PEDOT doped with algal, mammalian and synthetic dopants: polymer properties, protein and cell interactions, and influence of electrical stimulation on neuronal cell differentiation.

Poly(3,4-ethylenedioxythiophene) (PEDOT) films were electrochemically polymerised with several synthetic (dodecylbenzosulfonic acid (DBSA)) and biological (dextran sulphate (DS), chondroitin sulphate (CS), alginic acid (ALG) and ulvan (ULV)) dopant anions, and their physical, mechanical and electrochemical properties characterised. PEDOT films incorporating the biological dopants ALG and ULV produced films of the greatest surface roughness (46 ± 5.1 and 31 ± 1.9 nm, respectively), and demonstrated significantly lower shear modulus values relative to all other PEDOT films (2.1 ± 0.1 and 1.2 ± 0.2 MPa, respectively). Quartz crystal microgravimetry was used to study the adsorption of the important extracellular matrix protein fibronectin, revealing protein adsorption to be greatest on PEDOT doped with DS, followed by DBSA, ULV, CS and ALG. Electrical stimulation experiments applying a pulsed current using a biphasic waveform (250 Hz) were undertaken using PEDOT doped with either DBSA or ULV. Electrical stimulation had a significant influence on cell morphology and cell differentiation for PEDOT films with either dopant incorporated, with the degree of branching per cell increased by 10.5× on PEDOT-DBSA and 6.5× on PEDOT-ULV relative to unstimulated cells, and mean neurite length per cell increasing 2.6× and 2.2× on stimulated vs. unstimulated PEDOT-DBSA and PEDOT-ULV, respectively. We demonstrate the cytocompatibility of synthetic and biologically doped PEDOT biomaterials, including the new algal derived polysaccharide dopant ulvan, which, along with DBSA doped PEDOT, is shown to significantly enhance the differentiation of PC12 neuronal cells under electrical stimulation.

Conductive and protein resistant polypyrrole films for dexamethasone delivery.

The development of inherently conducting polymers as controllable/programmable drug delivery systems has attracted significant interest in medical bionics, and the interfacial properties of the polymers, in particular, protein adsorption characteristics, is integral to the stability of the overall performance. Herein we report a hybrid conducting system based on polypyrrole doped with an anti-inflammatory prodrug, dexamethasone phosphate (DexP), upon which post-surface modification was conducted to render the polymer more biostable. We firstly investigated the influence of the current density and DexP concentration on the physiochemical properties and surface characteristics of the resulting polymer films. Films were then surface modified with thiolated poly(ethylene glycol). The influence of surface modification on inhibition of nonspecific protein adsorption to the polymer surfaces was evaluated using electrochemistry and quartz crystal microbalance. Furthermore, studies were undertaken to examine the effect of surface coatings on the drug release behaviour triggered by electrical stimulation. Our results demonstrated that both the physiochemical and interfacial properties of conducting polymers can be modulated to enhance the performance of the materials as biocompatible drug delivery systems. This provides important insight into molecular engineering of conducting polymers to facilitate their applications in medical bionics.