A microfluidic device for the automated electrical readout of low-density glass-slide microarrays

Emerging biosensors integrated with microfluidic devices: a promising analytical tool for on-site detection of mycotoxins

Rapid and sensitive detection of mycotoxins in foodstuffs is of great significance. As a powerful detection tool, biosensing technologies and microfluidic devices have shown a great potential in rapid and on-site detection of mycotoxins. This review comprehensively summarized the latest advances on the construction of microfluidic biosensors and their promising applications in on-site detection of mycotoxins. Finally, future challenges and chances in this significant and promising field were proposed.

Microfluidic sensors for the detection of emerging contaminants in water: A review

In recent years, numerous emerging contaminants have been identified in surface water, groundwater, and drinking water. Developing novel sensing methods for detecting diverse emerging pollutants in water is urgently needed, as even at low concentrations, these pollutants can pose a serious threat to human health and environmental safety. Traditional testing methods are based on laboratory equipment, which is highly sensitive but complex to operate, costly, and not suitable for on-site monitoring. Microfluidic sensors offer several benefits, including rapid evaluation, minimal sample usage, accurate liquid manipulation, compact size, automation, and in-situ detection capabilities. They provide promising and efficient analytical tools for high-performance sensing platforms in monitoring emerging contaminants in water. In this paper, recent research advances in microfluidic sensors for the detection of emerging contaminants in water are reviewed. Initially, a concise overview is provided about the various substrate materials, corresponding microfabrication techniques, different driving forces, and commonly used detection techniques for microfluidic devices. Subsequently, a comprehensive analysis is conducted on microfluidic detection methods for endocrine-disrupting chemicals, pharmaceuticals and personal care products, microplastics, and perfluorinated compounds. Finally, the prospects and future challenges of microfluidic sensors in this field are discussed.

Resistive Pulse Sensing on a Capillary-Assisted Microfluidic Platform for On-Site Single-Particle Analyses

Capillary-assisted flow is valuable for utilizing microfluidics-based electrical sensing platforms at on-site locations by simplifying microfluidic operations and system construction; however, incorporating capillary-assisted flow in platforms requires easy microfluidic modification and stability over time for capillary-assisted flow generation and sensing performance. Herein, we report a capillary-assisted microfluidics-based electrical sensing platform using a one-step modification of polydimethylsiloxane (PDMS) with polyethylene glycol (PEG). As a model of electrical sensing platforms, this work focused on resistive pulse sensing (RPS) using a micropore in a microfluidic chip for label-free electrical detection of single analytes, and filling the micropore with an electrolyte is the first step to perform this RPS. The PEG-PDMS surfaces remained hydrophilic after ambient storage for 30 d and assisted in generating an electrolyte flow for filling the micropore with the electrolyte. We demonstrated the successful detection and size analysis of micrometer particles and bacterial cells based on RPS using the microfluidic chip stored in a dry state for 30 d. Combining this capillary-assisted microfluidic platform with a portable RPS system makes on-site detection and analysis of single pathogens possible.

Research progress on pesticide residue detection based on microfluidic technology

The problem of pesticide residue contamination has attracted widespread attention and poses a risk to human health. The current traditional pesticide residue detection methods have difficulty meeting rapid and diverse field screening requirements. Microfluidic technology integrates functions from sample preparation to detection, showing great potential for quick and accurate high-throughput detection of pesticide residues. This paper reviews the latest research progress on microfluidic technology for pesticide residue detection. First, the commonly used microfluidic materials are summarized, including silicon, glass, paper, polydimethylsiloxane, and polymethyl methacrylate. We evaluated their advantages and disadvantages in pesticide residue detection applications. Second, the current pesticide residue detection technology based on microfluidics and its application to real samples are summarized. Finally, we discuss this technology's present challenges and future research directions. This study is expected to provide a reference for the future development of microfluidic technology for pesticide residue detection.

Bi-functional antibody-CRISPR/Cas12a ribonucleoprotein conjugate for improved immunoassay performance

Protein conjugates are commonly used in biochemistry, including diagnostic platforms such as antibody-based immunoassays. Antibodies can be bound to a variety of molecules creating conjugates with desirable functions, particularly for imaging and signal amplification. Cas12a is a recently discovered programable nuclease with the remarkable capability to amplify assay signals due to its trans-cleavage property. In this study, we directly conjugated antibody with Cas12a/gRNA ribonucleoprotein without the loss of function in either constituent. The conjugated antibody was suitable for immunoassays and the conjugated Cas12a was capable of amplifying the signal produced in an immunosensor without the need to change the original assay protocol. We applied the bi-functional antibody-Cas12a/gRNA conjugate to successfully detect two different types of targets, a whole pathogenic microorganism, Cryptosporidium, and a small protein, cytokine IFN-γ, with sensitivity reaching one single microorganism per sample and 10 fg/mL for IFN-γ, respectively. With simple substitution of the antibody conjugated with the Cas12a/gRNA RNP, this approach can potentially be applied to increase sensitivity of a variety of immunoassays for a broad range of different analytes.

