Integrated electrochemical microfluidic sensor with hierarchically porous nanoarrays modified graphene fiber microelectrode for bioassay

On-Chip Electrochemical Sensor Based on 3D Graphene Assembly Decorated Ultrafine RuCu Alloy Nanocatalyst for In Situ Detection of NO in Living Cells

In this work, we developed 3D ionic liquid (IL) functionalized graphene assemblies (GAs) decorated by ultrafine RuCu alloy nanoparticles (RuCu-ANPs) via a one-step synthesis process, and integrated it into a microfluidic sensor chip for in situ electrochemical detection of NO released from living cells. Our findings have demonstrated that RuCu-ANPs on 3D IL-GA exhibit high density, uniform distribution, lattice-shaped arrangement of atoms, and extremely ultrafine size, and possess high electrocatalytic activity to NO oxidation on the electrode. Meanwhile, the 3D IL-GA with hierarchical porous structures can facilitate the efficient electron/mass transfer at the electrode/electrolyte interface and the cell culture. Moreover, the graft of IL molecules on GA endows it with high hydrophilicity for facile and well-controllable printing on the electrode. Consequently, the resultant electrochemical microfluidic sensor demonstrated excellent sensing performances including fast response time, high sensitivity, good anti-interference ability, high reproducibility, long-term stability, as well as good biocompatibility, which can be used as an on-chip sensing system for cell culture and real-time in situ electrochemical detection of NO released from living cells with accurate and stable characteristics in physiological conditions.

Radially Aligned Carbon Nanotube Glass Fiber Composites as Ion-Selective Microelectrodes

Detection of ions is challenging due to their small size, rapid diffusion, and high mobility, especially for assaying in samples of low volumes. Among the traditional analytical methods, potentiometric ion-selective electrodes (ISE) have become a popular choice for detecting ions as they are cost-effective, user-friendly and can be miniaturized, making them useful for on-site analysis. In this context, radially aligned carbon nanotubes (RACNT) directly grown on glass fibers (GF) via the chemical vapor deposition method is investigated as a solid contact material for the fabrication of ion-selective microelectrodes (μISE) upon incorporating specific ionophores within a polymeric encapsulation membrane. As an illustration, sensitive detection of ammonium ions is accomplished by the fabricated μISE (plasticized PVC membrane containing nonactin ionophores), which yielded a LOD and a linear response range between 7.5 × 10-6 and 1.0 × 10-5 to 1.0 × 10-1 M, respectively. The μISE fabricated with RACNT-GF as an interface material exhibited improvements in LOD and enhanced the detection selectivity as compared to a conventional ISE fabricated using planar solid contact materials such as graphite. We hypothesize that the fabricated μISE with a high surface area and mechanical durability maximize the accommodation of ionophores in the barrier membrane for yielding improved potentiometric responses. Experimental results illustrate that the μISE possesses the potential to be utilized for the fabrication of selective and sensitive ISE upon incorporation of specific ionophores with RACNT-GF composites.

Advances in Microfluidic Paper-Based Analytical Devices (µPADs): Design, Fabrication, and Applications

Microfluidic Paper-based Analytical Devices (µPADs) have emerged as a new class of microfluidic systems, offering numerous advantages over traditional microfluidic chips. These advantages include simplicity, cost-effectiveness, stability, storability, disposability, and portability. As a result, various designs for different types of assays are developed and investigated. In recent years, µPADs are combined with conventional detection methods to enable rapid on-site detection, providing results comparable to expensive and sophisticated large-scale testing methods that require more time and skilled personnel. The application of µPAD techniques is extensive in environmental quality control/analysis, clinical diagnosis, and food safety testing, paving the way for on-site real-time diagnosis as a promising future development. This review focuses on the recent research advancements in the design, fabrication, material selection, and detection methods of µPADs. It provides a comprehensive understanding of their principles of operation, applications, and future development prospects.

Ordered mesoporous hairbrush-like nanocarbon assembled microfibers for solid-phase microextraction of benzene series in oilfield sewage

