Integrated and finger-actuated microfluidic chip for point-of-care testing of multiple pathogens

A phosphorylated guanidine chitosan and UiO-66-NH2 modified magnetic nanoparticle platform for enrichment and detection of multiple bacteria

Wastewater-based epidemiology (WBE) is a powerful tool for early warning of infectious disease outbreaks. Hence, a rapid and portable pathogen monitoring system is urgent needed for on-site detection. In this work, we first reported synthesis of an artificial modulated wide-spectrum bacteria capture nanoparticle (Arg-CSP@UiO@Fe3O4). Arginine-modified phosphorylated chitosan (Arg-CSP) coating could provide strongly positive charged guanidinium group for pathogen interaction by electrostatic attraction, and UiO-66-NH2 layer could help Arg-CSP graft onto Fe3O4 magnetic particles. The capture efficiency of Arg-CSP@UiO@Fe3O4 reached 92.2 % and 97.3 % for Escherichia coli (E.coli) and Staphylococcus epidermidis (S.epidermidis)within 40 min, in 10 mL sample. To prevent pathogen degradation in sewage, a portable nucleic acid extraction-free method was also developed. UiO-66-NH2 could disintegrate in buffer with high concentration of PO43- for bacterium desorption, and then nucleic acid of the bacteria was released by heating. The DNA template concentration obtained by this method was 779.28 times higher than that of the direct thermal lysis product and 8.63 times higher than that of the commercial kit. Afterwards, multiple detection of bacteria was realized by loop-mediated isothermal amplification (LAMP). Artificial regulated pathogen desorption could prevent non-specific adsorption of nucleic acid by nanoparticles. The detection limit of Arg-CSP@UiO@Fe3O4-LAMP method was 80 cfu/mL for E.coli and 300 cfu/mL for S.epidermidis. The accuracy and reliability of the method was validated by spiked sewage samples. In conclusion, this bio-monitoring system was able to detect multiple bacteria in environment conveniently and have good potential to become an alternative solution for rapid on-site pathogen detection.

Reagent storage and delivery on integrated microfluidic chips for point-of-care diagnostics

Microfluidic-based point-of-care diagnostics offer several unique advantages over existing bioanalytical solutions, such as automation, miniaturisation, and integration of sensors to rapidly detect on-site specific biomarkers. It is important to highlight that a microfluidic POC system needs to perform a number of steps, including sample preparation, nucleic acid extraction, amplification, and detection. Each of these stages involves mixing and elution to go from sample to result. To address these complex sample preparation procedures, a vast number of different approaches have been developed to solve the problem of reagent storage and delivery. However, to date, no universal method has been proposed that can be applied as a working solution for all cases. Herein, both current self-contained (stored within the chip) and off-chip (stored in a separate device and brought together at the point of use) are reviewed, and their merits and limitations are discussed. This review focuses on reagent storage devices that could be integrated with microfluidic devices, discussing further issues or merits of these storage solutions in two different sections: direct on-chip storage and external storage with their application devices. Furthermore, the different microvalves and micropumps are considered to provide guidelines for designing appropriate integrated microfluidic point-of-care devices.

A one-step process for multi-gradient wettability modification on a polymer surface

The surface modification technique is applied in microfluidic devices to modify wettability and achieve different flow velocities. Currently available methods for poly(dimethylsiloxane) (PDMS) surfaces may reliably induce wettability changes, but only one area can be altered at a time. This work introduces the controlled gradient oxygen plasma modification (CGPM) technique, which layers several resin masks with varying porosities on top of the PDMS surface. Selective wettability of the PDMS surface can be achieved by varying the oxygen plasma density above the modified material's surface by manipulation of the porosity value. Through the implementation of the COMSOL plasma module, the impact of the mask's porosity, through-hole size, distribution, and distance from the PDMS surface on wettability was studied. The suggested CGPM approach was characterized by contact angle measurements. During the 25-second CGPM procedure, the PDMS surface's contact angle continually changed from 8.77° to 76.98°. An integrated microfluidic device was created and manufactured to identify D-dimers to illustrate this method. In comparison with standard oxygen plasma treatment, the D-dimer assay was finished in 10 minutes and had a dynamic range of 1-1000 ng mL-1, with a peak fluorescence signal augmentation of 78.3% and an average fluorescence intensity enhancement of 31.1%.

