Aug 10, 2010
Up-conversion nanoparticles wrapped in glucose
Up-conversion nanoparticles have attracted considerable attention due to their unique luminescent properties and promising applications in biomedical engineering. Synthesis of monodisperse up-conversion nanocrystals with a hydrophobic surface has been achieved. However, scientists are still searching for the ultimate surface-modification method that accomplishes both high luminescence and good biocompatibility.
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.
About the author
This study was conducted by research teams from the Department of Materials Physics and the Institute of Physical Chemistry at Zhejiang Normal University (ZJNU) and the Division of Bioengineering at the National University of Singapore (NUS). Dr Zhengquan Li is an associate professor at ZJNU whose interest is focused on the synthesis and application of lanthanide nanocrystals. He performed the synthesis and surface-modification work in this research. Dr Huichen Guo is a research staff member at the NUS who is interested in studying the interaction between cells and nanoparticles. She has carefully evaluated the biocompatibility and cell-imaging capability of the developed nanoparticles. Dr Haisheng Qian and Dr Yong Hu have contributed a lot in the characterization of these nanoparticles and in the data analysis.