Integrated microneedle-smartphone nucleic acid amplification platform for in-field diagnosis of plant diseases

In-situ fixation (ISF): A rapid, reusable, and high-throughput nucleic acid extraction method for plant molecular analysis

Rapid, sensitive, and high-throughput nucleic acid testing (NAT) is crucial for diverse applications in plant breeding and crop protection, including genotyping, transgenic detection, and pathogen diagnosis. However, efficient plant DNA/RNA extraction methods suitable for point-of-care testing remain a significant challenge due to the complex plant cell composition. Here, we present a novel in-situ fixation (ISF) method that eliminates the need for sample grinding, water bath, centrifugation, and pipetting, enabling rapid (6 min) and high-throughput (96 samples) nucleic acid extraction from plant leaves. The ISF method fixes DNA/RNA within the cells, allowing reuse of the extraction reagents without cross-contamination. The extracted nucleic acids are suitable for various NAT techniques, including PCR, RT-PCR, qPCR, and LAMP. We demonstrate the integration of ISF with qPCR and LAMP for rapid detection of genetically modified content and plant pathogens. Furthermore, an ISF-based high-throughput device was developed for efficient genotyping of rice hybrid offspring. The ISF method's simplicity, reusability, and compatibility with field-deployable isothermal amplification offer a promising solution for on-site, rapid, and cost-effective plant molecular analysis.

Sensing technology empowering food safety: research progress of SERS-assisted multimodal biosensing toward food hazard factors

Food is the main source of human energy and nutrition, but once it is contaminated with hazardous factors, such as biotoxins, pesticide residues, etc., it will seriously damage health. This paper reviews the research progress of biosensors based on surface-enhanced Raman scattering (SERS) in the detection of food hazard factors. First, the basic principle, substrate and assay mode of SERS technology, as well as related design and sensing strategy mechanisms, are introduced. Then, the design idea of multimodal biosensors combining SERS with microfluidic, fluorescence, colorimetric, electrochemical (EC), molecular imprinting and other technologies is expounded to improve the analysis accuracy and specificity. Then the application results of multimodal biosensors based on SERS sensing toward food hazard factors are discussed, and the necessity of its development is illustrated. Finally, the future development direction of this field is prospected, which provides a reference for promoting the research and application of multimodal biosensors based on SERS.

Non-destructive seed genotyping via microneedle-based DNA extraction

Crop breeding plays an essential role in addressing food security by enhancing crop yield, disease resistance and nutritional value. However, the current crop breeding process faces multiple challenges and limitations, especially in genotypic evaluations. Traditional methods for seed genotyping remain labour-intensive, time-consuming and cost-prohibitive outside of large-scale breeding programs. Here, we present a handheld microneedle (MN)-based seed DNA extraction platform for rapid, non-destructive and in-field DNA isolation from crop seeds for instant marker analysis. Using soybean seeds as a case study, we demonstrated the use of polyvinyl alcohol (PVA) MN patches for the successful extraction of DNA from softened soybean seeds. This extraction technology maintained high seed viability, showing germination rates of 82% and 79%, respectively, before and after MN sampling. The quality of MN-extracted DNA was sufficient for various genomic analyses, including PCR, LAMP and whole-genome sequencing. Importantly, this MN patch method also allowed for the identification of specific genetic differences between soybean varieties. Additionally, we designed a 3D-printed extraction device, which enabled multiplexed seed DNA extraction in a microplate format. In the future, this method could be applied at scale and in-field for crop seed DNA extraction and genotyping analysis.

Smartphones as a platform for molecular analysis: concepts, methods, devices and future potential

Over the past 15 years, smartphones have had a transformative effect on everyday life. These devices also have the potential to transform molecular analysis over the next 15 years. The cameras of a smartphone, and its many additional onboard features, support optical detection and other aspects of engineering an analytical device. This article reviews the development of smartphones as platforms for portable chemical and biological analysis. It is equal parts conceptual overview, technical tutorial, critical summary of the state of the art, and outlook on how to advance smartphones as a tool for analysis. It further discusses the motivations for adopting smartphones as a portable platform, summarizes their enabling features and relevant optical detection methods, then highlights complementary technologies and materials such as 3D printing, microfluidics, optoelectronics, microelectronics, and nanoparticles. The broad scope of research and key advances from the past 7 years are reviewed as a prelude to a perspective on the challenges and opportunities for translating smartphone-based lab-on-a-chip devices from prototypes to authentic applications in health, food and water safety, environmental monitoring, and beyond. The convergence of smartphones with smart assays and smart apps powered by machine learning and artificial intelligence holds immense promise for realizing a future for molecular analysis that is powerful, versatile, democratized, and no longer just the stuff of science fiction.

