An electricity- and instrument-free infectious disease sensor based on a 3D origami paper-based analytical device

Eco-sustainable point-of-care devices: Progress in paper and fabric based electrochemical and colorimetric biosensors

Monitoring real-time health conditions is a rinsing demand in a pandemic prone era. Wearable Point-of-Care (POC) devices with paper and fabric-based sensors are emerging as simple, low-cost, portable, and disposable analytical tools for development of green POC devices (GPOCDs). Capabilities of passive fluid transportation, compatibility with biochemical analytes, disposability and high degree of tunability using vivid device fabrication strategies enables development of highly sensitive and economically feasible POC sensors in particularly post COVID-19 pandemic outbreak. Herein we focus mainly on development of biosensors for testing body fluids in the last 5 years using microfluidic technique through electrochemical and colorimetric principle which forms the two most competing sensing techniques providing quantitative and qualitative assessment modalities respectively and forms almost 80 % of the diagnostic platform worldwide. Present review highlights use of these popular substrates as well as various fabrication strategies for realization of GPOCDs ranging from costly and highly sophisticated photolithography to low cost, non conventional techniques like use of correction ink or marker based devices to even novel pop-up/origami induced patterning techniques. Insights into the advancements in colorimetric technique like distance, count or even text based semi-quantitative read-out modality as a on-hand diagnostic information has also been provided. Finally, future outlooks with other interdisciplinary modalities like use of novel materials, incorporation of digital tools like artificial intelligence (AI), machine learning (ML) and strategies for sensitivity and reliability improvement of future GPOCDs have also been discussed.

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.

Development of a Semiquantitative Barcode Readout Approach for Paper-Based Analytical Devices (PADs) for Enzymatic H2O2 and Glucose Detection

The integration of barcode technology with smartphones on paper-based analytical devices (PADs) presents a promising approach to bridging manual detection with digital interpretation and data storage. However, previous studies of 1D barcode approaches have been limited to providing only a "yes/no" response for analyte detection. Herein, a method of using barcode readout for semiquantitative signal detection on PADs has been achieved through the integration of barcode technology with a distance-based measurement concept on PADs. To demonstrate the feasibility of this concept, a PAD fabrication strategy incorporating barcodes was explored, using the enzymatic reaction between horseradish peroxidase (HRP), 3,3'-diaminobenzidine (DAB), and H2O2 as a model system. The enzyme-catalyzed polymerization of DAB to polyDAB in the presence of hydrogen peroxide results in the appearance of color observable by the naked eye inside a paperfluidic channel, with the color-changed length depending on the H2O2 concentration. At the same time, the barcode pattern displayed as a result of this distance-based color evolution overlaid with a paper-based barcode layer can be read using a smartphone application. Parameters affecting the signal readout performance were studied. The developed device can be used to detect H2O2 concentrations in the range of 0.25 to 10 mM within 90 min with 79.6% of barcode signals correctly readable. Additionally, results from different smartphone models showed a consistent reading performance (78.4-79.6%). Finally, the quantification of glucose levels in artificial urine samples was demonstrated. This developed PAD signaling strategy offers end-users more simplicity and can be used as a standalone device or in conjunction with other digital devices.

Highly catalytic Prussian blue analogues and their application on the three-dimensional origami paper-based sweat sensors

Prussian blue analogues (PBAs) are promising materials due to their rich active sites and straightforward synthesis. However, their limited conductivity and electron transfer inefficiency hinder practical applications. This study utilizes a simple one-pot synthesis approach to produce a tungsten-disulfide (WS2) and iron-cobalt Prussian blue analogue composite (WS2-PBA), enhancing conductivity and electron transfer rate performance. Through the inclusion of sodium citrate into the solution, the S-edge site concentration of WS2 increases. This augmentation introduces additional active sites and defects into the catalyst, enhancing its catalytic activity. The effectiveness of the WS2-PBA 3D-Origami paper device for lactate detection in sweat is also evaluated for biomedical applications. The device demonstrated a robust relationship between the lactate concentration and current intensity (R2 = 0.997), with a detection limit of 1.83 mM. Additionally, this platform has successfully detected lactate in clinical sweat, correlating with the high-performance liquid chromatography test results, suggesting promising prospects for clinical diagnosis. In the future, the excellent catalytic and Rct performance of the WS2-PBA will enable its use in biomedical applications.

