Recent progress, challenges, and prospects of fully integrated mobile and wearable point-of-care testing systems for self-testing

Culture-Free Quantification of Bacteria Using Digital Fluorescence Imaging in a Tunable Magnetic Capturing Cartridge for Onsite Food Testing

Accurate, onsite detection of pathogenic bacteria from food matrices is required to rapidly respond to pathogen outbreaks. However, accurately detecting whole-cell bacteria in large sample volumes without an enrichment step remains a challenge. Therefore, bacterial samples must be concentrated, identified, and quantified. We developed a tunable magnetic capturing cartridge (TMCC) and combined it with a portable digital fluorescence reader for quick, onsite, quantitative detection of Staphylococcus aureus. The TMCC platform integrates an absorption pad impregnated with water-soluble polyvinyl alcohol (PVA) with an injection-molded polycarbonate (PC) plate that has a hard magnet on its back and an acrylonitrile-butadiene-styrene case. An S. aureus-specific antibody conjugated with magnetic nanoparticles was used to concentrate bacteria from a large-volume sample and capture bacteria within the TMCC. The retention time for capturing bacteria on the TMCC was adjusted by controlling the concentration and volume of the PVA solution. Concentrated bacterial samples bound to target-specific aptamer probes conjugated with quantum dots were loaded into the TMCC for a controlled time, followed by attachment of the bacteria to the PC plate and removal of unbound aptamer probes with wash buffer. The captured bacteria were quantified using a digital fluorescence reader equipped with an embedded program that automatically counts fluorescently tagged bacteria. The bacterial count made using the TMCC was comparable to a standard plate count (R² = 0.9898), with assay sensitivity and specificity of 94.3 and 100%, respectively.

Photocatalysis engineered hydrophilic reactors on hydrophobic paper for the visual and colorimetric assay of alkaline phosphatase activity

Taking advantage of the intrinsic photocatalysis of TiO₂, hydrophilic reactor arrays were lithographically patterned on a hydrophobic paper via a simple UV irradiation. As a proof-of-concept, alkaline phosphatase (ALP) was used as the model analyte for colorimetric analysis. As ALP can induce hydrolysis of pyrophosphate-Zn(II) framework, the released Zn²⁺ ions are subsequently coordinated with red-colored zincon to form blue-colored zincon-Zn(II) chelate complex, and these color differences were applied for further colorimetric assay. The sensing platform showed response to ALP ranging from 20 ~ 800 U L^-1 with a detection limit of 3 U L^-1, and the recoveries of ALP in serum samples were in the range 95.7 ~ 104.5% with relative standard deviations from 2.10 to 3.84%. Additionally, the distinct wettability features of the proposed sensing platform effectively prevent lateral fluid spread out of hydrophilic reactors, thus allowing not only the use of minimum amount of analyte but it has also a high potential for simultaneous quantification of multiple samples.

All-printed point-of-care immunosensing biochip for one drop blood diagnostics

Designing and preparing a fast and easy-to-use immunosensing biochip are of great significance for clinical diagnosis and biomedical research. In particular, sensitive, specific, and early detection of biomarkers in trace samples promotes the application of point-of-care testing (POCT). Here, we demonstrate an all-printed immunosensing biochip with the characteristics of hydrodynamic enrichment and photonic crystal-enhanced fluorescence. Direct quantitative detection of cardiac biomarkers via one drop of blood is achieved in 10 min. After simulating the hydrodynamic behavior of one droplet serum on the printed assay, creatine kinase-MB (CK-MB) has been recognized and located on the photonic crystal arrays. Benefiting from the fluorescence enhancement effect, quantitative detection of CK-MB has been demonstrated from 0.01 ng ml^-1 to 100 ng ml^-1, which is superior to the conventional enzyme-linked immunosorbent assay (ELISA). This strategy provides a general and easy-to-use approach for fast quantitative detection of biomarkers, which would be improved further for portable clinical diagnostics and home medical monitoring.

Electrochemical Profiling of Plants

The profiling, or fingerprinting, of distinct varieties of the Plantae kingdom is based on the bioactive ingredients, which are systematically segregated to perform their detailed analysis. The secondary products portray a pivotal role in defining the ecophysiology of distinct plant species. There is a crucial role of the profiling domain in understanding the various features, characteristics, and conditions related to plants. Advancements in variable technologies have contributed to the development of highly specific sensors for the non-invasive detection of molecules. Furthermore, many hyphenated techniques have led to the development of highly specific integrated systems that allow multiplexed detection, such as high-performance liquid chromatography, gas chromatography, etc., which are quite cumbersome and un-economical. In contrast, electrochemical sensors are a promising alternative which are capable of performing the precise recognition of compounds due to efficient signal transduction. However, due to a few bottlenecks in understanding the principles and non-redox features of minimal metabolites, the area has not been explored. This review article provides an insight to the electrochemical basis of plants in comparison with other traditional approaches and with necessary positive and negative outlooks. Studies consisting of the idea of merging the fields are limited; hence, relevant non-phytochemical reports are included for a better comparison of reports to broaden the scope of this work.

Multi-Mode Compact Microscopy for High-Contrast and High-Resolution Imaging

We report a multi-mode compact microscope (MCM) for high-contrast and high-resolution imaging. The MCM consists of two LED illuminations, a magnification lens, a lift stage, and a housing with image processing and LED control boards. The MCM allows multi-modal imaging, including reflection, transmission, and higher magnification modes. The dual illuminations also provide high-contrast imaging of various targets such as biological samples and microcircuits. The high dynamic range (HDR) imaging reconstruction of MCM increases the dynamic range of the acquired images by 1.36 times. The microlens array (MLA)-assisted MCM also improves image resolution through the magnified virtual image of MLA. The MLA-assisted MCM successfully provides a clear, magnified image by integrating a pinhole mask to prevent image overlap without additional alignment. The magnification of MLA-assisted MCM was increased by 3.92 times compared with that of MCM, and the higher magnification mode demonstrates the image resolution of 2.46 μm. The compact portable microscope can provide a new platform for defect inspection or disease detection on site.

