Recent advances in cancer therapies via carbon nanomaterials functionalized with porphyrins and analogues

Graphene oxide (GO) and graphene quantum dots (GQDs) are carbon nanomaterials with increasing importance as delivery platforms of traditional anticancer drugs [1,2]. Here, we explore some breakthroughs (A-D) in the synthesis of new hybrid materials comprising GO/GQDs and photosensitizing molecules (porphyrins or phthalocyanines, Pcs) and their synergistic contributions in conventional cancer therapies, as photodynamic therapy (PDT) or in deoxyribonucleic acid (DNA) G- quadruplex (G4) sensing and stabilization, as follows: A: Tetracationic porphyrins (TMPyP, Zn-TMPyP and P1-C 5 ) were loaded onto GO/GQDs and their photo-antiproliferative activity was evaluated under red light (625 nm) against T24 human bladder cancer (BC) cells [3]. The hybrids showed a high photodynamic activity, namely Zn-TMPyP@GQDs (IC 50 : 0.37 μg/mL). B: Four tetracationic ZnPcs were assembled on GO to develop multifunctional “turn-off-on” G4 sensors [4]. GO induced a re-organization of the ZnPcs mostly to J-aggregates and quenched their original fluorescence, which was then recovered in the presence of G4 [(T 2 G 5 T) 4 ]. This suggested the progressive release of ZnPcs from GO to detect and stabilize G4 (K D up to 1.92 μM) over time. C: GQDs were covalently attached to DNA sequences, shaping their folding properties and generating luminescent GQDs-supported G4, which allow the anchoring of cationic porphyrins, as TMPyP. These arrays could be potentially used in biosensing or mediated drug delivery processes. D: New π-expanded porphyrin derivatives containing terpyridine motifs at meso positions (tpy- porphyrin) were synthesized and explored to enhance non-covalent interactions of neutral porphyrins with GO and GO functionalized with Au nanoparticles. Acknowledgements The authors are grateful to the University of Aveiro and to the Fundação para a Ciência e a Tecnologia (FCT) for the financial support to LAQV-REQUIMTE (Ref. UIDB/50006/2020) and CICECO-Aveiro Institute of Materials (Ref. UIDP/50011/2020 & LA/P/0006/2020). Ana R. Monteiro thanks the FCT for the PhD grant SFRH/BD/137356/2018. Catarina I. V. Ramos acknowledges her research contract REF.-047-88-ARH/2018.