Research Progress and Future Trends of Microfluidic Paper-Based Analytical Devices in In-Vitro Diagnosis

Pipette-operable microfluidic devices with hydrophobic valves in sequential dispensing with various liquid samples: multiplex disease assay by RT-LAMP

Microfluidic dispensing technologies often require additional equipment, posing challenges for their integration into point-of-care testing (POCT) applications. In response to this challenge, we have developed a pipette-operable microfluidic device fabricated using 3D printing technology for precise liquid dispensing. This device features three reaction chambers and three distinct hydrophobic valves to control the flow direction of liquids. Through these valves, the pipette-operable microfluidic device can sequentially dispense and isolate the liquid into the three reaction chambers, allowing for the individual conduction of three distinct reactions. These hydrophobic valves, with optimized flow resistance and burst pressure, can sustain a volumetric flow rate of up to 25 μL s-1, making them compatible with a standard pipette, a syringe, or a dropper operation. Furthermore, the device is successfully used to operate with various liquids, including BSA, DMEM, FBS, plasma, and blood, representing that the device has the potential to be used for various applications. Additionally, distinct RT-LAMP primer sets have been incorporated for diagnosing SARS-CoV-2, influenza A, and influenza B within each chamber through lyophilization. This pipette-operable microfluidic device serves as a versatile tool for diagnosing these three diseases using a single loading process, with results readable by the naked eye or image assay within 30 minutes of incubation. Finally, the design concepts are extended to engineer a microfluidic device with 20 reaction chambers, offering significant potential for multi-disease diagnostics.

A smartphone-based diagnostic analyzer for point-of-care milk somatic cell counting

BACKGROUND

Mastitis, a pervasive and detrimental disease in dairy farming, poses a significant challenge to the global dairy industry. Monitoring the milk somatic cell count (SCC) is vital for assessing the incidence of mastitis and the quality of raw cow's milk. However, existing SCC detection methods typically require large-scale instruments and specialized operators, limiting their application in resource-constrained settings such as dairy farms and small-scale labs. To address these limitations, this study introduces a novel, smartphone-based, on-site SCC testing method that leverages smartphone capabilities for milk somatic cell identification and enumeration, offering a portable and user-friendly testing platform.

RESULTS

The central findings of our study demonstrate the effectiveness of the proposed method for counting milk somatic cells. Its on-site applicability, facilitated by the microfluidic chip, optical system, and smartphone integration, heralds a paradigm shift in point-of-care testing (POCT) for dairy farms and smaller laboratories. This approach bypasses complex processing and presents a user-friendly solution for real-time SCC monitoring in resource-limited settings. This device boasts several unique features: small size, low cost (<$1,000 total manufacturing cost and <$1 per test), and high accuracy. Remarkably, it delivers test results within just 2 min. Actual-sample testing confirmed its consistency with results from the commercial Bentley FTS/FCM cytometer, affirming the reliability of the proposed method. Overall, these results underscore the potential for transformative change in dairy farm management and laboratory testing practices.

SIGNIFICANCE

In summary, this study concludes that the proposed smartphone-based method significantly contributes to the accessibility and ease of SCC testing in resource-limited environments. By fostering the use of POCT technology in food safety control, particularly in the dairy industry, this innovative approach has the potential to revolutionize the monitoring and management of mastitis, ultimately benefiting the global dairy sector.

A Facile Method to Fabricate an Enclosed Paper-Based Analytical Device via Double-Sided Patterning for Ionic Contaminant Detection

Microfluidic paper-based analytical devices (μPADs) have been developed for use in a variety of diagnosis and analysis fields. However, conventional μPADs with an open-channel system have limitations for application as analytical platforms mainly because of the evaporation and contamination of the sample solution. This study demonstrates the design and fabrication of an enclosed three-dimensional(3D)-μPAD and its application as a primary early analysis platform for ionic contaminants. To generate the hydrophobic PDMS barrier, double-sided patterning is carried out using a PDMS blade-coated stamp mold that is fabricated using 3D printing. The selective PDMS patterning can be achieved with controlled PDMS permeation of the cellulose substrate using 3D-designed stamp molds. We find the optimal conditions enabling the formation of enclosed channels, including round shape pattern and inter-pattern distance of 10 mm of stamp design, contact time of 0.5 min, and spacer height of 300 µm of double-sided patterning procedure. As a proof of concept, this enclosed 3D-μPAD is used for the simultaneous colorimetric detection of heavy metal ions in a concentration range of 0.1-2000 ppm, including nickel (Ni2+), copper (Cu2+), mercury (Hg2+), and radioactive isotope cesium-137 ions (Cs+). We confirm that qualitative analysis and image-based quantitative analysis with high reliability are possible through rapid color changes within 3 min. The limits of detection (LOD) for 0.55 ppm of Ni2+, 5.05 ppm of Cu2+, 0.188 ppm of Hg2+, and 0.016 ppm of Cs+ are observed, respectively. In addition, we confirm that the analysis is highly reliable in a wide range of ion concentrations with CV values below 3% for Ni2+ (0.56%), Cu2+ (0.45%), Hg2+ (1.35%), and Cs+ (2.18%). This method could be a promising technique to develop a 3D-μPAD with various applications as a primary early analysis device in the environmental and biological industries.

