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Electroactive polymers (EAPs) have been investigated as materials for use in a range of biomedical applications, ranging from cell culture, electrical stimulation of cultured cells as well as controlled delivery of growth factors and drugs. Despite their excellent drug delivery ability, EAPs are susceptible to biofouling thus they often require surface functionalisation with antifouling coatings to limit unwanted non-specific protein adsorption. Here we demonstrate the surface modification of para toluene sulfonate (pTS) doped polypyrrole with the glycoprotein lubricin (LUB) to produce a self-assembled coating that both prevents surface biofouling while also serving as a high-capacity reservoir for cationic drugs which can then be released passively via diffusion or actively via an applied electrical potential. We carried out our investigation in two parts where we initially assessed the antifouling and cationic drug delivery ability of LUB tethered on a gold surface using quartz crystal microbalance with dissipation monitoring (QCM) to monitor molecular interactions occurring on a gold sensor surface. After confirming the ability of tethered LUB nano brush layers on a gold surface, we introduced an electrochemically grown EAP layer to act as the immobilisation surface for LUB before subsequently introducing the cationic drug doxorubicin hydrochloride (DOX). The release of cationic drug was then investigated under passive and electrochemically stimulated conditions. High-performance liquid chromatography (HPLC) was then carried out to quantify the amount of DOX released. It was shown that the amount of DOX released from nano brush layers of LUB tethered on gold and EAP surfaces could be increased by up to 30% per minute by applying a positive electrochemically stimulating pulse at 0.8 V for one minute. Using bovine serum albumin (BSA), we show that DOX loaded LUB tethered on para toluene sulfonic acid (pTS) doped polypyrrole retained antifouling ability of up to 75% when compared to unloaded tethered LUB. This work demonstrates the unique, novel ability of tethered LUB to actively participate in the delivery of cationic therapeutics on different substrate surfaces. This study could lead to the development of versatile multifunctional biomaterials for use in wide range of biomedical applications, such as dual drug delivery and lubricating coatings, dual drug delivery and antifouling coatings, cellular recording and stimulation. [Display omitted] • Lubricin self-assembly on gold and EAP substrates has minimal impact on charge transfer. • Lubricin self-assembly on gold and EAP substrates has minimal impact on charge transfer. Demonstrated that tethered LUB provides a high loading potential for cationic drugs. • Self-assembled coating that prevents surface biofouling while also serving as a high-capacity reservoir for cationic drugs. [ABSTRACT FROM AUTHOR]

• A new synthesis strategy using surface-tethered dopants enables the fabrication of transparent conductive polymers only a few nanometers thick. • Lubricin can be used as a surface-tethered dopant for electropolymerization. • Ultrathin and transparent conducting polymers are electrochemically prepared using lubricin as a dopant. The electrochemical growth of conductive polymer films is a convenient synthesis route but challenging to control due to local variability in the reaction kinetics. Here we report a new method for electropolymerizing highly reproducible conductive polypyrrole films that are just nanometers thick, highly conductive and possess intrinsic optical transparencies comparable to ITO. The synthesis method utilizes a surface-tethered dopant molecule, in this case a self-assembled monolayer of the highly anionic protein lubricin (LUB), to template and thus control the 3-dimensional growth of the polypyrrole when the electrochemical polymerization reaction is performed in a pyrrole monomer solution containing no additional dopant molecules or ions. Because the tethered dopant controls where and how much polypyrrole growth occurs, this method effectively decouples the fine film morphology, thickness, and spatial-growth from the polymerization reaction kinetics and represents a paradigm shift in the electrochemical polymerization of conductive polymer films. Poorly controllable electrochemical growth synthesis route is being challenged here by a tethered dopant system, using self-assembled layers of lubricin (LUB). The growth of these conductive polymer films is controlled by the structure and morphology of the tethered LUB layer dopant, leading to an nanometers-thin and ultra-uniform thin conductive film, ideally suited to coating micro/nanostructured or intricately shaped electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]

Using a newly invented surface-tethered dopant approach for the electrochemical polymerization growth of conductive polymer films, nanocomposites are created consisting of two distinct phases of polypyrrole (PPy) and Poly(3,4-ethylene dioxythiophene) (PEDOT). The growth of the conductive nanocomposite films takes advantage of the unique way in which a conductive polymer film forms when grown using a surface-tethered dopant, starting out as a highly nanoporous film that gradually becomes more and more solid as additional polymer deposition occurs preferentially within the nanopores rather than at the films outer surface. Nanocomposite films can thus be fabricated simply and controllably by first growing one nanoporous conductive polymer film followed by the deposition of a second conductive polymer within the nanopores of the first. This study investigates the morphological and electrochemical properties of nanocomposite films grown using a surface-tethered dopant and how these properties are affected by simple changes in electrochemical polymerization parameters. [Display omitted] [ABSTRACT FROM AUTHOR]