Multifunctional Flexible Humidity Sensor Systems Towards Noncontact Wearable Electronics

In the past decade, the global industry and research attentions on intelligent skin-like electronics have boosted their applications in diverse fields including human healthcare, Internet of Things, human-machine interfaces, artificial intelligence and soft robotics. Among them, flexible humidity sensors play a vital role in noncontact measurements relying on the unique property of rapid response to humidity change. This work presents an overview of recent advances in flexible humidity sensors using various active functional materials for contactless monitoring. Four categories of humidity sensors are highlighted based on resistive, capacitive, impedance-type and voltage-type working mechanisms. Furthermore, typical strategies including chemical doping, structural design and Joule heating are introduced to enhance the performance of humidity sensors. Drawing on the noncontact perception capability, human/plant healthcare management, human-machine interactions as well as integrated humidity sensor-based feedback systems are presented. The burgeoning innovations in this research field will benefit human society, especially during the COVID-19 epidemic, where cross-infection should be averted and contactless sensation is highly desired.

Smartphone-Based Techniques Using Carbon Dot Nanomaterials for Food Safety Analysis

The development of portable and efficient nanoprobes to realize the quantitative/qualitative onsite determination of food pollutants is of immense importance for safeguarding human health and food safety. With the advent of the smartphone, the digital imaging property causes it to be an ideal diagnostic substrate to point-of-care analysis probes. Besides, merging the versatility of carbon dots nanostructures and bioreceptor abilities has opened an innovative assortment of construction blocks to design advanced nanoprobes or improving those existing ones. On this ground, massive endeavors have been made to combine mobile phones with smart nanomaterials to produce portable (bio)sensors in a reliable, low cost, rapid, and even facile-to-implement area with inadequate resources. Herein, this work outlines the latest advancement of carbon dots nanostructures on smartphone for onsite detecting of agri-food pollutants. Particularly, we afford a summary of numerous approaches applied for target molecule diagnosis (pesticides, mycotoxins, pathogens, antibiotics, and metal ions), for instance microscopic imaging, fluorescence, colorimetric, and electrochemical techniques. Authors tried to list those scaffolds that are well-recognized in complex media or those using novel constructions/techniques. Lastly, we also point out some challenges and appealing prospects related to the enhancement of high-efficiency smartphone based carbon dots systems.

A Point-of-Care Device for Fully Automated, Fast and Sensitive Protein Quantification via qPCR

This paper presents a fully automated point-of-care device for protein quantification using short-DNA aptamers, where no manual sample preparation is needed. The device is based on our novel aptamer-based methodology combined with real-time polymerase chain reaction (qPCR), which we employ for very sensitive protein quantification. DNA amplification through qPCR, sensing and real-time data processing are seamlessly integrated into a point-of-care device equipped with a disposable cartridge for automated sample preparation. The system’s modular nature allows for easy assembly, adjustment and expansion towards a variety of biomarkers for applications in disease diagnostics and personalised medicine. Alongside the device description, we also present a new algorithm, which we named PeakFluo, to perform automated and real-time quantification of proteins. PeakFluo achieves better linearity than proprietary software from a commercially available qPCR machine, and it allows for early detection of the amplification signal. Additionally, we propose an alternative way to use the proposed device beyond the quantitative reading, which can provide clinically relevant advice. We demonstrate how a convolutional neural network algorithm trained on qPCR images can classify samples into high/low concentration classes. This method can help classify obese patients from their leptin values to optimise weight loss therapies in clinical settings.

A Review on Potential Electrochemical Point-of-Care Tests Targeting Pandemic Infectious Disease Detection: COVID-19 as a Reference

Fast and accurate point-of-care testing (POCT) of infectious diseases is crucial for diminishing the pandemic miseries. To fight the pandemic coronavirus disease 2019 (COVID-19), numerous interesting electrochemical point-of-care (POC) tests have been evolved to rapidly identify the causal organism SARS-CoV-2 virus, its nucleic acid and antigens, and antibodies of the patients. Many of those electrochemical biosensors are impressive in terms of miniaturization, mass production, ease of use, and speed of test, and they could be recommended for future applications in pandemic-like circumstances. On the other hand, self-diagnosis, sensitivity, specificity, surface chemistry, electrochemical components, device configuration, portability, small analyzers, and other features of the tests can yet be improved. Therefore, this report reviews the developmental trend of electrochemical POC tests (i.e., test platforms and features) reported for the rapid diagnosis of COVID-19 and correlates any significant advancements with relevant references. POCTs incorporating microfluidic/plastic chips, paper devices, nanomaterial-aided platforms, smartphone integration, self-diagnosis, and epidemiological reporting attributes are also surfed to help with future pandemic preparedness. This review especially screens the low-cost and easily affordable setups so that management of pandemic disease becomes faster and easier. Overall, the review is a wide-ranging package for finding appropriate strategies of electrochemical POCT targeting pandemic infectious disease detection.

Programmable CRISPR-Cas9 microneedle patch for long-term capture and real-time monitoring of universal cell-free DNA

Recent advances in biointerfaces have led to the development of wearable devices that can provide insights into personal health. As wearable modules, microneedles can extract analytes of interest from interstitial fluid in a minimally invasive fashion. However, some microneedles are limited by their ability to perform highly effective extraction and real-time monitoring for macromolecule biomarkers simultaneously. Here we show the synergetic effect of CRISPR-activated graphene biointerfaces, and report an on-line wearable microneedle patch for extraction and in vivo long-term monitoring of universal cell-free DNA. In this study, this wearable system enables real-time monitoring of Epstein-Barr virus, sepsis, and kidney transplantation cell-free DNA, with anti-interference ability of 60% fetal bovine serum, and has satisfactory stable sensitivity for 10 days in vivo. The experimental results of immunodeficient mouse models shows the feasibility and practicability of this proposed method. This wearable patch holds great promise for long-term in vivo monitoring of cell-free DNA and could potentially be used for early disease screening and prognosis.

Real-time sensing of biomarkers via the use of wearable devices is a major aim of personalised medicine. Here, authors demonstrate an on-line wearable microneedle patch for real-time capture and monitoring of universal cell-free DNA.

