Electrochemical biosensors based on two dimensional nano-materials for disease diagnosis

Development of techniques for early and effective diagnosis of diseases is of paramount importance to people and society. It is known that many diseases can be directly detected by monitoring trace amount of the disease-related biomarkers in one's blood, urine, saliva or even breath. So far, large analytical instruments are mainly used to test the various disease-related biomarkers, however, their large size, complex operation and high price have restricted their wider application for disease diagnosis. To overcome this problem, the development of a variety of miniaturized sensors for biomarker detection plays a key role in the health care industry. The recent advance in nanomaterials and nanotechnology has enabled biosensors with high sensitivity, good selectivity and fast response. Over the last decade, graphene, which is the thinnest and most representative two dimensional (2D) material, has aroused great research interest because of its exceptional electronic, optical and mechanical properties. Other kinds of 2D materials, such as hexagonal BN (h-BN) and transition metal dichalcogenides (TMDs) derived from their layered bulk crystals, have also been intensively investigated in recent years due to their promising properties and a broad range of applications such as electronics, optoelectronics, catalysis, energy storage devices and so on. Especially, these 2D materials have been extensively used to fabricate sensors in recent years. For example, due to its excellent electrical conductivity, large surface area and rapid electron transfer rate, reduced graphene oxide (rGO) is suitable to detect biological materials with the ability to greatly amplify the electrochemical sensing signals. The typical graphene analogue, molybdenum disulfide (MoS₂), also can be used to fabricate biosensors. These 2D materials which have shown attractive physical, chemical and catalytic properties are expected to offer more opportunities for developing biosensors with improved sensitivity, flexibility and wearability. This mini-review summarizes the preparation and application of graphene and MoS₂-based electrochemical sensors that can be potentially used for disease detection, such as diabetes, lung cancer and prostate cancer. Especially those sensors based on rGO or MoS₂ hybridized with metal nanoparticles or organic materials will be discussed. These sensors can be classified based on the surface recognition molecules used, such as enzymes, DNAs, anti-body and so on. High-yield preparation of 2D materials at low cost remains challenge, and the development of efficient techniques for sensor fabrication is urgent needed. With more and more 2D materials being prepared and investigated, such as black phosphate, metal carbides, metal nitrides and so on, developing of novel sensing systems requires continuous efforts to achieve enhanced sensitivity and selectivity. More importantly, sensor arrays for simultaneous multi-target detection will be one of the main challenges for future development.