Multiplex sample-to-answer detection of bacteria using a pipette-actuated capillary array comb with integrated DNA extraction, isothermal amplification, and smartphone detection

Smartphone-integrated visual inspection for enhancing agricultural product quality and safety: a review

The increasing emphasis on the quality and safety of agricultural products, which are vital to global trade and consumer health, has driven the innovation of cost-effective, convenient, and rapid smart detection technologies. Smartphones, with their interdisciplinary functionalities, have become valuable tools in quantification and analysis research. Acting as portable, affordable, and user-friendly analytical devices, smartphones are equipped with high-resolution cameras, displays, memory, communication modules, sensors, and operating systems (Android or IOS), making them powerful, palm-sized remote computers. This review delves into how visual inspection technology and smartphones have enhanced the quality and safety of agricultural products over the past decade. It also evaluates the key features and limitations of existing smart rapid inspection methods for agricultural products and anticipates future advancements, offering insights into the application of smart rapid inspection technology in agriculture.

In Situ Colorimetric LAMP Based on One-Step Modified Filter Paper to Screen Human Papillomavirus (HPV)16/18 from Clinical Samples

Cervical cancer is among the most common malignant tumors in women. The development of rapid screening techniques plays an important role in early screening for cancer treatment. We have developed an HPV screening method, which effectively combines the high-efficiency nucleic acid enrichment of chitosan-modified filter paper and the rapid visual detectability of colorimetric LAMP, along with the enhancement of the tolerance ability of the pH-sensitive LAMP reagent to acidic original samples, making the detection of HPV 16/18 easy to carry out and reliable, which is helpful for the epidemiological prevention and control strategies of HPV-induced cancer. This technique can simultaneously exhibit the "in situ amplification" capability of chitosan-modified filter paper and the nontemperature cycle dependence of visual LAMP detection. Therefore, DNA extraction and amplification can be performed efficiently and quickly within a single reaction where all DNA is concentrated in the QF paper disc. By embedding amino-modified filter paper into the plastic chip, a simple and reliable disposable chip was prepared for rapid HPV16 and HPV18 detection from clinical endometrial samples, and the results were 100% consistent with clinical diagnosis. More importantly, even after the sample was diluted 100-fold, HPV16/18-infected cells could be accurately identified, showing the advantages of the system in early cancer screening. Moreover, for endometrial samples containing plenty of cells, the filter paper could be used to enrich cells by filtration, preventing the acidic fluid from impacting pH-induced colorimetric LAMP detection and realizing direct amplification for HPV identification without nucleic acid extraction. This easy-to-operate system that can analyze a wide range of samples will be suitable for routine on-site HPV screening, dramatically extending the applications and utility for rapid, near-patient nucleic acid testing.

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.

Advances in the detection and diagnosis of tuberculosis using optical-based devices

Tuberculosis (TB), a bacterial infection caused by Mycobacterium tuberculosis, is highly contagious and can lead to severe health complications if left untreated. This review article discusses the importance of early detection and treatment and its global incidence and epidemiology, emphasizing its impact on vulnerable populations and its role as a major cause of death worldwide. Furthermore, it highlights the challenges faced with diagnosing TB. To overcome these challenges, point-of-care devices have emerged as promising tools for rapid and accurate TB detection. These include devices such as nucleic acid amplification tests (NAATs), lateral flow assays (LFAs), and microfluidic-based assays, which offer advantages such as rapid results, portability, and the ability to detect drug-resistant strains. Optical-based devices, such as photonic micro-ring sensors, silicon platform-based sensors, plasmonic-based platforms, microfluidics, and smartphone imaging, are some of the highlighted optical-based devices with the potential to detect TB. These devices can detect TB in sputum samples with high sensitivity and specificity. Optical-based diagnostic devices have the potential to offer the advantages of detecting low concentrations of target molecules and being adaptable to detect multiple targets simultaneously. Using these devices in a clinical setting makes them suitable for their application in improving access to diagnostic testing that enables earlier detection and treatment of TB. Furthermore, these devices would improve TB's global health issue, which requires comprehensive research, prevention, and treatment efforts.

