UMMS Affiliation

Department of Biochemistry and Molecular Pharmacology

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Biochemistry, Biophysics, and Structural Biology | Chemistry | Nanoscience and Nanotechnology | Nanotechnology


Upconversion Nanoparticles (UCNPs) enable direct measurement of the local temperature with high temporal and thermal resolution and sensitivity. Current studies focusing on small animals and cellular systems, based on continuous wave (CW) infrared excitation sources, typically lead to localized thermal heating. However, the effects of upconversion bioimaging at the molecular scale, where higher infrared intensities under a tightly focused excitation beam, coupled with pulsed excitation to provide higher peak powers, is not well understood. We report on the feasibility of 800 and 980 nm excited UCNPs in thermal sensing under pulsed excitation. The UCNPs report temperature ratiometrically with sensitivities in the 1 x 10(-4) K(-1) range under both excitation wavelengths. Our optical measurements show a ln(I525/I545) vs. 1/T dependence for both 800 nm and 980 nm excitations. Despite widespread evidence promoting the benefits of 800 nm over 980 nm CW excitation in avoiding thermal heating in biological imaging, in contrary, we find that given the pulsed laser intensities appropriate for single particle imaging, at both 800 and 980 nm, that there is no significant local heating in air and in water. Finally, in order to confirm the applicability of infrared imaging at excitation intensities compatible with single nanoparticle tracking, DNA tightropes were exposed to pulsed infrared excitations at 800 and 980 nm. Our results show no appreciable change in the viability of DNA over time when exposed to either wavelengths. Our studies provide evidence for the feasibility of exploring protein-DNA interactions at the single molecule scale, using UCNPs as a reporter.


800 nm, 980 nm, DNA denaturation, local thermal heating, pulsed excitation, upconversion thermal sensing

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Copyright © 2018 Green, Huang, Pan, Han and Lim. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

DOI of Published Version



Front Chem. 2018 Sep 24;6:416. doi: 10.3389/fchem.2018.00416. eCollection 2018. Link to article on publisher's site

Journal/Book/Conference Title

Frontiers in chemistry

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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.