The development of advanced functional nanomaterials for solid-phase microextraction (SPME) remains an imperative aspect of sample pretreatment. Herein, we introduce a novel SPME fiber consisting of graphene fibers modified with ordered mesoporous carbon nanotubes arrays (CNTAs) tailored for the determination of benzene series in oilfield wastewater, which is synthesized by an ionic liquid-assisted wet spinning process of graphene nanosheets, followed by a precisely controlled growth of metal-organic framework and subsequent pyrolysis treatment. The resulting robust microfiber structure resembles a "hairbrush" configuration, with a crumpled graphene fiber "stem" and high-order mesoporous CNTAs "hairs". This unique architecture significantly enhances the SPME capacity, as validated by gas chromatography-mass spectrometry. The hairbrush-like nanocarbon assembled microfibers possess structural characteristics, a high specific surface area, and numerous binding sites, offering efficient enrichment of benzene series compounds in oilfield wastewater, including benzene, ethylbenzene, m-xylene, p-xylene, and toluene. Our analysis demonstrates that these microfibers exhibit broad linear ranges (0.2-600 μg L-1), low detection limits (0.005-0.03 mg L-1), and excellent repeatability (3.2-5.5% for one fiber, 2.1-6.7% for fiber-to-fiber) for detection. When compared to commercial alternatives, these hairbrush-like nanocarbon-assembled microfibers exhibit significantly enhanced extraction efficiency for benzene series compounds.

Electrochemical Sensors Based on Transition Metal Materials for Phenolic Compound Detection

Electrochemical sensors have been recognized as crucial tools for monitoring comprehensive chemical information, especially in the detection of a significant class of molecules known as phenolic compounds. These compounds can be present in water as hazardous analytes and trace contaminants, as well as in living organisms where they regulate their metabolism. The sensitive detection of phenolic compounds requires highly efficient and cost-effective electrocatalysts to enable the development of high-performance sensors. Therefore, this review focuses on the development of advanced materials with excellent catalytic activity as alternative electrocatalysts to conventional ones, with a specific emphasis on transition metal-based electrocatalysts for the detection of phenolic compounds. This research is particularly relevant in diverse sectors such as water quality, food safety, and healthcare.

Fibrous wearable and implantable bioelectronics

Fibrous wearable and implantable devices have emerged as a promising technology, offering a range of new solutions for minimally invasive monitoring of human health. Compared to traditional biomedical devices, fibers offer a possibility for a modular design compatible with large-scale manufacturing and a plethora of advantages including mechanical compliance, breathability, and biocompatibility. The new generation of fibrous biomedical devices can revolutionize easy-to-use and accessible health monitoring systems by serving as building blocks for most common wearables such as fabrics and clothes. Despite significant progress in the fabrication, materials, and application of fibrous biomedical devices, there is still a notable absence of a comprehensive and systematic review on the subject. This review paper provides an overview of recent advancements in the development of fibrous wearable and implantable electronics. We categorized these advancements into three main areas: manufacturing processes, platforms, and applications, outlining their respective merits and limitations. The paper concludes by discussing the outlook and challenges that lie ahead for fiber bioelectronics, providing a holistic view of its current stage of development.

Microfluidic Gradient Culture Arrays for Cell Pro-oxidation Analysis Using Bipolar Electrochemiluminescence

A microfluidic gradient array is a widely used screening and analysis device, which has characteristics of high efficiency, high automation, and low consumption. Bipolar electrode electrochemiluminescence (BPE-ECL) has special value in microfluidic array chips. The combination of the microfluidic gradient and BPE arrays has potential for high-throughput screening. In this article, a microfluidic BPE array chip for gradient culture and conditional screening of cancer cells was designed. The generation of concentration gradients, continuous culture of cancer cells with high throughput, and drug screening through BPE-ECL of the Ru(bpy)₃²⁺/TPrA system can be performed in one chip. We tested gradient pro-oxidation of MCF-7 by ascorbic acid and the synergistic effect of pro-oxidation on doxorubicin. The method achieves high analysis efficiency through a BPE array while simplifying the tedious procedures required by cell culture methods.

Nanomaterial-Based Label-Free Electrochemical Aptasensors for the Detection of Thrombin

Thrombin plays a central role in hemostasis and its imbalances in coagulation can lead to various pathologies. It is of clinical significance to develop a fast and accurate method for the quantitative detection of thrombin. Electrochemical aptasensors have the capability of combining the specific selectivity from aptamers with the extraordinary sensitivity from electrochemical techniques and thus have attracted considerable attention for the trace-level detection of thrombin. Nanomaterials and nanostructures can further enhance the performance of thrombin aptasensors to achieve high sensitivity, selectivity, and antifouling functions. In highlighting these material merits and their impacts on sensor performance, this paper reviews the most recent advances in label-free electrochemical aptasensors for thrombin detection, with an emphasis on nanomaterials and nanostructures utilized in sensor design and fabrication. The performance, advantages, and limitations of those aptasensors are summarized and compared according to their material structures and compositions.

Sensitive electrochemical detection of metabisulphite in gastrointestinal fluids

Electrochemical detection of metabisulphite in simulated gastrointestinal fluids.