Abstract
Optical modulation of living cells activity by light-absorbing exogenous materials is gaining increasing interest, due to the possibility both to achieve high spatial and temporal resolution with a minimally invasive and reversible technique and to avoid the need of viral transfection with light-sensitive proteins. In this context, conjugated polymers represent ideal candidates for photo-transduction, due to their excellent optoelectronic and biocompatibility properties. In this work, we demonstrate that organic polymer nanoparticles, based on poly(3-hexylthiophene) conjugated polymer, establish a functional interaction with an in vitro cell model (Human Embryonic Kidney cells, HEK-293). They display photocatalytic activity in aqueous environment and, once internalized within the cell cytosol, efficiently generate reactive oxygen species (ROS) upon visible light excitation, without affecting cell viability. Interestingly, light-activated ROS generation deterministically triggers modulation of intracellular calcium ion flux, successfully controlled at the single cell level. In perspective, the capability of polymer NPs to produce ROS and to modulate Ca2+ dynamics by illumination on-demand, at non-toxic levels, may open the path to the study of biological processes with a gene-less approach and unprecedented spatio-temporal resolution, as well as to the development of new biotechnology tools for cell optical modulation.
Highlights
By and large, cells are essentially transparent and do not directly respond to light
P3HT NPs were administered to the HEK-293 cell culturing medium at the cell plating step, and their cytotoxicity was preliminarily evaluated by measuring cellular proliferation through the MTT method
We study the coupling mechanism at the abiotic/biotic interface between polymer NPs and living cells upon photoexcitation with visible light
Summary
Cells are essentially transparent and do not directly respond to light. Natural evolution resulted in the appearance of photoreceptors cells containing light-sensitive opsin proteins that provide a broad range of photo-induced functions (Morshedian and Fain, 2017). Polymer Nanoparticles Modulate Calcium Dynamics ago, scientists have explored possibilities to artificially induce light sensitivity in living tissues, in order to control physiological functions by photons. This does not mean copying nature in order to restore lost photo-functions in damaged organs, but it opens up a wealth of new applications in research, diagnostics and therapy. Light-induced cell control has a number of advantages with respect to more traditional electrical stimulation, such as space and time resolution, reduced invasiveness and selectivity. In spite of the important record of experimental results, it requires the viral transfer of the sample (cell or organ) with exogenous DNA, which raises important safety constraints for application in human subjects and is still considered to be a critical limitation
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