Engineered Nanomaterials: Array-based Sensing of Biological and Chemical Analytes

Abstract

Array-based sensing, also known as chemical nose/tongue analysis, offers an alternative platform for simultaneous differentiation of a wide range of analytes using a fixed number of cross-reactive receptors. The sensor elements in the optimized array interact with multiple analytes in an unbiased manner, and hence, the sensing pattern is unlike a specific mode of sensing. In arraybased sensing, the ideality of detection processes depends on the sensor element's versatile nature with highly active surface. The above criteria can be easily achieved through nanomaterials over small molecules. They provide a high surface to volume ratio, which makes them potential candidates for molecular recognition through surface adsorption phenomena. Also, the surface property can be engineered to facilitate smooth interaction with incoming analytes. The detection technique centered on optical methods is much more convenient and accessible than those based on electrical and mechanical approaches. Based on the optical activity of nano receptors, the array can be designed in two different ways: 1) Indicator binding assay, where the optically active nanomaterials like plasmonic nanoparticles and fluorescent nanodots behave as signal transducers themselves and can alter their optical response upon directly binding to the analytes and 2) Indicator displacement assay, where the binding activity of optically inactive nanomaterials can be monitored through external signal transducers. Depending on the nature of signal transducer elements, the array can be designed in two ways, i.e., single channel and multichannel, where individual and mixture of signal transducers are added respectively to the sensor array. The sensitivity and accuracy of the whole system can be further improved by adding competitive signal enhancer/depressor agents. This phenomenon is termed as “sequential ON-OFF strategy” in array-based sensing. In brief, this chapter will provide collective information about the working principle of different modes of array-based sensing and the advantages of different surface engineered nanomaterials as receptors in the pattern-based recognitions.