The effect of asymmetry and conjugation of biotin decorated nitrogen doped graphene quantum dots on morpholine porphyrin for photodynamic therapy

Novel asymmetric 5-(4-bromo)-10-15-20-tris-(4-morpholine)porphyrin (complex 1) and its Zn derivative (2) were synthesized, and the latter was quaternized to give 2Q, and their photodynamic therapy (PDT) activities were compared to those of the symmetric tetra-morpholine porphyrin (3) and its respective quaternized analogue (3Q). Respective porphyrins were further conjugated to biotin-nitrogen doped graphene quantum dots (B-NGQDs) through π-π stacking. It was observed that the asymmetric complexes and their conjugates had high singlet oxygen quantum yields when compared to the symmetrical porphyrin and their conjugates. PDT studies were performed using MCF-7 breast cancer line. It was observed that all the complexes/conjugates have negligible dark toxicity, and 2Q-B-NGQDs had a highest PDT efficiency with cell viability of 14.4% and IC50 of 1.41 µg/mL.