A Critical Review of Carbon Quantum Dots: From Synthesis toward Applications in Electrochemical Biosensors for the Determination of a Depression-Related Neurotransmitter

Abstract

Depression has become the leading cause of disability worldwide and is a global health burden. Quantitative assessment of depression-related neurotransmitter concentrations in human fluids is highly desirable for diagnosis, monitoring disease, and therapeutic interventions of depression. In this review, we focused on the latest strategies of CD-based electrochemical biosensors for detecting a depression-related neurotransmitter. We began this review with an overview of the microstructure, optical properties and cytotoxicity of CDs. Next, we introduced the development of synthetic methods of CDs, including the “Top-down” route and “Bottom-up” route. Finally, we highlighted detecting an application of CD-based electrochemical sensors in a depression-related neurotransmitter. Moreover, challenges and future perspectives on the recent progress of CD-based electrochemical sensors in depression-related neurotransmitter detection were discussed.

Synthesis of Doped/Hybrid Carbon Dots and Their Biomedical Application

“…These properties enable them to be used in a number of disciplines, as presented in Figure 1 . Doped or hybrid CDs consist of graphitic carbon and functional heteroatoms (nonmetal) attached with a carbonized core [ 5 , 6 , 7 , 8 , 9 , 10 ]. These are a relatively new type of nanomaterials and are considered to be promising for various applications [ 11 ].…”

“…Some of them were found to affect the physicochemical characteristic of the doped CDs [ 4 , 45 ] The impregnation of metal or nonmetal ions may also change the electronic properties of doped CDs, designing the HOMO-LUMO energy band gap that determines the photo-optical properties of the doped CDs [ 6 , 46 ]. Doping with elements which are essential to the human body, such as calcium, iron, copper, manganese, copper and nickel made these doped CDs of special importance [ 10 ]. Doping with elements such as Au, Ag, Ga, Zn, and Fe are also of some importance for catalysis and biomedical applications.…”

“…The light promotes up-conversion of the fluorescence characteristic, enhanced photo-induced electron transfer, and unique electron reservoir properties of the doped CDs. It also inhibits recombination of photo-induced electron-hole pairs [ 10 , 49 , 53 ]. All these effects occur due to the ROS generation.…”

“…Similarly, fluorescent CDs can be conjugated with magnetic nanoparticles to develop multimodal imaging platforms (optical and electromagnetic resonance). Ternary conjugates consisting of fluorescent CDs, NIR-responsive nanoparticles, and magnetic nanoparticles can be used in multimodal biomedical applications [ 10 , 49 , 53 ].…”

Photothermal Detection of MicroRNA Using a Horseradish Peroxidase-Encapsulated DNA Hydrogel With a Portable Thermometer

“…Alternatively, biosensors based on fluorescence, electrochemistry, photoelectrochemistry, and chemiluminescence are promising analytical technologies with high selectivity and sensitivity compared with conventional miRNA detection methods ( Zheng et al, 2019a ; Wang et al, 2020 ; Jin et al, 2021 ). Biosensing detection based on visual recognition and quantitation through a portable readout is potentially an ideal detection approach because output signals are obtained by simple portable analytical instruments or the naked eye which overcomes the limitations of assay readout methods dependent on complex, expensive, and bulky analytical equipment ( Qu et al, 2011 ; Fu et al, 2016 ; Zheng et al, 2019b ; Zhao et al, 2019 ; Xu et al, 2020 ; Xu et al, 2021 ).…”