more inert electrode alloys, and pharmacologic suppression of fibroblasts and leukocytes.

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Influence of artificial body fluids and medical sterilization procedures on chemical stability of Parylene C

Cited by 15 publications

References 8 publications

Analytical characterization of Parylene-C degradation mechanisms on Utah arrays: evaluation of in vitro Reactive Accelerated Aging model compared to multiyearin vivoimplantation

Analytical characterization of Parylene-C degradation mechanisms on Utah arrays: evaluation of in vitro Reactive Accelerated Aging model compared to multiyearin vivoimplantation

Anti-Reflux Ureteral Stent with Polymeric Flap Valve Using Three-Dimensional Printing: An In Vitro Study

Scanning electron microscopy of chronically implanted intracortical microelectrode arrays in non-human primates

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