Carbohydrate-coated lanthanide-doped upconverting nanoparticles for lectin recognition

In this study we have developed upconverting lanthanide (Ln(3+))-doped nanoparticles conjugated with glycodendrimers capable of recognizing lectins based on luminescence resonance energy transfer (LRET). Poly(amidoamine) (PAMAM) dendrimers were adsorbed on the surface of NaGdF4:Er3+, Yb3+ upconverting nanoparticles (LnNPs) via direct ligand-exchange followed by efficient thiourea linkage formation between the amine surface and p-isothiocyanatophenyl alpha-D-mannopyranoside for covalent carbohydrate derivatization. The resulting water dispersible and biocompatible mannose-coated PAMAM-LnNPs were used to recognize a lectin, Concanavalin A (a mannose binding protein) conjugated with tetramethylrhodamine (RITC-Con A) via LRET from the upconverting mannose-coated PAMAM-LnNPs, which act as energy donors to the RITC-labeled lectin molecules serving as energy acceptors. The energy transfer phenomenon from the mannose-coated PAMAM-LnNPs, following 980 nm excitation, to the RITC-Con A was observed with increasing emissions at 585 nm, as the concentration of lectin increases. These novel carbohydrate-coated LnNPs prove to be a novel tool to monitor the binding interaction with lectins in aqueous samples.