Paper-based sensors: affordable, versatile, and emerging analyte detection platforms

Paper-based sensors, often referred to as paper-based analytical devices (PADs), stand as a transformative technology in the field of analytical chemistry. They offer an affordable, versatile, and accessible solution for diverse analyte detection. These sensors harness the unique properties of paper substrates to provide a cost-effective and adaptable platform for rapid analyte detection, spanning chemical species, biomolecules, and pathogens. This review highlights the key attributes that make paper-based sensors an attractive choice for analyte detection. PADs demonstrate their versatility by accommodating a wide range of analytes, from ions and gases to proteins, nucleic acids, and more, with customizable designs for specific applications. Their user-friendly operation and minimal infrastructure requirements suit point-of-care diagnostics, environmental monitoring, food safety, and more. This review also explores various fabrication methods such as inkjet printing, wax printing, screen printing, dip coating, and photolithography. Incorporating nanomaterials and biorecognition elements promises even more sophisticated and sensitive applications.

Microfluidic systems for infectious disease diagnostics

Microorganisms, encompassing both uni- and multicellular entities, exhibit remarkable diversity as omnipresent life forms in nature. They play a pivotal role by supplying essential components for sustaining biological processes across diverse ecosystems, including higher host organisms. The complex interactions within the human gut microbiota are crucial for metabolic functions, immune responses, and biochemical signalling, particularly through the gut-brain axis. Viruses also play important roles in biological processes, for example by increasing genetic diversity through horizontal gene transfer when replicating inside living cells. On the other hand, infection of the human body by microbiological agents may lead to severe physiological disorders and diseases. Infectious diseases pose a significant burden on global healthcare systems, characterized by substantial variations in the epidemiological landscape. Fast spreading antibiotic resistance or uncontrolled outbreaks of communicable diseases are major challenges at present. Furthermore, delivering field-proven point-of-care diagnostic tools to the most severely affected populations in low-resource settings is particularly important and challenging. New paradigms and technological approaches enabling rapid and informed disease management need to be implemented. In this respect, infectious disease diagnostics taking advantage of microfluidic systems combined with integrated biosensor-based pathogen detection offers a host of innovative and promising solutions. In this review, we aim to outline recent activities and progress in the development of microfluidic diagnostic tools. Our literature research mainly covers the last 5 years. We will follow a classification scheme based on the human body systems primarily involved at the clinical level or on specific pathogen transmission modes. Important diseases, such as tuberculosis and malaria, will be addressed more extensively.

Self-Powered Microfluidics for Point-of-Care Solutions: From Sampling to Detection of Proteins and Nucleic Acids

Self-powered microfluidics presents a revolutionary approach to address the challenges of healthcare in decentralized and point-of-care settings where limited access to resources and infrastructure prevails or rapid clinical decision-making is critical. These microfluidic systems exploit physical and chemical phenomena, such as capillary forces and surface tension, to manipulate tiny volumes of fluids without the need for external power sources, making them cost-effective and highly portable. Recent technological advancements have demonstrated the ability to preprogram complex multistep liquid operations within the microfluidic circuit of these standalone systems, which enabled the integration of sensitive detection and readout principles. This chapter first addresses how the accessibility to in vitro diagnostics can be improved by shifting toward decentralized approaches like remote microsampling and point-of-care testing. Next, the crucial role of self-powered microfluidic technologies to enable this patient-centric healthcare transition is emphasized using various state-of-the-art examples, with a primary focus on applications related to biofluid collection and the detection of either proteins or nucleic acids. This chapter concludes with a summary of the main findings and our vision of the future perspectives in the field of self-powered microfluidic technologies and their use for in vitro diagnostics applications.