Loop-Mediated Isothermal Amplification Detection of Phytophthora kernoviae, P. ramorum, and the P. ramorum NA1 Lineage on a Microfluidic Chip and Smartphone Platform

Rapid, field-deployable assays such as loop-mediated isothermal amplification (LAMP) are critical for detecting nursery and forest pathogens such as Phytophthora ramorum and P. kernoviae to prevent pathogen spread. We developed and validated four LAMP assays for genus-level detection of Phytophthora spp., species-level detection of P. kernoviae and P. ramorum, and lineage-level detection of the P. ramorum NA1 lineage. The cross-reactivity of the two species-specific LAMP assays was evaluated using a set of 18 Phytophthora spp. known to infect nursery crop hosts. The correct target species were detected by the species-level LAMP assays. The Phytophthora spp. LAMP assay was evaluated against 27 Phytophthora spp. and other bacterial and fungal pathogens and reacted with all the Phytophthora spp. evaluated but no other bacterial or fungal species. The limit of detection (LOD) of the P. kernoviae LAMP was 100 fg/µl, and the LOD of the P. ramorum LAMP assay was 1 pg/µl of DNA. The NA1 LAMP assay was tested against the NA1, NA2, EU1, and EU2 lineages of P. ramorum and was lineage-specific but had a higher LOD (100 pg/µl) than the species-specific LAMP assays. Both P. ramorum and P. kernoviae LAMP assays were highly precise (>0.94) in detecting the respective pathogens in symptomatic rhododendron leaves and co-inoculation experiments. The four LAMP assays were run in tandem on a microfluidic chip and smartphone platform and can be used in the field to detect and monitor spread of these regulatory Phytophthora spp. in forest and/or nursery settings.

Portable solutions for plant pathogen diagnostics: development, usage, and future potential

The increasing prevalence of plant pathogens presents a critical challenge to global food security and agricultural sustainability. While accurate, traditional diagnostic methods are often time-consuming, resource-intensive, and unsuitable for real-time field applications. The emergence of portable diagnostic tools represents a paradigm shift in plant disease management, offering rapid, on-site detection of pathogens with high accuracy and minimal technical expertise. This review explores portable diagnostic technologies' development, deployment, and future potential, including handheld analyzers, smartphone-integrated systems, microfluidics, and lab-on-a-chip platforms. We examine the core technologies underlying these devices, such as biosensors, nucleic acid amplification techniques, and immunoassays, highlighting their applicability to detect bacterial, viral, and fungal pathogens in diverse agricultural settings. Furthermore, the integration of these devices with digital technologies, including the Internet of Things (IoT), artificial intelligence (AI), and machine learning (ML), is transforming disease surveillance and management. While portable diagnostics have clear advantages in speed, cost-effectiveness, and user accessibility, challenges related to sensitivity, durability, and regulatory standards remain. Innovations in nanotechnology, multiplex detection platforms, and personalized agriculture promise to further enhance the efficacy of portable diagnostics. By providing a comprehensive overview of current technologies and exploring future directions, this review underscores the critical role of portable diagnostics in advancing precision agriculture and mitigating the impact of plant pathogens on global food production.

Achieving precise dual detection: One-tube reverse transcription-recombinase aided amplification (RT-RAA) combined with lateral flow strip (LFS) assay for RNA and DNA target genes from pepper mild mottle virus and Colletotrichum species in crude plant samples

Ensuring the detection sensitivity of both RNA-derived and DNA-derived target genes in a single reaction has posed a significant challenge for on-site detection of plant pathogens. This challenge was addressed by developing a one-tube dual RT-RAA assay combined with LFS for the rapid on-site detection of pepper mild mottle virus (PMMoV) and four Colletotrichum species causing anthracnose in Solanaceous crops. By testing four different combinations of primer groups, two combinations were precisely adjusted within the dual RT-RAA system to balance amplification efficiency and maintain consistent levels of amplification in crude plant samples. Utilizing commercially accessible small-scale equipment and following a streamlined optimization strategy, the assay achieved a limit of detection of 0.32 copies/μL of target genes in the reaction. Importantly, it demonstrated no cross-reactivity with other plant pathogens, thereby affirming the high sensitivity and specificity of the developed dual RT-RAA-LFS detection assay. Moreover, the entire process took only 25 min from sample collection to the visible presentation of results. The assay was validated with 60 field samples and 10 seed samples, producing results consistent with reverse transcription quantitative polymerase chain reaction (RT-qPCR). Notably, it successfully detected PMMoV in systemic leaves without visible symptoms three days post-inoculation, underscoring its effectiveness in early disease detection. This streamlined strategy offers a valuable approach for rapid, low-cost, and highly sensitive on-site simultaneous detection of RNA genome-contained PMMoV and DNA genome-contained Colletotrichum species.

A Smartphone-Enabled Colorimetric Microneedle Sensing Platform for Rapid Detection of Ascorbic Acid in Fruits

Achieving rapid extraction and detection of analytical solutions from plant tissues to circumvent cumbersome procedures and reduce the dependence on detection instruments remains a challenge. Herein, a colorimetric microneedle integrated platform was developed for the rapid extraction and detection of plant fluids for testing purposes. Colorimetric microneedle patches (CMPs) offer a swift and effective method to swiftly extract and detect ascorbic acid (AA) within 10 min from various fruit crops like mango, nectarine, apple, pear, and kiwifruit, facilitated by a smartphone application. CMPs are constructed for the rapid and sensitive analysis of AA with good linearity amid the range 0.05-25 μM and a low limit of detection of 30 nM. The novel CMPs demonstrate significant potential as a rapid detection platform for AA in plants. CMPs offer significant advantages over traditional ultraviolet spectrophotometry, such as simplified operational procedures and accelerated extraction and detection processes. This establishes robust groundwork for conducting in situ extraction and molecular detection of diverse crops across a spectrum of application scenarios.

