Surface Functionalisation of Upconversion Nanoparticles with Different Moieties for Biomedical Applications

Abstract

Lanthanide ion doped upconversion nanoparticles (UCNPs) that can convert low-energy infrared photons into high-energy visible and ultraviolet photons, are becoming highly sought-after for advanced biomedical and biophotonics applications. Their unique luminescent properties enable UCNPs to be applied for diagnosis, including biolabeling, biosensing, bioimaging and multiple imaging modality, as well as therapeutic treatments including photothermal and photodynamic therapy, bio-reductive chemotherapy and drug delivery. For the employment of the inorganic nanomaterials into biological environment, it is critical to bridge the gap in between nanoparticles and biomolecules via surface modifications and subsequent functionalisation. This work reviews the various ways to surface modify and functionalise UCNPs so as to impart different functional molecular groups to the UCNPs surfaces for a board range of applications in biomedical areas. We discussed commonly used base functionalities, including –COOH, -NH2 and –SH, that are typically imparted to UCNP surfaces so as to provide further functional capacity.

Synthesis, Optical Properties, and Sensing Applications of LaF3:Yb3+/Er3+/Ho3+/Tm3+ Upconversion Nanoparticles

“…Therefore, the utilization of surface modification techniques was imperative to make these UCNPs water-dispersible for aqueous applications. As PEG exhibits strong hydrophilicity, PEG–imidazole was synthesized and used as a hydrophilic ligand to modify the surfaces of UCNPs via ligand exchange [ 45 , 46 , 47 ].…”