Effects of insertion conditions on tissue strain and vascular damage during neuroprosthetic device insertion

TLDR

Long‑term integration of neuroprosthetic devices is challenged by reactive responses that compromise the brain–device interface, and the contribution of physical insertion parameters to immediate damage is not well described. The study developed an ex vivo preparation using fluorescently labeled rat brain slices to capture real‑time images of tissue deformation during device insertion. The authors used this ex vivo rat brain slice preparation with fluorescent vasculature, performed qualitative and quantitative assessments of damage for devices of different tip shapes and speeds, and developed automated image analysis to quantify tissue deformation and compute mean effective strain. The study found that vascular damage—including severing, rupturing, and dragging—occurred even hundreds of micrometers from the insertion site, that slower insertions generally caused more damage, that cortical surface features such as pial vessels impeded insertion, that faster insertion of sharp devices produced lower mean effective strain, and that high variability suggests multiple biological factors influence insertion success.

Abstract

Long-term integration of neuroprosthetic devices is challenged by reactive responses that compromise the brain–device interface. The contribution of physical insertion parameters to immediate damage is not well described. We have developed an ex vivo preparation to capture real-time images of tissue deformation during device insertion using thick tissue slices from rat brains prepared with fluorescently labeled vasculature. Qualitative and quantitative assessments of damage were made for insertions using devices with different tip shapes inserted at different speeds. Direct damage to the vasculature included severing, rupturing and dragging, and was often observed several hundred micrometers from the insertion site. Slower insertions generally resulted in more vascular damage. Cortical surface features greatly affected insertion success; insertions attempted through pial blood vessels resulted in severe tissue compression. Automated image analysis techniques were developed to quantify tissue deformation and calculate mean effective strain. Quantitative measures demonstrated that, within the range of experimental conditions studied, faster insertion of sharp devices resulted in lower mean effective strain. Variability within each insertion condition indicates that multiple biological factors may influence insertion success. Multiple biological factors may contribute to tissue distortion, thus a wide variability was observed among insertions made under the same conditions.