Microneedle sensors for dermal interstitial fluid analysis

The rapid advancement in personalized healthcare has driven the development of wearable biomedical devices for real-time biomarker monitoring and diagnosis. Traditional invasive blood-based diagnostics are painful and limited to sporadic health snapshots. To address these limitations, microneedle-based sensing platforms have emerged, utilizing interstitial fluid (ISF) as an alternative biofluid for continuous health monitoring in a minimally invasive and painless manner. This review aims to provide a comprehensive overview of microneedle sensor technology, covering microneedle design, fabrication methods, and sensing strategy. Additionally, it explores the integration of monitoring electronics for continuous on-body monitoring. Representative applications of microneedle sensing platforms for both monitoring and therapeutic purposes are introduced, highlighting their potential to revolutionize personalized healthcare. Finally, the review discusses the remaining challenges and future prospects of microneedle technology.

Graphical Abstract

Corn-inspired high-density plasmonic metal-organic frameworks microneedles for enhanced SERS detection of acetaminophen

Effective monitoring of acetaminophen (APAP) dosage is crucial for preventing antipyretic abuse, ensuring therapeutic efficacy, and minimizing toxic effects. However, existing self-monitoring methods are limited. In this study, we designed a plasmonic microneedle (MN) sensor for real-time nondestructive monitoring of acetaminophen levels in dermal interstitial fluid (ISF) by employing a handheld Raman spectrometer. The fabricated MN sensor incorporated a high-density plasmonic MOFs known as HDPM, which unique structure of large specific surface area, specific pore structure as well as high density gold nanospheres packing enabled the excellent performance of selective ISF drug enrichment and surface-enhanced Raman scattering (SERS). The maximum electric field enhancement factor of the HDPM nanostructure could be calculated as 5.73 × 107. The developed HDPM@MNs was characterized with a core-shell type "soft on the outside and rigid on the inside" structure, which exhibited sufficient hardness and flexibility to penetrate the dermal tissue with little damage, and robust SERS enhancement effect in APAP detection without any interfering peaks. Through a hydrogel drug simulation experiment, the sensor demonstrated robust capabilities for acetaminophen enrichment and monitoring, exhibiting excellent stability and repeatability. The quantitative detection window spanned from 1 to 100 μM, with a low detection limit reaching 0.45 μM. Furthermore, by monitoring the concentration of acetaminophen in the interstitial fluid of rat skin at different doses and for different administration times, the HDPM@MNs can be used to determine the pharmacokinetics of acetaminophen in rats and the physiological characteristics associated with various dosage regimens. This work not only holds promise for drug monitoring but also provides a novel approach for nondestructive monitoring of other crucial low-abundance physiological markers.

Rapid and In-Field Sensing of Hydrogen Peroxide in Plant by Hydrogel Microneedle Patch

The rapidly changing climate is exacerbating the environmental stress that negatively impacts crop health and yield. Timely sensing of plant response to stress is beneficial to timely adjust planting conditions, promoting the healthy growth of plants, and improving plant productivity. Hydrogen peroxide (H2O2) is an important molecule of signal transduction in plants. However, the common methods for detecting H2O2  in plants are associated with certain drawbacks, such as long extraction time, cumbersome steps, dependence on large instruments, and difficulty in realizing in-field sensing. Therefore, it is urgent to establish more efficient detection methods to realize the rapid detection of H2O2 content in plants. In this research, poly (methyl vinyl ether-alt-maleic acid) (PMVE/MA) hydrogel microneedle (MN) patch for rapid extraction of leaf sap are prepared, and the extraction mechanism of PEG-crosslinked PMVE/MA hydrogel MN patch is studied. A method of rapid detection of H2O2 content in plants based on MN patch with optical detection technology is constructed. The hydrogel MN patch can be used for timely H2O2 analysis. This application enables new opportunities in plant engineering, and can be extended to the safety and health monitoring of other plants and animals.

Rapid Detection of Viral, Bacterial, Fungal, and Oomycete Pathogens on Tomatoes with Microneedles, LAMP on a Microfluidic Chip, and Smartphone Device

Rapid detection of plant diseases before they escalate can improve disease control. Our team has developed rapid nucleic acid extraction methods with microneedles and combined these with loop-mediated amplification (LAMP) assays for pathogen detection in the field. In this work, we developed LAMP assays for early blight (Alternaria linariae, A. alternata, and A. solani) and bacterial spot of tomato (Xanthomonas perforans) and validated these LAMP assays and two previously developed LAMP assays for tomato spotted wilt virus and late blight. Tomato plants were inoculated, and disease severity was measured. Extractions were performed using microneedles, and LAMP assays were run in tubes (with hydroxynaphthol blue) on a heat block or on a newly designed microfluidic slide chip on a heat block or a slide heater. Fluorescence on the microfluidic chip slides was visualized using EvaGreen and photographed on a smartphone. Plants inoculated with X. perforans or tomato spotted wilt virus tested positive prior to visible disease symptoms, whereas Phytophthora infestans and A. linariae were detected at the time of visual disease symptoms. LAMP assays were more sensitive than PCR, and the limit of detection was 1 pg of DNA for both A. linariae and X. perforans. The LAMP assay designed for early blight detected all three species of Alternaria that infect tomato and is thus an Alternaria spp. assay. This study demonstrates the utility of rapid microneedle extraction followed by LAMP on a microfluidic chip for rapid diagnosis of four important tomato pathogens.

