Conducting Nanomaterial Sensor Using Natural Receptors.

One of the recently emerging topics in biotechnology is natural receptors including G protein-coupled receptors, ligand-gated ion channels, enzyme-linked receptors, and intracellular receptors, due to their molecular specificity. These receptors, other than intracellular receptors, which are membrane proteins expressed on the cell membrane, can detect extracellular stimuli. Many researchers have utilized cells with natural receptors embedded in the cellular membrane for human sense-mimicking platforms based on electrochemical impedance spectroscopy, quartz crystal microbalances, surface plasmon resonance, and surface acoustic waves. In addition, integration of conducting nanomaterials and natural receptors allows highly sensitive and selective responses toward target molecules, enabling, for example, nanobioelectronic noses for odorants, nanobioelectronic tongues for tastants, and G-protein-coupled receptor sensors for hormones, dopamine, cadaverine, geosmin, trimethylamine, etc. Moreover, as a part of nanobioelectronic sensors, natural receptors can be produced in various forms, such as peptides, proteins, nanovesicles, and nanodiscs, and each sensor can provide an ultralow limit of detection. In this Review, we discuss biosensors with natural receptors and then especially focus on natural receptor-conjugated conducting nanomaterial sensors. To provide a fundamental understanding, the sections encompass (1) the fabrication of conducting nanomaterials, (2) the production of natural receptors, (3) the characteristics of natural receptors, (4) the technology for immobilizing both components, and (5) their sensing applications. Finally, perspective is given on a new development in the use of natural receptors in a wide range of industries, such as food, cosmetics, and healthcare. In addition, artificial olfactory codes will be characterized by signal processing in the near future, leading to human olfactory standardization.