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bioRxiv · 10.1101/2020.12.13.422566

Mechanically Matched Silicone Brain Implants Reduce Brain Foreign Body Response

Zhang, E.·Alameri, A.·Clement, J.-P.·Ng, A.·Kennedy, T. E.·Juncker, D.
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Abstract

Brain implants are increasingly used to treat neurological disorders and diseases. However, the brain foreign body response (FBR) elicited by implants affects neuro-electrical transduction and long-term reliability limiting their clinical adoption. The mismatch in Youngs modulus between silicon implants ([~]180 GPa) and brain tissue ([~]1-30 kPa) exacerbates the FBR resulting in the development of flexible implants from polymers such as polyimide ([~]1.5-2.5 GPa). However, a stiffness mismatch of at least two orders of magnitude remains. Here, we introduce (i) the first mechanically matched brain implant (MMBI) made from silicone ([~]20 kPa), (ii) new microfabrication methods, and (iii) a novel dissolvable sugar shuttle to reliably implant MMBIs. MMBIs were fabricated via vacuum-assisted molding using sacrificial sugar molds and were then encased in sugar shuttles that dissolved within 2 min after insertion into rat brains. Sections of rat neocortex implanted with MMBIs, PDMS implants, and silicon implants were analyzed by immunohistochemistry 3 and 9-weeks post-implantation. MMBIs resulted in significantly higher neuronal density and lower FBR within 50 {micro}m of the tissue-implant interface compared to PDMS and silicon implants suggesting that materials mechanically matched to brain further minimize the FBR and could contribute to better implant functionality and long-term reliability.

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Zhang, E., Alameri, A., Clement, J.-P., Ng, A., Kennedy, T. E., Juncker, D.. 2020-12-14. Mechanically Matched Silicone Brain Implants Reduce Brain Foreign Body Response. https://doi.org/10.1101/2020.12.13.422566

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