Polyethersulfone-Based Microfluidic Device Integrated with DNA Extraction on Paper and Recombinase Polymerase Amplification for the Detection of Salmonella enterica

Handheld RPA-based molecular POCT system for rapid, low-cost 8-plexed detection of respiratory pathogens at home

During seasonal influenza or emerging respiratory outbreaks, rapid home-based multiplex molecular point-of-care testing (POCT) for respiratory pathogens is crucial for early diagnosis and intervention, particularly in vulnerable populations. However, existing POCT systems, primarily designed for clinical settings, are often too complex, costly, and reliant on trained operators, limiting their suitability for home use. To overcome these barriers, we introduce a microfluidic cartridge-based system leveraging recombinase polymerase amplification (RPA) for multiplexed detection of respiratory pathogens in home environments. The microfluidic cartridge is designed with three parallel channels-each integrating a lysis chamber, an RPA chamber preloaded with lyophilized reagents, and an air storage chamber. Each detection channel enables extraction-free, single-channel 3-plex RPA assays, and by combining three-channel parallel detection, the system achieves simultaneous identification of eight respiratory pathogens and one internal control in under 25 min. A novel pneumatic pressure pumping strategy ensures precise flow control through dynamic bladder compression, paired with microchannel hydraulic resistance matching to guarantee uniform volumetric distribution and synchronized flow across all channels. Furthermore, a dynamic mixing method promotes homogeneous mixing of RPA reagents with lysed samples via a bidirectional flow between the lysis and RPA chambers, enhancing assay reliability. Our microfluidic design enables significant miniaturization, yielding a compact, lightweight system (<1 kg) suitable for handheld or desktop use. Its low power consumption (3 W) and remarkable cost-effectiveness ($1.4 per test) enhance the system's practicality and accessibility for home settings. Validation with 356 nasopharyngeal swabs further confirms its robust performance, achieving high sensitivity (>97%) and specificity (>99%), ensuring reliable at-home diagnosis of respiratory co-infections without requiring professional operation.

A colorimetric and surface-enhanced Raman scattering dual-mode "sandwich" immunosensor for ultrasensitive detection of Salmonella

Herein, a dual-mode approach combining colorimetry and surface-enhanced Raman scattering (SERS) were developed for Salmonella detection. Immunomagnetic beads were used to separate and concentrate the Salmonella. And the GOx@ZIF-90@PDA@pAbs were used as signal probe to catalyze glucose to form H2O2. In the presence of H2O2, tyramine (TYR) aggregation was brought on by HRP-catalyzed phenol polymerization, which led to the aggregation of AuNPs through the strong electrostatic interactions between TYR and AuNPs. Based on the enzymatic cascade catalyzed signal amplification induced AuNPs aggregation, the dual-mode method exhibited wide linear range (101-105 CFU/mL) and high sensitivity. The limit of detection (LOD) of colorimetric mode was 34 CFU/mL, while the LOD was 5 CFU/mL in SERS mode, which was 6.8-fold lower than that of colorimetric mode. Furthermore, the two modes demonstrated high specificity and applicability, which might be a promising method for rapid and sensitive detection of Salmonella to ensure food safety.

Rapid tuberculosis diagnosis from respiratory or blood samples by a low cost, portable lab-in-tube assay

Rapid portable assays are needed to improve diagnosis, treatment, and reduce transmission of tuberculosis (TB), but current tests are not suitable for patients in resource-limited settings with high TB burden. Here we report a low complexity, lab-in-tube system that is read by an integrated handheld device that detects Mycobacterium tuberculosis (Mtb) DNA in blood and respiratory samples from a variety of clinical settings. This microprocessor-controlled device uses an LCD user interface to control assay performance, automate assay analysis, and provide results in a simple readout. This point-of-care single-tube assay uses a DNA enrichment membrane and a low-cost cellulose disc containing lyophilized recombinase polymerase amplification and CRISPR-Cas12a reagents to attain single-nucleotide specificity and high sensitivity within 1 hour of sample application, without a conventional DNA isolation procedure. Assay results obtained with serum cell-free DNA isolated from a cohort of children aged 1 to 16 years detected pulmonary and extrapulmonary TB with high sensitivity versus culture and GeneXpert MTB/RIF results (81% versus 55% and 68%) and good specificity (94%), meeting the World Health Organization target product profile criteria for new nonsputum TB diagnostics. Changes in assay results for serum isolated during treatment were also highly predictive of clinical response. Results obtained with noninvasive sputum and saliva specimens from adults with bacteriologically confirmed pulmonary TB were also comparable to those reported for reference methods. This rapid and inexpensive lab-in-tube assay approach thus represents one means to address the need for point-of-care TB diagnostics useable in low-resource settings.

