Nanoconfinement Effect for Signal Amplification in Electrochemical Analysis and Sensing

Abstract

Owing to the urgent need for electrochemical analysis and sensing of trace target molecules in various fields such as medical diagnosis, agriculture and food safety, and environmental monitoring, signal amplification is key to promoting analysis and sensing performance. The nanoconfinement effect, derived from nanoconfined spaces and interfaces with sizes approaching those of target molecules, has witnessed rapid development for ultra‐sensitive analyzing and sensing. In this review, the two main types of nanoconfinement systems – confined nanochannels and planes – are assessed and recent progress is highlighted. The merits of each nanoconfinement system, the nanoconfinement effect mechanisms, and applications for electrochemical analysis and sensing are summarized and discussed. This review aims to help deepen the understanding of nanoconfinement devices and their effects in order to develop new analysis and sensing applications for researchers in various fields.

Bio-inspired Track-Etched Polymeric Nanochannels: Steady-State Biosensors for Detection of Analytes

“…Beyond the exploration of advanced yet low-cost micro/nanofabrication, the introduction of materials with meso- and micropores, for example, metal–organic frameworks, should advance the nanochannel-based sensors. , Moreover, with the rapid development of emerging technologies such as artificial intelligence, machine learning, big data, and data visualization, an underlying trend is rising that integrates these technologies with nanoconfinement effect-based analyzing and sensing technologies. Consequently, more sensitive and higher throughput sensing can be obtained with the in-depth use of data . Undoubtedly, the development of bio-inspired nanochannel-based sensors is far from complete.…”

“…Consequently, more sensitive and higher throughput sensing can be obtained with the in-depth use of data. 426 Undoubtedly, the develop-VOCABULARY Biological ion channels, protein-based pores embedded into biological membranes that allow selected ions to pass through the membrane; nanochannel-based biosensors, artificial nanochannel systems which are inspired by biological ion channels for detecting various analytes; steady state, a situation in which all state variables are constant in spite of ongoing processes that strive to change them; ionic gating, an important characteristic of ion channels which can be opened and closed to regulate ionic conduction in response to specific external stimulus alternation; ionic current rectification (also referred to as ionic rectification), when the ionic current for one voltage polarity is higher than that recorded for the same absolute value of opposite polarity…”

“Writing biochips”: high-resolution droplet-to-droplet manufacturing of analytical platforms

“…49 Moreover, droplet approaches allow for automated analysis of proteins in individual cells, 50 as well as biomolecular analyses at the single molecule level which could be exploited for signal amplification effects in electrochemical sensors. 48…”

“…In general, conducting biochemical microassays in droplets down to the femtoliter scale is enticing not only for fundamental science 44 or for reducing reagent consumption in multiplexed bioanalysis, 45 but also because downscaling allows the up-concentration and nanoconfinement effects which are beneficial features for optical detection 46,47 and electrochemicalbased 48 sensing of analytes. Such confinement is also crucial in microbiological systems, as observed for femtoliter droplet confinement of a few Streptococcus pneumoniae bacterial cells which permits cell-to-cell genetic transformation.…”

“…49 Moreover, droplet approaches allow for automated analysis of proteins in individual cells, 50 as well as biomolecular analyses at the single molecule level which could be exploited for signal amplification effects in electrochemical sensors. 48 A tremendous boost for droplet-based analysis has been enabled by microfluidic-based technologies, 51,52 enabling instrumental protocols for analyte detection, reagent addition and mixing resulting in rapid statistically relevant bioanalyses with minimal reagent consumption, 53 medical additive manufacturing, 54 and single-molecule-counting immunoassays. 55 The application of microfluidic devices allowed, for instance, the reduction of volume error down to ±0.06 fL (CV 0.6%), 56 the possibility of manipulating and merging droplets at volumes of the order of hundreds of femtoliters by exploiting surface acoustic waves of the order of 40 MHz, 57 or the employment of pulsed electric fields deforming the interface between an aqueous and an oil phase and pinching off droplets.…”