Mkit: A mobile nucleic acid assay based on a chitosan-modified minimalistic microfluidic chip (CM3-chip) and smartphone

Mobile sensing enabled by MS² technology, which integrates microfluidic and smartphone components, has seen many applications in recent years. In this direction, we developed an MS² platform (an integrated kit) for nucleic acid assay, which included a chitosan-modified minimalistic microfluidic chip (CM³-chip), a smartphone-based fluorescence detector (SF-detector), an APP for imaging and analysis, reagents, and accessories. Once the lysed sample was loaded into the CM³-chip modified by 1% concentration and 200-260 kDa molecular weight of chitosan, the following assay can be completed in approximately 1 h. The Mkit can detect 3 × 10° copies μL^-1 of plasmid DNA and its polymerase chain reaction (PCR) efficiency was 96.8%. The CM³-chip equipped for the Mkit can enrich nucleic acid from the pH = 5 of lysis buffer, instead of using conventional adsorption mediums such as the magnetic beads and silica gel membranes, which could result in unexpected impurity residuals and tedious cleaning operations. In addition, the performance of the Mkit equipped with the pristine chip was demonstrated to perform poorer than that coupled with the CM³-chip in which the enriched nucleic acid can be all used for "in-situ PCR". The universality, selectivity, and user-friendliness of the Mkit were also validated. We finally demonstrated the feasibility of the Mkit for testing artificially prepared infected samples. H5N6 and IAV-infected saliva samples provided the limits of detection of 5 × 10² copies mL^-1 and 3.24 × 10² copies mL^-1 per chamber, respectively. The streamlined assay and compact device should enable the great potential of the Mkit in research and potential diagnostic uses.

Elution-free DNA detection using CRISPR/Cas9-mediated light-up aptamer transcription: Toward all-in-one DNA purification and detection tube

Accurate and efficient detection of DNA is crucial for disease diagnosis and health monitoring. The traditional methods for DNA analysis involve multiple steps, including sample preparation, lysis, extraction, amplification, and detection. In this study, we present a one-step elution-free DNA analysis method based on the combination of clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated light-up aptamer transcription (CLAT) assay and a DNA-capturing poly(2-dimethylaminomethyl styrene) (pDMAMS)-coated tube. The sample solution and lysis buffer are added to the pDMAMS-coated tube, and the DNA is efficiently captured on the surface via electrostatic interaction and directly detected by CLAT assay. The ability of the CRISPR/Cas9 system to specifically recognize DNA enables direct detection of DNA captured on the pDMAMS-coated tube. The combination of CLAT assay and pDMAMS-coated tube simplifies DNA detection in a single tube without the need for complicated extraction steps, improving sensitivity. Our platform demonstrated attomolar sensitivity in the detection of target DNA in cell lysate (0.92 aM), urine (7.7 aM), and plasma (94.6 aM) samples within 1 h. The practical applicability of this method was further demonstrated in experiments with tumor-bearing mice. We believe that this approach brings us closer to an all-in-one DNA purification and detection tube system and has potential applications in tissue and liquid biopsies, as well as various other DNA sensing applications.

Portable general microfluidic device with complex electric field regulation functions for electrokinetic experiments

Electrokinetic sample manipulation is a key step for many kinds of microfluidic chips to achieve various functions, such as particle focusing and separation, fluid pumping and material synthesis. But these microfluidic experiments usually rely on large-scale signal generators for power supply, microscopes for imaging and other instruments for analysis, which hampers the portable process of microfluidic technology. Inspired by this situation, we herein designed a portable general microfluidic device (PGMD) with complex electric field regulation functions, which can accurately regulate static or continuous fluid samples. Through the graphical user interface (GUI) and modular design, the PGMD can generate multiple different electrical signals, and the micro-flow of fluid can be pumped through the built-in micropump, which can meet the requirements of most microfluidic experiments. Photos or videos of the microfluidic chip captured by the built-in microscope are received and displayed by a smartphone. We carried out a variety of microfluidic experiments such as induced-charge electroosmosis (ICEO), particle beam exit switching, thermal buoyancy flow and dielectrophoresis (DEP) on the PGMD. In addition, the PGMD can perform rapid microalgae concentration estimation in an outdoor environment, which can be used to guide microalgae cultivation, further demonstrating the development potential of this device in the field of microbial applications. Numerous results show that the PGMD has a high degree of integration and strong reliability, which expands the application of microfluidic electrokinetic experiments and provides technical support for the integration and portability of microfluidic experimental devices.

A sample-to-answer, quantitative real-time PCR system with low-cost, gravity-driven microfluidic cartridge for rapid detection of SARS-CoV-2, influenza A/B, and human papillomavirus 16/18