An All-in-One Platform for On-Site Multiplex Foodborne Pathogen Detection Based on Channel-Digital Hybrid Microfluidics

Recently, significant progress has been made in the development of microdevices for point-of-care infectious disease detection. However, most microdevices only allow limited steps, such as DNA amplification on the chip, while sample preparation, such as lysis and DNA extraction, is conducted off the chip using the traditional method. In this study, an all-in-one platform was developed, which incorporated all necessary procedures for nucleic acid detection. Our on-chip DNA extraction method utilized the magnetic bead-based technology on a hybrid channel-digital microfluidics (C-DMF) microdevice. It yielded high recovery rates, varying from 88.43% to 95.83%, with pathogen concentrations of 103-106 CFU/mL. In particular, the on-chip method exhibited significantly higher efficacy compared to the traditional off-chip manual method, for the DNA extraction of E. coli and S. aureus, representing Gram-negative and Gram-positive bacteria, respectively, at a sample concentration of 103 CFU/mL. To address the need for rapid and accessible diagnostics, colorimetric LAMP amplification was integrated into the proposed microdevice. The results were visually detectable with the naked eye, making it user-friendly for non-specialists. In addition, this platform demonstrated impressive sensitivity in simultaneously detecting common foodborne pathogens in spiked meat samples, achieving the LOD of 102-103 CFU/mL. The entire process, from sampling to result, was fully automated and only required approximately 60 min, offering promising applicability in resource-limited and on-site testing scenarios.

Advancements in the research of finger-actuated POCT chips

Microfluidic point-of-care testing (POCT) chips are used to enable the mixing and reaction of small sample volumes, facilitating target molecule detection. Traditional methods for actuating POCT chips rely on external pumps or power supplies, which are complex and non-portable. The development of finger-actuated chips has reduced operational difficulty and improved portability, promoting the development of POCT chips. This paper reviews the significance, developments, and potential applications of finger-actuated POCT chips. Three methods for controlling the flow accuracy of finger-actuated chips are summarized: direct push, indirect control, and sample injection control method, along with their respective advantages and disadvantages. Meanwhile, a comprehensive analysis of multi-fluid driving modes is provided, categorizing them into single-push multi-driving and multi-push multi-driving modes. Furthermore, recent research breakthroughs in finger-actuated chips are thoroughly summarized, and their structures, driving, and detection methods are discussed. Finally, this paper discusses the driving performance of finger-actuated chips, the suitability of detection scenarios, and the compatibility with existing detection technologies. It also provides prospects for the future development and application of finger-actuated POCT chips.

A fully integrated duplex RT-LAMP device for the detection of viral infections

Respiratory viruses can cause epidemics or pandemics, which are worldwide outbreaks of disease. The severity of these events varies depending on the virus, its characteristics, along with environmental factors. The frequency of epidemics and pandemics caused by respiratory viruses is difficult to predict, but the potential severity of such events underlines the importance of continued monitoring, research, and preparation for emerging infectious diseases. To help improve pandemic preparedness, we created a fully integrated duplex reverse transcription loop-mediated isothermal amplification (RT-LAMP) device targeting two respiratory viruses, influenza A/X-31 virus and bovine coronavirus, as a replacement for SARS-CoV-2. This device can be adapted to any other respiratory virus. In this study, we showed and evaluated a prototype of a microfluidic system, and showed that duplex RT-LAMP can detect and distinguish between the two viruses, with LoDs of 2,000 copies/ml for bovine coronavirus and 200 copies/ml for influenza A/X-31 virus.

Microfluidic chip and isothermal amplification technologies for the detection of pathogenic nucleic acid

The frequency of outbreaks of newly emerging infectious diseases has increased in recent years. The coronavirus disease 2019 (COVID-19) outbreak in late 2019 has caused a global pandemic, seriously endangering human health and social stability. Rapid detection of infectious disease pathogens is a key prerequisite for the early screening of cases and the reduction in transmission risk. Fluorescence quantitative polymerase chain reaction (qPCR) is currently the most commonly used pathogen detection method, but this method has high requirements in terms of operating staff, instrumentation, venues, and so forth. As a result, its application in the settings such as poorly conditioned communities and grassroots has been limited, and the detection needs of the first-line field cannot be met. The development of point-of-care testing (POCT) technology is of great practical significance for preventing and controlling infectious diseases. Isothermal amplification technology has advantages such as mild reaction conditions and low instrument dependence. It has a promising prospect in the development of POCT, combined with the advantages of high integration and portability of microfluidic chip technology. This study summarized the principles of several representative isothermal amplification techniques, as well as their advantages and disadvantages. Particularly, it reviewed the research progress on microfluidic chip-based recombinase polymerase isothermal amplification technology and highlighted future prospects.

