Lee Bong Han, McKinney Ryan Lee, Hasan Md Tanvir, Naumov Anton V
Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA.
Biosystems and Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Materials (Basel). 2021 Jan 29;14(3):616. doi: 10.3390/ma14030616.
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.
非侵入式温度传感对于分析人体中发生的生物过程是必要的，这些过程包括细胞酶活性、蛋白质表达和离子调节。为了在纳米尺度上探测温度敏感过程，基于分别通过自上而下（RGQDs）和自下而上（N-GQDs）方法从还原氧化石墨烯和葡萄糖胺前体合成的石墨烯量子点（GQDs），开发了新型发光纳米温度计。由于其3-6纳米的小尺寸、对温度变化的非侵入式光学敏感性以及高生物相容性，GQDs实现了生物安全的亚细胞分辨率传感。两种类型的GQDs在可见光和近红外区域都表现出对温度敏感但光稳定的荧光，在本工作中，RGQDs被用作传感机制。在25°C至49°C的水悬浮液中，对于可见光和近红外GQD发射，观察到高达19.3%的独特线性和可逆荧光猝灭。当GQD纳米温度计内化到HeLa细胞的细胞质中并在25°C至45°C进行体外测试时，观察到更明显的趋势，猝灭响应超过40%。我们的研究结果表明，在本工作中研究的自下而上和自上而下合成的GQDs的温度依赖性荧光猝灭可作为微观亚细胞生物环境中温度传感的非侵入式可逆/光稳定确定性机制。