Advances in microneedles for transdermal diagnostics and sensing applications

Microneedles, the miniaturized needles, which can pierce the skin with minimal invasiveness open up new possibilities for constructing personalized Point-of-Care (POC) diagnostic platforms. Recent advances in microneedle-based POC diagnostic systems, especially their successful implementation with wearable technologies, enable biochemical detection and physiological recordings in a user-friendly manner. This review presents an overview of the current advances in microneedle-based sensor devices, with emphasis on the biological basis of transdermal sensing, fabrication, and application of different types of microneedles, and a summary of microneedle devices based on various sensing strategies. It concludes with the challenges and future prospects of this swiftly growing field. The aim is to present a critical and thorough analysis of the state-of-the-art development of transdermal diagnostics and sensing devices based on microneedles, and to bridge the gap between microneedle technology and pragmatic applications.

Recent advances in hydrogel microneedle-based biofluid extraction and detection in food and agriculture

Microneedle (MN) technology has been extensively studied for its advantages of minimal invasiveness and user-friendliness. Notably, hydrogel microneedles (HMNs) have garnered considerable attention for biofluid extraction due to its high swelling properties and biocompatibility. This review provides a comprehensive overview of definition, materials, and fabrication methods associated with HMNs. The extraction mechanisms and optimization strategies for enhancing extraction efficiency are summarized. Moreover, particular emphasis is placed on HMN-based biofluid extraction and detection in the domains of food and agriculture, encompassing the detection of small molecules, nucleic acids, and other relevant analytes. Finally, current challenges and possible solutions associated with HMN-based biofluid extraction are discussed.

Recent advances of microneedles biosensors for plants

As the lack of plants can affect the energy operation of the entire ecosystem, monitoring and improving the health status of plants is crucial. However, ordinary biosensing platforms lack accuracy and timeliness in monitoring plant growth status. In addition, the prevention and control of plant diseases often involve spraying and administering drugs, which is inefficient and prone to pollution. Microneedles have unique dimensions and shapes, and they have significant advantages as biosensors in the fields of sensing, detection, and drug delivery. Recent evidence suggests that microneedle biosensors can become effective tools for plant diagnosis and treatment. In this review, the comprehensive development of the application of microneedle biosensors in the field of plants is introduced, as well as their manufacturing processes and sensing and detection functions. Furthermore, the application of microneedle biosensors in this field is discussed, and future development directions are proposed.

Sample-to-answer sensing technologies for nucleic acid preparation and detection in the field

Efficient sample preparation and accurate disease diagnosis under field conditions are of great importance for the early intervention of diseases in humans, animals, and plants. However, in-field preparation of high-quality nucleic acids from various specimens for downstream analyses, such as amplification and sequencing, is challenging. Thus, developing and adapting sample lysis and nucleic acid extraction protocols suitable for portable formats have drawn significant attention. Similarly, various nucleic acid amplification techniques and detection methods have also been explored. Combining these functions in an integrated platform has resulted in emergent sample-to-answer sensing systems that allow effective disease detection and analyses outside a laboratory. Such devices have a vast potential to improve healthcare in resource-limited settings, low-cost and distributed surveillance of diseases in food and agriculture industries, environmental monitoring, and defense against biological warfare and terrorism. This paper reviews recent advances in portable sample preparation technologies and facile detection methods that have been / or could be adopted into novel sample-to-answer devices. In addition, recent developments and challenges of commercial kits and devices targeting on-site diagnosis of various plant diseases are discussed.

Understanding the Genotypic and Phenotypic Structure and Impact of Climate on Phytophthora nicotianae Outbreaks on Potato and Tomato in the Eastern United States

Samples from potato fields with lesions with late blight-like symptoms were collected from eastern North Carolina in 2017 and the causal agent was identified as Phytophthora nicotianae. We have identified P. nicotianae in potato and tomato samples from North Carolina, Virginia, Maryland, Pennsylvania, and New York. Ninety-two field samples were collected from 46 fields and characterized for mefenoxam sensitivity, mating type, and simple sequence repeat genotype using microsatellites. Thirty-two percent of the isolates were the A1 mating type, while 53% were the A2 mating type. In six cases, both A1 and A2 mating types were detected in the same field in the same year. All isolates tested were sensitive to mefenoxam. Two genetic groups were discerned based on STRUCTURE analysis: one included samples from North Carolina and Maryland, and one included samples from all five states. The data suggest two different sources of inoculum from the field sites sampled. Multiple haplotypes within a field and the detection of both mating types in close proximity suggests that P. nicotianae may be reproducing sexually in North Carolina. There was a decrease in the average number of days with weather suitable for late blight, from 2012 to 2016 and 2017 to 2021 in all of the North Carolina counties where P. nicotianae was reported. P. nicotianae is more thermotolerant than P. infestans and grows at higher temperatures (25 to 35°C) than P. infestans (18 to 22°C). Late blight outbreaks have decreased in recent years and first reports of disease are later, suggesting that the thermotolerant P. nicotianae may cause more disease as temperatures rise due to climate change.