Solid-State Reaction Synthesis of Nanoscale Materials: Strategies and Applications

Nanomaterials (NMs) with unique structures and compositions can give rise to exotic physicochemical properties and applications. Despite the advancement in solution-based methods, scalable access to a wide range of crystal phases and intricate compositions is still challenging. Solid-state reaction (SSR) syntheses have high potential owing to their flexibility toward multielemental phases under feasibly high temperatures and solvent-free conditions as well as their scalability and simplicity. Controlling the nanoscale features through SSRs demands a strategic nanospace-confinement approach due to the risk of heat-induced reshaping and sintering. Here, we describe advanced SSR strategies for NM synthesis, focusing on mechanistic insights, novel nanoscale phenomena, and underlying principles using a series of examples under different categories. After introducing the history of classical SSRs, key theories, and definitions central to the topic, we categorize various modern SSR strategies based on the surrounding solid-state media used for nanostructure growth, conversion, and migration under nanospace or dimensional confinement. This comprehensive review will advance the quest for new materials design, synthesis, and applications.

Ultrathin Al-air batteries by reducing the thickness of solid electrolyte using aerosol jet printing

Flexible Al–air batteries have great potential in the field of wearable electronic devices. However, how to reduce the thickness of the battery and improve their applicability in wearable applications is still an unresolved thorny problem. Therefore, this article focuses on the strategies to minimize the thickness of the solid electrolyte for flexible Al–air batteries. In this paper, an innovative aerosol jet printing method is used to prepare the ultrathin neutral electrolyte with a thickness of 18.3–74.5 μm. This study discusses the influence of the thickness and ion concentration on the conductance of the electrolyte in detail. The ultrathin electrolyte has been applied to the flexible Al–air battery, and the battery performance has been explored. The cell pack composed of single cells is light and thin, and can successfully drive small electrical equipment. This study provided new ideas for the preparation of ultrathin electrolyte for flexible energy products.

Laser-Induced Graphene-Based Wearable Epidermal Ion-Selective Sensors for Noninvasive Multiplexed Sweat Analysis

Wearable sweat sensors are a rapidly rising research area owing to their convenience for personal healthcare and disease diagnosis in a real-time and noninvasive manner. However, the fast and scalable fabrication of flexible electrodes remains a major challenge. Here, we develop a wearable epidermal sensor for multiplexed sweat analysis based on the laser-induced graphene (LIG) technique. This simple and mask-free technique allows the direct manufacturing of graphene electrode patterns on commercial polyimide foils. The resulting LIG devices can simultaneously monitor the pH, Na⁺, and K⁺ levels in sweat with the sensitivities of 51.5 mV/decade (pH), 45.4 mV/decade (Na⁺), and 43.3 mV/decade (K⁺), respectively. Good reproducibility, stability, and selectivity are also observed. On-body testing of the LIG-based sensor integrated with a flexible printed circuit board during stationary cycling demonstrates its capability for real-time sweat analysis. The concentrations of ions can be remotely and wirelessly transmitted to a custom-developed smartphone application during the period in which the sensor user performs physical activities. Owing to the unique advantages of LIG technique, including facile fabrication, mass production, and versatile, more physiological signals (glucose, uric acid, tyrosine, etc.) could be easily expanded into the LIG-based wearable sensors to reflect the health status or clinical needs of individuals.

Recent progress in electrospun nanomaterials for wearables

Wearables have garnered significant attention in recent years not only as consumer electronics for entertainment, communications, and commerce but also for real-time continuous health monitoring. This has been spurred by advances in flexible sensors, transistors, energy storage, and harvesting devices to replace the traditional, bulky, and rigid electronic devices. However, engineering smart wearables that can seamlessly integrate with the human body is a daunting task. Some of the key material attributes that are challenging to meet are skin conformability, breathability, and biocompatibility while providing tunability of its mechanical, electrical, and chemical properties. Electrospinning has emerged as a versatile platform that can potentially address these challenges by fabricating nanofibers with tunable properties from a polymer base. In this article, we review advances in wearable electronic devices and systems that are developed using electrospinning. We cover various applications in multiple fields including healthcare, biomedicine, and energy. We review the ability to tune the electrical, physiochemical, and mechanical properties of the nanofibers underlying these applications and illustrate strategies that enable integration of these nanofibers with human skin.

Virus Detection: From State-of-the-Art Laboratories to Smartphone-Based Point-of-Care Testing

Infectious virus outbreaks pose a significant challenge to public healthcare systems. Early and accurate virus diagnosis is critical to prevent the spread of the virus, especially when no specific vaccine or effective medicine is available. In clinics, the most commonly used viral detection methods are molecular techniques that involve the measurement of nucleic acids or proteins biomarkers. However, most clinic-based methods require complex infrastructure and expensive equipment, which are not suitable for low-resource settings. Over the past years, smartphone-based point-of-care testing (POCT) has rapidly emerged as a potential alternative to laboratory-based clinical diagnosis. This review summarizes the latest development of virus detection. First, laboratory-based and POCT-based viral diagnostic techniques are compared, both of which rely on immunosensing and nucleic acid detection. Then, various smartphone-based POCT diagnostic techniques, including optical biosensors, electrochemical biosensors, and other types of biosensors are discussed. Moreover, this review covers the development of smartphone-based POCT diagnostics for various viruses including COVID-19, Ebola, influenza, Zika, HIV, et al. Finally, the prospects and challenges of smartphone-based POCT diagnostics are discussed. It is believed that this review will aid researchers better understand the current challenges and prospects for achieving the ultimate goal of containing disease-causing viruses worldwide.