The pandemic of coronavirus disease 2019 (COVID-19), due to the novel coronavirus (SARS-CoV-2), has created an unprecedented threat to the global health system, especially in resource-limited areas. This challenge shines a spotlight on the urgent need for a point-of-care (POC) quantitative real-time PCR (qPCR) test for sensitive and rapid diagnosis of viral infections. In a POC system, a closed, single-use, microfluidic cartridge is commonly utilized for integration of nucleic acid preparation, PCR amplification and florescence detection. But, most current cartridge systems often involve complicated nucleic acid extraction via active pumping that relies on cumbersome external hardware, causing increases in system complexity and cost. In this work, we demonstrate a gravity-driven cartridge design for an integrated viral RNA/DNA diagnostic test that does not require auxiliary hardware for fluid pumping due to adopted extraction-free amplification. This microfluidic cartridge only contains two reaction chambers for nucleic acid lysis and amplification respectively, enabling a fast qPCR test in less than 30 min. This gravity-driven pumping strategy can help simplify and minimize the microfluidic cartridge, thus enabling high-throughput (up to 12 test cartridges per test) molecular detection via a small cartridge readout system. Thus, this work addresses the scalability limitation of POC molecular testing and can be run in any settings. We verified the analytical sensitivity and specificity of the cartridge testing for respiratory pathogens and sexually transmitted diseases using SARS-CoV-2, influenza A/B RNA samples, and human papillomavirus 16/18 DNA samples. Our cartridge system exhibited a comparable detection performance to the current gold standard qPCR instrument ABI 7500. Moreover, our system showed very high diagnostic accuracy for viral RNA/DNA detection that was well validated by ROC curve analysis. The sample-to-answer molecular testing system reported in this work has the advantages of simplicity, rapidity, and low cost, making it highly promising for prevention and control of infectious diseases in poor-resource areas.

Biosensors for rapid detection of bacterial pathogens in water, food and environment

Conventional techniques (e.g., culture-based method) for bacterial detection typically require a central laboratory and well-trained technicians, which may take several hours or days. However, recent developments within various disciplines of science and engineering have led to a major paradigm shift in how microorganisms can be detected. The analytical sensors which are widely used for medical applications in the literature are being extended for rapid and on-site monitoring of the bacterial pathogens in food, water and the environment. Especially, within the low-resource settings such as low and middle-income countries, due to the advantages of low cost, rapidness and potential for field-testing, their use is indispensable for sustainable development of the regions. Within this context, this paper discusses analytical methods and biosensors which can be used to ensure food safety, water quality and environmental monitoring. In brief, most of our discussion is focused on various rapid sensors including biosensors and microfluidic chips. The analytical performances such as the sensitivity, specificity and usability of these sensors, as well as a brief comparison with the conventional techniques for bacteria detection, form the core part of the discussion. Furthermore, we provide a holistic viewpoint on how future research should focus on exploring the synergy of different sensing technologies by developing an integrated multiplexed, sensitive and accurate sensors that will enable rapid detection for food safety, water and environmental monitoring.

Smartphone-Based Multiplexed Biosensing Tools for Health Monitoring

Many emerging technologies have the potential to improve health care by providing more personalized approaches or early diagnostic methods. In this review, we cover smartphone-based multiplexed sensors as affordable and portable sensing platforms for point-of-care devices. Multiplexing has been gaining attention recently for clinical diagnosis considering certain diseases require analysis of complex biological networks instead of single-marker analysis. Smartphones offer tremendous possibilities for on-site detection analysis due to their portability, high accessibility, fast sample processing, and robust imaging capabilities. Straightforward digital analysis and convenient user interfaces support networked health care systems and individualized health monitoring. Detailed biomarker profiling provides fast and accurate analysis for disease diagnosis for limited sample volume collection. Here, multiplexed smartphone-based assays with optical and electrochemical components are covered. Possible wireless or wired communication actuators and portable and wearable sensing integration for various sensing applications are discussed. The crucial features and the weaknesses of these devices are critically evaluated.

Modular micro-PCR system for the onsite rapid diagnosis of COVID-19

Effective containment of the COVID-19 pandemic requires rapid and accurate detection of the pathogen. Polymerase chain reaction (PCR) remains the gold standard for COVID-19 confirmation. In this article, we report the performance of a cost-effective modular microfluidic reverse transcription (RT)-PCR and RT-loop mediated isothermal amplification (RT-LAMP) platform, Epidax®, for the point-of-care testing and confirmation of SARS-CoV-2. This platform is versatile and can be reconfigured either for screening using endpoint RT-PCR or RT-LAMP tests or for confirmatory tests using real-time RT-PCR. Epidax® is highly sensitive and detects as little as 1 RNA copy per µL for real-time and endpoint RT-PCR, while using only half of the reagents. We achieved comparable results with those of a commercial platform when detecting SARS-CoV-2 viruses from 81 clinical RNA extracts. Epidax® can also detect SARS-CoV-2 from 44 nasopharyngeal samples without RNA extraction by using a direct RT-PCR assay, which shortens the sample-to-answer time to an hour with minimal user steps. Furthermore, we validated the technology using an RT-LAMP assay on 54 clinical RNA extracts. Overall, our platform provides a sensitive, cost-effective, and accurate diagnostic solution for low-resource settings.

