Histological evaluation of flexible neural implants; Flexibility limit for reducing the tissue response?

Heui Chang Lee, Fredrik Ejserholm, Janak Gaire, Seth Currlin, Jens Schouenborg, Lars Wallman, Martin Bengtsson, Kinam Park, Kevin J. Otto

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskriftPeer review

61 Citeringar (SciVal)

Sammanfattning

Objective. Flexible neural probes are hypothesized to reduce the chronic foreign body response (FBR) mainly by reducing the strain-stress caused by an interplay between the tethered probe and the brain's micromotion. However, a large discrepancy of Young's modulus still exists (3-6 orders of magnitude) between the flexible probes and the brain tissue. This raises the question of whether we need to bridge this gap; would increasing the probe flexibility proportionally reduce the FBR? Approach. Using novel off-stoichiometry thiol-enes-epoxy (OSTE+) polymer probes developed in our previous work, we quantitatively evaluated the FBR to four types of probes with different softness: silicon (∼150 GPa), polyimide (1.5 GPa), OSTE+Hard (300 MPa), and OSTE+Soft (6 MPa). Main results. We observed a significant reduction in the fluorescence intensity of biomarkers for activated microglia/macrophages and blood-brain barrier (BBB) leakiness around the three soft polymer probes compared to the silicon probe, both at 4 weeks and 8 weeks post-implantation. However, we did not observe any consistent differences in the biomarkers among the polymer probes. Significance. The results suggest that the mechanical compliance of neural probes can mediate the degree of FBR, but its impact diminishes after a hypothetical threshold level. This infers that resolving the mechanical mismatch alone has a limited effect on improving the lifetime of neural implants.

Originalspråkengelska
Artikelnummer036026
TidskriftJournal of Neural Engineering
Volym14
Utgåva3
DOI
StatusPublished - 2017 maj 4

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  • Annan medicinteknik

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