Abstract
Graphene quantum dots (GQDs) and carbon dots (CDs) are among the latest research frontiers in carbon-based nanomaterials. They provide interesting attributes to current electrochemical biosensing due to their intrinsic low toxicity, high solubility in many solvents, excellent electronic properties, robust chemical inertness, large specific surface area, abundant edge sites for functionalization, great biocompatibility, low cost, and versatility, as well as their ability for modification with attractive surface chemistries and other modifiers/nanomaterials. In this review article, the use of GQDs and CDs as signal tags or electrode surface modifiers to develop electrochemical biosensing strategies is critically discussed through the consideration of representative approaches reported in the last five years. The advantages and disadvantages arising from the use of GQDs and CDs in this context are outlined together with the still required work to fulfil the characteristics needed to achieve suitable electrochemical enzymatic and affinity biosensors with applications in the real world.
Highlights
The increasingly challenging demands of molecular determination have led to great research efforts to improve the analytical performance of electrochemical biosensors, enhancing their unique features for practical point-of-care (POC) analysis in terms of cost and portability and for direct analysis in complex biological matrices even for multiple target analytes
The excellent properties provided by Graphene quantum dots (GQDs) and carbon dots (CDs) for the immobilization of bioreceptors and for the electrocatalysis of many relevant compounds (H2O2, O2, dopamine, etc.) mean that such nanomaterials are more frequently used in electrochemical biosensing mainly as electrode modifiers, and, and increasingly, in regards to GQDs, as advanced labels [13]
This laccase biosensor relied on the electrostatic interactions of the enzyme at the surface of the MoS2/GQDs/screen-printed carbon electrode (SPCE) and showed an attractive performance for the chronoamperometric determination of caffeic acid, chlorogenic acid, and epicatechin, achieving limit of detection (LOD) of 0.32, 0.19, and 2.4 μM, respectively
Summary
The increasingly challenging demands of molecular determination have led to great research efforts to improve the analytical performance of electrochemical biosensors, enhancing their unique features for practical point-of-care (POC) analysis in terms of cost and portability and for direct analysis in complex biological matrices even for multiple target analytes. It is well known that nanostructuration of working electrodes with nanosized carbon modifiers provides attractive new features, such as easy physical adsorption onto electrodes through van der Waals forces; fast electron transfer kinetics due to their extremely high conductivity along particular directions; high surface area, which enhances biomolecules’ adsorption; highly selective and tunable catalysts due to their unique electronic or plasmonic structure; and tunable surface chemistry towards the direction of the assembly for particular capture probe or analyte species [1] Their excellent biological compatibility, ease of preparation, and organic functionalization make carbon-based nanomaterials excellent carriers for loading numerous signal elements, such as enzymes, oligonucleotides, antibodies, Nanomaterials 2019, 9, 634; doi:10.3390/nano9040634 www.mdpi.com/journal/nanomaterials. The following sections highlight representative strategies involving mostly GQDs, and CDs, in electrochemical biosensing related to the preparation of both enzymatic and affinity biosensors
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