A visual portable microfluidic experimental device with multiple electric field regulation functions

High portability and miniaturization are two of the most important objectives pursued by microfluidic methods. However, there remain many challenges for the design of portable and visual microfluidic devices (e.g., electrokinetic experiments) due to the use of a microscope and power supply. To this end, we report a visual portable microfluidic experimental device (PMED) with multiple electric field regulation functions, which can realize the electric field regulation functions of various basic microfluidic experiments through modular design. The internal reaction process of the microfluidic chip is displayed by a smartphone, and the experimental results are analyzed using a mobile phone application (APP). Taking the induced-charge electroosmosis (ICEO) particle focusing phenomenon as an example, we carried out detailed experiments on PMED and obtained conclusions consistent with numerical simulations. In addition to ICEO experiments, other functions such as alternating electroosmosis (ACEO), thermal buoyancy convection, and dielectrophoresis (DEP) can be realized by replacing module-specific covers. The device expands the application of microfluidic experiments and provides a certain reference for the further integration and portability of subsequent microfluidic experiment devices.

A sample-to-answer DNA detection microfluidic system integrating sample pretreatment and smartphone-readable gradient plasmonic photothermal continuous-flow PCR

We report a microfluidic system integrating sample pretreatment and smartphone-readable gradient plasmonic photothermal continuous-flow PCR, paving the way for low-cost and rapid implementation of PCR diagnostics.

Amplification-free smartphone-based attomolar HBV detection

Classical gold standard HBV detection relies on expensive devices and complicated procedures, thus is always restricted in large-scale hospitals and centers for disease control and prevention. To extend HBV detection to primary clinics especially in underdeveloped areas, we design amplification-free smartphone-based attomolar HBV detecting technique based on single molecule sensing. Verified by synthesized HBV target DNA, this technique reaches a detection limit at attomolar concentration (100 aM); and verified by 110 clinical samples, it also reaches a rather high sensitivity of 10⁴ copy/mL (≈2000 IU/mL) with a high accuracy of 93.64% certificated by gold standard HBV detecting devices. Besides, this technique can quantify HBV viral load in 70 min only using portable and inexpensive devices as well as simple operations. Because of its cost-effective, field-portable and operable design, highly sensitive and selective detecting capability and wireless data connectivity, this technique can be potentially used in mobile HBV diagnoses and share HBV epidemic information especially in resource limited situations.

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.

A portable centrifugal genetic analyzer for multiplex detection of feline upper respiratory tract disease pathogens

We present a portable genetic analyzer with an integrated centrifugal disc which is equipped with a glass-filter extraction column for purifying nucleic acid (NA) and multiple reaction chambers for analyzing major feline upper respiratory tract disease (FURTD) pathogens. We targeted four kinds of FURTD including Feline herpesvirus 1 (FHV), Mycoplasma felis (MPF), Bordetella bronchiseptica (BDB), and Chlamydophila felis (CDF). The portable genetic analyzer consists of a spinning motor, two pairs of Peltier heaters, two Minco heater, fluorescent optics, a touchscreen, and software for data analysis, so loop-mediated isothermal amplification (LAMP) or polymerase chain reaction (PCR) can be performed. The overall size of the genetic analyzer was 28 cm × 28 cm × 26 cm and the weight was 10 kg, which was deliverable for point-of-care testing (POCT). Owing to the sophisticated microchannel design and spinning program, the serial injection of the sample solution, the washing solution, and the elution solution was executed through a glass filter membrane for nucleic acid (NA) extraction, and then the cocktail with the purified genome was aliquoted into 9 reaction chambers for LAMP or PCR. The whole process for the LAMP reaction or the PCR was completed within 1.5 h. The fluorescence profiles by a scanning mode showed the matched results between the LAMP and the PCR.

Sample-to-answer COVID-19 nucleic acid testing using a low-cost centrifugal microfluidic platform with bead-based signal enhancement and smartphone read-out

With its origin estimated around December 2019 in Wuhan, China, the ongoing SARS-CoV-2 pandemic is a major global health challenge. The demand for scalable, rapid and sensitive viral diagnostics is thus particularly pressing at present to help contain the rapid spread of infection and prevent overwhelming the capacity of health systems. While high-income countries have managed to rapidly expand diagnostic capacities, such is not the case in resource-limited settings of low- to medium-income countries. Aiming at developing cost-effective viral load detection systems for point-of-care COVID-19 diagnostics in resource-limited and resource-rich settings alike, we report the development of an integrated modular centrifugal microfluidic platform to perform loop-mediated isothermal amplification (LAMP) of viral RNA directly from heat-inactivated nasopharyngeal swab samples. The discs were pre-packed with dried n-benzyl-n-methylethanolamine modified agarose beads used to selectively remove primer dimers, inactivate the reaction post-amplification and allowing enhanced fluorescence detection via a smartphone camera. Sample-to-answer analysis within 1 hour from sample collection and a detection limit of approximately 100 RNA copies in 10 μL reaction volume were achieved. The platform was validated with a panel of 162 nasopharyngeal swab samples collected from patients with COVID-19 symptoms, providing a sensitivity of 96.6% (82.2-99.9%, 95% CI) for samples with Ct values below 26 and a specificity of 100% (90-100%, 95% CI), thus being fit-for-purpose to diagnose patients with a high risk of viral transmission. These results show significant promise towards bringing routine point-of-care COVID-19 diagnostics to resource-limited settings.