Portable DNA extraction integrated with LAMP-CRISPR/Cas12a technology for on-site detection of Salmonella Typhimurium

The infection and outbreak of Salmonella typhimurium (S. typhimurium) highlight the need for developing a reliable on-site detection strategy fitting to various settings. However, due to the requirement of specialized instruments and trained personnel, traditional detection methods have to be implemented in laboratories and are not ideal for on-site applications. To achieve a sample-to-answer and field-deployable detection for S. typhimurium, we developed an integrated nucleic acid detection platform combining single-vial of loop-mediated isothermal amplification (LAMP)-clustered regularly interspaced short palindromic repeat (CRISPR)/Cas12a system, portable device and smartphone app. This platform enables the extraction, concentration, and purification of DNA, amplification of the target, and output of visual fluorescent signals within 1 h. With this detection platform, 102 CFU/mL of S. typhimurium in food and environmental matrix was able to be accurately detected. This method demonstrated excellent selectivity. Also, an auxiliary smartphone application was developed to achieve simplified result interpretation. Our method exhibited potential to better control and respond to outbreaks of foodborne diseases, especially in low-resource settings.

Recent developments in isothermal amplification technology for rapid detection of SARS-CoV-2

Coronavirus disease 2019 (COVID-19), an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread globally, posing a significant threat to human health. Rapid and accurate detection of infectious disease pathogens is of crucial practical significance for early screening, timely intervention, and outbreak prevention. However, conventional diagnostic methods are increasingly unable to meet clinical demands. Recently developed isothermal analysis methods offer mild reaction conditions and reduce dependence on specialized instruments. These convenient, fast, and reliable methods show great promise for diagnosing infectious pathogens, especially for on-site detection in areas without laboratories or with limited resources. Among them, loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification (RPA), which integrate various widely used detection techniques, stand out as rapidly advancing and relatively mature isothermal nucleic acid amplification technologies. This review outlines several representative isothermal amplification technologies and associated detection methods. We summarize the latest advancements in LAMP and RPA technologies for the rapid detection of SARS-CoV-2 and discuss the future prospects of isothermal amplification in diversified testing.

Thermo-responsive 3D nanostructures for enhanced performance in food-poisoning bacterial analysis

The growing risk of bacterial food poisoning due to global warming has necessitated the development of methods for accurate detection of food-poisoning bacteria. Despite extensive efforts to develop enhanced bacterial-capture methods, challenges associated with the release of the captured bacteria have limited the sensitivity of bacterial detection. In this study, thermo-responsive intelligent 3D nanostructures to improve food-poisoning bacterial analysis performance were fabricated by introducing a thermo-responsive polymer onto an urchin-like 3D nanopillar substrate (URCHANO). A co-polymer of methacryloyl glycinamide and benzyl acrylate (MNAGA-Bn 5%) was introduced as a thermo-responsive co-polymer onto URCHANO using an electron-transfer atom-transfer radical-polymerization method to fabricate Thermo-URCHANO. A temperature-related analysis of the surface properties of Thermo-URCHANO revealed a hydrophobic-to-hydrophilic transition at 37 °C, which facilitated the release of bacteria captured within the nanostructure. In a one-pot analysis to capture and analyze various food-poisoning bacteria in kitchenware (gloves and aprons) and food items (eggs and sausages), mimicking real-life environments, specimens collected using Thermo-URCHANO showed lower Ct values than those collected with uncoated URCHANO, indicating greater bacterial detection. This method could effectively release captured bacteria through temperature changes, improving extraction efficiency during swab collection. While Thermo-URCHANO needs further optimization, it is expected to enhance bacterial analysis performance and sensitivity.

