1. Antibacterial activity of photosensitizers immobilized onto solid supports via mechanochemical treatment

Photodynamic antimicrobial chemotherapy is based on the ability of photosensitizers to transfer energy absorbed under illumination to dissolved oxygen or to organic substrates, thus exciting them and producing active free radicals and radical ions. Free and liposome-encapsulated photosensitizers, as well as photosensitizers which are immobilized onto solid supports, are known to effectively eradicate bacterial cells. In the present work, we report a novel technique for the mechanochemical immobilization of photosensitizers onto solid supports. Neutral Red was shown to bind covalently to a pre-synthesized copolymer of salicylic acid and formaldehyde. This photosensitizer, as well as Methylene Blue and Rose Bengal, were deeply absorbed and incorporated into talc under mechanochemical treatment. The immobilized photosensitizers were active against Gram-positive and Gram-negative bacteria in all cases. Correspondence/Reprint request: Dr. Marina Nisnevitch, Ariel University, Kiryat-ha-Mada, 3, 40700 Ariel, Israel. E-mail: [email protected] Marina Nisnevitch et al. 2