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Article

Graphene Quantum Dots as Intracellular Imaging-Based Temperature Sensors

1
Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA
2
Biosystems and Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Anton Naumov
Materials 2021, 14(3), 616; https://doi.org/10.3390/ma14030616
Received: 18 December 2020 / Revised: 23 January 2021 / Accepted: 26 January 2021 / Published: 29 January 2021
(This article belongs to the Special Issue Bio-Nanomaterials)
Non-invasive temperature sensing is necessary to analyze biological processes occurring in the human body, including cellular enzyme activity, protein expression, and ion regulation. To probe temperature-sensitive processes at the nanoscale, novel luminescence nanothermometers are developed based on graphene quantum dots (GQDs) synthesized via top-down (RGQDs) and bottom-up (N-GQDs) approaches from reduced graphene oxide and glucosamine precursors, respectively. Because of their small 3–6 nm size, non-invasive optical sensitivity to temperature change, and high biocompatibility, GQDs enable biologically safe sub-cellular resolution sensing. Both GQD types exhibit temperature-sensitive yet photostable fluorescence in the visible and near-infrared for RGQDs, utilized as a sensing mechanism in this work. Distinctive linear and reversible fluorescence quenching by up to 19.3% is observed for the visible and near-infrared GQD emission in aqueous suspension from 25 °C to 49 °C. A more pronounced trend is observed with GQD nanothermometers internalized into the cytoplasm of HeLa cells as they are tested in vitro from 25 °C to 45 °C with over 40% quenching response. Our findings suggest that the temperature-dependent fluorescence quenching of bottom-up and top-down-synthesized GQDs studied in this work can serve as non-invasive reversible/photostable deterministic mechanisms for temperature sensing in microscopic sub-cellular biological environments. View Full-Text
Keywords: graphene quantum dots; nanothermometry; fluorescence; in vitro; temperature sensing graphene quantum dots; nanothermometry; fluorescence; in vitro; temperature sensing
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MDPI and ACS Style

Lee, B.H.; McKinney, R.L.; Hasan, M.T.; Naumov, A.V. Graphene Quantum Dots as Intracellular Imaging-Based Temperature Sensors. Materials 2021, 14, 616. https://doi.org/10.3390/ma14030616

AMA Style

Lee BH, McKinney RL, Hasan MT, Naumov AV. Graphene Quantum Dots as Intracellular Imaging-Based Temperature Sensors. Materials. 2021; 14(3):616. https://doi.org/10.3390/ma14030616

Chicago/Turabian Style

Lee, Bong H., Ryan L. McKinney, Md. T. Hasan, and Anton V. Naumov 2021. "Graphene Quantum Dots as Intracellular Imaging-Based Temperature Sensors" Materials 14, no. 3: 616. https://doi.org/10.3390/ma14030616

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