Metal Oxide Nanostructures as Biological Nanosensors for the Detection of Urea and Glucose

The nanobiotechnology is a branch of nanotechnology combining several branches of basic sciences and grows festally over the past decade. It is often used in many different fields of medical sciences such as detection and diagnosis of cancers, drug delivery, imaging markers, cellular targeting, neurological, neurovascular cancer diseases, cytotoxicity, etc. Over various medical applications, these days nanobiotechnology is largely used in sensing applications. Towards this direction, some biomedical devices in operation such as electrochemical and biochemical biosensors are applied for identifying bio-species rely on the method of biomolecule immobilization. A recent trend is to understand and explore the biocompatibility of nanostructured materials (in particular metal oxide) synthesized by various techniques. In this pathway, the inorganic semiconductor metal oxide nanostructures play a crucial role in the manufacturing of biosensors because they possess operation at low temperature, good thermal stability, chemical inertness with biomolecules, large surface area, etc. It enables for quick examination in vivo and the potential for the integration of the manufacture of electrochemical sensors as devices, biosensors, or biochips owing to their tiny size and huge surface area. These materials are usually utilized to create sensors that are considerably superior to traditional spectroscopic measurements since they can be integrated into an online monitoring system. A typical biosensor is an analytical tool that precisely interacts with an analyte by using biological components. Chemical compounds as analytes are to be measured by biological sensors. Enzymes, nucleic acids, antibodies, lectins, whole cells, complete organs, or tissue slices are typically employed as biological materials. There are two possible types of interaction between the biological components utilized in the biosensors and the analyte such as (i) the analyte could change into a different chemical compound (by enzymatic biosensors) and (ii) the biological material on the biosensors may simply bind to the analyte (e.g. nucleic acid, antibodies; associated biosensors called affinity biosensors). Among commercial biosensors, the most well-known is the blood glucose biosensor, which uses an enzyme to break down blood glucose and convert the sugar into its metabolites. Beta-D-glucose is oxidized by the dimeric protein GOx to D-glucono-1,5-lactone, finally hydrolyzed into gluconic acid. To create a biosensor that is effective, it is necessary to incorporate certain attributes. For example, (i) the sensor should exhibit a high level of specificity toward the analyte being measured, (ii) the reaction employed should be minimally influenced by external factors such as temperature, pH, and stirring, (iii) the device's response should be proportionate across a wide concentration ranges of analyte, (iv) it must be both compact and biocompatible, if the biosensor is intended for use inside the body, (v) the biosensor should be cost-effective, simple to operate, and small in size and (vi) the device should be robust enough to withstand frequent use. In this chapter, a compact literature and brief introduction of the prepared nanomaterials and with application of nano-biodevices such as nanosensors of urea and glucose are presented. The present chapter also shows the fabrication and characterization of nanostructures such as ZnO and SnO₂, and thereafter the prepared nanostructures are used as biosensors using the solution/precipitation process. Finally, the future studies and directions of metal oxide nanostructures and their possible sensing applications are spotlighted at the end of this chapter.