Recent Advances in DNA Origami-Enabled Optical Biosensors for Multi-Scenario Application

Over the past few years, significant progress has been made in DNA origami technology due to the unrivaled self-assembly properties of DNA molecules. As a highly programmable, addressable, and biocompatible nanomaterial, DNA origami has found widespread applications in biomedicine, such as cell scaffold construction, antimicrobial drug delivery, and supramolecular enzyme assembly. To expand the scope of DNA origami application scenarios, researchers have developed DNA origami structures capable of actively identifying and quantitatively reporting targets. Optical DNA origami biosensors are promising due to their fast-to-use, sensitive, and easy implementation. However, the conversion of DNA origami to optical biosensors is still in its infancy stage, and related strategies have not been systematically summarized, increasing the difficulty of guiding subsequent researchers. Therefore, this review focuses on the universal strategies that endow DNA origami with dynamic responsiveness from both de novo design and current DNA origami modification. Various applications of DNA origami biosensors are also discussed. Additionally, we highlight the advantages of DNA origami biosensors, which offer a single-molecule resolution and high signal-to-noise ratio as an alternative to traditional analytical techniques. We believe that over the next decade, researchers will continue to transform DNA origami into optical biosensors and explore their infinite possible uses.

Microfluidics for detection of food pathogens: recent trends and opportunities

Safe and healthy food is the fundamental right of every citizen. Problems caused by foodborne pathogens have always raised a threat to food safety and human health. Centers for Disease Control and Prevention (CDC) estimates that around 48 million people are affected by food intoxication, and 3000 people succumb to death. Hence, it is inevitable that an approach that is efficient, reliable, sensitive, and rapid approach that can replace the conventional analytical methods such as microbiological and biochemical methods, high throughput next-generation sequence (NGS), polymerase chain reaction (PCR), and enzyme-linked immunosorbent assay (ELISA), etc. Even though the accuracy of conventional methods is high, it is tedious; increased consumption of reagents/samples, false positives, and complex operations are the drawbacks of these methods. Microfluidic devices have shown remarkable advances in all branches of science. They serve as an alternative to conventional ways to overcome the abovementioned drawbacks. Furthermore, coupling microfluidics can improve the efficiency and accuracy of conventional methods such as surface plasma resonance, loop-mediated isothermal amplification, ELISA, and PCR. This article reviewed the progress of microfluidic devices in the last ten years in detecting foodborne pathogens. Microfluidic technology has opened the research gateway for developing low-cost, on-site, portable, and rapid assay devices. The article includes the application of microfluidic-based devices to identify critical food pathogens and briefly discusses the necessary research in this area.

Phage-based magnetic capture method as an aid for real-time recombinase polymerase amplification detection of Salmonella spp. in milk

Salmonella is a major cause of foodborne diseases worldwide. Conventional rapid assays for detecting Salmonella in real samples often encounter severe matrix interference or detect a limited number of species of a genus, resulting in inaccurate detection. In this study, we developed a method that combined phage-based magnetic capture with real-time recombinase polymerase amplification (RPA) for the rapid, highly sensitive, and specific detection of Salmonella in milk with an ultra-low detection limit. The Felix O-1 phage-conjugated magnetic beads (O-1 pMBs) synthesized in this method showed excellent capture ability for Salmonella spp. and ideal specificity for non-Salmonella strains. After O-1 pMBs-based magnetic separation, the limit of detection of the real-time RPA assay was 50 cfu/mL in milk samples, which was significantly increased by a magnitude of 3 to 4 orders. The method exhibited a high sensitivity (compatibility) of 100% (14/14) for all tested Salmonella serotype strains and an ideal specificity (exclusivity) of 100% (7/7) for the tested non-Salmonella strains. The entire detection process, including Salmonella capture, DNA extraction, and real-time RPA detection, was completed within 1.5 h. Furthermore, milk samples spiked with 10 cfu/25 mL of Salmonella were detected positive after being cultured in buffered peptone water for only 3 h. Therefore, the proposed method could be an alternative for the rapid and accurate detection of Salmonella.

Critical review and recent advances of emerging real-time and non-destructive strategies for meat spoilage monitoring

Monitoring and evaluating food quality, especially meat quality, has received a growing interest to ensure human health and decrease waste of raw materials. Standard analytical approaches used for meat spoilage assessment suffer from time consumption, being labor-intensive, operation complexity, and destructiveness. To overcome shortfalls of these traditional methods and monitor spoilage microorganisms or related metabolites of meat products across the supply chain, emerging analysis devices/systems with higher sensitivity, better portability, on-line/in-line, non-destructive and cost-effective property are urgently needed. Herein, we first overview the basic concepts, causes, and critical monitoring indicators associated with meat spoilage. Then, the conventional detection methods for meat spoilage are outlined objectively in their strengths and weaknesses. In addition, we place the focus on the recent research advances of emerging non-destructive devices and systems for assessing meat spoilage. These novel strategies demonstrate their powerful potential in the real-time evaluation of meat spoilage.