Engineering of 2D artificial nanozyme-based blocking effect-triggered colorimetric sensor for onsite visual assay of residual tetracycline in milk

Accurate and low-cost onsite assay of residual antibiotics in food and agriculture-related matrixes (e.g., milk) is of significant importance for evaluating and controlling food pollution risk. Herein, we employed hybrid Cu-doped-g-C₃N₄ nanozyme to engineer smartphone-assisted onsite visual sensor for reliable and precise reporting the levels of tetracycline (TC) residues in milk through π-π stacking-triggered blocking effect. Benefiting from the synergetic effects of Cu²⁺ and g-C₃N₄ nanosheet, Cu-doped-g-C₃N₄ nanocomposite exhibited an improved peroxidase-like activity, which could effectively catalyze H₂O₂ to oxidate colorless TMB into steel-blue product oxTMB. Interestingly, owing to the blocking effect caused by the π-π stacking interaction between TC tetraphenyl skeleton and Cu-doped-g-C₃N₄ nanozyme, the affinity of Cu-doped-g-C₃N₄ nanocomposite toward the catalytic substrates was remarkably blocked, resulting in a TC concentration-dependent fading of solution color. Using smartphone-assisted detection a simple, low-cost, reliable, and sensitive portable colorimetric sensor-based nanozyme for onsite visual monitoring the residual TC in milk was successfully developed with a detection limit of 86.27 nM. Of particular mention is that this detection limit is comparable to most other reported colorimetric methods and below most official allowable residue thresholds in milk matrixes. This work gave a novel insight to integrate two-dimensional (2D) artificial nanozymes-based π-π stacking-triggered blocking effect with smartphone-assisted detection for developing efficient and low-cost colorimetric point-of-care testing of the risk factors in food and agriculture-related matrixes.

In-situ preparation of lactate-sensing membrane for the noninvasive and wearable analysis of sweat

In the wearable electrochemical biosensors, sensing signal duration is significantly dependent on the long-term stability of functional materials modified on the flexible substrate, the effect of pH changes of sweat on the sensing device and signal fluctuation caused by the bending of sensor. Here, we proposed a wearable biosensor based on the lactate-sensing membrane mainly constituted by Prussian blue (PB), reduced graphene oxide (rGO), Au nanoparticles and lactate oxidase (LOx). Based on the in-situ layer-by-layer spin-coating preparation method, the electrode surface was covered with an extensive and uniform PB/GO membrane with a high stability. After the electro-reduction of GO to rGO and the combination of urchin-like Au particles with sufficient tentacles to LOx, the sensing membrane showed the improved electron transport from the enzyme active center to the electrode. Therefore, the wearable biosensor achieved a high sensitivity of 40.6 μA mM^-1 cm^-2 in a range of 1-222 μM and a low sensitivity of 1.9 μA mM^-1 cm^-2 in a wide range of 0.222-25 mM, satisfying the requirement of the typical test. In addition, with the excellent running and mechanical stability, the lactate biosensor was successfully applied on volunteers' skin for real-time monitoring of perspiration in vivo. The results were comparable with ex vivo measurements achieved by a commercial lactate sensor. The wearable electrochemical biosensor provides a good candidate in the future for the evaluation of human sweat in sports and biomedical fields.

Dual-Modal Immunochromatographic Test for Sensitive Detection of Zearalenone in Food Samples Based On Biosynthetic Staphylococcus aureus-Mediated Polymer Dot Nanocomposites

The rapid detection of toxins is of great significance to food security and human health. In this work, a dual-modality immunochromatographic test (DICT) mediated by Staphylococcus aureus (SA)-biosynthesized polymer dots (SABPDs) was constructed for sensitive monitoring of zearalenone (ZEN) in agro products. The SABPDs as potent microorganism nanoscaffolds with excellent solubility, brightness, and stability were ingeniously fabricated employing hydroquinone and SA as precursors in the Schiff base reaction and a self-assembly technique. Thanks to the fact that they not only preserved an intact microsphere for loading Fc regions of monoclonal antibodies (mAbs) and the affinity of their labeled mAbs to antigen but also generated superb colorimetric-fluorescent dual signals, the versatile SABPDs manifested unique possibilities as the new carriers for dual-readout ICT with remarkable enhancement in sensitivity in ZEN screening (limit of detection = 0.036 ng/mL, which was 31-fold lower than that of traditional gold nanoparticle-based ICT). Ultimately, the proposed immunosensor performed well in millet and corn samples with satisfactory recoveries, demonstrating its potential for point-of-care testing. This work offers a bio-friendly strategy for biosynthesizing cell-based PD vehicles with bimodal signals for food safety analysis.

Emerging biosensing and transducing techniques for potential applications in point-of-care diagnostics

With the deepening of our understanding in life science, molecular biology, nanotechnology, optics, electrochemistry and other areas, an increasing number of biosensor design strategies have emerged in recent years, capable of providing potential practical applications for point-of-care (POC) diagnosis in various human diseases. Compared to conventional biosensors, the latest POC biosensor research aims at improving sensor precision, cost-effectiveness and time-consumption, as well as the development of versatile detection strategies to achieve multiplexed analyte detection in a single device and enable rapid diagnosis and high-throughput screening. In this review, various intriguing strategies in the recognition and transduction of POC (from 2018 to 2021) are described in light of recent advances in CRISPR technology, electrochemical biosensing, and optical- or spectra-based biosensing. From the perspective of promoting emerging bioanalytical tools into practical POC detecting and diagnostic applications, we have summarized key advances made in this field in recent years and presented our own perspectives on future POC development and challenges.

Paper-Based Flow Sensor for the Detection of Hyaluronidase via an Enzyme Hydrolysis-Induced Viscosity Change in a Polymer Solution

Hyaluronidase (HAase) is implicated in inflammation, cancer development, and allergic reaction. The detection of HAase is significantly important in clinical diagnosis and medical treatment. Herein, we propose a new principle for the development of equipment-free and label-free paper-based flow sensors based on the enzymatic hydrolysis-induced viscosity change in a stimuli-responsive polymer solution, which increases the water flow distance on the pH indicator paper. The detection of HAase is demonstrated as an example. This facile and versatile method can overcome the potential drawbacks of traditional hydrogel-based sensors, including complex preparation steps, slow response time, or low sensitivity. Moreover, it can also avoid the use of specialized instruments, labeled molecules, or functionalized nanoparticles in the sensors developed using the polymer solutions. Using this strategy, the detection of HAase is achieved with a limit of detection as low as 0.2 U/mL. Also, it works well in human urine. Additionally, the detection of tannic acid, which is an inhibitor of HAase, is also fulfilled. Overall, a simple, efficient, high-throughput, and low-cost detection method is developed for the rapid and quantitative detection of HAase and its inhibitor without the use of labeled molecules, synthetic particles, and specialized instruments. As only minimal reagents of HAase, HA, and paper are used, it is very promising in the development of commercial kits for point-of-care testing.