Recent progress in smartphone-based techniques for food safety and the detection of heavy metal ions in environmental water

Emerging smartphone-based point-of-care tests (POCTs) are cost-effective, precise, and easy to implement in resource-limited areas. Thus, they are considered a potential alternative to conventional diagnostic testing. This review explores food safety and the detection of metal ions in environmental water based on unprecedented smartphone technology. Specifically, we provide an overview of various methods used for target analyte detection (antibiotics, enzymes, mycotoxins, pathogens, pesticides, small molecules, and metal ions), such as colorimetric, fluorescence, microscopic imaging, and electrochemical methods. This paper performs a comprehensive review of smartphone-based POCTs developed in the last three years (2018-2020) and evaluates their relative advantages and limitations. Moreover, we discuss the imperative role of new technology in the progress of POCTs. Sensor materials (metal nanoparticles, carbon dots, quantum dots, organic substrates, etc.) and detection techniques (paper-based, later flow assay, microfluidic platform, etc.) involved in POCTs based on smartphones, and the challenges faced by these techniques, are addressed.

MS2 device: smartphone-facilitated mobile nucleic acid analysis on microfluidic device

Mobile sensing based on the integration of microfluidic devices and smartphones, so-called MS2 technology, has enabled many applications over recent years and continues to stimulate growing interest in both research communities and industries. In particular, MS2 technology has been proven to be able to be applied to molecular diagnostic analysis and can be implemented for basic research and clinical testing. However, the currently reported MS2-based nucleic acid analysis system has limited use in practical applications, because it is not integrated with quantitative PCR, multiplex PCR, and isothermal amplification functions, and lacks temperature control, image acquisition and real-time processing units with excellent performance. To provide a more universal and powerful platform, we here developed a novel MS2 device by integrating a thermocycler, a multi fluorescence detection unit, a PCR chip, an isothermal chip, and a smartphone. The MS2 device was approximately 325 mm (L) × 200 mm (W) × 200 mm (H) in volume and only 5 kg in weight, and showed an average power consumption of about 38.4 W. The entire nucleic acid amplification and analysis could be controlled through a self-made smartphone App. The maximum heating and cooling rates were 5 °C s-1 and 4 °C s-1, respectively. The entire PCR could be completed within 65 min. The temperature uniformity was less than 0.1 °C. Besides, the temperature stability over time (30 min) was within ±0.04 °C. Four optical channels were integrated (FAM, HEX, TAMRA, and ROX) on the MS2 device. In particular, the PCR-based detection sensitivity reached 1 copy per μL, and the amplification efficiency was calculated to be 106.8%. Besides, the MS2 device also was compatible with multiplex PCR and isothermal amplification. In short, the MS2 device showed performance consistent with that of traditional commercial equipment. Thus, the MS2 device provides an easy and integrated experimental platform for molecular diagnostic-related research and potential medical diagnostic applications.

High-throughput human DNA purification on a centrifugal microfluidic device for rapid forensic sex-typing

We introduce a novel centrifugal disc for purifying nucleic acid (NA) in a high-throughput manner to perform the human sex-typing of forensic samples. The centrifugal disc was designed with double-sided etched channels to fabricate 30 extraction units, which was capable of purifying 30 forensic samples in a single run. In order to introduce the washing solution (70% ethanol) and the elution buffer for the 30 extraction units in an automatic manner, we designed the aliquoting chambers that were connected with a zigzag delivery channel. The super-hydrophobic zigzag-shaped aliquot structure plays a crucial role in automatically dividing the washing solution and the elution buffer into 30 aliquots with one injection shot. The Whatman glass filter paper was used as an NA extraction matrix and sophisticated passive valves were equipped to avoid the overflowing of these buffers to the neighboring chamber during the injection. To operate the disc, we developed a portable workstation that consists of a buffer storage system, a buffer injection system, and a spinning unit. The entire process was automatically operated by the in-house portable workstation. Genomic DNA extraction using thirty forensic samples was completed in 10 min. Using the purified genomic DNA, we performed a loop-mediated isothermal amplification (LAMP) reaction for sex-typing by targeting the human alphoid repeat sequence of the Y-chromosome and the human 18S rRNA. The combination of the high-throughput centrifugal disc for NA extraction and the LAMP reaction enables us to complete the genetic sex-typing in 30 min.

