Graphene Nanoflake Antibody Conjugates for Multimodal Imaging of Tumors

Graphene-based materials are promising scaffolds for use in the design of tailored-made nanomedicines. Herein, the synthesis and characterization of a series of multifunctional carboxylated graphene nanoflakes (GNFs) conjugated to monoclonal antibodies (mAbs) for tumor-specific binding and modulation of pharmacokinetics is presented. GNF–mAb constructs are coupled to a fluorophore (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene [BODIPY]) for applications in optical imaging, a paramagnetic Gd3+ complex, [GdDOTAGA(H2O)]−, and the hexadentate chelate desferrioxamine B (DFO) for radiolabeling with 89Zr4+ (t1/2 = 78.41 h) ions and applications in dual-modality positron emission tomography/magnetic resonance imaging (PET/MRI). Experimental properties of [89Zr]GdDOTAGA–ZrDFO–GNF–trastuzumab are tested in extensive chemical, spectroscopic, radiochemical, and cellular assays in vitro, and assessment of the pharmacokinetics by PET imaging in mice bearing a human ovarian cancer model illustrates the potential of using GNF–mAbs to develop multifunctional PET/MRI probes

Multi-functionalised graphene nanoflakes as tumour-targeting theranostic drug-delivery vehicles

Graphene nanoflakes (GNFs) consist of a graphene sheet approximately 30 nm in diameter with a pristine aromatic system and an edge terminated with carboxylic acid groups. Their high water solubility and relative ease of functionalisation using carboxylate chemistry means that GNFs are potential scaffolds for the synthesis of theranostic agents. In 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 potent anti-mitotic drug (R)-ispinesib, (iii) the chelate desferrioxamine B (DFO), and (iv) an albumin-binding tag reported to extend pharmacokinetic half-life in vivo. Subsequent 68Ga radiochemistry and experiments in vitro and in vivo were used to evaluate the performance of GNFs in theranostic drug design. Efficient 68Ga-radiolabelling was achieved and 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 was shown that GNFs loaded with (R)-ispinesib inhibited the kinesin spindle protein (KSP) and induced G2/M-phase cell cycle arrest. Cellular uptake and blocking experiments demonstrated that GNFs functionalised with the Glu-NH-C(O)-NH-Lys ligand showed specificity toward PSMA expressing cells (LNCaP). The distribution profile and excretion rates of 68Ga-radiolabelled GNFs in athymic nude mice was evaluated using time–activity curves derived from dynamic positron-emission tomography (PET). Image analysis indicated that GNFs have low accumulation and retention in background tissue, with rapid renal clearance. In summary, our study shows that GNFs are suitable candidates for use in theranostic drug design