Researchers from the Department of Materials Physics and the Institute of Physical Chemistry at Zhejiang Normal University, China, have recently developed a facile method to coat up-conversion nanocrystals with a carbonized glucose shell. The team used lanthanide-doped NaYF4 nanocrystals as an example. By encapsulating the hydrophobic nanocrystals inside the water pools of a microemulsion containing glucose, a thin glucose shell of 2–5 nm could be wrapped around the nanocrystals by inducing crosslink and carbonization of the glucose molecules at elevated temperature. Owing to the thin and biocompatible nature of the glucose shell, these modified up-conversion nanocrystals not only exhibit strong up-conversion fluorescence, but also show good biocompatibility. These properties give the material an advantage over conventionally used silica-coated up-conversion nanocrystals.

To the researchers' surprise, the glucose-coated nanocrystals also display a rapid endocytosis rate when cultured with some cancer cells. Considerable numbers of nanoparticles can be taken up by cells within the first 3 hours and strong emission from the sustained cells is distinguishable after just 30 min of incubation. The scientists explain that these results might be attributed to two aspects: i) the optimal particle size for endocytosis; and ii) glucose transporters on the cell surface. They believe that these nanoparticles may be extremely useful for rapid detection, screening and diagnosis in future biomedical engineering applications.

The researchers presented their results in the journal Nanotechnology.