Advanced Signal-Amplification Strategies for Paper-Based Analytical Devices: A Comprehensive Review

Paper-based analytical devices (PADs) have emerged as a promising approach to point-of-care (POC) detection applications in biomedical and clinical diagnosis owing to their advantages, including cost-effectiveness, ease of use, and rapid responses as well as for being equipment-free, disposable, and user-friendly. However, the overall sensitivity of PADs still remains weak, posing a challenge for biosensing scientists exploiting them in clinical applications. This review comprehensively summarizes the current applicable potential of PADs, focusing on total signal-amplification strategies that have been applied widely in PADs involving colorimetry, luminescence, surface-enhanced Raman scattering, photoacoustic, photothermal, and photoelectrochemical methods as well as nucleic acid-mediated PAD modifications. The advances in signal-amplification strategies in terms of signal-enhancing principles, sensitivity, and time reactions are discussed in detail to provide an overview of these approaches to using PADs in biosensing applications. Furthermore, a comparison of these methods summarizes the potential for scientists to develop superior PADs. This review serves as a useful inside look at the current progress and prospective directions in using PADs for clinical diagnostics and provides a better source of reference for further investigations, as well as innovations, in the POC diagnostics field.

Advances in point-of-care nucleic acid extraction technologies for rapid diagnosis of human and plant diseases

Global health and food security constantly face the challenge of emerging human and plant diseases caused by bacteria, viruses, fungi, and other pathogens. Disease outbreaks such as SARS, MERS, Swine Flu, Ebola, and COVID-19 (on-going) have caused suffering, death, and economic losses worldwide. To prevent the spread of disease and protect human populations, rapid point-of-care (POC) molecular diagnosis of human and plant diseases play an increasingly crucial role. Nucleic acid-based molecular diagnosis reveals valuable information at the genomic level about the identity of the disease-causing pathogens and their pathogenesis, which help researchers, healthcare professionals, and patients to detect the presence of pathogens, track the spread of disease, and guide treatment more efficiently. A typical nucleic acid-based diagnostic test consists of three major steps: nucleic acid extraction, amplification, and amplicon detection. Among these steps, nucleic acid extraction is the first step of sample preparation, which remains one of the main challenges when converting laboratory molecular assays into POC tests. Sample preparation from human and plant specimens is a time-consuming and multi-step process, which requires well-equipped laboratories and skilled lab personnel. To perform rapid molecular diagnosis in resource-limited settings, simpler and instrument-free nucleic acid extraction techniques are required to improve the speed of field detection with minimal human intervention. This review summarizes the recent advances in POC nucleic acid extraction technologies. In particular, this review focuses on novel devices or methods that have demonstrated applicability and robustness for the isolation of high-quality nucleic acid from complex raw samples, such as human blood, saliva, sputum, nasal swabs, urine, and plant tissues. The integration of these rapid nucleic acid preparation methods with miniaturized assay and sensor technologies would pave the road for the "sample-in-result-out" diagnosis of human and plant diseases, especially in remote or resource-limited settings.

Detection of Bacterial and Viral Pathogens Using Photonic Point-of-Care Devices

Infectious diseases caused by bacteria and viruses are highly contagious and can easily be transmitted via air, water, body fluids, etc. Throughout human civilization, there have been several pandemic outbreaks, such as the Plague, Spanish Flu, Swine-Flu, and, recently, COVID-19, amongst many others. Early diagnosis not only increases the chance of quick recovery but also helps prevent the spread of infections. Conventional diagnostic techniques can provide reliable results but have several drawbacks, including costly devices, lengthy wait time, and requirement of trained professionals to operate the devices, making them inaccessible in low-resource settings. Thus, a significant effort has been directed towards point-of-care (POC) devices that enable rapid diagnosis of bacterial and viral infections. A majority of the POC devices are based on plasmonics and/or microfluidics-based platforms integrated with mobile readers and imaging systems. These techniques have been shown to provide rapid, sensitive detection of pathogens. The advantages of POC devices include low-cost, rapid results, and portability, which enables on-site testing anywhere across the globe. Here we aim to review the recent advances in novel POC technologies in detecting bacteria and viruses that led to a breakthrough in the modern healthcare industry.

Multiplex and visual detection of African Swine Fever Virus (ASFV) based on Hive-Chip and direct loop-mediated isothermal amplification

African swine fever is caused by African swine fever virus (ASFV), and has a mortality rate approaching 100%. It has already caused tremendous economy lost around the world. Without effective vaccine, rapid and accurate on-site detection plays an indispensable role in controlling outbreaks. Herein, by combining Hive-Chip and direct loop-mediated isothermal amplification (LAMP), we establish a multiplex and visual detection platform. LAMP primers targeting five ASFV genes (B646L, B962L, C717R, D1133L, and G1340L) were designed and pre-fixed in Hive-Chip. On-chip LAMP showed the limits of detection (LOD) of ASFV synthetic DNAs and mock samples are 30 and 50 copies per microliter, respectively, and there is no cross-reaction among the target genes. The overall performance of our platform is comparable to that of the commercial kits. From sample preparation to results readout, the entire process takes less than 70 min. Multiplex detection of real samples of ASFV and other swine viruses further demonstrates the high sensitivity and specificity of Hive-Chip. Overall, our platform provides a promising option for on-site, fast and accurate detection of ASFV.

