Ratiometric fluorescent sensing of melatonin based on inner filter effect and smartphone established detection

Himanshu Kumar; Sangeeta Obrai

doi:10.1016/j.saa.2023.123309

Ratiometric fluorescent sensing of melatonin based on inner filter effect and smartphone established detection

Spectrochim Acta A Mol Biomol Spectrosc. 2024 Jan 5:304:123309. doi: 10.1016/j.saa.2023.123309. Epub 2023 Aug 30.

Authors

Himanshu Kumar¹, Sangeeta Obrai²

Affiliations

¹ Department of Chemistry, Dr. B.R. Ambedkar National Institute of Technology, Jalandhar, Punjab 144011, India.
² Department of Chemistry, Dr. B.R. Ambedkar National Institute of Technology, Jalandhar, Punjab 144011, India. Electronic address: obrais@nitj.ac.in.

PMID: 37716042
DOI: 10.1016/j.saa.2023.123309

Abstract

Melatonin (MLT) is a crucial neurohormone having inhibitory effects over various types of cancer. In this work, 3,6-Diaminocarbazole (DAC), a fluorescent probe is utilized to detect MLT in a highly sensitive, selective and facile way. The unique feature of present work is that MLT is sensed by ratiometric fluorescent technique based on the inner filter effect (IFE) using DAC at an emission wavelength of 310 nm. As a result, a noticeable change in color from red to cyan is observed and the quantitative analysis of fluorescence signals at these wavelengths are used to detect MLT observing a linear relationship between the ratio of emission intensities and the concentration of MLT over a linear range of 0 to 78 μM. DAC can accurately measure the detailed quantity of MLT with a limit of detection of 30 nM and has proved to be an efficient sensing probe due to its excellent molar absorptivity and high photoluminescence quantum yield (PLQY). Sensing characterization was carried out UV-Vis, steady-state, and time- resolved fluorescence spectroscopic techniques. The smartphone app "RGB colour detector" value has been successfully linked with the considerable detectable color changes of DAC on addition of MLT. HOMO-LUMO have been calculated using DFT with B3LYP/6-31G(d,p) level and band gaps of 3.77 eV and 4.91 eV were found for DAC and MLT, respectively. Electrons are not allowed energetically to transfer from MLT to DAC, as is evident from their band gaps. Therefore, IFE can be considered the foremost method in fluorescence quenching of present investigation. The developed sensor was verified by spiking of MLT in human serum.

Keywords: 3,6-Diaminocarbazole (DAC); Density Functional Theory (DFT).; Fluorescence spectroscopy; Inner filter effect (IFE); Limit of Detection (LOD); Melatonin (MLT); Ratiometric Fluorescence (RF).