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Polyethylene glycol-functionalized bis(arylidene)cycloalkanone photosensitizers for two-photon excited photodynamic therapy

We report the properties of two series of polyethylene glycol-functionalized bis(arylidene)cycloalkanone photosensitizers designed for two-photon excited photodynamic therapy (PDT) with the aim to reveal the effect of the size of central ring on the two-photon excited PDT efficiency. These photosensitizers are the derivatives of bis(arylidene) cyclopentanone (B2, B3) and bis(arylidene) cyclobutanone (Q1-Q4). The bis(arylidene) cyclopentanone type photosensitizers were found to have larger two-photon absorption cross sections than the bis(arylidene) cyclopentanone ones with the same substituents. The singlet oxygen yields of the bis(arylidene) cyclobutanone derivatives are higher than the data of bis(arylidene) cyclopentanone derivatives. All the studied photosensitizers showed no obvious toxicity under dark situation. One- and two-photon excited PDT activities were successfully demonstrated by in vitro cell experiments. Owing to the capability of destructing the cancerous cells under two-photon irradiation, bis(arylidene)cycloalkanone based photosensitizers with proper substituents can be good candidates for two-photon excited PDT applications in the future.