Novel Pumping Methods for Microfluidic Devices: A Comprehensive Review

This review is an account of methods that use various strategies to control microfluidic flow control with high accuracy. The reviewed systems are divided into two large groups based on the way they create flow: passive systems (non-mechanical systems) and active (mechanical) systems. Each group is presented by a number of device fabrications. We try to explain the main principles of operation, and we list advantages and disadvantages of the presented systems. Mechanical systems are considered in more detail, as they are currently an area of increased interest due to their unique precision flow control and "multitasking". These systems are often applied as mini-laboratories, working autonomously without any additional operations, provided by humans, which is very important under complicated conditions. We also reviewed the integration of autonomous microfluidic systems with a smartphone or single-board computer when all data are retrieved and processed without using a personal computer. In addition, we discuss future trends and possible solutions for further development of this area of technology.

Recent Progress in Spectroscopic Methods for the Detection of Foodborne Pathogenic Bacteria

Detection of foodborne pathogens at an early stage is very important to control food quality and improve medical response. Rapid detection of foodborne pathogens with high sensitivity and specificity is becoming an urgent requirement in health safety, medical diagnostics, environmental safety, and controlling food quality. Despite the existing bacterial detection methods being reliable and widely used, these methods are time-consuming, expensive, and cumbersome. Therefore, researchers are trying to find new methods by integrating spectroscopy techniques with artificial intelligence and advanced materials. Within this progress report, advances in the detection of foodborne pathogens using spectroscopy techniques are discussed. This paper presents an overview of the progress and application of spectroscopy techniques for the detection of foodborne pathogens, particularly new trends in the past few years, including surface-enhanced Raman spectroscopy, surface plasmon resonance, fluorescence spectroscopy, multiangle laser light scattering, and imaging analysis. In addition, the applications of artificial intelligence, microfluidics, smartphone-based techniques, and advanced materials related to spectroscopy for the detection of bacterial pathogens are discussed. Finally, we conclude and discuss possible research prospects in aspects of spectroscopy techniques for the identification and classification of pathogens.

A cascade Fermat spiral microfluidic mixer chip for accurate detection and logic discrimination of cancer cells

Since cancer has emerged as one of the most serious threats to human health, the highly sensitive determination of cancer cells is of significant importance to improve the accuracy of early clinical diagnosis. In our investigation, a novel cascade Fermat spiral microfluidic mixer chip (CFSMMC) combined with fluorescence sensors as a point-of-care (POC) testing system is successfully fabricated to detect and differentiate cancer cells (MCF-7) from normal cells with excellent sensitivity and selectivity. Here, copper ions (Cu²⁺) with peroxidase properties can catalyze the oxidation of the non-fluorescent substrate Amplex Red (AR) to the highly fluorescent resorufin (ox-AR) in the presence of hydrogen peroxide (H₂O₂). Subsequently, thanks to the quenching response of AS1411-AuNPs to ox-AR in the microchannel and the binding of AS1411 to nucleolin on the surface of cancer cells, a CFSMMC-based POC system is established for the highly sensitive detection and identification of human breast cancer cells in a "turn on" manner. The change in fluorescence intensity is linearly related to the concentration of MCF-7, ranging from 10² to 10⁷ cells per mL with a limit of detection (LOD) as low as 17 cells per mL. Interestingly, the cascaded AND logic gate is integrated with CFSMMC for the first time to distinguish cancer cells from normal cells under the control of logic functions, which exhibits great potential in the development of one-step rapid and intelligent detection and logic discrimination.

