A Separation‐Sensing Membrane Performing Precise Real‐Time Serum Analysis During Blood Drawing

Advances in nanostructured material-based non-enzymatic electrochemical glucose sensors

Non-enzymatic electrochemical sensors that use functional materials to directly catalyze glucose have shown great promise in diabetes management, food control, and bioprocess inspection owing to the advantages of high sensitivity, long-term stability, and low cost. Recently, in order to produce enhanced electrochemical behavior, significant efforts have been devoted to the preparation of functional materials with regular nanostructure, as it provides high specific surface area and well-defined strong active sites for electrochemical sensing. However, the structure-performance correlation in this field has not been reviewed thoroughly in the literature. This review aims to present a comprehensive report on advanced zero- to three-dimensional nanostructures based on the geometric feature and to discuss in depth their structural effects on enzyme-free electrochemical detection of glucose. It starts by illustrating the sensing principles of nanostructured materials, followed by a detailed discussion on the structural effects related to the features of each dimension. The structure-performance correlation is explored by comparing the performance derived from diverse dimensional architectures, which is beneficial for the better design of regular nanostructure to achieve efficient enzyme-free sensing of glucose. Finally, future directions of non-enzymatic electrochemical glucose sensors to solve emerging challenges and further improve the sensing performance are also proposed.

A Paper-Based Fluorescent Sensor for Rapid Early Screening of Oral Squamous Cell Carcinoma

Various types of sensors play an irreplaceable role in the detection of biomarkers, but their high cost and complicated operation make it difficult to benefit ordinary people. Herein, we develop a low-cost, double-layered, paper-based fluorescent sensor (CP/HQ) structurally consisting of the upper reaction layer loaded with two oxidases (lactate oxidase and choline oxidase) and the bottom fluorescent layer that physically associates with the porphine-grafted composite fluorescent polymer colloids (PF-PDMTP/HQ). Based on the dramatic and rapid fluorescence decrease of porphine induced by the oxidation between saliva and oxidases and subsequent fluorescence resonance energy transfer from oxidized hydroquinone, the resultant fluorescent paper sensor enables us to achieve visual detection of OSCC, which was further recognized by smartphone scanning as the grayscale variation. It was found that the linear sensing range of grayscale value are 10-200 μM for lactic acid and 10-100 μM for choline, with LODs of 5.7 and 8.9 μM, respectively. More importantly, the sensor can achieve a powerful detection capability comparable to that of high-performance liquid chromatography (HPLC) in clinical settings with simple operation, demonstrating its great application potential. Our proposed sensor not only improves the accuracy of OSCC diagnosis but also provides a valuable attempt for the device modification of polymer-sensing systems and the development of non-invasive and easy-to-operate disease screening methods.

Recent advances in determination applications of emerging films based on nanomaterials

Sensitive and facile detection of analytes is crucial in various fields such as agriculture production, food safety, clinical diagnosis and therapy, and environmental monitoring. However, the synergy of complicated sample pretreatment and detection is an urgent challenge. By integrating the inherent porosity, processability and flexibility of films and the diversified merits of nanomaterials, nanomaterial-based films have evolved as preferred candidates to meet the above challenge. Recent years have witnessed the flourishment of films-based detection technologies due to their unique porous structures and integrated physical/chemical merits, which favors the separation/collection and detection of analytes in a rapid, efficient and facile way. In particular, films based on nanomaterials consisting of 0D metal-organic framework particles, 1D nanofibers and carbon nanotubes, and 2D graphene and analogs have drawn increasing attention due to incorporating new properties from nanomaterials. This paper summarizes the progress of the fabrication of emerging films based on nanomaterials and their detection applications in recent five years, focusing on typical electrochemical and optical methods. Some new interesting applications, such as point-of-care testing, wearable devices and detection chips, are proposed and emphasized. This review will provide insights into the integration and processability of films based on nanomaterials, thus stimulate further contributions towards films based on nanomaterials for high-performance analytical-chemistry-related applications.

