The control of biological functions is crucial for the in-depth understanding of physiological/pathogenic processes, as for the development of novel, ad hoc therapeutic modalities to fight specific diseases. In this regard, light-induced cell control is characterized by lower invasiveness, better space and time resolution, with respect to more traditional electrical-based methods. Exogenous inorganic and organic semiconducting materials have attracted considerable interest, since they can be employed as photoactive transducers to trigger the biological activity, without any need for viral transfection [1]. In particular, semiconducting polymers offer great biocompatibility and stability together with geometrical adaptability. Among them, the green light-absorbing poly(3-hexylthiophene) (P3HT) was successfully employed for the modulation of the physiological activity of different cell models [2-4], including the boosting of both proliferation and tubulogenesis of endothelial cells [5]. The latter result is particularly appealing in view of the regeneration of the cardiovascular tissue for application in cardiovascular disease therapies.

Here, we realize smart biointerfaces between red-light absorbing conjugated polymers and cardiovascular cells. The aim of our work is to study the cellular response both to the polymers alone and in combination with red light excitation. The latter is particularly favorable in view of in vivo applications, given the higher penetration of red light within living tissues, as compared to lower visible wavelengths. We show that conjugated polymers in form of nanoparticles lead to either enhancement or reduction of the angiogenic response of model endothelial cells, depending on the material type and the presence/absence of the light stimulus. Furthermore, we observe that semiconducting polymer thin films efficiently modulates, upon red light photoexcitation, the physiological properties of Cardiomyocytes. In particular, we demonstrate that polymer-mediated photostimulation modulates both the Ca²⁺ dynamics and the electrical properties of the cells. Very interestingly, we observe an anti-arrhythmogenic effect, unequivocally triggered by polymer photoexcitation.

Overall, our results support the possibility to employ red light-responsive conjugated polymers to regulate cardiovascular functions, in a drug-free, touchless, repeatable, and spatio-temporally controlled manner.