An ultrasensitive colorimetric and fluorescence dual-readout assay for glutathione with a carbon dot–MnO₂ nanosheet platform based on the inner filter effect

Abstract

An ultrasensitive colorimetric and fluorescence dual-readout assay based on carbon dot–MnO2 nanosheets platform was developed for GSH detection in human body fluid samples.

Carbon dot composites for bioapplications: a review

“…Following the “on–off” strategy, Wu et al established a fluorometric nanoprobe with N-doped CDs for the sensitive detection of GSH, in which the PL of CDs was in a reverse relationship with the concentration of GSH due to the thiol group triggered IFE. 344,345 On the other hand, Cai and co-workers designed novel “on–off–on” biosensors using CD–MnO 2 nanocomposites for the sensing of GSH. 346,347 In this system, the PL of CDs was initially quenched by MnO 2 nanosheets through energy transfer between the two; in the presence of the target analyte GSH, the MnO 2 nanosheets were reduced to Mn 2+ ions, causing the release of CDs and restoration of CDs’ PL (Fig.…”

“…For instance, in Yan and co-workers’ study, glyoxylic acid-modified CDs (GA-CDs) were used as a FRET ratiometric fluorescent probe for the detection of Cu 2+ in aqueous solution. 388 Similarly, Chen et al also applied cyclam-functionalized CDs as a FRET nanoprobe for the detection of Cu 2+ and S. 2–389 In addition to the above examples, the detection of other important metal ions such as Ag + , Cu 2+ , Cr 6+ , and Pb 2+ has also been successfully realized with CD composite-based sensing platforms. 390–401…”

Review of 2D MnO2 Nanosheets as FRET-Based Nanodot Fluorescence Quenchers in Chemosensing Applications

“…While most of the fluorescent dots@MnO 2 nanocomposites-based sensors were built on the FRET phenomenon, He et al proposed an inner filter effect (IFE)-based fluorescence mechanism for GSH sensing, in which CDs and MnO 2 NSs were used as fluorophores and absorbers, respectively . The emission spectrum of CDs centered at 440 nm (Figure a) was well overlapped with the absorption spectrum of MnO 2 NSs (Figure b), which suggests that fluorescence quenching may be caused by FRET or IFE.…”

“…(c) Fluorescence lifetime of CDs, a CDs@MnO 2 NSs mixture, and a CDs@MnO 2 NSs mixture reacted with GSH. Adapted with permission from ref . Copyright 2021 RSC.…”

“…Variation in the levels of GSH has been directly linked to several diseases including liver damage, psoriasis, leucocyte loss, cancer, and HIV infection . A good number of CDs@MnO 2 conjugate-based sensing systems have been reported in the past few years. ,− The first GSH sensing studies based on the CDs@MnO 2 nanoconjugate were reported by Lin and co-workers and He’s group in 2015 (Figure a). , Lin’s group synthesized the carboxyl-functionalized CDs using citric acid and aminohexanoic acid . Fluorescence of the CDs (10 μg/mL) was significantly quenched up to 87% quenching efficiency by adding MnO 2 NSs from 0 to 30 μg/mL to achieve a FRET pair between them via electrostatic interaction (Figure b).…”