Scalable Printing of Prussian Blue Analogue@Au Edge-Rich Microcubes as Flexible Biosensing Microchips Performing Ultrasensitive Sucrose Fermentation Monitoring

Sucrose is one of the most applied carbon sources in the fermentation process, and it directly determines the microbial metabolism with its concentration fluctuation. Meanwhile, sucrose also plays a key role of a protective agent in the production of biological vaccines, especially in the new mRNA vaccines for curing COVID-19. However, rapid and precise detection of sucrose is always desired but unrealized in industrial fermentation and synthetic biology research. In order to address the above issue, we proposed an ultrasensitive biosensor microchip achieving accurate sucrose recognition within only 12 s, relying on the construction of a Prussian blue analogue@Au edge-rich (PBA@AuER) microarchitecture. This special geometric structure was formed through exactly inducing the oriented PBA crystallization toward a certain plane to create more regular and continuous edge features. This composite was further transformed to a screen-printed ink to directly and large-scale fabricate an enzymatic biosensor microchip showing ultrahigh sensitivity, a wide detection range, and a low detection limit to the accurate sucrose recognition. As confirmed in a real alcohol fermentation reaction, the as-prepared microchip enabled us to accurately detect the sucrose and glucose concentrations with outstanding reusability (more than 300 times) during the whole process through proposing a novel analytical strategy for the binary mixture substrate system.

Membranes for the life sciences and their future roles in medicine

Since the global outbreak of COVID-19, membrane technology for clinical treatments, including extracorporeal membrane oxygenation (ECMO) and protective masks and clothing, has attracted intense research attention for its irreplaceable abilities. Membrane research and applications are now playing an increasingly important role in various fields of life science. In addition to intrinsic properties such as size sieving, dissolution and diffusion, membranes are often endowed with additional functions as cell scaffolds, catalysts or sensors to satisfy the specific requirements of different clinical applications. In this review, we will introduce and discuss state-of-the-art membranes and their respective functions in four typical areas of life science: artificial organs, tissue engineering, in vitro blood diagnosis and medical support. Emphasis will be given to the description of certain specific functions required of membranes in each field to provide guidance for the selection and fabrication of the membrane material. The advantages and disadvantages of these membranes have been compared to indicate further development directions for different clinical applications. Finally, we propose challenges and outlooks for future development.

In situ fabrication of urchin-like Cu@carbon nanoneedles based aptasensor for ultrasensitive recognition of trace mercury ion

Mercury ion (Hg²⁺) is a strong toxic heavy ion that causes severe damages to the environment and readily accumulates in the food chain. However, it remains a major challenge to realize a sensitive and precise recognition of Hg²⁺ with a trace concentration for early identifying the pollution source. In this work, a novel electrochemical aptasensor was designed to achieve an ultrasensitive and quantitative detection of trace Hg²⁺, relying on an urchin-like architecture of Cu@carbon nanoneedles (Cu@CNNs) as the electroactive probe. This specific nanostructure was in-situ constructed through a controllable pyrolysis process, serving as a signal magnifier and DNA loading platform owing to its outstanding electrocatalysis and large specific surface areas. Meanwhile, an exonuclease III-assisted cycling amplification strategy was designed to efficiently amplify the signal strength of trace Hg²⁺via the consecutive release of report probes in nicking reaction. This as-prepared Hg²⁺ aptasensor exhibited an ultralow detection limit of 3.7 fM (7 × 10^-6 ppm) and a wide linear range from 10 fM to 10 μM, together with the satisfactory stability and reusability for assay in real water samples. It is highly expected that this Cu@CNNs based aptasensor will have tremendous potentials in the early warning and efficient pollution monitoring of heavy metal ions.

