Solid-State Nanochannel with Multiple Signal Outputs for Furin Detection Based on the Biocompatible Condensation Reaction

Solid-state nanochannels based on electro-optical dual signals for detection of analytes

The sensitive detection of analytes of different sizes is crucial significance for environmental protection, food safety and medical diagnostics. The confined space of nanochannels provides a location closest to the molecular reaction behaviors in real systems, thereby opening new opportunities for the precise detection of analytes. However, due to the susceptibility to external interference on the confined space of nanochannels, the high sensitivity nature of the current signals through the nanochannels is more troubling for the detection reliability. Combining highly sensitive optical signals with the sensitive current signals of solid-state nanochannels establishes a nanochannel detection platform based on electro-optical dual signals, potentially offering more sensitive, specific, and accuracy detection of analytes. This review summarizes the last five years of applications of solid-state nanochannels based on electro-optical dual signals in analytes detection. Firstly, the detection principles of solid-state nanochannels and the construction strategies of nanochannel electro-optical sensing platforms are discussed. Subsequently, the review comprehensively outlines the applications involving nanochannels with electrical signals combined with fluorescence signals, electrical signals combined with surface-enhanced Raman spectroscopy signals, and electrical signals combined with other optical signals in analyte detection. Additionally, the perspectives and difficulties of nanochannels are investigated on the basis of electro-optical dual signals.

Construction of "ant-like tentacle" structure for ultra-sensitive detection of low-concentration ammonia through colorimetric fluorescent dual-signal gas-sensitive cotton fabric

Detection and monitoring of ammonia (NH3) are crucial in various industries, including plant safety management, food freshness testing, and water pollution control. Nevertheless, creating portable, low-cost, highly sensitive, and easily regenerated ppm-level NH3 sensors poses a significant challenge. In this investigation, an innovative "ant-like tentacle" fabrication strategy was proposed, and a colorimetric fluorescent dual-signal gas-sensitive cotton fabric (PAH-fabric) for NH3 detection was successfully prepared by conventional dyeing using suitable molecular-level photoacid (PAH) sensitive units. The visual recognition lower detection limit of the ultra-low is 1.09 ppm-level. PAH-fabric is not only straightforward, convenient, and cost-effective to prepare, but it can also be efficiently regenerated and recycled multiple times (maintaining excellent gas-sensitive performance even after 100 cycles) by strategically leveraging volatile acid fumigation. Detailed molecular reaction mechanisms involved in the NH3 response and PAH-fabric regeneration are elucidated. PAH-fabric, available either as a portable kit or an alarm system, offers a promising approach for ultra-low NH3 detection. The demonstrated "ant-like tentacle" fabrication strategy introduces numerous possibilities for designing and developing sensors with adjustable response thresholds, particularly those requiring high sensitivity.

A Portable Device for in Situ Noninvasive Monitoring of Cell Secretions and Communications with Fluorescence and Nanochannel Electrochemistry

In situ monitoring of cell secretions and communications plays a fundamental role in screening of disease diagnostic biomarkers and drugs. Quantitative detection of cell secretions and monitoring of intercellular communication have been separately reported, which often rely on target labeling or complex pretreatment steps, inevitably causing damage to the target. Simultaneous in situ noninvasive detection of cell secretions and monitoring of intercellular communication are challenging and have never been reported. Herein, we smartly developed a portable device for in situ label-free monitoring of cell secretions and communications with fluorescence and ion-transport-based nanochannel electrochemistry. Based on the dual signal mode, a series of nonelectroactive secretions were sensitively and accurately quantified. The detection limits for VEGF, MUC1, and ATP were 3.84 pg/mL, 32.7 pg/mL, and 47.4 fM (3σ/S), which were 1/3.9, 1/1.1, and 1/41 of those of commercial ELISA kits, respectively. More interestingly, under the released secretions, the gradual opening of the nanochannel connected the two cells in the left and right chambers of the device; thus, the secretion mediated intercellular communication can be monitored. The proposed platform may provide a promising tool for understanding the mechanism of intercellular communication and discovering new therapeutic targets.

Advances in nanofluidic field-effect transistors: external voltage-controlled solid-state nanochannels for stimulus-responsive ion transport and beyond

Ion channels, intricate protein structures facilitating precise ion passage across cell membranes, are pivotal for vital cellular functions. Inspired by the remarkable capabilities of biological ion channels, the scientific community has ventured into replicating these principles in fully abiotic solid-state nanochannels (SSNs). Since the gating mechanisms of SSNs rely on variations in the physicochemical properties of the channel surface, the modification of their internal architecture and chemistry constitutes a powerful strategy to control the transport properties and, consequently, render specific functionalities. In this framework, both the design of the nanofluidic platform and the subsequent selection and attachment of different building blocks gain special attention. Similar to biological ion channels, functional SSNs offer the potential to finely modulate ion transport in response to various stimuli, leading to innovations in a variety of fields. This comprehensive review delves into the intricate world of ion transport across stimuli-responsive SSNs, focusing on the development of external voltage-controlled nanofluidic devices. This kind of field-effect nanofluidic technology has attracted special interest due to the possibility of real-time reconfiguration of the ion transport with a non-invasive strategy. These properties have found interesting applications in drug delivery, biosensing, and nanoelectronics. This document will address the fundamental principles of ion transport through SSNs and the construction, modification, and applications of external voltage-controlled SSNs. It will also address future challenges and prospects, offering a comprehensive perspective on this evolving field.