Integrating microneedle DNA extraction to hand-held microfluidic colorimetric LAMP chip system for meat adulteration detection

Most microfluidic-based "sample-in-result-out" systems suffer sophisticated microfluidic production processes, high-cost chips, and expensive instruments. They cannot be used in the meat market as well as farmer's markets in rural areas. Here, we developed a hand-held microfluidic chip system for on-site meat species qualitative authentication detection which integrated a simple microneedle DNA extraction and a visual loop-mediated isothermal amplification (LAMP). The chip can be used by easily pricking meat samples, simply hand-shaking the chip, and readily available isothermal heating instead of a complicated DNA extraction process and microfluidic control device. The system demonstrates high specificity and sensitivity for selected six species of meat samples and low to 1% simulated adulteration could be detected within 60 min. Besides, the whole cost was less than 1 dollar. The integrated hand-held microfluidic detection system offers a simple, fast, low-cost "sample-in-result-out" point-of-care device which could be extended to medical diagnosis and animal/plant disease identification.

Can Metabolomic Approaches Become a Tool for Improving Early Plant Disease Detection and Diagnosis with Modern Remote Sensing Methods? A Review

The various areas of ultra-sensitive remote sensing research equipment development have provided new ways for assessing crop states. However, even the most promising areas of research, such as hyperspectral remote sensing or Raman spectrometry, have not yet led to stable results. In this review, the main methods for early plant disease detection are discussed. The best proven existing techniques for data acquisition are described. It is discussed how they can be applied to new areas of knowledge. The role of metabolomic approaches in the application of modern methods for early plant disease detection and diagnosis is reviewed. A further direction for experimental methodological development is indicated. The ways to increase the efficiency of modern early plant disease detection remote sensing methods through metabolomic data usage are shown. This article provides an overview of modern sensors and technologies for assessing the biochemical state of crops as well as the ways to apply them in synergy with existing data acquisition and analysis technologies for early plant disease detection.

Current and emerging trends in techniques for plant pathogen detection

Plant pathogenic microorganisms cause substantial yield losses in several economically important crops, resulting in economic and social adversity. The spread of such plant pathogens and the emergence of new diseases is facilitated by human practices such as monoculture farming and global trade. Therefore, the early detection and identification of pathogens is of utmost importance to reduce the associated agricultural losses. In this review, techniques that are currently available to detect plant pathogens are discussed, including culture-based, PCR-based, sequencing-based, and immunology-based techniques. Their working principles are explained, followed by an overview of the main advantages and disadvantages, and examples of their use in plant pathogen detection. In addition to the more conventional and commonly used techniques, we also point to some recent evolutions in the field of plant pathogen detection. The potential use of point-of-care devices, including biosensors, have gained in popularity. These devices can provide fast analysis, are easy to use, and most importantly can be used for on-site diagnosis, allowing the farmers to take rapid disease management decisions.

Abaxial leaf surface-mounted multimodal wearable sensor for continuous plant physiology monitoring

Wearable plant sensors hold tremendous potential for smart agriculture. We report a lower leaf surface-attached multimodal wearable sensor for continuous monitoring of plant physiology by tracking both biochemical and biophysical signals of the plant and its microenvironment. Sensors for detecting volatile organic compounds (VOCs), temperature, and humidity are integrated into a single platform. The abaxial leaf attachment position is selected on the basis of the stomata density to improve the sensor signal strength. This versatile platform enables various stress monitoring applications, ranging from tracking plant water loss to early detection of plant pathogens. A machine learning model was also developed to analyze multichannel sensor data for quantitative detection of tomato spotted wilt virus as early as 4 days after inoculation. The model also evaluates different sensor combinations for early disease detection and predicts that minimally three sensors are required including the VOC sensors.

Microneedle-based transdermal detection and sensing devices

Microneedles have been expected for the construction of next-generation biosensors towards personalization, digitization, and intellectualization due to their metrics of minimal invasiveness, high integration, and favorable biocompatibility. Herein, an overview of state-of-the-art microneedle-based detection and sensing systems is presented. First, the designs of microneedle devices based on extraction mechanisms are concluded, corresponding to different geometries and materials of microneedles. Second, the targets of equipment-assisted microneedle detections are summarized, as well as the objective significance, revealing the current performance and potential scenarios of these microneedles. Third, the trend towards highly integrated sensors is elaborated by emphasizing the sensing principles (colorimetric, fluorometric and electronic manner). Finally, the key challenges to be tackled and the perspectives on future development are discussed.

