Photosensitizer with High Efficiency Generated in Cells via Light-Induced Self-Oligomerization of 4,6-Dibromothieno[3,4-b]thiophene Compound Entailing a Triphenyl Phosphonium Group.

Photodynamic therapy (PDT) has emerged as an attractive alternative in cancer therapy, but therapeutic effects suffer from low photosensitizing efficiency and poor retention of photosensitizes in cancer cells. This paper reports the photosensitizers which show absorption and emission in the long-wavelength region and high photosensitizing efficiency can be formed in situ in cells from 4,6-dibromothieno[3,4-b]thiophene derivative (TT-5-P) after white light irradiation. The self-oligomerization of TT-5-P is uptaken in cells upon light irradiation-induced cell apoptosis simultaneously and efficiently. In addition, the formation of oligomers (TT-5-Ps) enhances the retention time in cells remarkably, which is advantageous for boosting the photodynamic therapy efficiency. Moreover, the selectivity toward tumor cells of TT-5-P can be improved obviously via the formation of complex of TT-5-P with albumin. This in situ photoinduced self-oligomerization strategy can be utilized to design effective biomaterials for long-term imaging and improved therapy.