A Mosquito Inspired Strategy to Implant Microprobes into the Brain

Abstract

Mosquitos are among the deadliest insects on the planet due to their ability to transmit diseases like malaria through their bite. In order to bite, a mosquito must insert a set of micro-sized needles through the skin to reach vascular structures. The mosquito uses a combination of mechanisms including an insertion guide to enable it to bite and feed off of larger animals. Here, we report on a biomimetic strategy inspired by the mosquito insertion guide to enable the implantation of intracortical microelectrodes into the brain. Next generation microelectrode designs leveraging ultra-small dimensions and/or flexible materials offer the promise of increased performance, but present difficulties in reliable implantation. With the biomimetic guide in place, the rate of successful microprobe insertion increased from 37.5% to 100% due to the rise in the critical buckling force of the microprobes by 3.8-fold. The prototype guides presented here provide a reproducible method to augment the insertion of small, flexible devices into the brain. In the future, similar approaches may be considered and applied to the insertion of other difficult to implant medical devices.

A microfabricated, 3D-sharpened silicon shuttle for insertion of flexible electrode arrays through dura mater into brain

“…Force and tissue compression are important metrics to gauge neural tissue damage, but a single unit count weeks after implant is required to fully demonstrate a neural recording technology for chronic use. Recently, promising strategies for insertion of flexible polymer devices through rat dura have been demonstrated (Shoffstall et al, 2018, Zhao et al, 2019, but such methods have not yet reported chronic, single-unit recordings in freely behaving animals. Here, we evaluated our single unit count at 95 days.…”

“…Another complementary insertion strategy uses an insertion guide, as recently demonstrated for insertion of SMP devices through rat dura (Shoffstall et al, 2018). Inspired by the labium that guides the proboscis of the female mosquito, a guide at the insertion site increases the critical buckling load of the inserted device itself.…”

“…Other solutions include syringe injection , Schuhmann et al, 2018 or, to reduce the amount of fluid injected to the brain parenchyma, fluidic microdrive insertion (Vitale et al, 2018). Devices have also been frozen for insertion , or coated with adjustable shape memory polymer (SMP; Simon et al, 2017), which can penetrate dura when combined with an insertion guide (Shoffstall et al, 2018). One straightforward solution is to temporarily attach the flexible array to a hard shuttle, such as silicon , Felix et al, 2012, Chen et al, 2017, Patel et al, 2015, diamond (Na et al, 2018), or tungsten (Zhao et al, 2019) that is shape-matched to the device itself and can be retracted once the array has been inserted to its target depth in the brain.…”

“…Using this shuttle, we report successful implantation and recording of local field potential (LFP) and single units from devices targeted to the orbitofrontal cortex (OFC), for at least 95 days. Although promising strategies for insertion of flexible polymer devices through rat dura have recently been demonstrated (Shoffstall et al, 2018, Zhao et al, 2019, such methods have not yet yielded chronic, high-quality recordings in freely behaving animals. This is the first in vivo demonstration of successful chronic neural recording using a method to implant through a membrane with Young's modulus in the range 0.1-1 mPa (Maikos et al, 2008), corresponding to the rat dura or primate pia.…”

Biomimetics – Nature's roadmap to insights and solutions for burden of lifestyle diseases

“…Nevertheless, there has been some progress in the medically focused biomimetics. Bio‐inspired products intended for medical application are being developed including tenacious biological glues with anti‐proliferative, anti‐inflammatory and anti‐microbial activity based on sticky proteins (natures glue) secreted by the bivalve mussel species microprobes for brain surgery based on mosquito skin penetration , the red sweat of the hippopotamus that have antibiotic and sunscreen activity , and development of anti‐microbial surfaces modelled after the diamond‐like architecture of shark skin .…”