The Application of Graphene Quantum Dots in Electrochemical Immunosensors for Cancer Diagnosis: A Review

Cancer occurs from the transition of healthy cells into tumor cells in various stages, including carcinogenesis/tumorigenesis or oncogenesis, that often emerges from a pre-cancerous lesion to a malignant tumor [۱-۳]. Recently, cancer research has been given a lot of attention because this disease is one of the most significant leading cause of human mortality [۴, ۵]. The cancer diagnostics has gone through substantial transformation due to recent advancements in nanotechnology science which leads to fabricating miniaturized biosensors for the use in early and efficient diagnosis [۶, ۷]. Therefore, the early diagnosis of cancer is critical for reducing the cancer-related deaths because of the high sensitive and rapid cancer marker detection in primary phases which leads to the increment chances of treatment and enhancing cancer patients lives [۸]. Various examples of biomarkers are of great importance including, carcinoembryonic antigen (CEA), cancer antigens (e.g., CA-۱۲۵, CA-۱۴۵, and CA-۱۹۹) prostate-specific antigen (PSA), IL-۱۳ soluble receptor Ra۲ (IL-۱۳sRa۲), cadherin-۱۷ (CDH-۱۷), hydrogen peroxide (H۲O۲) and interleukin ۶/۸ (IL-۶/۸) [۹]. Over the past decades, biosensors research and development has gained extensive attentions due to their potential in early disease diagnosis and real-time health monitoring [۱۰]. Biosensors are devices designed to measure biological or chemical molecules/reactions. A biosensor is typically composed of three main components: a bioreceptor, an analyte, and a transducer. A bioreceptor is a biological recognition molecule/element that specifically detects and binds to a target substance, which is called an analyte. An analyte is the biological or chemical substance that is going to be measured e.g., glucose, enzyme, hormones, etc. Transducer is the element that converts the biological interaction into measurable signals.[۱۱] The biological or chemical event is converted to the electrical signal by the means of these analytical devices which are commonly classified based on the bioreceptors type involved in the bio-recognition events like enzyme [۱۲], antibody [۱۳], peptide [۱۴], aptamer [۱۵], DNA [۱۶], and molecularly imprinted polymer (MIP)-based sensors [۱۷, ۱۸], or based on the type of transducer which is used, including electrochemical [۱۹], optical [۲۰], piezoelectric [۲۱], and calorimetric biosensors [۲۲]. Among the aforementioned sensors, the one which employs the antibody as a bio-recognition element is regarded as one the most significant sensing platforms which are often described as immunosensor, since they operate based on the immunoreaction (i.e., specific recognition) between antigens and antibodies [۲۳, ۲۴]. Using the quantum dots (QDs) as the core components of a biosensor has attracted notable interest due to the unique optical, electrical, and magnetic properties. QDs typically ranging in size from about ۲ to ۱۰ nanometers. They exhibit unique, size-dependent optical and electronic properties resulting from the quantum confinement effect.[۲۵] Graphene quantum dots (QDs) are carbon-based zero-dimensional semiconductor nanocrystals composed of small graphene fragments arranged in a honeycomb structure. GQDs exhibit high electrical conductivity, large electroactive surface area, easy surface functionalization, low toxicity, and biocompatibility. Their size is typically ranging from ۱-۵۰ nm, which is similar to the size of biomolecules, making them ideal for biosensor applications[۲۶, ۲۷]. Cancer biomarkers can be found in tumor tissue and fluids such as serum, plasma, saliva, urine, cerebrospinal fluid, and peritoneal fluid [۲۸]. QDs can be synthesized using either top-down or bottom-up methods. In top-down methods larger carbon structures are broken down through methods such as hydrothermal/solvothermal synthesis, electrochemical oxidation, exfoliation, etc. On the other hand, in bottom-up methods GQDs are produced from molecular precursors through chemical synthesis, pyrolysis, or microwave assisted methods[۲۶]. The main aim of this review is to highlight the recent advancements in the realm of GQDs-based electrochemical immunosensors for early and rapid cancer diagnosis. Furthermore, we shed light on the desired characteristics of GQDs, their synthesis methods, and the general mechanism of electrochemical immunosensors.

کلیدواژه ها:

Graphene quantum dots (QDs) ، Electrochemical biosensors ، Immunosensors ، Cancer diagnosis