Singlet oxygen photo-production by perylene bisimide derivative Langmuir-Schaefer films for photodynamic therapy applications

A perylene bisimide (PBI) derivative was utilized as photosensitizer for photodynamic therapy (PDT) applications, due to its high efficiency in singlet oxygen generation upon photoexcitation. It was immobilized onto a hydrophobized solid support, by means of the Langmuir-Schaefer (LS) technique, to achieve a preliminary medical device able to induce death of cancer cells in vitro. First, PBI derivative solutions, at two different concentrations (4.2 × 10−5 and 1.5 × 10−4 M) were chosen, based on the different PBI aggregation state, to be spread onto a water subphase in a Langmuir trough. Physico-chemical and morphological characterizations of the floating films were performed. Then the floating layers were transferred onto quartz substrates. The resulting multilayer LS films were characterized by spectroscopic measurements showing that the photochemical properties of the PBI derivative were well preserved even when immobilized. The LS film that exhibited the highest efficiency in the singlet oxygen production under light excitation was assessed in in vitro tests on human cervical carcinoma C13 cell line and the photo-toxicity was measured. This study revealed absence of cytotoxicity in dark conditions and a high photo-cytotoxicity toward cancer cells, making it a promising photoactive device.