Micropatterning Photoconductive Peptide Assemblies on Stiff and Soft Biomaterial Substrates

The propagation of electrical signals in the human heart relies on organized conduction pathways to optimally function and pump blood into the rest of the body. Mimicking this directionality across interconnected myocytes in vitro is currently achieved by patterning the cells themselves, which are often subjected to external stimulatory cues that are rarely localized or have controlled anisotropy. Here, we demonstrate an approach to interface micropatterned optoelectronic peptides with cardiomyocytes, whereby the engineered biomolecular structures dictate the organization of cells in a substrate, while also presenting photocurrent-generating electrodes of defined microscale geometries. To this end, we utilized surface modification strategies that allowed for the creation of stable micropatterns of quaterthiophene-bearing peptide assemblies on both glass (∼GPa range) and gelatin hydrogel (∼20 kPa) substrates that last for multiple days within an aqueous environment. The pH-sensitive assembly behavior of π-conjugated peptides was also investigated as to how it evolves at various stages of the patterning process and impacts material scattering once they are imprinted on different substrates. Neonatal rat ventricular myocytes (NRVMs) seeded on gelatin scaffolds that had been interfaced with π-conjugated peptide micropatterns saw improvements to their orientational order parameter (OOP) of both the actin cytoskeleton and z-lines, which were not observed for those cultured on isotropic controls or on microgrooved gelatin samples. Additionally, the micropatterned π-conjugated peptide platform was shown to exhibit photocurrent-generating properties on both gelatin and glass substrates in aqueous cell culture environments. The peptide-based platform discussed here provides a potential approach to confine conductive biomaterials within microscale features in vitro while simultaneously providing an avenue for light-based localized stimulation of electroactive tissues.