Hydrogel–Electrospun Fiber Mat Composite Coatings for Neural Prostheses

Abstract

Achieving stable, long-term performance of implanted neural prosthetic devices has been challenging because of implantation related neuron loss and a foreign body response that results in encapsulating glial scar formation. To improve neuron–prosthesis integration and form chronic, stable interfaces, we investigated the potential of neurotrophin-eluting hydrogel–electrospun fiber mat (EFM) composite coatings. In particular, poly(ethylene glycol)-poly(ε-caprolactone) (PEGPCL) hydrogel–poly(ε-caprolactone) EFM composites were applied as coatings for multielectrode arrays. Coatings were stable and persisted on electrode surfaces for over 1 month under an agarose gel tissue phantom and over 9 months in a PBS immersion bath. To demonstrate drug release, a neurotrophin, nerve growth factor (NGF), was loaded in the PEGPCL hydrogel layer, and coating cytotoxicity and sustained NGF release were evaluated using a PC12 cell culture model. Quantitative MTT assays showed that these coatings had no significant toxicity toward PC12 cells, and neurite extension at day 7 and 14 confirmed sustained release of NGF at biologically significant concentrations for at least 2 weeks. Our results demonstrate that hydrogel–EFM composite materials can be applied to neural prostheses to improve neuron–electrode proximity and enhance long-term device performance and function.

Matrigel coatings for Parylene sheath neural probes

“…The final concentration of DEX is similar to other slow‐release DEX coatings that have reduced astrocytic responses . Others reported using 1 mg/mL NGF solution added to hydrogel to form coatings or reported a release of 8 ng of NGF from a hydrogel, which would be available from the amount of coating deposited on our probes. A hydrogel coating containing 100 μg/mL of BDNF was used to support the growth of neurons; the eluate from the hydrogel was reported to have a similar affect as adding 100 ng/mL of solution directly to a cell culture …”

Fabrication and evaluation of magnetic hydrogel fiber based on micro fluidic device

“…As scaffolds, hydrogels are used to provide bulk and mechanical constitution to a tissue construct, whether cells are adhered to or suspended within the 3D gel framework. When cellular adhesion directly to the gel is favored over suspension within the scaffold, incorporation of various cell nutrition materials into the hydrogel structure can dramatically increase the tendency for cellular growth, differentiation and proliferation [6][7][8][9]. To generate microengineered hydrogels and related hydrogel and cell complex, many techniques have been investigated such as emulsification, photolithography, micromolding and microfluidic synthesis [10][11][12].…”

Controlled delivery for neuro-bionic devices

“…Reducing the biodegradability of coating materials can significantly prolong the duration of sustained release as achieved by introducing a poly(ε-caprolactone) (PCL) component into the PEGPCL hydrogel coating [28]. Similarly introduction of the PCL component via electrospinning extends the duration of sustained release [29]. Other approaches used to control the delivery of neurotrophin involve chemical modification to promote protein-matrix interactions, and varying the porosity of hydrogel coatings.…”

“…Three approaches are reviewed here. The first involves drug-eluting structures formulated with anti-inflammatory drugs [21,22,23,24,25] and neurotrophin-eluting hydrogels [26,27,28,29,30,31]. The second approach involves integration of microfluidic channels into neural prostheses for in situ delivery of bioactive molecules with high temporal and spatial resolution [32,33,34,35,36,37,38,39].…”