Graphene Quantum Dot-Based Electrochemical Immunosensors for Biomedical Applications

Abstract

In the area of biomedicine, research for designing electrochemical sensors has evolved over the past decade, since it is crucial to selectively quantify biomarkers or pathogens in clinical samples for the efficacious diagnosis and/or treatment of various diseases. To fulfil the demand of rapid, specific, economic, and easy detection of such biomolecules in ultralow amounts, numerous nanomaterials have been explored to effectively enhance the sensitivity, selectivity, and reproducibility of immunosensors. Graphene quantum dots (GQDs) have garnered tremendous attention in immunosensor development, owing to their special attributes such as large surface area, excellent biocompatibility, quantum confinement, edge effects, and abundant sites for chemical modification. Besides these distinct features, GQDs acquire peroxidase (POD)-mimicking electro-catalytic activity, and hence, they can replace horseradish peroxidase (HRP)-based systems to conduct facile, quick, and inexpensive label-free immunoassays. The chief motive of this review article is to summarize and focus on the recent advances in GQD-based electrochemical immunosensors for the early and rapid detection of cancer, cardiovascular disorders, and pathogenic diseases. Moreover, the underlying principles of electrochemical immunosensing techniques are also highlighted. These GQD immunosensors are ubiquitous in biomedical diagnosis and conducive for miniaturization, encouraging low-cost disease diagnostics in developing nations using point-of-care testing (POCT) and similar allusive techniques.

Applications of Graphene Quantum Dots in Biomedical Sensors

“…These studies could specifically and sensitively detect target analytes by virtue of multiplexing electrodes such as screen-printed carbon electrodes (SPCE), screen-printed gold electrodes (SPGE) glassy carbon electrodes (GCE), etc. These sensing platforms have been validated to perform cost-effective, trustworthy, utterly sensitive and exact detection of target biomolecules for governing healthcare systems [79]. Moreover, some biosensors have been reported to offer multiplexed ability for concurrent detection of multiple biomolecules [80,81].…”

“…They are built upon a WE (i.e., transducer and recognition system), a CE and a RE for computing the electrical signal response [245,246]. Among all the GQD-based electrochemical sensors working on different kinds of receptors (i.e., antibody sensors, MIP-sensors, DNA sensors, aptasensors and enzyme-based sensors), an antibody-sensing system has been widely studied [79]. It is often known as an immunosensor, because its function is solely influenced by the immunoreaction [247,248].…”

“…It is often known as an immunosensor, because its function is solely influenced by the immunoreaction [247,248]. Such sensing platforms involve antibodies exhibiting excellent affinity for their corresponding target biomolecules [11,79,249]. Taking immunoreactions into an account, typical immunosensors can work on several assay-modes.…”

“…(i.e., competitive, direct, sandwich or indirect modes) [250][251][252][253]. Such assay formats work on the unique mechanisms and usually entail the events mentioned below [11,79]:…”

“…In this work, acetic Figure 19. Experimental steps to fabricate a GCE for detecting breast cancer [79].…”