Microneedle-based interstitial fluid extraction for drug analysis: Advances, challenges, and prospects

Similar to blood, interstitial fluid (ISF) contains exogenous drugs and biomarkers and may therefore substitute blood in drug analysis. However, current ISF extraction techniques require bulky instruments and are both time-consuming and complicated, which has inspired the development of viable alternatives such as those relying on skin or tissue puncturing with microneedles. Currently, microneedles are widely employed for transdermal drug delivery and have been successfully used for ISF extraction by different mechanisms to facilitate subsequent analysis. The integration of microneedles with sensors enables in situ ISF analysis and specific compound monitoring, while the integration of monitoring and delivery functions in wearable devices allows real-time dose modification. Herein, we review the progress in drug analysis based on microneedle-assisted ISF extraction and discuss the related future opportunities and challenges.

Novel Microneedle Patch-Based Surface-Enhanced Raman Spectroscopy Sensor for the Detection of Pesticide Residues

Pesticide residues are a global threat to human health, and conventional sensors fail to simultaneously detect pesticide residues on the surface and inside agricultural products. In this work, we present a new microneedle (MN) patch-based surface-enhanced Raman spectroscopy (SERS) sensor. The needles and the basement of MNs can simultaneously detect pesticide residues on the surface and inside agricultural products. The Ag nanoparticles and sodium hyaluronate/poly(vinyl alcohol) (HA/PVA) hydrogel used in this MN patch-based sensor efficiently amplify the Raman signals of the pesticide residues. In addition, the HA/PVA hydrogel can effectively and quickly collect the residues, allowing this sensor to detect pesticide residues more conveniently. Furthermore, the stepped structure of the MNs increases the sensor's surface area. Experimental results show that the sensor can detect thiram and thiabendazole (TBZ) pesticide residues with detection limits of 10^-7 and 10^-8 M, respectively. The detection process is minimally invasive and not harmful to agricultural products. The application of this MN patch-based SERS sensor can be extended to the safety and health monitoring of other plants and animals.

Principles and Applications of Loop-Mediated Isothermal Amplification to Point-of-Care Tests

For the identification of nucleic acids, which are important biomarkers of pathogen-mediated diseases and viruses, the gold standard for NA-based diagnostic applications is polymerase chain reaction (PCR). However, the requirements of PCR limit its application as a rapid point-of-care diagnostic technique. To address the challenges associated with regular PCR, many isothermal amplification methods have been developed to accurately detect NAs. Isothermal amplification methods enable NA amplification without changes in temperature with simple devices, as well as faster amplification times compared with regular PCR. Of the isothermal amplifications, loop-mediated isothermal amplification (LAMP) is the most studied because it amplifies NAs rapidly and specifically. This review describes the principles of LAMP, the methods used to monitor the process of LAMP, and examples of biosensors that detect the amplicons of LAMP. In addition, current trends in the application of LAMP to smartphones and self-diagnosis systems for point-of-care tests are also discussed.

Direct Capture and Early Detection of Lyme Disease Spirochete in Skin with a Microneedle Patch

Borrelia burgdorferi sensu lato family of spirochetes causes Lyme disease (LD) in animals and humans. As geographic territory of ticks expands across the globe, surveillance measures are needed to measure transmission rates and provide early risk testing of suspected bites. The current standard testing of LD uses an indirect two-step serological assay that detects host immune reactivity. Early detection remains a challenge because the host antibody response develops several weeks after infection. A microneedle (MN) device was developed to sample interstitial fluid (ISF) and capture spirochetes directly from skin. After sampling, the MN patch is easily dissolved in water or TE buffer, and the presence of spirochete DNA is detected by PCR. Performance was tested by spiking porcine ear skin with inactivated Borrelia burgdorferi, which had an approximate recovery of 80% of spirochetes. With further development, this simple direct PCR method could be a transformative approach for early detection of the causative agent of Lyme disease and enable rapid treatment to patients when infection is early, and numbers of systemic spirochetes are low.

Advances and challenges in developing smart, multi-functional microneedles for biomedical applications

Microneedles (MNs) have been developed as minimally invasive tools for diagnostic and therapeutic applications. However, in recent years, there has been an increasing interest in developing smart multi-functional MN devices to provide automated and closed-loop systems for body fluid extraction, biosensing, and drug delivery in a stimuli-responsive manner. Although this technology is still in its infancy and far from being translated into the clinic, preclinical trials have shown some promise for the broad applications of multi-functional MN devices. The main challenge facing the fabrication of smart MN patches is the integration of multiple modules, such as drug carriers, highly sensitive biosensors, and data analyzers in one miniaturized MN device. Researchers have shown the feasibility of creating smart MNs by integrating stimuli-responsive biomaterials and advanced microscale technologies, such as microsensors and microfluidic systems, to precisely control the transportation of biofluids and drugs throughout the system. These multi-functional MN devices can be envisioned in two distinct strategies. The first type includes individual drug delivery and biosensing MN units with a microfluidic system and a digital analyzer responsible for fluid transportation and communication between these two modules. The second type relies on smart biomaterials that can function as drug deliverers and biosensors by releasing drugs in a stimuli-responsive manner. These smart biomaterials can undergo structural changes when exposed to external stimuli, such as pH and ionic changes, mimicking the biological systems. Studies have demonstrated a high potential of hydrogel-based MN devices for a wide variety of biomedical applications, such as drug and cell delivery, as well as interstitial fluid extraction. Biodegradable hydrogels have also been advantageous for fabricating multi-functional MNs due to their high loading capacity and biocompatibility with the drug of choice. Here, we first review a set of MN devices that can be employed either for biosensing or delivery of multiple target molecules and compare them to the conventional and more simple systems, which are mainly designed for single-molecule sensing or delivery. Subsequently, we expand our insight into advanced MN systems with multiple competencies, such as body fluid extraction, biosensing, and drug delivery at the point of care. The improvement of biomaterials knowledge and biofabrication techniques will allow us to efficiently tune the next generation of smart MNs and provide a realistic platform for more effective personalized therapeutics. This article is protected by copyright. All rights reserved.

