Study on the use of carboxymethyl chitosan grafted with pyroglutamic acid for photodamage repair.

To develop high-efficiency materials for skin photodamage repair, in this study, carboxymethyl chitosan-pyroglutamic acid (CMCS-Pyr) was synthesized by grafting pyroglutamic acid onto carboxymethyl chitosan (CMCS) via an amide reaction， achieving a grafting rate of 19.28%. Rheological analysis identified 10% as the optimal application concentration of CMCS-Pyr. In vitro experiments demonstrated that the material had a hemolysis rate of less than 5% and no skin irritation. It exhibits multiple free radical scavenging capacities, with ABTS, DPPH and ·OH radical scavenging rates of 52.8%, 50.9% and 90.5%, respectively. CMCS-Pyr could significantly enhance the superoxide dismutase (SOD) activity of HaCaT cells, and promote cell migration as well as collagen synthesis. In animal experiments based on the mouse UVB-induced skin photodamage model, CMCS-Pyr remarkably increased the water content and maximum tensile strength of damaged skin, inhibited the expressions of matrix metalloproteinase-9 (MMP-9) and nuclear factor-kappa B p65 (NF-κB-p65), and reduced the malondialdehyde (MDA) content. Transcriptome and quantitative real-time polymerase chain reaction (qPCR) analyses confirmed that CMCS-Pyr up-regulated the expressions of genes such as COL1 and COL3 and down-regulated inflammatory factors by regulating the MAPK/NF-κB signaling pathway, thereby exerting a synergistic effect of anti-inflammation, anti-oxidation and pro-repair. Collectively, CMCS-Pyr is a promising material for skin photodamage repair.