A method and a composition for photochemical cross linking of collagen by photoactive agent in-vivo are presented. The method includes a non-toxic photoactive formulation of the composition with collagen, which is administered to treatment area locally; followed by irradiation with suitable wavelength. In one of the embodiment liposomal formulated mTHPC is added to the collagen and is irradiated with a 652 nm laser, resulting in producing efficient collagen scaffolds with strengthen and stabilized microstructure, thus improving the physiochemical properties of the collagen scaffold. It improves the thermostability, mechanical property and swelling ratio of newly formed scaffold. Photochemical cross-linked collagens shows antimicrobial effect, when irradiated with suitable wavelength it disinfects the treatment site and curbs microbial growth.