"ON-OFF" RGD SIGNALING USING AZOBENZENE PHOTOSWITCH-MODIFIED SURFACES

When engineering new biomaterials, one of the first requirement is the design of versatile systems where the accessibility of engrafted biomolecules can be regulated at wish. The chance to regulate the presentation of such biological cues stand on some new strategies adopted to achieve controlled responsiveness in a dynamic way, exploiting several external triggers. The modification of peptide or protein ligands with light-sensitive moieties represents a powerful method to achieve the temporal control of their bioactivity using light. In our work GRGDS sequence was coupled with an azobenzene unit to provide the possibility of a photocontrolled exposure of such peptide, after tethering it on a solid substrate. The final aim of this research, indeed, concerns the development of a smart platform in which the capability to tune cell adhesion response can be achieved exploiting light as trigger. The designed azoderivative was synthesized and characterized by means of UV-Visible spectroscopy, which confirmed that the typical photoswitching behavior of the azobenzene unit was preserved, even after the introduction of the peptide. After an exhaustive characterization in solution the synthesized azoderivative was grafted on a silanized glass surface, exploiting the "click" chemistry strategy. A comprehensive chemical and topographical characterization of such substrate with Raman spectroscopy and atomic force microscopy, was followed by the investigation of the photoresponsive behavior on solid substrate through the water contact angle technique, recording local changes in wettability related to the isomerization of the azobenzene domain upon light stimuli. Finally, the developed photoresponsive platform was tested for biological applications, through adhesion assays with human umbilical vein endothelial cells (HUVECs), in order to evaluate the possibility of a controlled adhesion upon external light stimuli.