Multi-functionalised graphene nanoflakes as tumour-targeting theranostic drug-delivery vehicles
Abstract
Graphene nanoflakes (GNFs) contain a graphene sheet roughly 30 nm across having a pristine aromatic system as well as an edge ended with carboxylic acidity groups. Their high water solubility and relative easy functionalisation using carboxylate chemistry implies that GNFs are potential scaffolds for that synthesis of theranostic agents. Within this work, GNFs were multi-functionalised with derivatives of (i) a peptide-based Glu-NH-C(O)-NH-Lys ligand that binds prostate-specific membrane antigen (PSMA), (ii) a powerful anti-mitotic drug (R)-ispinesib, (iii) the chelate desferrioxamine B (DFO), and (iv) an albumin-binding tag reported to increase pharmacokinetic half-existence in vivo. Subsequent 68Ga radiochemistry and experiments in vitro as well as in vivo were utilised to judge the performance of GNFs in theranostic drug design. Efficient 68Ga-radiolabelling was achieved and also the particle-loading of (R)-ispinesib and Glu-NH-C(O)-NH-Lys was confirmed using cellular assays. Using dose-response curves and FACS analysis it had been proven that GNFs packed with (R)-ispinesib inhibited the kinesin spindle protein (KSP) and caused G2/M-phase cell cycle arrest. Cellular uptake and blocking experiments shown that GNFs functionalised using the Glu-NH-C(O)-NH-Lys ligand demonstrated specificity toward PSMA expressing cells (LNCaP). The distribution profile and excretion rates of 68Ga-radiolabelled GNFs in athymic nude rodents was evaluated using time-activity curves produced from dynamic positron-emission tomography (PET). Image analysis established that Ispinesib GNFs have low accumulation and retention in background tissue, with rapid kidney clearance. In conclusion, our study implies that GNFs are appropriate candidates to be used in theranostic drug design.