Photophysical properties and photodynamic therapy activity of a meso-tetra(4-carboxyphenyl)porphyrin tetramethyl ester-graphene quantum dot conjugate

Novel meso-tetra(4-carboxyphenyl) porphyrin tetramethyl ester metal derivatives were synthesised and characterized. These derivatives were interacted with graphene quantum dots (GDQs). Spectroscopic evidence that was obtained showed that the resultant conjugates were stable due to the strong p-p stacking interaction between the GQDs and the porphyrins. The fluorescence and singlet oxygen generating behaviour of the porphyrins and the nanoconjugates were investigated following incorporation. The dark toxicity and photodynamic therapy activities of the porphyrins and the nanoconjugates were successfully studied using MCF-7 breast cancer cells. Cell viability for the dark toxicity was more than 90% for all complexes. The PDT activities at the highest concentration of 120 mg ml(-1) showed a decrease in cell viability down to 15.2% for the GaClTMPP-GQDs.