Fluorescent Nanosensor for pH and Temperature Measurements Based on Carbon Dots

Abstract

The rapid technological progress and the continuous deepening of knowledge in the natural Sciences make methods for the diagnosis and treatment of various diseases at the molecular level more and more relevant. The implementation of such methods requires tools that allow monitoring the parameters that determine the state of the body at the cellular level. For example, the pH value plays a vital role in many cellular processes, and even small changes in its values (about 0.1 units) seriously affect the state of the whole organism. Temperature is another important parameter that characterizes the state of the cell. Temperature monitoring at the cellular level is important, for example, in photothermal therapy, also the increase of temperature may indicate inflammatory processes in the body. Despite the active development of cellular nanosensorics, the problem of creating a sensor that is able to determine several parameters of the cellular environment simultaneously remains very urgent. Due to such properties as non-toxicity, biocompatibility, and sensitivity of photoluminescence (PL) to changes in the environment, recently synthesized carbon dots (CDs) have great potential for use in biomedicine as multimodal cellular sensor.
This study considers the possibility of simultaneous determination of the pH and temperature of a liquid medium from the PL spectra of CDs synthesized using the hydrothermal method from citric acid and ammonia aqueous solutions. The dependence of the PL of aqueous suspensions of CDs on pH was studied in the range of its variation from 5 to 9.21 with a change in temperature from 22 to 81°C. A high sensitivity of the CDs PL to changes in the specified environmental parameters was found: the PL intensity of CDs decreases monotonically with an increase in pH and temperature.
In this study, artificial neural networks are used to solve the two-parameter inverse problem of determining pH and temperature from the PL spectra of carbon dots. The application of the perceptron to the obtained database of the PL spectra of CDs in water provided the simultaneous determination of the temperature and pH of the environment with an accuracy of 0.67°C and 0.005, respectively. The results provide broad prospects for the development of an efficient optical multimodal cellular nanosensor based on CDs.
This study has been supported by Russian Foundation for Basic Research (Projects No. 20-32-70150 (K.A.Laptinskiy, T.A.Dolenko) and No. 19-01-00738 (S.A.Burikov, S.A.Dolenko)). The contribution of O.E.Sarmanova (programming and training of neural networks) was supported by the Foundation for the Advancement of Theoretical Physics and Mathematics “BASIS” (Project No. 19-2-6-6-1).

Speaker

Maria Yurevna Khmeleva
Faculty of Physics, Lomonosov Moscow State University
Russia

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