CRISPR/Cas12a-powered immunosensor suitable for ultra-sensitive whole Cryptosporidium oocyst detection from water samples using a plate reader

Waterborne pathogens, such as Cryptosporidium parvum, pose a major threat to public health globally, and this requires screening of drinking and environmental water for low number of contaminating microbes. However, current detection approaches generally require trained experts with sophisticated instruments, and are not suitable for large-scale screening and rapid outbreak response. Recent advances in ultrasensitive CRISPR/Cas-based biosensing continue to expand the range of detectable molecular targets, however single microbes could not be directly detected so far, especially in environmental samples. Here, we report an ultrasensitive CRISPR/Cas12a-powered immunosensing method suitable for microbial detection which links antibody-based recognition with CRISPR/Cas12a-based fluorescent signal amplification through an antibody-DNA conjugate. This approach is shown here to detect whole 4 µm size Cryptosporidium parvum oocysts with a linear range from 6.25 - 1600 oocysts/mL, at a maximum sensitivity of single oocyst per sample. Its potential to apply to various complex sample matrices has also been demonstrated. After sample dilution by factor of 10, we were able to detect 10 oocysts from a back-wash mud samples from water treatment plate. This method uses the same experimental setup (plate reader) as a conventional ELISA assay thus reducing the need for microscopy-based identification of Cryptosporidium, which represents the gold-standard but requires high level expertise and time-consuming manual counting. This work highlights the potential of CRISPR/Cas-based biosensing for water quality assessment and ultrasensitive whole pathogen detection.

Soft and flexible material-based affinity sensors

Recent advances in biosensors and point-of-care (PoC) devices are poised to change and expand the delivery of diagnostics from conventional lateral-flow assays and test strips that dominate the market currently, to newly emerging wearable and implantable devices that can provide continuous monitoring. Soft and flexible materials are playing a key role in propelling these trends towards real-time and remote health monitoring. Affinity biosensors have the capability to provide for diagnosis and monitoring of cancerous, cardiovascular, infectious and genetic diseases by the detection of biomarkers using affinity interactions. This review tracks the evolution of affinity sensors from conventional lateral-flow test strips to wearable/implantable devices enabled by soft and flexible materials. Initially, we highlight conventional affinity sensors exploiting membrane and paper materials which have been so successfully applied in point-of-care tests, such as lateral-flow immunoassay strips and emerging microfluidic paper-based devices. We then turn our attention to the multifarious polymer designs that provide both the base materials for sensor designs, such as PDMS, and more advanced functionalised materials that are capable of both recognition and transduction, such as conducting and molecularly imprinted polymers. The subsequent content discusses wearable soft and flexible material-based affinity sensors, classified as flexible and skin-mountable, textile materials-based and contact lens-based affinity sensors. In the final sections, we explore the possibilities for implantable/injectable soft and flexible material-based affinity sensors, including hydrogels, microencapsulated sensors and optical fibers. This area is truly a work in progress and we trust that this review will help pull together the many technological streams that are contributing to the field.

Analytical Protein Microarrays: Advancements Towards Clinical Applications

Protein microarrays represent a powerful technology with the potential to serve as tools for the detection of a broad range of analytes in numerous applications such as diagnostics, drug development, food safety, and environmental monitoring. Key features of analytical protein microarrays include high throughput and relatively low costs due to minimal reagent consumption, multiplexing, fast kinetics and hence measurements, and the possibility of functional integration. So far, especially fundamental studies in molecular and cell biology have been conducted using protein microarrays, while the potential for clinical, notably point-of-care applications is not yet fully utilized. The question arises what features have to be implemented and what improvements have to be made in order to fully exploit the technology. In the past we have identified various obstacles that have to be overcome in order to promote protein microarray technology in the diagnostic field. Issues that need significant improvement to make the technology more attractive for the diagnostic market are for instance: too low sensitivity and deficiency in reproducibility, inadequate analysis time, lack of high-quality antibodies and validated reagents, lack of automation and portable instruments, and cost of instruments necessary for chip production and read-out. The scope of the paper at hand is to review approaches to solve these problems.