Paper-based colorimetric sensors for point-of-care testing

By eliminating the need for sample transportation and centralized laboratory analysis, point-of-care testing (POCT) enables on-the-spot testing, with results available within minutes, leading to improved patient management and overall healthcare efficiency. Motivated by the rapid development of POCT, paper-based colorimetric sensing, a powerful analytical technique that exploits the changes in color or absorbance of a chemical species to detect and quantify analytes of interest, has garnered increasing attention. In this review, we strive to provide a bird's eye view of the development landscape of paper-based colorimetric sensors that harness the unique properties of paper to create low-cost, easy-to-use, and disposable analytical devices, thematically covering both fundamental aspects and categorized applications. In the end, we authors summarized the review with the remaining challenges and emerging opportunities. Hopefully, this review will ignite new research endeavors in the realm of paper-based colorimetric sensors.

A Low-Cost Microfluidic-Based Detection Device for Rapid Identification and Quantification of Biomarkers-Based on a Smartphone

The sensitive and rapid detection of microsamples is crucial for early diagnosis of diseases. The short response times and low sample volume requirements of microfluidic chips have shown great potential in early diagnosis, but there are still shortcomings such as complex preparation processes and high costs. We developed a low-cost smartphone-based fluorescence detection device (Smartphone-BFDD) without precision equipment for rapid identification and quantification of biomarkers on glass capillary. The device combines microfluidic technology with RGB image analysis, effectively reducing the sample volume to 20 μL and detection time to only 30 min. For the sensitivity of the device, we constructed a standard sandwich immunoassay (antibody-antigen-antibody) in a glass capillary using the N-protein of SARS-CoV-2 as a biological model, realizing a low limit of detection (LOD, 40 ng mL^-1). This device provides potential applications for different biomarkers and offers wide use for rapid biochemical analysis in biomedical research.

Electrical/Optical Biosensing and Regulating Technology

Biosensing has emerged as a powerful tool for exploring biomedical mechanisms [...].

Trends in Paper-Based Sensing Devices for Clinical and Environmental Monitoring

Environmental toxic pollutants and pathogens that enter the ecosystem are major global issues. Detection of these toxic chemicals/pollutants and the diagnosis of a disease is a first step in efficiently controlling their contamination and spread, respectively. Various analytical techniques are available to detect and determine toxic chemicals/pathogens, including liquid chromatography, HPLC, mass spectroscopy, and enzyme-linked immunosorbent assays. However, these sensing strategies have some drawbacks such as tedious sample pretreatment and preparation, the requirement for skilled technicians, and dependence on large laboratory-based instruments. Alternatively, biosensors, especially paper-based sensors, could be used extensively and are a cost-effective alternative to conventional laboratory testing. They can improve accessibility to testing to identify chemicals and pollutants, especially in developing countries. Due to its low cost, abundance, easy disposal (by incineration, for example) and biocompatible nature, paper is considered a versatile material for the development of environmentally friendly electrochemical/optical (bio) sensor devices. This review presents an overview of sensing platforms constructed from paper, pointing out the main merits and demerits of paper-based sensing systems, their fabrication techniques, and the different optical/electrochemical detection techniques that they exploit.

Multiplex Detection of Infectious Diseases on Microfluidic Platforms

Infectious diseases contribute significantly to the global disease burden. Sensitive and accurate screening methods are some of the most effective means of identifying sources of infection and controlling infectivity. Conventional detecting strategies such as quantitative polymerase chain reaction (qPCR), DNA sequencing, and mass spectrometry typically require bulky equipment and well-trained personnel. Therefore, mass screening of a large population using conventional strategies during pandemic periods often requires additional manpower, resources, and time, which cannot be guaranteed in resource-limited settings. Recently, emerging microfluidic technologies have shown the potential to replace conventional methods in performing point-of-care detection because they are automated, miniaturized, and integrated. By exploiting the spatial separation of detection sites, microfluidic platforms can enable the multiplex detection of infectious diseases to reduce the possibility of misdiagnosis and incomplete diagnosis of infectious diseases with similar symptoms. This review presents the recent advances in microfluidic platforms used for multiplex detection of infectious diseases, including microfluidic immunosensors and microfluidic nucleic acid sensors. As representative microfluidic platforms, lateral flow immunoassay (LFIA) platforms, polymer-based chips, paper-based devices, and droplet-based devices will be discussed in detail. In addition, the current challenges, commercialization, and prospects are proposed to promote the application of microfluidic platforms in infectious disease detection.