Micropatterned Polypyrrole: A Combination of Electrical and Topographical Characteristics for the Stimulation of Cells

Abstract

Electrically conducting polymers such as polypyrrole (PPy) are important biomaterials in neural engineering applications, including neural probes, nerve conduits, and scaffolds for tissue and nerve regeneration. Surface modification of these polymers can introduce other valuable characteristics for neural interfacing in addition to electrical conductivity, such as topographical features and chemical bioactivity. Here, the patterning of PPy to create topographical cues for cells is reported. In particular, 1 and 2 µm wide PPy microchannels are fabricated using electron-beam (e-beam) lithography and electropolymerization. A systematic analysis of parameters controlling PPy micropatterning is performed, and finds that microchannel depth, roughness, and morphology are highly dependent on the e-beam writing current, polymerization current, PPy/dopant concentrations, and the polymerization time. Embryonic hippocampal neurons cultured on patterned PPy polarize (i.e., defined an axon) faster on this modified material, with a twofold increase in the number of cells with axons compared to cells cultured on unmodified PPy. These topographical features also have an effect on axon orientation but do not have a significant effect on overall axon length. This is the first investigation that studies controlled PPy patterning with small dimensions (i.e., less than 5 µm) for ** Funding for this work was provided by grants from the Gillson Longenbaugh Foundation and NIH (R01 EB004529). We thank the Welch Foundation and SPRING for partial financial support in the CNM facilities. We acknowledge Maeve Cooney's assistance with manuscript and figure editing.

Applications of conducting polymers and their issues in biomedical engineering

“…It was observed that the anodic peak potential (Epa) values upon incorporation of NGF to the CP PPy was found to shift to more positive values, increasing the applied charge, and thereby indicating more deposition of PPy and NGF (Gomez et al 2007). Moreover, at higher current density, it was noticed that the amount of NGF incorporated was less than at lower current densities because of either slow diffusion or denaturing of the incorporated NGF when excessive current was applied (Gomez et al 2007). Kim et al (2006) have reported the incorporation of both collagen and NGF into PPy, and confirmed the activity of both biomolecules through the neurite outgrowth of PC12 cells.…”

“…This would provide for very intimate contact between cells and the CP (as depicted in figure 16), ensuring continuous electrical contact between the electrode and the tissue (Richardson-Burns et al 2007). Moreover, the topographical patterns can provide contact guidance cues to primary neurons (Gomez et al 2007). The surface roughness properties of the CP films can be tailored by modifying the CP synthesis temperature.…”

A 3D Electroactive Polypyrrole-Collagen Fibrous Scaffold for Tissue Engineering

“…Polypyrrole has demonstrated cell and tissue compatibility in vivo and in vitro [12,22,23]. Human umbilical vein endothelial cells demonstrated higher cell doubling times when cultured on polypyrrole composite substrates [24].…”

Neuronal Differentiation of Embryonic Stem Cell Derived Neuronal Progenitors Can Be Regulated by Stretchable Conducting Polymers

“…[10][11][12][13][14][15][16][17] Conducting polymers (CPs) provide a unique microenvironment for proliferation and differentiation of cells. [18][19][20][21] The electronic and ionic characteristics of these electrochemically active polymers have been utilized in the generation of neuronal probes and biosensors. [22][23][24] The prospect of having such smart-electrode interface on flexible-stretchable substrates opens up a valuable gateway to monitor and control biological events.…”