Photosensitive-Stamp-Inspired Scalable Fabrication Strategy of Wearable Sensing Arrays for Noninvasive Real-Time Sweat Analysis

Wearable sweat sensing is essential to the development of personalized health monitoring in a noninvasive manner with molecular-level insight. Hence, there is an increasing demand for convenient, facile, and efficient fabrication of wearable sensing arrays. Inspired by a photosensitive stamp (PS), we present herein a simple, low-cost, and eco-friendly vacuum filtration-transfer printing method (termed PS-VFTP) for the scalable preparation of single-walled carbon nanotube (SWCNT) based flexible electrode arrays. This method can economically yield customized flexible SWCNT arrays with praiseworthy performance, such as high reproducibility, precision, uniformity, conductivity, and mechanical stability. In addition, the flexible SWCNT arrays can be easily functionalized into high-performance electrochemical sensors for the simultaneous monitoring of sweat metabolites (glucose, lactate) and electrolytes (Na⁺, K⁺). The integration of wearable sensing arrays with a signal acquisition and processing circuit system in the intelligent wearable sensors empowers them to realize noninvasive, real-time, and in situ sweat analysis during exercise. More meaningfully, such a PS-VFTP strategy can be easily expanded to the economical manufacturing of other flexible electronic devices.

How to Assess the Measurement Performance of Mobile/Wearable Point-of-Care Testing Devices? A Systematic Review Addressing Sweat Analysis

Recent advances in technologies for biosensor integration in mobile or wearable devices have highlighted the need for the definition of proper validation procedures and technical standards that enable testing, verification and validation of the overall performance of these solutions. Thus, reliable assessment—in terms of limits of detection/quantitation, linearity, range, analytical and diagnostic sensitivity/specificity, accuracy, repeatability, reproducibility, cross-reactivity, diagnostic efficiency, and positive/negative prediction—still represents the most critical and challenging aspect required to progress beyond the status of feasibility studies. Considering this picture, this work aims to review and discuss the literature referring to the available methods and criteria reported in the assessment of the performance of point-of-care testing (PoCT) devices within their specific applications. In particular, without losing generality, we focused on mobile or wearable systems able to analyze human sweat. In performing this review, the focus was on the main challenges and trends underlined in the literature, in order to provide specific hints that can be used to set shared procedures and improve the overall reliability of the identified solutions, addressing the importance of sample management, the sensing components, and the electronics. This review can contribute to supporting an effective validation of mobile or wearable PoCT devices and thus to spreading the use of reliable approaches outside hospitals and clinical laboratories.

Viscosity-Based Flow Sensor on Paper for Quantitative and Label-Free Detection of α-Amylase and Its Inhibitor

α-Amylase (AMS) in human serum is a critical biomarker for the early diagnosis of pancreatic damage. In addition, the inhibition of α-amylase has long been thought to decrease the occurrence of diabetes. Thus, it is critical to construct a facile and convenient method for the determination of AMS and its inhibitor. In this study, we demonstrate a novel amylase sensor based on translating the viscosity change of the aqueous solution into the difference of the water diffusion length on a pH paper strip. AMS can be quantitatively detected by measuring the viscosity change of the amylopectin solution in the presence of AMS with different concentrations. The paper-based AMS sensor has a very high sensitivity with a detection limit of 0.017 U/mL and also shows excellent specificity. In addition, the inhibitory effect of acarbose on AMS is demonstrated with the IC₅₀ value determined to be 21.66 ± 1.13 μg/mL. Furthermore, it is also evaluated for the detection of AMS in human serum samples of healthy people and acute pancreatitis patients. The difference in amylase levels between the two groups is unambiguously distinguished. Overall, this study provides a very simple, cost-effective, equipment-free, high-throughput, and label-free method for rapid and quantitative detection of α-amylase and may have significant applications in the diagnosis of acute pancreatitis and the screening of AMS inhibitors.

Clinical Care of Hyperthyroidism Using Wearable Medical Devices in a Medical IoT Scenario

This paper presents an in-depth study and analysis of clinical care of patients with hyperthyroidism using wearable medical devices in the context of medical IoT scenarios. According to the use scenario of the gateway and the connectivity of the equipment, the hardware architecture, hardware interfaces, functionality, and performance of the gateway were briefly designed, so as to monitor patients with hyperthyroidism more comprehensively and save labor costs. The gateway can provide access to different devices and adaptation functions to different hardware interfaces and provide hardware support for the subsequent deployment of the proposed new medical communication protocols and related information systems. A medical data convergence information system based on multidevice management and multiprotocol parsing was designed and implemented. The system enables the management and configuration of different medical devices and access to data through the targeted parsing of the underlying medical device communication protocols. The system also provides the automatic adaptation of multiple types of underlying medical device communication protocols and automatic parsing of multiple versions and can provide multiple devices to process fused data streams or device information and data from a single device. The use of event-driven asynchronous communication eliminates the tight dependency on service invocation in the synchronous communication approach. The use of a metadata-based data model structure enables model extensions to accommodate the impact of iterative business requirements on the database structure. Real-time patient physiological data transmission for intraoperative monitoring based on the MQTT protocol and video transmission for intraoperative patient monitoring based on the RTMP protocol were implemented. The development of the intelligent medical monitoring service system was completed, and the system was tested, optimized, and deployed. The functionality and performance of the system were tested, the performance issue of slow query speed was optimized, and the deployment of the project using Docker containers was automated.

