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Levodopa has been a standard drug for treating Parkinson's disease since the 1960s, but it has caused many side effects such as wearing-off, motor fluctuation, and dystonia. In this work, we developed glutathione-conjugated carbon quantum dots (GSH-CQDs) as a novel fluorescent sensor for sensitive and selective detection of levodopa. The GSH-CQDs were prepared by EDC/NHS coupling reaction of glutathione (GSH) with amine-functionalized CQDs (N-CQDs) synthesized using meta-phenylenediamine and ethylenediamine. The synthesized GSH-CQDs emitted bright green fluorescence with a high quantum yield (QY) of 22.42 ± 6.88%. However, upon the addition of levodopa to GSH-CQDs under alkaline conditions, the fluorescence of GSH-CQDs was quenched. Since levodopa is converted to dopaquinone in an alkaline environment, it is presumed that thiol groups of GHS-CQDs form covalent bonds with dopaquinone, causing fluorescence quenching through photoinduced electron transfer. Therefore, as the concentration of levodopa increased, the fluorescence intensity of GSH-CQDs was gradually decreased. Under optimal conditions, a linear response was observed in the range of 0.05-1 μM, and limit of detection (LOD) was determined to be 0.057 μM. The GSH-CQDs exhibited high specificity to levodopa over other non-target biological substances, quinone derivatives, and Parkinson's medications. Furthermore, the capability of this GSH-CQDs sensor for monitoring levodopa in human serum were validated with excellent precision and recovery rates of 100.20-103.33%. Copyright © 2021 Elsevier B.V. All rights reserved.

Citation

Seok Won Park, Tae Eun Kim, Yun Kyung Jung. Glutathione-decorated fluorescent carbon quantum dots for sensitive and selective detection of levodopa. Analytica chimica acta. 2021 Jun 22;1165:338513

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PMID: 33975692

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