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Water-soluble conducting polymers are of interest to enable more versatile processing in aqueous media as well as to facilitate interactions with biomolecules. Here, we report a substituted poly(3,4-ethylenedioxythiophene) derivative (PEDOT-S:H) that is fully water-soluble and selfdoped. When electrochemically oxidizing a PEDOT-S:H thin film, the film detaches from the under-laying electrode. The oxidation of PEDOT-S:H starts with an initial phase of swelling followed by cracking before it finally disrupts and detaches from the electrode. We investigated the detachment mechanism and found that parameters such as the size, charge and concentration of ions in the electrolyte, the temperature and also the pH influence the characteristics of detachment. When oxidizing PEDOT-S:H, the positively charged polymer backbone is balanced by anions from the electrolyte solution and also by the sulphonate groups on the side chains (more self-doping). From our experiments, we conclude that detachment of the PEDOT-S:H film upon oxidation occurs in part due to swelling caused by an inflow of solvated anions and associated water, and in part due to rearrangements and strain within the film, caused by more self-doping. We believe that PEDOT-S:H detachment can be of interest in a number of different applications, including addressed and active control of the release of materials such as biomolecules and cell cultures.

Conjugated polymers have been used in several applications for electronic control of cell cultures over the last years. We have shown detachment of human endothelial cells using a thin film of a self-doped water-soluble conjugated polymer. Upon electrochemical oxidation, the film swells, cracks and finally detaches taking cells cultured on top along with it. The polymer can be patterned using standard photolithography. The detachment only occurs above a threshold potential of +0.7 V and this fact has been used to create a simple actively addressed matrix, based on a resistor network placed in an encapsulated back plane. The matrix has individually detachable pixels. In this paper we have evaluated detachment of human primary keratinocytes and fibroblasts using PEDOT-S:H. In addition, we have studied effects of serum proteins, added as nutrients to the cell culture medium, on the detachment properties. It was found that at prolonged incubation times protein adhesion effectively stopped the detachment. Using shorter incubation times before detachment, both keratinocytes and fibroblasts can be detached using a regular planar device as well as the matrix device for selective detachment. Spatial control of detachment could be of use when selecting cells for clonal expansion and in order to obtain a homogeneous starting population of cells aimed for tissue engineering purposes.

Biofilms are ubiquitous in many human activities, constituting a threat or an advantage depending on the context of application. It is therefore of great interest to obtain new materials to study and control how biofilms are formed. Here, heparin and DBS (dodecylbenzenesulfonate) are incorporated as counter-ions to the PEDOT (poly(3,4-ethylenedioxythiophene)) backbone, forming conducting polymer thin-films. Polymer synthesis is based on electrodeposition, allowing for the adjustment, during fabrication, of properties like charge and hydrophobicity, important in bacterial adhesion. The electrochemical redox state of the polymer is of fundamental importance in Salmonella enterica Serovar Typhimurium biofilm modulation. Oxidized composites show increased levels of biofilm growth compared to reduced and pristine polymer films. As a result, biofilm formation is modulated by the application of a low electric voltage. Moreover, biofilm morphology and topology are affected by both the electrochemical redox state and the incorporated counter-ion, making these materials a useful tool in biofilm engineering.

Graphical Abstract Let it grow: The conjugated polymer poly(3,4-ethylenedioxythiophene) (PEDOT) was synthesized with heparin as the counterion to form a cell culture substrate. The surface of PEDOT:heparin in the neutral state associated biologically active growth factors (see picture). Electrochemical in situ oxidation of PEDOT during live cell culture decreased the bioavailability of the growth factor and created an exact onset of neural stem cell differentiation., funding agencies|Swedish Research Council (VR)||Swedish Foundation for Strategic Research (SSF; the OBOE center)||Karolinska Institute||VR||Onnesjo foundation||Linkoping University

An electronic detachment technology based on thin films of a poly(3,4-ethylene-dioxythiophene) derivative is evaluated for controlled release of human epithelial cells. When applying a potential of 1 V, the redox-responsive polymer films detach and disintegrate and at the same time release cells cultured on top in the absence of any enzymatic treatment with excellent preservation of membrane proteins and cell viability.