In vivo “real-time” monitoring of glucose in the brain with an amperometric enzyme-based biosensor based on gold coated tungsten (W-Au) microelectrodes

Abstract

Biosensors based on Pt or Pt/Ir based needle-type microelectrodes have been successfully employed for continuous in vivo real-time brain biomonitoring of biomarkers such as glutamate and glucose. However, when implanted, these biosensors often bend, thereby damaging its surface and degrading its bioanalytical properties. In addition, downscaling of Pt and Pt/Ir needle-type biosensors, to improve the spatial resolution and decrease tissue damage, is technically challenging. In that sense, we investigated whether the use of a material with low malleability, tungsten (W), coated with a highly conductive material, gold (Au) could be as an alternative for conventional needle-type based biosensors.Therefore, we developed implantable needle-type (50 m Ø) gold coated tungsten (W-Au) amperometric microbiosensors. First, we evaluated electrochemically, the ability of W-Au microelectrodes (50 m Ø) to continuously monitor changes in H 2 O 2 . After, we functionalized, using a layer-by-layer assembly, the surface of W-Au microelectrodes. First with permselective membrane(s) (Nafion and Nafion-PPD) and after with an enzymatic hydrogel, containing an enzyme selective for glucose (glucose oxidase). Both the enzyme loading and the applied potential were optimized and the performance of functionalized W-Au microelectrodes and fully assembled biosensors was evaluated electrochemically. Additionally, the surface of bare and functionalized microelectrodes was also characterized by imaging techniques (scanning electron microscopy).In vivo experiments revealed that, W-Au based glucose biosensors, were able to accurately monitor, in real-time, changes in brain glucose in response to relevant pharmacological challenges.

In-Vivo Corrosion Characterization and Assessment of Absorbable Metal Implants

“…Li et al [77] have designed, fabricated and characterized a micro-needle biosensor attached to a new smart catheter and equipped with LabVIEW data acquisition program that is capable of monitoring glucose and oxygen in patients with traumatic brain injuries. A similar technique was used on an invasive needle-type oxygen micro-sensor (microelectrode) for real-time monitoring of glucose in the brain [78]. The microelectrodes were made from a needle-type Pt/C fiber and a gold coated W-Au needle (50 µm diameter, 2 mm length, 3.147 mm 2 of surface area).…”

Core-shell gold-nickel nanostructures as highly selective and stable nonenzymatic glucose sensor for fermentation process

“…Therefore, the addition of a second metal, i.e. to generate bimetallic nanoparticles or nanocomposites [28][29][30][31][32][33][34][35] , is often used to improve the sensor performance. In principle, the second metal can effectively manipulate the electronic and geometric properties of the nanoparticles, leading to their higher selectivity and reactivity.…”

A Multichannel Flexible Optoelectronic Fiber Device for Distributed Implantable Neurological Stimulation and Monitoring

“…To evaluate the damage of the flexible optoelectronic fiber to the brain tissue intuitively, commercially available gold‐coated tungsten electrodes were selected as control for the biocompatibility study. The biosafety of such electrodes has been verified by many studies, [ 47–49 ] thus, they can provide acknowledged benchmarks for the biocompatibility of our devices. A flexible optoelectronic fiber and a commercial electrode were implanted simultaneously to a rat that was then allowed to recover for 2 weeks ( Figure a).…”