Acetophenone substituted phthalocyanines and their graphene quantum dots conjugates as photosensitizers for photodynamic antimicrobial chemotherapy against Staphylococcus aureus.

• Acetophenone substituted phthalocyanines (Pcs) are conjugated to graphene quantum dots (GQDs) by self-assembly. • InPc and its conjugate gave higher singlet oxygen quantum yields compared to the rest. • The photodynamic antimicrobial chemotherapy activity of phthalocyanines and nanoconjugates were tested against S. aureus. • The InPc conjugate with GQDs showed better photoantibacterial activity compared to the rest of the Pcs and conjugates. This work reports on the synthesis and characterization of novel acetophenone substituted phthalocyanines along with the self-assembled nanoconjugates formed via π-π stacking interaction between the synthesized unmetalated (2), zinc (3) and indium (4) phthalocyanines and graphene quantum dots (GQDs) to form 2 @GQDs, 3 @GQDs and 4 @GQDs. The complexes and conjugates exhibited high singlet oxygen ranging from 0.20 to 0.79 in DMSO for Pcs and nanoconjugates where in all cases, the indium complexes showed the highest singlet oxygen quantum yields. The photodynamic antimicrobial chemotherapy activity of both phthalocyanines and nanoconjugates were tested against Staphylococcus aureus. 4 @GQDs was found to be highly effective causing a 9.68 log reduction of the bacteria at 10 μM (based on Pc) when compared to 3.77 log reduction of 3 @GQDs. [ABSTRACT FROM AUTHOR]