Exploiting Photoelectric Activities and Piezoelectric Properties of NaNbO3 Semiconductors for Point-of-Care Immunoassay

Point-of-care testing (POCT) technology has made major breakthroughs in community medicine and physician office situations, in tandem with the more ubiquitous and intensive usage of highly integrated quick detection equipment for illness diagnosis, personal care, and mobile healthcare. Although the photoelectrochemical (PEC)-based POCT platform offers the benefits of cheap cost and good user engagement, its commercialization is still limited by the photodetection components' downsizing and mobility, among other factors. In this work, a novel highly integrated PEC biosensor aided by piezophototronics to enhance the efficiency of PEC testing was reported for flexible detection of cancer-associated antigens in biological fluids (prostate-specific antigen, PSA, used as an example). Multiple signal enhancement strategies, including a magnetic bead-linked enzyme-linked immune system catalyzing the production of ascorbic acid from the substrate and a piezoelectric-assisted enhancement strategy, were used for sensitive detection of the analyte to be tested in human body fluids. Unlike the electron transfer mechanism in heterojunctions, piezoelectric semiconductors promote the transfer of electrons and holes by generating piezoelectric potentials in the ultrasonic field, thus contributing to the performance of the PEC testbed. Under optimized conditions, the test platform achieves good correspondence for PSA at 0.02-40 ng mL^-1. Impressively, the test devices are comparable to or even superior to gold standard ELISA kits in terms of cost approval and batch testing. This research demonstrates the potential of piezoelectric semiconductors for POC applications in revolutionary PECs and offers innovative thoughts for the development of new PEC bioanalytical components.

Wave-shaped microfluidic chip assisted point-of-care testing for accurate and rapid diagnosis of infections

BACKGROUND

Early diagnosis and classification of infections increase the cure rate while decreasing complications, which is significant for severe infections, especially for war surgery. However, traditional methods rely on laborious operations and bulky devices. On the other hand, point-of-care (POC) methods suffer from limited robustness and accuracy. Therefore, it is of urgent demand to develop POC devices for rapid and accurate diagnosis of infections to fulfill on-site militarized requirements.

METHODS

We developed a wave-shaped microfluidic chip (WMC) assisted multiplexed detection platform (WMC-MDP). WMC-MDP reduces detection time and improves repeatability through premixing of the samples and reaction of the reagents. We further combined the detection platform with the streptavidin-biotin (SA-B) amplified system to enhance the sensitivity while using chemiluminescence (CL) intensity as signal readout. We realized simultaneous detection of C-reactive protein (CRP), procalcitonin (PCT), and interleukin-6 (IL-6) on the detection platform and evaluated the sensitivity, linear range, selectivity, and repeatability. Finally, we finished detecting 15 samples from volunteers and compared the results with commercial ELISA kits.

RESULTS

Detection of CRP, PCT, and IL-6 exhibited good linear relationships between CL intensities and concentrations in the range of 1.25-40 μg/ml, 0.4-12.8 ng/ml, and 50-1600 pg/ml, respectively. The limit of detection of CRP, PCT, and IL-6 were 0.54 μg/ml, 0.11 ng/ml, and 16.25 pg/ml, respectively. WMC-MDP is capable of good adequate selectivity and repeatability. The whole detection procedure takes only 22 min that meets the requirements of a POC device. Results of 15 samples from volunteers were consistent with the results detected by commercial ELISA kits.

CONCLUSIONS

WMC-MDP allows simultaneous, rapid, and sensitive detection of CRP, PCT, and IL-6 with satisfactory selectivity and repeatability, requiring minimal manipulation. However, WMC-MDP takes advantage of being a microfluidic device showing the coefficients of variation less than 10% enabling WMC-MDP to be a type of point-of-care testing (POCT). Therefore, WMC-MDP provides a promising alternative to POCT of multiple biomarkers. We believe the practical application of WMC-MDP in militarized fields will revolutionize infection diagnosis for soldiers.

Bridging the gap between development of point-of-care nucleic acid testing and patient care for sexually transmitted infections

The incidence rates of sexually transmitted infections (STIs), including the four major curable STIs - chlamydia, gonorrhea, trichomoniasis and, syphilis - continue to increase globally, causing medical cost burden and morbidity especially in low and middle-income countries (LMIC). There have seen significant advances in diagnostic testing, but commercial antigen-based point-of-care tests (POCTs) are often insufficiently sensitive and specific, while near-point-of-care (POC) instruments that can perform sensitive and specific nucleic acid amplification tests (NAATs) are technically complex and expensive, especially for LMIC. Thus, there remains a critical need for NAAT-based STI POCTs that can improve diagnosis and curb the ongoing epidemic. Unfortunately, the development of such POCTs has been challenging due to the gap between researchers developing new technologies and healthcare providers using these technologies. This review aims to bridge this gap. We first present a short introduction of the four major STIs, followed by a discussion on the current landscape of commercial near-POC instruments for the detection of these STIs. We present relevant research toward addressing the gaps in developing NAAT-based STI POCT technologies and supplement this discussion with technologies for HIV and other infectious diseases, which may be adapted for STIs. Additionally, as case studies, we highlight the developmental trajectory of two different POCT technologies, including one approved by the United States Food and Drug Administration (FDA). Finally, we offer our perspectives on future development of NAAT-based STI POCT technologies.

Recent advances in porous microneedles: materials, fabrication, and transdermal applications

In the past two decades, microneedles (MNs), as a painless and simple drug delivery system, have received increasing attention for various biomedical applications such as transdermal drug delivery, interstitial fluid (ISF) extraction, and biosensing. Among the various types of MNs, porous MNs have been recently researched owing to their distinctive and unique characteristics, where porous structures inside MNs with continuous nano- or micro-sized pores can transport drugs or biofluids by capillary action. In addition, a wide range of materials, including non-polymers and polymers, were researched and used to form the porous structures of porous MNs. Adjustable porosity by different fabrication methods enables the achievement of sufficient mechanical strength by optimising fluid flows inside MNs. Moreover, biocompatible porous MNs integrated with biosensors can offer portable detection and rapid measurement of biomarkers in a minimally invasive manner. This review focuses on several aspects of current porous MN technology, including material selection, fabrication processes, biomedical applications, primarily covering transdermal drug delivery, ISF extraction, and biosensing, along with future prospects as well as challenges.

