Advanced optical nanocrystals yield luminescent biomarkers

Researchers from the National University of Singapore’s (NUS) Department of Chemistry have developed an efficient upconversion process in nanoparticles, ensuring a broad tunability of light emission that could be used in bioimaging applications. Their novel approach involved finding a chemical structure that can exhibit efficient upconversion properties through a special arrangement of energy levels—synthesizing lanthanide-doped core-shell nanocrystals resulted in advanced optical properties that can control light.

Upconversion is a nonlinear optical process where two low-energy photons of an incident beam can be converted into a single photon of higher energy, which can then be easily distinguished from the background. Upconversion emission materials are ideal for bioimaging due to their effectiveness as contrast agents for detecting cancer cells—more so when the background emission of non-cancerous tissues can be minimized. These materials could be used as biomarkers for luminescent labeling of cancerous cells. Opaque tissues can be turned into glassy, transparent substances by using these biomarkers, which rely on near-infrared (near-IR) excitation.

The team—led by Associate Professor Xiaogang Liu—prepared nanoparticles that could demonstrate an upconversion emission ranging from violet, blue, and green to red and yellow, with significantly longer IR excitation wavelengths up to 980 nm. Using light with 980 nm wavelength yields transparency of living tissues high in IR, enhancing opportunity for using these nanoparticles in cancer detection. What's more, the multiple emission colors the team demonstrated can potentially be used for multiple cell markers, photodynamic therapy (PDT), and drug delivery.

The team has recently filed a related patent for their discovery, and they are working with clinicians to develop clinical diagnostic models for use in a practical manner.

The team's work is published in Nature Materials, and was funded by Singapore’s Agency for Science, Technology and Research (A*STAR) and Ministry of Education. For more information, please visit http://www.nature.com/nmat/journal/vaop/ncurrent/abs/nmat3149.html.

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