Surface modification of neural recording electrodes with conducting polymer/biomolecule blends

Abstract

The interface between micromachined neural microelectrodes and neural tissue plays an important role in chronic in vivo recording. Electrochemical polymerization was used to optimize the surface of the metal electrode sites. Electrically conductive polymers (polypyrrole) combined with biomolecules having cell adhesion functionality were deposited with great precision onto microelectrode sites of neural probes. The biomolecules used were a silk-like polymer having fibronectin fragments (SLPF) and nonapeptide CDPGYIGSR. The existence of protein polymers and peptides in the coatings was confirmed by reflective microfocusing Fourier transform infrared spectroscopy (FTIR). The morphology of the coating was rough and fuzzy, providing a high density of bioactive sites for interaction with neural cells. This high interfacial area also helped to lower the impedance of the electrode site and, consequently, to improve the signal transport. Impedance spectroscopy showed a lowered magnitude and phase of impedance around the biologically relevant frequency of 1 kHz. Cyclic voltammetry demonstrated the intrinsic redox reaction of the doped polypyrrole and the increased charge capacity of the coated electrodes. Rat glial cells and human neuroblastoma cells were seeded and cultured on neural probes with coated and uncoated electrodes. Glial cells appeared to attach better to polypyrrole/SLPF-coated electrodes than to uncoated gold electrodes. Neuroblastoma cells grew preferentially on and around the polypyrrole/CDPGYIGSR-coated electrode sites while the polypyrrole/CH(3)COO(-)-coated sites on the same probe did not show a preferential attraction to the cells. These results indicate that we can adjust the chemical composition, morphology, electronic transport, and bioactivity of polymer coatings on electrode surfaces on a multichannel micromachined neural probe by controlling electrochemical deposition conditions.

Electrochemically controlled release of dexamethasone from conducting polymer polypyrrole coated electrode

“…This is the tail of the ~1 eV (~8066 cm -1 ) bipolaron absorption band, which is the signature for electrical conductivity of conducting polymers [42,43]. The broad band around 1550 cm -1 is the characteristic absorption frequency for double bond vibration of the pyrrole ring [9,37,44,45]. Proof of the presence of dexamethasone in the deposited film is clearly seen by the appearance of peaks at 3200-3500 cm -1 (hydroxyl), 2850-3000 cm -1 (methyl) and 1665-1760 cm -1 (carbonyl).…”

“…Polypyrrole has been electrically deposited onto the electrode site of the neural recording arrays together with CDPGYIGSR, a peptide fragment from laminin [9,37], to improve the neuron-electrode connection in vivo.…”

Conducting polymer-hydrogels for medical electrode applications

“…The thickness and morphology of the film are primarily controlled by the amount of electric charge passed between the counter and working electrodes. Additionally, biofunctionality can be easily imparted to CPs during electrodeposition through the incorporation of biological entities such as silk-like protein fragments (SLPF) [59], hyaluronic acid (HA) [60,61], various laminin peptides [1,2,59,62], enzymes [28,[63][64][65][66], polymeric amino acids [67,68], growth factors [2,11,69,70] and whole cells [71]. Electrodeposition is the most commonly used method for coating conventional metallic bioelectrodes.…”

“…Many CPs have demonstrated negligible toxicity across a wide range of cell types and explants, including clonal neural cells [1,2,11,140], primary neuroblastomas [59], cardiomyocytes [141], glial cells [59] and spiral ganglion explants [20]. It has also been shown that CPs provide a more conducive environment for cell attachment and growth than bare metal electrodes [1,13], and that CPs loaded with neurotrophins can stimulate neurite growth of target cells [2,6,69].…”

The design of electrospun PLLA nanofiber scaffolds compatible with serum-free growth of primary motor and sensory neurons

“…Instead of using primary neurons harvested from the nervous system, most in vitro testing of biomaterials relies on the use of renewable cell lines [1,2,[9][10][11][12][13] or, more rarely, primary cells grown in media supplemented with serum [1,3,14,15]. Both of these approaches have significant drawbacks.…”