Lab on a body for biomedical electrochemical sensing applications: The next generation of microfluidic devices

This chapter highlights applications of microfluidic devices toward on-body biosensors. The emerging application of microfluidics to on-body bioanalysis is a new strategy to establish systems for the continuous, real-time, and on-site determination of informative markers present in biofluids, such as sweat, interstitial fluid, blood, saliva, and tear. Electrochemical sensors are attractive to integrate with such microfluidics due to the possibility to be miniaturized. Moreover, on-body microfluidics coupled with bioelectronics enable smart integration with modern information and communication technology. This chapter discusses requirements and several challenges when developing on-body microfluidics such as difficulties in manipulating small sample volumes while maintaining mechanical flexibility, power-consumption efficiency, and simplicity of total automated systems. We describe key components, e.g., microchannels, microvalves, and electrochemical detectors, used in microfluidics. We also introduce representatives of advanced lab-on-a-body microfluidics combined with electrochemical sensors for biomedical applications. The chapter ends with a discussion of the potential trends of research in this field and opportunities. On-body microfluidics as modern total analysis devices will continue to bring several fascinating opportunities to the field of biomedical and translational research applications.

Graphene-enabled wearable sensors for healthcare monitoring

Wearable sensors in healthcare monitoring have recently found widespread applications in biomedical fields for their non- or minimal-invasive, user-friendly and easy-accessible features. Sensing materials is one of the major challenges to achieve these superiorities of wearable sensors for healthcare monitoring, while graphene-based materials with many favorable properties have shown great efficiency in sensing various biochemical and biophysical signals. In this paper, we review state-of-the-art advances in the development and modification of graphene-based materials (i.e., graphene, graphene oxide and reduced graphene oxide) for fabricating advanced wearable sensors with 1D (fibers), 2D (films) and 3D (foams/aerogels/hydrogels) macroscopic structures. We summarize the structural design guidelines, sensing mechanisms, applications and evolution of the graphene-based materials as wearable sensors for healthcare monitoring of biophysical signals (e.g., mechanical, thermal and electrophysiological signals) and biochemical signals from various body fluids and exhaled gases. Finally, existing challenges and future prospects are presented in this area.

A centrifugal microfluidic chip for point-of-care testing of staphylococcal enterotoxin B in complex matrices

Staphylococcal enterotoxin B (SEB) is a typical biological toxin that causes food poisoning. Currently reported SEB detection methods have the drawbacks of sophisticated sample preparation and being time-consuming and labor-intensive. Herein, we propose a strategy based on an immune sandwich structure operating on a centrifugal microfluidic chip for point-of-care testing (POCT) of SEB. The fluorescent microparticle-labeled primary antibody (CM-EUs-Ab₁), capture antibody (CAb), and goat anti-mouse IgG antibody (SAb) were modified on the bond area, T-area, and C-area, respectively. When SEB was added, it first reacted with the CM-EUs-Ab₁ through the specific recognition between SEB and the Ab₁. Then, under capillarity, the conjugates of SEB and the CM-EUs-Ab₁ were captured by the CAb when they flowed to the T-area, and the remaining CM-EUs-Ab₁ bound with the SAb in the C-area. Finally, this chip was put into a dry fluorescence detection analyzer for centrifugation and on-site detection of SEB. The fluorescence intensity ratio of the T-area to the C-area was positively correlated with the concentration of SEB. The resulting linear range was 0.1-250 ng mL^-1, and the limit of detection (3σ/k) was 68 pg mL^-1. This POCT platform only needs 20 μL of sample and can realize the full process of detection within 12 min. This chip also exhibits good stability for 35 days. Additionally, the proposed method has been successfully utilized for the detection of SEB in urine, milk, and juice without any pre-treatment of the samples. Thus, this platform is expected to be applied to food safety testing and clinical diagnosis.

Large-Area Interfaces for Single-Molecule Label-free Bioelectronic Detection

Bioelectronic transducing surfaces that are nanometric in size have been the main route to detect single molecules. Though enabling the study of rarer events, such methodologies are not suited to assay at concentrations below the nanomolar level. Bioelectronic field-effect-transistors with a wide (μm²-mm²) transducing interface are also assumed to be not suited, because the molecule to be detected is orders of magnitude smaller than the transducing surface. Indeed, it is like seeing changes on the surface of a one-kilometer-wide pond when a droplet of water falls on it. However, it is a fact that a number of large-area transistors have been shown to detect at a limit of detection lower than femtomolar; they are also fast and hence innately suitable for point-of-care applications. This review critically discusses key elements, such as sensing materials, FET-structures, and target molecules that can be selectively assayed. The amplification effects enabling extremely sensitive large-area bioelectronic sensing are also addressed.

Nanomaterials for IoT Sensing Platforms and Point-of-Care Applications in South Korea

Herein, state-of-the-art research advances in South Korea regarding the development of chemical sensing materials and fully integrated Internet of Things (IoT) sensing platforms were comprehensively reviewed for verifying the applicability of such sensing systems in point-of-care testing (POCT). Various organic/inorganic nanomaterials were synthesized and characterized to understand their fundamental chemical sensing mechanisms upon exposure to target analytes. Moreover, the applicability of nanomaterials integrated with IoT-based signal transducers for the real-time and on-site analysis of chemical species was verified. In this review, we focused on the development of noble nanostructures and signal transduction techniques for use in IoT sensing platforms, and based on their applications, such systems were classified into gas sensors, ion sensors, and biosensors. A future perspective for the development of chemical sensors was discussed for application to next-generation POCT systems that facilitate rapid and multiplexed screening of various analytes.

Recent Advances and Applications in Paper-Based Devices for Point-of-Care Testing

Point-of-care testing (POCT), as a portable and user-friendly technology, can obtain accurate test results immediately at the sampling point. Nowadays, microfluidic paper-based analysis devices (μPads) have attracted the eye of the public and accelerated the development of POCT. A variety of detection methods are combined with μPads to realize precise, rapid and sensitive POCT. This article mainly introduced the development of electrochemistry and optical detection methods on μPads for POCT and their applications on disease analysis, environmental monitoring and food control in the past 5 years. Finally, the challenges and future development prospects of μPads for POCT were discussed.