A carbon-black-embedded poly(dimethylsiloxane)-paper hybrid device for energy-efficient nucleic-acid amplification in point-of-care testing

A paper-based device patterned with a carbon-black-poly(dimethylsiloxane) (PDMS) mixture is developed as a heating platform for nucleic-acid amplification tests. The photothermal effect of carbon black under 808 nm laser irradiation is used to conduct loop-mediated isothermal amplification (LAMP) to detect Escherichia coli (E. coli) O157:H7, a foodborne pathogen. We characterize the heat generation of carbon black by changing its concentration and the hardness of PDMS. Then, we optimize the minimum laser power required to perform LAMP. The proposed paper-based device requires less than 15 min to perform LAMP, and the result can be confirmed based on the color change observed by the naked eye. The rfbE gene of E. coli O157:H7 is specifically amplified, with a detection limit of 10² CFU mL^-1. Amplification is also performed by using a laboratory-made laser-diode device, which consumes only 2 W h during its operation. The low cost, disposability, and easy fabrication of the paper-based device make it a powerful tool for point-of-care testing.

Microfluidics-based strategies for molecular diagnostics of infectious diseases

Traditional diagnostic strategies for infectious disease detection require benchtop instruments that are inappropriate for point-of-care testing (POCT). Emerging microfluidics, a highly miniaturized, automatic, and integrated technology, are a potential substitute for traditional methods in performing rapid, low-cost, accurate, and on-site diagnoses. Molecular diagnostics are widely used in microfluidic devices as the most effective approaches for pathogen detection. This review summarizes the latest advances in microfluidics-based molecular diagnostics for infectious diseases from academic perspectives and industrial outlooks. First, we introduce the typical on-chip nucleic acid processes, including sample preprocessing, amplification, and signal read-out. Then, four categories of microfluidic platforms are compared with respect to features, merits, and demerits. We further discuss application of the digital assay in absolute nucleic acid quantification. Both the classic and recent microfluidics-based commercial molecular diagnostic devices are summarized as proof of the current market status. Finally, we propose future directions for microfluidics-based infectious disease diagnosis.

Advances in the Rapid Diagnostic of Viral Respiratory Tract Infections

Viral infections are a significant public health problem, primarily due to their high transmission rate, various pathological manifestations, ranging from mild to severe symptoms and subclinical onset. Laboratory diagnostic tests for infectious diseases, with a short enough turnaround time, are promising tools to improve patient care, antiviral therapeutic decisions, and infection prevention. Numerous microbiological molecular and serological diagnostic testing devices have been developed and authorised as benchtop systems, and only a few as rapid miniaturised, fully automated, portable digital platforms. Their successful implementation in virology relies on their performance and impact on patient management. This review describes the current progress and perspectives in developing micro- and nanotechnology-based solutions for rapidly detecting human viral respiratory infectious diseases. It provides a nonexhaustive overview of currently commercially available and under-study diagnostic testing methods and discusses the sampling and viral genetic trends as preanalytical components influencing the results. We describe the clinical performance of tests, focusing on alternatives such as microfluidics-, biosensors-, Internet-of-Things (IoT)-based devices for rapid and accurate viral loads and immunological responses detection. The conclusions highlight the potential impact of the newly developed devices on laboratory diagnostic and clinical outcomes.

A magnet-actuated microfluidic array chip for high-throughput pretreatment and amplification and detection of multiple pathogens

The outbreak of global infectious diseases has posed a significant threat to public health, requiring the rapid and accurate diagnosis of pathogens promptly for society to implement immediate control measures to prevent widespread pandemics.

Sample Preparation for Lab-on-a-Chip Systems in Molecular Diagnosis: A Review

Rapid and low-cost molecular analysis is especially required for early and specific diagnostics, quick decision-making, and sparing patients from unnecessary tests and hospitals from extra costs. One way to achieve this objective is through automated molecular diagnostic devices. Thus, sample-to-answer microfluidic devices are emerging with the promise of delivering a complete molecular diagnosis system that includes nucleic acid extraction, amplification, and detection steps in a single device. The biggest issue in such equipment is the extraction process, which is normally laborious and time-consuming but extremely important for sensitive and specific detection. Therefore, this Review focuses on automated or semiautomated extraction methodologies used in lab-on-a-chip devices. More than 15 different extraction methods developed over the past 10 years have been analyzed in terms of their advantages and disadvantages to improve extraction procedures in future studies. Herein, we are able to explain the high applicability of the extraction methodologies due to the large variety of samples in which different techniques were employed, showing that their applications are not limited to medical diagnosis. Moreover, we are able to conclude that further research in the field would be beneficial because the methodologies presented can be affordable, portable, time efficient, and easily manipulated, all of which are strong qualities for point-of-care technologies.