Recent Advances in Clustered Regularly Interspaced Short Palindromic Repeats-Based Biosensors for Point-of-Care Pathogen Detection

Infectious pathogens are pressing concerns due to their heavy toll on global health and socioeconomic infrastructure. Rapid, sensitive, and specific pathogen detection methods are needed more than ever to control disease spreading. The fast evolution of clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostics (CRISPR-Dx) has opened a new horizon in the field of molecular diagnostics. This review highlights recent efforts in configuring CRISPR technology as an efficient diagnostic tool for pathogen detection. It starts with a brief introduction of different CRISPR-Cas effectors and their working principles for disease diagnosis. It then focuses on the evolution of laboratory-based CRISPR technology toward a potential point-of-care test, including the development of new signaling mechanisms, elimination of preamplification and sample pretreatment steps, and miniaturization of CRISPR reactions on digital assay chips and lateral flow devices. In addition, promising examples of CRISPR-Dx for pathogen detection in various real samples, such as blood, saliva, nasal swab, plant, and food samples, are highlighted. Finally, the challenges and perspectives of future development of CRISPR-Dx for infectious disease monitoring are discussed.

When smartphone enters food safety: A review in on-site analysis for foodborne pathogens using smartphone-assisted biosensors

Pathogens are one of the supreme threats for the public health around the world in food supply chain. The on-site monitoring is an emerging trend for screening pathogens during the food processing and preserving. Traditional analytical tools have been unable to satisfy the current demands. Smartphones have enormous potentials for achieving on-site detection of foodborne pathogens, with intrinsic advantages such as small size, high accessibility, fast processing speed, and powerful imaging capacity. This review aims to synthesize the current advances in smartphone-assisted biosensors (SABs) for sensing foodborne pathogens, and briefly put forward the problem that consist in the research. We present the role of nanotechnology and recognition modes targeting foodborne pathogens in SABs, and discuss the signal conversion platforms coupling with smartphone. The challenges and perspectives in SABs are also proposed. The smartphone analytics area is moving forward, and it much be subject to careful quality standards and validation.

SMART-LAMP: A Smartphone-Operated Handheld Device for Real-Time Colorimetric Point-of-Care Diagnosis of Infectious Diseases via Loop-Mediated Isothermal Amplification

Nucleic acid amplification diagnostics offer outstanding features of sensitivity and specificity. However, they still lack speed and robustness, require extensive infrastructure, and are neither affordable nor user-friendly. Thus, they have not been extensively applied in point-of-care diagnostics, particularly in low-resource settings. In this work, we have combined the loop-mediated isothermal amplification (LAMP) technology with a handheld portable device (SMART-LAMP) developed to perform real-time isothermal nucleic acid amplification reactions, based on simple colorimetric measurements, all of which are Bluetooth-controlled by a dedicated smartphone app. We have validated its diagnostic utility regarding different infectious diseases, including Schistosomiasis, Strongyloidiasis, and COVID-19, and analyzed clinical samples from suspected COVID-19 patients. Finally, we have proved that the combination of long-term stabilized LAMP master mixes, stored and transported at room temperature with our developed SMART-LAMP device, provides an improvement towards true point-of-care diagnosis of infectious diseases in settings with limited infrastructure. Our proposal could be easily adapted to the diagnosis of other infectious diseases.

Loop-Mediated Isothermal Amplification for Detection of Plant Pathogens in Wheat (Triticum aestivum)

