Synthesis of double-clickable functionalised graphene oxide for biological applications

Azide-and alkyne-double functionalised graphene oxide (Click(2) GO) was synthesised and characterised with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA) and Raman spectroscopy. Fourteen-percentage increase in azide content was found, after pre-treatment of GO with metachloroperoxybenzoic acid (mCPBA), determined with elemental analysis. No effect on A549 cell viability was found, up to 100 mu g mL(-1) and 72 h of incubation, determined with the modified lactate dehydrogenase (mLDH) assay. Two sequential copper(I) catalysed azide-alkyne cycloaddition (CuAAC) reactions were performed to conjugate the propargylmodified blood-brain barrier targeting peptide Angiopep-2, and a bis-azide polyethylene glycol (M-W = 3500), to the Click(2) GO. The final conjugate was characterised with ATR-FTIR and TGA.