Small bioactive molecules as dual functional co-dopants for conducting polymers

Abstract

Biological responses to neural interfacing electrodes can be modulated via biofunctionalisation of conducting polymer (CP) coatings. This study investigated the use of small bioactive molecules with anti-inflammatory properties. Specifically, anionic dexamethasone phosphate (DP) and valproic acid (VA) were used to dope the CP poly(ethylenedioxythiophene) (PEDOT). The impact of DP and VA on material properties was explored both individually and together as a codoped system, compared to the conventional dopant p-toluenesulfonate (pTS). Electrical properties of DP and VA doped PEDOT were reduced in comparison to PEDOT/pTS, however co-doping with both DP and VA was shown to significantly improve the electroactivity of PEDOT in comparison the individually doped coatings.Similarly, while the individually doped PEDOT coatings were mechanically friable, the inclusion of both dopants during electropolymerisation was shown to attenuate this response. In a whole-blood model of inflammation all DP and VA doped CPs retained their bioactivity, causing a significant reduction in levels of the pro-inflammatory cytokine TNF-a. These studies demonstrated that small charged bioactive molecules are able act as dopants for CPs and that co-doping with ions of varied size and doping affinity may provide a means of addressing the limitations of large bulky bimolecular dopants. Fig. 2 SEM micrographs of PEDOT coatings doped with (clockwise from top left) pTS, DP, DP + VA and VA taken at 2500Â magnification.

Conducting Polymers for Neural Prosthetic and Neural Interface Applications

“…To both incorporate a drug as a dopant and then deliver it in a controlled manner, the molecule must also be relatively small, to enable it to move through the polymer matrix. Both DP and valproic acid (VA) have been used to dope CPs and have been investigated as anti‐inflammatory molecules . When the charged drug is delivered by the application of an electrical potential, it is important to realize that the CP component of the material may become undoped and lose its electroactivity.…”

A New Drug Delivery System Based on Tauroursodeoxycholic Acid and PEDOT

“…Adhesion tests were performed to assess whether the increased thickness of PEDOT–TUDCA may facilitate film delamination, compared to the thinner PEDOT–DEX films. To this purpose, we employed a modified ASTM International standard test method for measuring adhesion by test tape, which was reported in the literature as an effective tool to evaluate the delamination due to mechanical stress of conductive polymer films . EIS was collected before and after the adhesion test to quantify any possible increased resistivity due to film delamination.…”

A critical review of cell culture strategies for modelling intracortical brain implant material reactions

“…The indirect conditioned media approach investigates the influence of soluble factors from the material and its subsequent effect on the cells, via transfer of conditioned media or soluble extract into the cell culture media [81]. products and changes in protein expression with enzyme linked immunosorbent assay (ELISA) [99] and western blots. Changes at the gene expression level can also be assessed through DNA analysis using techniques such as polymerase chain reaction (PCR).…”

“…In vitro blood studies are conducted with either whole blood or blood plasma to assess: protein absorption [106], clot formation [107], platelet adhesion [108], and leukocyte activation and cytokine production [99,109]. The most relevant studies using whole blood or blood plasma utilize human blood samples, although in some instances non-human derived blood is used [107].…”

“…Materials that encourage cell attachment or interaction are commonly assessed for the adhesion of proteins, platelets [108] and blood clotting [109]. The materials are also assessed for their effect on leukocyte activation and the production of cytokines and chemokines [99,104].…”