Rotary Valve-Assisted Fluidic System Coupling with CRISPR/Cas12a for Fully Integrated Nucleic Acid Detection

Of late, many nucleic acid analysis platforms have been established, but there is still room for constructing integrated nucleic acid detection systems with high nucleic acid extraction efficiency, low detection cost, and convenient operation. In this work, a simple rotary valve-assisted fluidic chip coupling with CRISPR/Cas12a was established to achieve fully integrated nucleic acid detection. All of the detection reagents were prestored on the fluidic chip. With the aid of the rotary valve and syringe, the liquid flow and stirring can be precisely controlled. The nucleic acid extraction, loop-mediated isothermal amplification (LAMP) reaction, and CRISPR detection could be completed in 80 min. A clean reservoir and an air reservoir on the fluidic chip were designed to effectively remove the remaining ethanol. With Vibrio parahaemolyticus as the targets, the detection sensitivity of the fluidic chip could reach 3.1 × 10¹ copies of target DNA per reaction. A positive sample could be sensitively detected by CRISPR/Cas12a to produce a green fluorescent signal, while a negative sample generated no fluorescent signal. Further, the fluidic chip was successfully applied for detection of spiked shrimp samples, which showed the same detection sensitivity. A great feasibility for real-sample detection was showed by the fluidic chip. The proposed detection platform did not need expensive centrifugal instruments or pumps, which displayed its potential to become a powerful tool for food safety analysis and clinical diagnostics, especially in the resource-limited areas.

Challenges and Perspectives for Biosensing of Bioaerosol Containing Pathogenic Microorganisms

As an important route for disease transmission, bioaerosols have received increasing attention. In the past decades, many efforts were made to facilitate the development of bioaerosol monitoring; however, there are still some important challenges in bioaerosol collection and detection. Thus, recent advances in bioaerosol collection (such as sedimentation, filtration, centrifugation, impaction, impingement, and microfluidics) and detection methods (such as culture, molecular biological assay, and immunological assay) were summarized in this review. Besides, the important challenges and perspectives for bioaerosol biosensing were also discussed.

Stretch-driven microfluidic chip for nucleic acid detection

Molecular diagnosis is an essential means to detect pathogens. The portable nucleic acid detection chip has excellent prospects in places where medical resources are scarce, and it is also of research interest in the field of microfluidic chips. Here, the article developed a new type of microfluidic chip for nucleic acid detection where stretching acts as the driving force. The sample entered the chip by applying capillary force. The strain valve was opened under the action of tensile force, and the spring pump generated the power to drive the fluid to flow to the detection chamber in a specific direction. The detection of coronavirus disease 2019 (COVID-19) was realized on the chip. The RT-LAMP amplification system was adopted to observe the liquid color in the detection chamber to decide whether the sample tested positive or negative qualitatively.

Human sensor-inspired supervised machine learning of smartphone-based paper microfluidic analysis for bacterial species classification

Bacteria identification has predominantly been conducted using specific bioreceptors such as antibodies or nucleic acid sequences. This approach may be inappropriate for environmental monitoring when the user does not know the target bacterial species and for screening complex water samples with many unknown bacterial species. In this work, we investigate the supervised machine learning of the bacteria-particle aggregation pattern induced by the peptide sets identified from the biofilm-bacteria interface. Each peptide is covalently conjugated to polystyrene particles and loaded together with bacterial suspensions onto paper microfluidic chips. Each peptide interacts with bacterial species to a different extent, leading to varying sizes of particle aggregation. This aggregation changes the surface tension and viscosity of the liquid flowing through the paper pores, altering the flow velocity at different extents. A smartphone camera captures this flow velocity without being affected by ambient and environmental conditions, towards a low-cost, rapid, and field-ready assay. A collection of such flow velocity data generates a unique fingerprinting profile for each bacterial species. Support vector machine is utilized to classify the species. At optimized conditions, the training model can predict the species at 93.3% accuracy out of five bacteria: Escherichia coli, Staphylococcus aureus, Salmonella Typhimurium, Enterococcus faecium, and Pseudomonas aeruginosa. Flow rates are monitored for less than 6 s and the sample-to-answer assay time is less than 10 min. The demonstrated method can open a new way of analyzing complex biological and environmental samples in a biomimetic manner with machine learning classification.