Photochemical Nitric Oxide Release from S-Nitrosothiol-Functionalized Chitosan

S-nitrosothiols (RSNOs) are nitric oxide (NO) donor molecules with potential biomedical applications since they mimic NO biological functions, such as vasodilation and inflammatory process regulation. In this work, chitosan (CS), a natural biopolymer widely used as a biomaterial, is functionalized with thioglycolic acid (TGA) or mercaptosuccinic acid (MSA) in reactions mediated by a carbodiimide, yielding CS with thiol contents of 88 mu mol g(-1) (CS-TGA) and 126 mu mol g(-1) (CS-MSA). The subsequent S-nitrosation of CS-TGA and CS-MSA generates the corresponding S-nitroso derivatives, CS-TGA(SNO) and CS-MSA(SNO). The UV-Vis spectral changes associated with the S-NO bond cleavage of CS-TGA(SNO) and CS-MSA(SNO), monitored in solution over 18 days of storage in a common refrigerator, reveal that these S-nitroso CS derivatives display enhanced thermal stability in the dark, with half-life values of 36.1 for CS-TGA(SNO) and 16.1 days for CS-MSA(SNO). Conversely, CS-TGA(SNO) and CS-MSA(SNO) can release NO photochemically on-demand under visible light irradiation in a first-order process triggered by photon absorption that leads to a half-life of 33 min for both S-nitroso CS. These results show that CS-TGA(SNO) and CS-MSA(SNO) may emerge as new CS-based biomaterials for providing light-triggered local NO release in biomedical applications.