Innovations in infectious disease testing: Leveraging COVID-19 pandemic technologies for the future

Innovations in infectious disease testing have improved our abilities to detect and understand the microbial world. The 2019 novel coronavirus infectious disease (COVID-19) pandemic introduced new innovations including non-prescription “over the counter” infectious disease tests, mass spectrometry-based detection of COVID-19 host response, and the implementation of artificial intelligence (AI) and machine learning (ML) to identify individuals infected by the severe acute respiratory syndrome - coronavirus – 2 (SARS-CoV-2). As the world recovers from the COVID-19 pandemic; these innovative solutions will give rise to a new era of infectious disease tests extending beyond the detection of SARS-CoV-2. To this end, the purpose of this review is to summarize current trends in infectious disease testing and discuss innovative applications specifically in the areas of POC testing, MS, molecular diagnostics, sample types, and AI/ML.

Advances and applications of nanophotonic biosensors

Nanophotonic devices, which control light in subwavelength volumes and enhance light-matter interactions, have opened up exciting prospects for biosensing. Numerous nanophotonic biosensors have emerged to address the limitations of the current bioanalytical methods in terms of sensitivity, throughput, ease-of-use and miniaturization. In this Review, we provide an overview of the recent developments of label-free nanophotonic biosensors using evanescent-field-based sensing with plasmon resonances in metals and Mie resonances in dielectrics. We highlight the prospects of achieving an improved sensor performance and added functionalities by leveraging nanostructures and on-chip and optoelectronic integration, as well as microfluidics, biochemistry and data science toolkits. We also discuss open challenges in nanophotonic biosensing, such as reducing the overall cost and handling of complex biological samples, and provide an outlook for future opportunities to improve these technologies and thereby increase their impact in terms of improving health and safety.

Simple manual roller pump-driven valve-free microfluidic solution exchange system for urgent bioassay

We introduce a simple-to-use manual roller pump (MRP)-driven and valve-free microfluidic system for sequential solution exchange, followed by a bioassay to detect protein. The polydimethylsiloxane (PDMS)/glass-based disposable device comprises a reaction chamber, multiple micro-flow channels (μFCs), and air vents. The practical solution exchange was realized by sequential injection and withdrawal of several solutions into and from the reaction chamber through constricted μFCs by utilizing changing air pressure of an MRP when a small cylindrical roller was pressed and rolled over a soft silicone tube using a finger. Furthermore, we investigated the effect of surface hydrophobicity on solution exchange. A sandwich fluorescence-based immunoassay to detect human interleukin 2 (IL-2) was performed using this simple microfluidic scheme to demonstrate its suitability for analytical bioassays. The system allowed quick IL-2 detection in 20 min in a pre-functionalized device with a detection limit of 80 pg mL⁻¹ and a range of 125 pg mL⁻¹ to 2.0 ng mL⁻¹. We have thus developed a microfluidic scheme that non-experts can efficiently perform and that can be the fundamental module for low-cost bioassays necessary for emergencies and situations where resources are constrained.

We report an easy microfluidic solution exchange system that employs a finger-driven manual roller pump (MRP) and valveless micro-flow structures to enable minimally trained personnel to execute instantaneous stepwise bioassays.

Electronic Textiles for Wearable Point-of-Care Systems

Traditional public health systems are suffering from limited, delayed, and inefficient medical services, especially when confronted with the pandemic and the aging population. Fusing traditional textiles with diagnostic, therapeutic, and protective medical devices can unlock electronic textiles (e-textiles) as point-of-care platform technologies on the human body, continuously monitoring vital signs and implementing round-the-clock treatment protocols in close proximity to the patient. This review comprehensively summarizes the research advances on e-textiles for wearable point-of-care systems. We start with a brief introduction to emphasize the significance of e-textiles in the current healthcare system. Then, we describe textile sensors for diagnosis, textile therapeutic devices for medical treatment, and textile protective devices for prevention, by highlighting their working mechanisms, representative materials, and clinical application scenarios. Afterward, we detail e-textiles' connection technologies as the gateway for real-time data transmission and processing in the context of 5G technologies and Internet of Things. Finally, we provide new insights into the remaining challenges and future directions in the field of e-textiles. Fueled by advances in chemistry and materials science, textile-based diagnostic devices, therapeutic devices, protective medical devices, and communication units are expected to interact synergistically to construct intelligent, wearable point-of-care textile platforms, ultimately illuminating the future of healthcare system in the Internet of Things era.

Instant Preparation of Ultraclean Gold Nanothorns under Ambient Conditions for SERS Kit-Enabled Mobile Diagnosis

Availability of surface-enhanced Raman scattering (SERS) substrates with good stability, high sensitivity, and a clean surface is crucial for the practical usefulness of the SERS technology in biochemical sensing, especially for point-of-care testing (POCT). Hereby, we develop a "ready-to-use" SERS kit, which requires only 20 s to fabricate ultraclean gold nanothorn (AuNT)-based SERS chips under ambient conditions with simple solution processing steps. By varying the thickness of the pre-coated platinum (Pt) nanolayer, we can control the size and number density of the grown AuNT. Taking advantage of the ultraclean surface of the instantly obtained fresh AuNT, Raman reporter molecules can also be immediately modified, by means of which specific detection of three analytes including H₂O₂, NO₂^-, and ClO^- is realized. Furthermore, we propose the concept of an SERS kit and apply it to smartphone-based Raman analysis for POCT applications. This on-site preparation method solves the long-standing challenges hindering the practical use of SERS substrates, such as complicated fabrication processes, interference of residual surfactants, poor surface stability, and easy contamination. Besides performing SERS analysis conveniently and quickly, this SERS kit-enabled POCT technology can integrate remote data terminals and medical resources, which shows great potential for environmental protection or online-healthcare systems.