Photoswitchable Gel Properties Of Self-assembly Peptide

Gel is a class of soft matter materials with three-dimensional nanonetwork structures,and such molecules that are capable of forming gel called gelators.Gelators are able to swell in water or other liquids by capturing solvent molecules thus forming gelly structure.There are two kinds of gelators including polymer gelators and low molecular weight gelators.The polymer gel consists of interconnected polymer chains.While,low molecular weight gels are consisted of self-assembled gelators driven by intermolecular forces to form nanofibers or nanotube.Then the fibrous nanostructures cross link with each other to form higher-order spatial net structures.Peptides are one of the most common biological small molecules,which are widely used as small molecule gelation factors due to their unique hydrophilicity,diversity as well as biocompatibility.In recent years,research on hydrogels has progressed from static materials to smart materials.Stimuli responsive gels,also known as "smart gels",refer to a series of physical or chemical property changes that can occur in response to external stimuli(e.g.,temperature,ultrasound,p H,light,enzymes,etc.),thereby achieving specific functions.Herein,we manipulate the gel properties using light which is convenient,contact free,and spatiotemporally controllable.Photoresponsive gel-solution transitions endow supramolecular peptide gels with a powerful ability to release on-demand cargos in a controllable manner.Photophysical peptide gelators were reported for this purpose but their gel-sol transitions were not sufficient.An anthracene-peptide conjugate gelator,which subjects to photo-chemically regulated gel-sol switches,has not been re-ported.In this work,we report an anthracene-peptide gelator Nap-Phe-Phe-Lys(anthracene)-OH(Mo-Nap-An)which,under365 nm laser irradiation,is efficiently con-verted to its dimer Di-Nap-An,accompanied by a gel-sol transition(or nanofiber-nanoparticle transformation from the micro perspective)in a co-solvent of 40% THF.Reversely,upon 254 nm light irradiation,Di-Nap-An is con-verted to Mo-Nap-An,switching the solution to gel.This work provides a facile bottom-up strategy of“smart” photogelator design for efficient and photochemical control of gel properties.