RESUMEN
Conjugated polymers have been proposed as promising materials for scaffolds in tissue engineering applications. The restricted processability and biodegradability of conjugated polymers limit their use for biomedical applications however. Here we synthesised a block-co-polymer of aniline tetramer and PCL (AT-PCL), and processed it into fibrous non-woven scaffolds by electrospinning. We showed that fibronectin (Fn) adhesion was dependant on the AT-PCL oxidative state, with a reduced Fn unfolding length on doped membranes. Furthermore, we demonstrated the cytocompatibility and potential of these membranes to support the growth and osteogenic differentiation of MC3T3-E1 over 21 days.
RESUMEN
Cardiac tissue engineering via the use of stem cells is the future for repairing impaired heart function that results from a myocardial infarction. Developing an optimised platform to support the stem cells is vital to realising this, and through utilising new 'smart' materials such as conductive polymers we can provide a multi-pronged approach to supporting and stimulating the stem cells via engineered surface properties, electrical, and electromechanical stimulation. Here we present a fundamental study on the viability of cardiac progenitor cells on conductive polymer surfaces, focusing on the impact of surface properties such as roughness, surface energy, and surface chemistry with variation of the polymer dopant molecules. The conductive polymer materials were shown to provide a viable support for both endothelial and cardiac progenitor cells, while the surface energy and roughness were observed to influence viability for both progenitor cell types. Characterising the interaction between the cardiac progenitor cells and the conductive polymer surface is a critical step towards optimising these materials for cardiac tissue regeneration, and this study will advance the limited knowledge on biomaterial surface interactions with cardiac cells.
RESUMEN
Polymer-based electrodes for interfacing biological tissues are becoming increasingly sophisticated. Their many functions place them at the cross-roads of electromaterials, biomaterials, and drug-delivery systems. For conducting polymers, the mechanism of conductivity requires doping with anionic molecules such as extracellular matrix molecules, a process that distinguishes them as biomaterials and provides a means to control interactions at the cellular-electrode interface. However, due to their complex structure, directly observing the selective binding of target molecules or proteins has so far eluded researchers. This situation is compounded by the polymer's ability to adopt different electronic states that alter the polymer-dopant interactions. Here, the ability to resolve sub-molecular binding specificity between sulfate and carboxyl groups of dopants and heparin binding domains of human plasma fibronectin is demonstrated. The interaction exploits a form of biological 'charge complementarity' to enable specificity. When an electrical signal is applied to the polymer, the specific interaction is switched to a non-specific, high-affinity binding state that can be reversibly controlled using electrochemical processes. Both the specific and non-specific interactions are integral for controlling protein conformation and dynamics. These details, which represent the first direct measurement of biomolecular recognition between a single protein and any type of organic conductor, give new molecular insight into controlling cellular interactions on these polymer surfaces.
RESUMEN
Phase imaging in atomic force microscopy (AFM) is a useful technique for determining dissipative tip-sample interactions related to changes in the material surface properties such as local stiffness or adhesion. In this work, we applied both phase imaging and phase spectroscopy measurements to conducting polymer (polypyrrole) doped with either hyaluronic acid or chondroitin sulfate. As observed in previous studies, phase-separated regions correlating with the characteristic nodular topography of polypyrrole and attributed to crystalline (doped) and amorphous (undoped) regions were observed. However, through additional phase spectroscopy measurements, we show that the phase-separated regions can arise due to variation in attractive and repulsive tip-sample interactions across the polymer surface. We show that these attractive and repulsive interactions are dependent on the redox state and degree of doping and suggest that they are related to phase separation of the polymer surface charge and/or energy. The latter may have implications for these materials when under investigation in a fluid, or biological, environment. For example, such surface variations will play a role in electrostatic forces, which in turn can influence protein and cellular interactions.