Multifunctional Nanobiomaterials for Neural Interfaces

Abstract

Neural electrodes are designed to interface with the nervous system and provide control signals for neural prostheses. However, robust and reliable chronic recording and stimulation remains a challenge for neural electrodes. Here, a novel method for the fabrication of soft, low impedance, high charge density, and controlled releasing nanobiomaterials that can be used for the surface modification of neural microelectrodes to stabilize the electrode/tissue interface is reported. The fabrication process includes electrospinning of anti‐inflammatory drug‐incorporated biodegradable nanofibers, encapsulation of these nanofibers by an alginate hydrogel layer, followed by electrochemical polymerization of conducting polymers around the electrospun drug‐loaded nanofibers to form nanotubes and within the alginate hydrogel scaffold to form cloud‐like nanostructures. The three‐dimensional conducting polymer nanostructures significantly decrease the electrode impedance and increase the charge capacity density. Dexamethasone release profiles show that the alginate hydrogel coating slows down the release of the drug, significantly reducing the burst effect. These multifunctional materials are expected to be of interest for a variety of electrode/tissue interfaces in biomedical devices.

Optical and Electrochemical Methods for Determining the Effective Area and Charge Density of Conducting Polymer Modified Electrodes for Neural Stimulation

“…Iridium oxide undergoes redox reactions to increase the charge passed during cyclic voltammetry, and hence the charge density 5 . Similarly, doped conducting polymers undergo a range of Faradaic and non-Faradaic reactions that result in a larger charge density [9][10][11][12][13][14] . More exotic materials, including carbon nanotubes, graphene, titanium nitride and tantalum oxide have also been reported [15][16][17] .…”

Conducting polymer-hydrogels for medical electrode applications

“…Nanostructured hydrogels could potentially be used as templates to synthesize CP-hydrogels with specific structures (category A, figure 3). As an illustration of this approach using a degradable polymer rather than a hydrogel, Abidian et al [3,4,7,25,118] electrodeposited 100 to 600 nm diameter CP nanofibrils by using electrospun poly(L-lactic acid) (PLLA) and poly(lactic-co-glycolic acid) (PLGA) nanofibres as a template. Either PEDOT or PPy was directly electrodeposited on the gold neural probe coated with the electrospun polymers.…”

“…Electrodes are conventionally fabricated from platinum, platinum alloys and gold. Surface modification of metallic electrodes has been extensively studied with a view to increasing the integration of biological tissue and minimizing foreign body encapsulation at the electrode interface [1][2][3][4][5]. In addition, improved communication between synthetic and biological systems will allow medical devices to perform more efficiently by permitting the use of smaller charges to elicit a neural response [6][7][8][9].…”

“…Several research groups have explored the functionalization of CPs with biological molecules, specifically growth factors [2,18,20,21], cell adhesion proteins [1,10,22,23] and anti-inflammatory drugs [3,24]. Although bioactivity has been successfully imparted to a variety of CPs, Green et al [1,2] reported that large peptides and growth factors significantly disrupt the mechanical stability and long-term electrochemical performance of bioactive CP coatings.…”

“…Thus CPs alone may not be sufficient to create a long-term stable interface between synthetic implant devices and neural tissue. More recently, design and development of CP-hydrogel blends have been proposed as an approach to overcoming some of the limitations that CPs used alone may present [3,[25][26][27][28]. The underlying premise of this approach is that hydrogels may act to modulate and improve mechanical properties, as well as provide a low-fouling surface and a depot for water soluble, bioactive agents.…”