Azobenzene-Substituted Poly-Thiophene Nanoparticles for The Photo-Stimulation of Living Cells

The use of biocompatible exogenous materials for the stimulation of living organisms avoiding genetic manipulation has been extensively proposed as an effective strategy. Poly-thiophenes have been employed for in vitro and in vivo photo-stimulation in the past years. Polymer nanoparticles in close proximity to the cells can induce a perturbation in the membrane due to a charge displacement in the material, resulting in a physiological response. Similarly, azobenzene-based molecules, able to insert in cells’ membrane, can induce modifications in the membrane which can be reverted through photo-switching between trans- and cis-isomer. At the same time, such photochromic molecules have also proved to be effective in interacting with bacteria.<br/><br/>Here, we report the synthesis of a poly-thiophene with simple azobenzene substituents and the fabrication of nanoparticles. The proposed material, in the form of nanoparticles, shows a good affinity with living cells and can also induce a physiological response upon light excitation of the isomerization band. Such a system enables the simultaneous utilization of two different stimulation paradigms which may allow more precise targeting in the case of particularly functionalized azobenzene substituents. In fact, excitation bands of the thiophene and azobenzene substituents are spectrally separated. Tuning of the absorption and selectivity may be obtained with more specific azobenzene derivatives. Combination of the two different stimulation mechanisms may result in increased response when required. Moreover, such approach enables increased spatial resolution due to light confinement and limits inflammatory response associated with more invasive techniques. The electronic and optical properties of those systems also make them interesting for sensing application, since the geometrical conformation of the azobenzene branches has been found to influence the optical characteristics of the poly-thiophene backbone.