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Hive-Chip firstly realized simultaneous detection of multiple genes of ASFV, largely avoiding false-negative results.

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Without nucleic acid extraction, direct LAMP was firstly incorporated into the Hive-Chip for visual detection.

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Because very little operation and no complicate instrument is required, on-site detection is possible for this platform.

A scalable microfluidic chamber array for sample-loss-free and bubble-proof sample compartmentalization by simple pipetting

Sample compartmentalization is a pivotal technique in many bioanalytical applications, such as multiplex polymerase chain reaction (PCR) and digital PCR (dPCR). In this study, we successfully developed a novel self-compartmentalization device containing an array of microchambers, each of which is connected to a main microchannel with three capillary burst valves (CBVs) for fluid switching and partitioning. As these CBVs can be automatically opened in a predefined sequence, an incoming solution can be spontaneously directed into the chamber and held in place without further mixing. After that, either air or oil can be loaded into the main channel to isolate each chamber completely. By optimizing the relative burst pressures of the CBVs, a 100% sample utilization rate can be achieved even using a manual pipette and air bubbles in the sample cannot interfere with the loading. In addition, the number of the microchambers in an array can be easily scaled from a few to tens of thousands. To verify the feasibility of this self-compartmentalization method, we successfully conducted mock multiplex loop-mediated isothermal amplifications (LAMP) in an array that contains 144 microchambers, proving that our design method will provide a robust and versatile platform for various sample discretization purposes in the future.

[Detection methods for results of a loop-mediated isothermal amplification of DNA.]

The loop mediated isothermal amplification (LAMP) was developed by T. Notomi et al. in 2000. It has become one of the most promising methods for point-of-care diagnostics due to its accuracy, sensitivity and ease of execution. In this review, various methods for detecting the results of the LAMP reaction are considered; their advantages and disadvantages are revealed. Methods for detecting LAMP results can be divided into indirect and direct. Indirect methods aimed at detecting changes in the chemical composition of the reaction mixture include real-time turbidimetry, fluorescence detection with calcein, colorimetric detection with hydroxynaphthol blue, and detection using modified gold nanoparticles. Direct methods based on the detection of accumulation amplicons during the reaction include fluorimetric detection with intercalating dyes, resonance fluorescence energy transfer, enzyme immunoassay, immunochromatography, using cationic polymers and gold nanoparticles. The development in the field of point-of-care diagnostics is characterized by a pronounced tendency to miniaturization, the LAMP reaction on microchips and microfluidic devices with an electrochemical or optical detection method. The most promising for the diagnosis of infectious diseases are turbidimetry methods and the use of intercalating dyes. The development of portable domestic instruments for detecting of LAMP results based on real-time fluorescence detection or turbidimetry will contribute to the widespread introduction of the method into clinical laboratory diagnostic practice. A literature research was conducted in the Pubmed ncbi based on keywords.

An ultraportable and versatile point-of-care DNA testing platform

Point-of-care testing (POCT) has broad applications in resource-limited settings. Here, a POCT platform termed POCKET (point-of-care kit for the entire test) is demonstrated that is ultraportable and versatile for analyzing multiple types of DNA in different fields in a sample-to-answer manner. The POCKET is less than 100 g and smaller than 25 cm in length. The kit consists of an integrated chip (i-chip) and a foldable box (f-box). The i-chip integrates the sample preparation with a previously unidentified, triple signal amplification. The f-box uses a smartphone as a heater, a signal detector, and a result readout. We detected different types of DNA from clinics to environment to food to agriculture. The detection is sensitive (<10³ copies/ml), specific (single-base differentiation), speedy (<2 hours), and stable (>10 weeks shelf life). This inexpensive, ultraportable POCKET platform may become a versatile sample-to-answer platform for clinical diagnostics, food safety, agricultural protection, and environmental monitoring.

