Photoreactivity of Thiophene-Based Core@Shell Nanoparticles: The Effect of Photoinduced Charge Separation on In Vivo ROS Production

Here, we show that in thiophene-based core@shell nanoparticles, namely, P3HT@PTDO NPs, the nanosegregation of the materials results in a peculiar photoreactivity, which, together with their soft and biocompatible nature, makes them interesting bioplatforms. By combining macroscopic and microscopic Kelvin probe measurements, we show that the surface of core@shell NPs becomes rich in negative charges under light illumination-due to the promotion of photogenerated electrons from the inner P3HT core to the outer oxidized PTDO shell-making them more reactive to the environment (air dopants, water, substrate, etc.). Fluorometric and electron paramagnetic resonance (EPR) techniques revealed the formation of transient reactive oxygen species (ROS) upon illumination of aqueous suspensions of NPs, indicating their photoredox reactivity. Detailed analysis permitted to reveal a type I mechanism in ROS generation, ruling out the formation of potentially biodamaging singlet oxygen species. Finally, the biocompatibility of these systems was tested in cells and Hydra polyps. Core@shell NPs exhibit perfect viability and allow the modulation of ROS generation depending on the shell's oxygenation degree, both in vitro and in vivo, in agreement with EPR measurements.