Confined Water Dominates Ion/Molecule Transport in Hydrogel Nanochannels

Current artificial nanochannels rely more on charge interactions for intelligent mass transport. Nevertheless, popular charged nanochannels would lose their advantages in long-term applications. Confined water, an indispensable transport medium in biological nanochannels, dominating the transport process in the uncharged nanochannels perfectly provides a new perspective. Herein, we achieve confined-water-dominated mass transport in hydrogel nanochannels (HNCs) constructed by in situ photopolymerization of acrylic acid (PAA) hydrogel in anodic alumina (AAO) nanochannels. HNCs show selectivity to Na+ transport and a high transport rate of molecules after introducing Na+/Li+, compared with other alkali metal ions like Cs+/K+. The mechanism given by ATR-FTIR shows that the hydrogen-bonding structure of confined water in HNCs is destabilized by Na+/Li+, which facilitates mass transport, but is constrained by Cs+/K+, resulting in transport inhibition. This work elucidates the relationship between confined water and mass transport in uncharged nanochannels while also presenting a strategy for designing functional nanochannel devices.

Early monitoring-to-warning Internet of Things system for emerging infectious diseases via networking of light-triggered point-of-care testing devices

Early monitoring and warning arrangements are effective ways to distinguish infectious agents and control the spread of epidemic diseases. Current testing technologies, which cannot achieve rapid detection in the field, have a risk of slowing down the response time to the disease. In addition, there is still no epidemic surveillance system, implementing prevention and control measures is slow and inefficient. Motivated by these clinical needs, a sample-to-answer genetic diagnosis platform based on light-controlled capillary modified with a photocleavable linker is first developed, which could perform nucleic acid separation and release by light irradiation in less than 30 seconds. Then, on site polymerase chain reaction was performed in a handheld closed-loop convective system. Test reports are available within 20 min. Because this method is portable, rapid, and easy to operate, it has great potential for point-of-care testing. Additionally, through multiple device networking, a real-time artificial intelligence monitoring system for pathogens was developed on a cloud server. Through data reception, analysis, and visualization, the system can send early warning signals for disease control and prevention. Thus, anti-epidemic measures can be implemented effectively, and deploying and running this system can improve the capabilities for the prevention and control of infectious diseases.

Detection of Unfolded Cellular Proteins Using Nanochannel Arrays with Probe-Functionalized Outer Surfaces

Nanochannel technology has emerged as a powerful tool for label-free and highly sensitive detection of protein folding/unfolding status. However, utilizing the inner walls of a nanochannel array may cause multiple events even for proteins with the same conformation, posing challenges for accurate identification. Herein, we present a platform to detect unfolded proteins through electrical and optical signals using nanochannel arrays with outer-surface probes. The detection principle relies on the specific binding between the maleimide groups in outer-surface probes and the protein cysteine thiols that induce changes in the ionic current and fluorescence intensity responses of the nanochannel array. By taking advantage of this mechanism, the platform has the ability to differentiate folded and unfolded state of proteins based on the exposure of a single cysteine thiol group. The integration of these two signals enhances the reliability and sensitivity of the identification of unfolded protein states and enables the distinction between normal cells and Huntington's disease mutant cells. This study provides an effective approach for the precise analysis of proteins with distinct conformations and holds promise for facilitating the diagnoses of protein conformation-related diseases.

Solid-State Nanopore/Nanochannel Sensing of Single Entities

Solid-state nanopores/nanochannels, with their high stability, tunable geometry, and controllable surface chemistry, have recently become an important tool for constructing biosensors. Compared with traditional biosensors, biosensors constructed with solid-state nanopores/nanochannels exhibit significant advantages of high sensitivity, high specificity, and high spatiotemporal resolution in the detection single entities (such as single molecules, single particles, and single cells) due to their unique nanoconfined space-induced target enrichment effect. Generally, the solid-state nanopore/nanochannel modification method is the inner wall modification, and the detection principles are the resistive pulse method and the steady-state ion current method. During the detection process, solid-state nanopore/nanochannel is easily blocked by single entities, and interfering substances easily enter the solid-state nanopore/nanochannel to generate interference signals, resulting in inaccurate measurement results. In addition, the problem of low flux in the detection process of solid-state nanopore/nanochannel, these defects limit the application of solid-state nanopore/nanochannel. In this review, we introduce the preparation and functionalization of solid-state nanopore/nanochannel, the research progress in the field of single entities sensing, and the novel sensing strategies on solving the above problems in solid-state nanopore/nanochannel single-entity sensing. At the same time, the challenges and prospects of solid-state nanopore/nanochannel for single-entity electrochemical sensing are also discussed.

Precisely Detecting the Telomerase Activities by an AIEgen Probe with Dual Signal Outputs after Cell-Cycle Synchronization

By maintaining the telomere lengths, telomerase can make the tumor cells avoid the apoptosis, thus, achieving the cell immortalization. In the past, a series of telomerase detection systems have been developed through utilizing the unique characteristic of telomerase extended primer. However, fluctuation of telomerase activity, along with the cell cycle progression, leads to ambiguous detection results. Here, we reported a dual signal output detection strategy based on cell-cycle synchronization for precisely detecting telomerase activities by using a new AIEgen probe SSNB. Experimental and simulating calculation results demonstrated that positively charged SSNB could interact with DNA through the electrostatic interaction and π-π interaction, as well as the hydrogen bonds. The aggregation of SSNB caused by the extended template strand primer (TP) could be observed in tumor cells, thus, indicating the telomerase activity in various cell lines. Furthermore, after cell cycle synchronization, it was found that the telomerase activity in the S phase was the highest, no matter from the fluorescence intensity or the ROS generation situation. Dual signal outputs of SSNB verified the significance and necessity of cell-cycle synchronization detection for telomerase activity. This strategy could open a new window for the biotargets of which activity is variational in time dimension.