Paper-based microfluidics for rapid diagnostics and drug delivery

Paper is a common material that is promising for constructing microfluidic chips (lab-on-a-paper) for diagnostics and drug delivery for biomedical applications. In the past decade, extensive research on paper-based microfluidics has accumulated a large number of scientific publications in the fields of biomedical diagnosis, food safety, environmental health, drug screening and delivery. This review focuses on the recent progress on paper-based microfluidic technology with an emphasis on the design, optimization and application of the technology platform, in particular for medical diagnostics and drug delivery. Novel advances have concentrated on engineering paper devices for point-of-care (POC) diagnostics, which could be integrated with nucleic acid-based tests and isothermal amplification experiments, enabling rapid sample-to-answer assays for field testing. Among the isothermal amplification experiments, loop-mediated isothermal amplification (LAMP), an extremely sensitive nucleic acid test, specifically identifies ultralow concentrations of DNA/RNA from practical samples for diagnosing diseases. We thus mainly focus on the paper device-based LAMP assay for the rapid infectious disease diagnosis, foodborne pathogen analysis, veterinary diagnosis, plant diagnosis, and environmental public health evaluation. We also outlined progress on paper microfluidic devices for drug delivery. The paper concludes with a discussion on the challenges of this technology and our insights into how to advance science and technology towards the development of fully functional paper devices in diagnostics and drug delivery.

A Novel Microfluidic Device Integrated with Chitosan-Modified Capillaries for Rapid ZIKV Detection

The outbreak of Zika virus (ZIKV) has posed a great challenge to public health in recent years. To address the urgent need of ZIKV RNA assays, we integrate the microfluidic chip embedded with chitosan-modified silicon dioxide capillaries, smartphone-based detection unit to be a C³-system for the rapid extraction and detection of ZIKV RNA. The C³-system is characterized by: (1) four chitosan-modified silicon dioxide capillaries integrated in the microfluidic chip for target ZIKV RNA enrichment and “in situ PCR” (polymerase chain reaction) amplification; (2) smartphone-based point of care (POC) device consisting of a pneumatic subsystem for controlling the nucleic acid extraction processes in the microfluidic chip, a heating subsystem for sample lysis and PCR amplification, and an optical subsystem for signal acquisition. The entire detection processes including sample lysis, ZIKV RNA enrichment, and reverse-transcription polymerase chain reaction (RT-PCR) is achieved in the microfluidic chip. Moreover, PCR buffers can be directly loaded into the chitosan-modified silicon dioxide capillaries for “in situ PCR”, in which the captured ZIKV RNA is directly used for downstream PCR without any loss. ZIKV RNA extracted by the C³-system can be successfully recovered at very low concentrations of 50 transducing units (TU)/mL from crude human saliva. This means that our method of detecting viremia in patients infected with ZIKV is reliable.

A Fully Integrated In Vitro Diagnostic Microsystem for Pathogen Detection Developed Using a "3D Extensible" Microfluidic Design Paradigm

Microfluidics is facing critical challenges in the quest of miniaturizing, integrating, and automating in vitro diagnostics, including the increasing complexity of assays, the gap between the macroscale world and the microscale devices, and the diverse throughput demands in various clinical settings. Here, a "3D extensible" microfluidic design paradigm that consists of a set of basic structures and unit operations was developed for constructing any application-specific assay. Four basic structures-check valve (in), check valve (out), double-check valve (in and out), and on-off valve-were designed to mimic basic acts in biochemical assays. By combining these structures linearly, a series of unit operations can be readily formed. We then proposed a "3D extensible" architecture to fulfill the needs of the function integration, the adaptive "world-to-chip" interface, and the adjustable throughput in the X, Y, and Z directions, respectively. To verify this design paradigm, we developed a fully integrated loop-mediated isothermal amplification microsystem that can directly accept swab samples and detect Chlamydia trachomatis automatically with a sensitivity one order higher than that of the conventional kit. This demonstration validated the feasibility of using this paradigm to develop integrated and automated microsystems in a less risky and more consistent manner.

A smartphone-assisted microfluidic chemistry analyzer using image-based colorimetric assays for multi-index monitoring of diabetes and hyperlipidemia

A smartphone-assisted microfluidic chemistry analyzer using an image-based colorimetric detection method was successfully developed for the simultaneous analysis of three diabetes- and hyperlipidemia-related indexes, glucose (GLU), triglyceride (TG), and total cholesterol (TC). A fan-shaped microfluidic chip was designed and optimized to reliably allocate a premixed serum sample into four reaction chambers by a simple pipetting. The color changes of the peroxidase-H₂O₂ enzymatic reactions in the chambers were captured and analyzed using a smartphone-controlled analyzer with a LED light source and a CCD camera. The highly quantitative relationships between the analyte concentrations and the color characteristic values of the green channel of the captured images were successfully established, enabling accurate and reproducible detections of GLU, TG, and TC simultaneously at a low cost. The parallel analyses of 111 serum samples using our system and a conventional chemistry analyzer were conducted, yielding an excellent correlation and consistency between these two systems. This study proved the feasibility of performing the multi-index monitoring of diabetes, hyperlipidemia, and other chronic diseases on a point-of-care platform at a high fidelity, but a low cost.