Wheat plants can be infected by a variety of pathogen species, with some of them causing similar symptoms. For example, Zymoseptoria tritici and Parastagonospora nodorum often occur together and form the Septoria leaf blotch complex. Accurate detection of wheat pathogens is essential in applying the most appropriate disease management strategy. Loop-mediated isothermal amplification (LAMP) is a recent molecular technique that was rapidly adopted for detection of plant pathogens and can be implemented easily for detection in field conditions. The specificity, sensitivity, and facility to conduct the reaction at a constant temperature are the main advantages of LAMP over immunological and alternative nucleic acid-based methods. In plant pathogen detection studies, LAMP was able to differentiate related fungal species and non-target strains of virulent species with lower detection limits than those obtained with PCR. In this review, we explain the amplification process and elements of the LAMP reaction, and the variety of techniques for visualization of the amplified products, along with their advantages and disadvantages compared with alternative isothermal approaches. Then, a compilation of analyses that show the application of LAMP for detection of fungal pathogens and viruses in wheat is presented. We also describe the modifications included in real-time and multiplex LAMP that reduce common errors from post-amplification detection in traditional LAMP assays and allow discrimination of targets in multi-sample analyses. Finally, we discuss the utility of LAMP for detection of pathogens in wheat, its limitations, and current challenges of this technique. We provide prospects for application of real-time LAMP and multiplex LAMP in the field, using portable devices that measure fluorescence and turbidity, or facilitate colorimetric detection. New technologies for detection of plant pathogen are discussed that can be integrated with LAMP to obtain elevated analytical sensitivity of detection.

Rapid Extraction of Plant Nucleic Acids by Microneedle Patch for In-Field Detection of Plant Pathogens

Plant diseases pose a significant threat to global food security. Molecular diagnosis currently plays a crucial role in mitigating the negative impacts of plant diseases by accurately identifying the disease-causing pathogens and revealing their genotypes. However, current molecular assays are constrained to the laboratory because of the cumbersome protocols involved in plant nucleic acid extraction. To streamline this, we have developed a polymeric microneedle (MN) patch-based nucleic acid extraction method, which can be applied to various plant tissues and easily performed in field settings without using bulky laboratory equipment. The MN patch instantly isolates both host and pathogen's DNA and RNA from plant leaves by two simple steps: press and rinse with a buffer solution or nuclease-free water. The MN-extracted DNA and RNA are purification-free and directly applicable to downstream molecular assays such as polymerase chain reaction (PCR), reverse transcription-polymerase chain reaction (RT-PCR), loop-mediated isothermal amplification (LAMP), and reverse transcription loop-mediated isothermal amplification (RT-LAMP). Here, we describe the fabrication procedures of the MN patch and demonstrate the application of the MN method by extracting Phytophthora infestans DNA and tomato spotted wilt virus (TSWV) RNA from infected tomato leaves. After MN extraction, we directly utilize the MN-extracted nucleic acid samples to run PCR, RT-PCR, LAMP, or RT-LAMP reactions to amplify various biomarker genes, such as the ribulose-bisphosphate carboxylase (rbcL) gene of host tomato DNA, internal transcribed spacer (ITS) region of P. infestans DNA, and nucleocapsid (N) gene of TSWV RNA. Furthermore, this simple and rapid nucleic acid method can be integrated with portable nucleic acid amplification platforms such as smartphone-based microscopy devices to achieve "sample-to-answer" detection of plant pathogens directly in the field.

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.

Development of a Novel Loop Mediated Isothermal Amplification Assay (LAMP) for the Rapid Detection of Epizootic Haemorrhagic Disease Virus

Epizootic haemorragic disease (EHD) is an important disease of white-tailed deer and can cause a bluetongue-like illness in cattle. A definitive diagnosis of EHD relies on molecular assays such as real-time RT-qPCR or conventional PCR. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) is a cost-effective, specific, and sensitive technique that provides an alternative to RT-qPCR. We designed two sets of specific primers targeting segment-9 of the EHD virus genome to enable the detection of western and eastern topotypes, and evaluated their performance in singleplex and multiplex formats using cell culture isolates (n = 43), field specimens (n = 20), and a proficiency panel (n = 10). The limit of detection of the eastern and western RT-LAMP assays was estimated as ~24.36 C_T and as ~29.37 C_T in relation to real-time RT-qPCR, respectively, indicating a greater sensitivity of the western topotype singleplex RT-LAMP. The sensitivity of the western topotype RT-LAMP assay, relative to the RT-qPCR assay, was 72.2%, indicating that it could be theoretically used to detect viraemic cervines and bovines. For the first time, an RT-LAMP assay was developed for the rapid detection of the EHD virus that could be used as either a field test or high throughput screening tool in established laboratories to control the spread of EHD.

Point-of-Care Toolkit for Multiplex Molecular Diagnosis of SARS-CoV-2 and Influenza A and B Viruses

Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) is still spreading around the globe causing immense public health and socioeconomic problems. As the infection can progress with mild symptoms that can be misinterpreted as the flu, self-testing methods that can positively identify SARS-CoV-2 are needed to effectively track and prevent the transmission of the virus. In this work, we report a point-of-care toolkit for multiplex molecular diagnosis of SARS-CoV-2 and influenza A and B viruses in saliva samples. Our assay is physically programmed to run a sequence of chemical reactions on a paper substrate and internally generate heat to drive these reactions for an autonomous extraction, purification, and amplification of the viral RNA. Using our assay, we could reliably detect SARS-CoV-2 and influenza viruses at concentrations as low as 50 copies/μL visually from a colorimetric analysis. The capability to autonomously perform a traditionally labor-intensive genetic assay on a disposable platform will enable frequent, on-demand self-testing, a critical need to track and contain this and future outbreaks.