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Invited Reviews
Contributing Editor: Venkatesan Renugopalakrishnan
This section of Journal of Materials Research is reserved for papers that are reviews of literature in a given area.
I.
INTRODUCTION
Biosensor technology has truly revolutionized the quality of human life by providing selective, sensitive, and rapid (point-of-care) detection tools for disease diagnosis and monitoring. Whether it is detection of disease specific, small molecule metabolites like glucose, protein biomarkers, DNA or pathogenic microorganisms, biosensors are being increasingly used in developing advanced detection techniques in healthcare and medicine.
In general, a biosensor can be broadly defined as a device which can detect presence of chemical or biological molecules like enzymes or proteins or nucleic acid, microorganisms, using specific biorecognition elements like receptors, antibodies, enzymes, substrate etc. The information about specific binding of analyte to biorecognition element is converted into a measurable output as a signal using the transducer. Depending upon the type of transducer used, biosensors can be categorized as electrochemical, optical, thermal, piezoelectric etc. To limit the scope of this review, we will be specifically focusing on the electrical/electrochemical biosensors used in healthcare. In electrical/electrochemical biosensors, transducer element converts the biological event such as affinity capture or biocatalytical conversion corresponding to concentration of analyte into an electrical signal such as current or voltage, based on either amperometric, potentiometric, conductometric, or field effect transistor principles. Figure 1 shows the basic design of electrochemical/electrical biosensor.
FIG. 1.
Schematic of electrochemical/electrical biosensor design.
[Figure Omitted; See PDF]With the discovery of carbon nanomaterials and advancement in nanofabrication methods and tools, carbon nanotubes (CNTs) and graphene have been extensively explored as transducer elements in the development of biosensor devices. Graphene, in particular has become a popular choice in the development of electrochemical biosensor devices due to its excellent electrical, chemical, and material properties which include large surface area, charge carrier concentrations, and exceptional electron mobility with ballistic electron transport. Moreover the reactivity of graphene edges and functional groups introduced in the basal plane due to its synthesis procedure for e.g., oxygen containing groups introduced during graphene oxide synthesis by Hummer's method are crucial in electrochemical reactions and its functionalization with biorecognition elements.
In this paper, we specifically review electrical/electrochemical biosensors developed using...