Photoactive grafted polysaccharide and use thereof in cosmetics

A cosmetic process for caring for the skin, more particularly facial skin, in particular wrinkled skin, comprising:

• (i) a step consisting in applying to the skin a composition comprising, in a physiologically acceptable medium, a grafted polysaccharide (I),
• (ii) a step consisting in exposing the treated skin to light radiation, preferably for at least 5 seconds,
• the grafted polymer (I) being a polysaccharide polymer grafted with photoactive groups of azide or diazirine type of formula:
• PS—(O—CO-L-X)a(OH)b (I)
• in which PS denotes the basic backbone of the polysaccharide bearing the hydroxyl groups;
• L is a linear, branched or cyclic, saturated or unsaturated divalent hydrocarbon-based group comprising from 1 to 20 carbon atoms, which may be interrupted with one or more non-adjacent heteroatoms chosen from sulfur, oxygen, or —NH—, —COO—, —CONH—, —O—CO—NH— or —NH—CO—NH— groups, said divalent group being optionally substituted with one or more groups chosen from hydroxyl, amine, thiol, carboxylic acid, amide, cyano, and acyl (C1-C4)amino groups;
• X denotes a photoactive group of azide or diazirine type;
• a denotes the content of OH groups substituted with the photoactive group;
• b denotes the content of unsubstituted free OH groups;
• a being between 0.02 and 0.5;
• b being between 0.5 and 0.98;
• and a+b=1.