Method for lysis and paper-based elution-free DNA extraction with colourimetric isothermal amplification

Nucleic acid amplification testing has great potential for point-of-need diagnostic testing with high detection sensitivity and specificity. Current sample preparation is limited by a tedious workflow requiring multiple steps, reagents and instrumentation, hampering nucleic acid testing at point of need. In this study, we present the use of mixed cellulose ester (MCE) paper for DNA binding by ionic interaction under molecular crowding conditions and fluid transport by wicking. The poly(ethylene) glycol-based (PEG) reagent simultaneously provides the high pH for alkaline lysis and crowding effects for ionic binding of the DNA under high salt conditions. In this study, we introduce Paper-based Abridged Solid-Phase Extraction with Alkaline Poly(ethylene) Glycol Lysis (PASAP). The anionic mixed cellulose ester (MCE) paper is used as solid phase and allows for fluid transport by wicking, eliminating the need for pipetting skills and the use of a magnet to retain beads. Following the release of DNA from the cells due to the lytic activity of the PASAP solution, the DNA binds to the anionic surface of the MCE paper, concentrating at the bottom while the sample matrix is transported towards the top by wicking. The paper was washed by dipping it in 40% isopropanol for 10 s. After air-drying for 30 s, the bottom section of the paper (3 mm × 4 mm) was snapped off using the cap of a PCR tube and immersed in the colourimetric loop-mediated isothermal amplification (cLAMP) solution for direct amplification and colourimetric detection. The total sample processing was completed in 15 min and ready for amplification. cLAMP enabled the detection of 102 CFU/mL of Escherichia coli (E. coli) from culture media and the detection of E. coli in milk < 103 CFU/mL (10 CFU) after incubation at 68 °C for 60 min, demonstrating applicability of the method to complex biological samples.

Sensitive, Semiquantitative, and Portable Nucleic Acid Detection of Rabies Virus Using a Personal Glucose Meter

Rabies is a zoonotic infection with the potential to infect all mammals and poses a significant threat to mortality. Although enzyme-linked immunosorbent tests and real-time reverse transcription-quantitative polymerase chain reaction (RT-qPCR) have been established for rabies virus (RABV) detection, they require skilled staff. Here, we introduce a personal glucose meter (PGM)-based nucleic acid (NA-PGM) detection method to diagnose RABV. This method ensures sensitive and convenient RABV diagnosis through hybridization of reverse transcription-recombinase aided amplification (RT-RAA) amplicons with probes labeled with sucrose-converting enzymes, reaching a detection level as low as 6.3 copies/μL equivalent to 12.26 copies. NA-PGM allows for the differentiation of RABV from other closely related viruses. In addition, NA-PGM showed excellent performance on 65 clinical samples with a 100% accuracy rate compared with the widely adopted RT-qPCR method. Thus, our developed NA-PGM method stands out as sensitive, semiquantitative, and portable for RABV detection, showcasing promise as a versatile platform for a wide range of pathogens.

Fast detection of bacterial gut pathogens on miniaturized devices: an overview

INTRODUCTION

Gut microbes pose challenges like colon inflammation, deadly diarrhea, antimicrobial resistance dissemination, and chronic disease onset. Development of early, rapid and specific diagnosis tools is essential for improving infection control. Point-of-care testing (POCT) systems offer rapid, sensitive, low-cost and sample-to-answer methods for microbe detection from various clinical and environmental samples, bringing the advantages of portability, automation, and simple operation.

AREAS COVERED

Rapid detection of gut microbes can be done using a wide array of techniques including biosensors, immunological assays, electrochemical impedance spectroscopy, mass spectrometry and molecular biology. Inclusion of Internet of Things, machine learning, and smartphone-based point-of-care applications is an important aspect of POCT. In this review, the authors discuss various fast diagnostic platforms for gut pathogens and their main challenges.

EXPERT OPINION

Developing effective assays for microbe detection can be complex. Assay design must consider factors like target selection, real-time and multiplex detection, sample type, reagent stability and storage, primer/probe design, and optimizing reaction conditions for accuracy and sensitivity. Mitigating these challenges requires interdisciplinary collaboration among scientists, clinicians, engineers, and industry partners. Future efforts are essential to enhance sensitivity, specificity, and versatility of POCT systems for gut microbe detection and quantification, advancing infectious disease diagnostics and management.