The micro-volume liquid focusing effect in Janus membrane and its biosensing application

The micro-volume analysis and specific detection are both essential requirements in the field of chemical sensing and biological testing. Membrane prefiltration can be used to improve the selectivity and accuracy of detection. But for traditional porous membrane filtration, it is difficult to achieve the transmembrane transport of micro-volume liquid due to the influence of lateral diffusion on membrane surface. Herein, we studied the focused transmembrane transport of micro-volume liquid in the porous polyethersulfone membrane with asymmetric (Janus) surface wettability. The hydrophilic layer (polydopamine) and hydrophobic layer (fluoropolymer) were deposited with controllable thickness by dip-coating and roller-assisted liquid printing. The micro-volume liquid focusing effect was verified by experiments such as visual wetting circle and fluorescent tracer. The liquid focusing effect of as-prepared Janus membrane was integrated with glucose test strip in the application of micro-volume liquid biosensing. Compared with conventional porous membrane, detected signal amplitude and response time were improved 7.5× and 2.7×, respectively. In summary, this research studied the dynamics of liquid transport through Janus membrane and provides a new strategy for microfluidic detection applications through balancing detection volume, time and selectivity by the advantage of micro-volume liquid focusing effect.

MOF-enzyme hybrid nanosystem decorated 3D hollow fiber membranes for in-situ blood separation and biosensing array

Modified metal-organic frameworks (MOFs) doping with enzymes exhibit high enzyme stability and catalytic performance, which is a research hotspot in the field of enzyme-based sensing. Although the MOF-enzyme constitutes a 3D structure in the nanoscale, the macroscopic assembly configuration still stays in 1D or 2D structures, limiting sensing applications towards complex biological targets. Herein, the MOF-enzyme hybrid nanosystem was assembled into 3D porous conductive supports via a controllable physical embedding method, displaying high enzymatic loading, stability and cascade catalytic performance. The modified MOFs combing with enzymes served as a sensing reaction system, and the conductive hollow fiber membranes (HFMs) served as a functional platform. The multifunctional device integrates pumpless hydrodynamic transport, interconnected conductive polymer, and blood separation modules, showing fast capillary fluid flow, trace sampling (3 μL), high selectivity and accuracy. The linear sensing range was in 2-24 mM glucose, 0.05-6 mM lactic acid, and 0.1-10 mM cholesterol, respectively, with sensitivities of 24.2, 150, 73.6 nA mM^-1. Furthermore, this strategy of modular assembly of biosensing array can easily implement multiplex metabolites detection simultaneously.

Target-Dependent Gating of Nanopores Integrated with H-Cell: Toward A General Platform for Photoelectrochemical Bioanalysis

Herein we present a proof-of-concept study of target-dependent gating of nanopores for general photoelectrochemical (PEC) bioanalysis in an H-cell. The model system was constructed upon a left chamber containing ascorbic acid (AA), the antibody modified porous anodic alumina (AAO) membrane separator, and a right chamber placed with the three-electrode system. The sandwich immunocomplexation and the associated enzymatic generation of biocatalytic precipitation (BCP) in the AAO nanopores would regulate the diffusion of AA from the left cell to the right cell, leading to a varied photocurrent response of the ZnInS nanoflakes photoelectrode. Exemplified by fatty-acid-banding protein (FABP) as the target, the as-developed protocol achieved good performance in terms of sensitivity, selectivity, reproducibility, as well as efficient reutilization of the working electrode. On the basis of an H-cell, this work features a new protocol of target-dependent gating-based PEC bioanalysis, which can serve as a general PEC analytical platform for various other targets of interest.

A Three-Dimensional Sensor to Recognize Amyloid-β in Blood Plasma of Patients

Detecting amyloid beta (Aβ) in unpurified blood to diagnose Alzheimer's disease (AD) is challenging owing to low concentrations of Aβ and the presence of many other substances in the blood. Here, we propose a 3D sensor for AD diagnosis using blood plasma, with pairs of 3D silicon micropillar electrodes with a comprehensive circuit configuration. The sensor is developed with synthesized artificial peptide and impedance analysis based on a maximum signal-to-noise ratio. Its sensitivity and selectivity were verified using an in vitro test based on samples of human blood serum, which showed its feasibility for application in diagnosis of AD by testing blood plasma of the AD patient. The 3D sensor is designed to improve reliability by checking the impedance of each pair multiple times via constructing a reference pair and a working pair on the same sensor. Therefore, we demonstrate the ability of the 3D sensor to recognize cases of AD using blood plasma and introduce its potential as a self-health care sensor for AD patients.