Paper-based colorimetric sensors for point-of-care testing

By eliminating the need for sample transportation and centralized laboratory analysis, point-of-care testing (POCT) enables on-the-spot testing, with results available within minutes, leading to improved patient management and overall healthcare efficiency. Motivated by the rapid development of POCT, paper-based colorimetric sensing, a powerful analytical technique that exploits the changes in color or absorbance of a chemical species to detect and quantify analytes of interest, has garnered increasing attention. In this review, we strive to provide a bird's eye view of the development landscape of paper-based colorimetric sensors that harness the unique properties of paper to create low-cost, easy-to-use, and disposable analytical devices, thematically covering both fundamental aspects and categorized applications. In the end, we authors summarized the review with the remaining challenges and emerging opportunities. Hopefully, this review will ignite new research endeavors in the realm of paper-based colorimetric sensors.

A 3D paper microfluidic device for enzyme-linked assays: Application to DNA analysis

A paper microfluidic device capable of conducting enzyme-linked assays is presented: a microfluidic enzyme-linked paper analytical device (μEL-PAD). The system exploits a wash-free sandwich coupling to form beads/analyte/enzyme complexes, which are subsequently added to the vertical flow device composed of wax-printed paper, waxed nitrocellulose membrane and absorbent/barrier layers. The nitrocellulose retains the bead complexes without disrupting the flow, enabling for an efficient washing step. The entrapped complexes then interact with the chromogenic substrate stored on the detection paper, generating a color change on it, quantified with an open-source smartphone software. This is a universal paper-based technology suitable for high-sensitivity quantification of many analytes, such as proteins or nucleic acids, with different enzyme-linked formats. Here, the potential of the μEL-PAD is demonstrated to detect DNA from Staphylococcus epidermidis. After generation of isothermally amplified genomic DNA from bacteria, Biotin/FITC-labeled products were analyzed with the μEL-PAD, exploiting streptavidin-coated beads and antiFITC-horseradish peroxidase. The μEL-PAD achieved a limit of detection (LOD) and quantification <10 genome copies/μL, these being at least 70- and 1000-fold lower, respectively, than a traditional lateral flow assay (LFA) exploiting immobilized streptavidin and antiFITC-gold nanoparticles. It is envisaged that the device will be a good option for low-cost, simple, quantitative, and sensitive paper-based point-of-care testing.

Advancement in Paper-Based Electrochemical Biosensing and Emerging Diagnostic Methods

The utilization of electrochemical detection techniques in paper-based analytical devices (PADs) has revolutionized point-of-care (POC) testing, enabling the precise and discerning measurement of a diverse array of (bio)chemical analytes. The application of electrochemical sensing and paper as a suitable substrate for point-of-care testing platforms has led to the emergence of electrochemical paper-based analytical devices (ePADs). The inherent advantages of these modified paper-based analytical devices have gained significant recognition in the POC field. In response, electrochemical biosensors assembled from paper-based materials have shown great promise for enhancing sensitivity and improving their range of use. In addition, paper-based platforms have numerous advantageous characteristics, including the self-sufficient conveyance of liquids, reduced resistance, minimal fabrication cost, and environmental friendliness. This study seeks to provide a concise summary of the present state and uses of ePADs with insightful commentary on their practicality in the field. Future developments in ePADs biosensors include developing novel paper-based systems, improving system performance with a novel biocatalyst, and combining the biosensor system with other cutting-edge tools such as machine learning and 3D printing.

Hollow microneedle microfluidic paper-based chip for biomolecules rapid sampling and detection in interstitial fluid

The interstitial fluid (ISF) contains rich bioinformation for disease diagnosis and healthcare monitoring. However, the efficient sampling and detection of the biomolecules in ISF is still challenging. Herein, we develop a facile but versatile ISF analysis platform by combining controllable hollow microneedles (HMNs) and elaborate microfluidic paper-based analytical devices (μPADs). The HMNs and μPADs was fixed in a bottom PDMS layer. A top PDMS layer containing a cylindrical cavity to produce negative pressure for sampling was packaged on the bottom PDMS layer. The HMNs enable efficient and swift sampling of sufficient ISF to the μPADs through one-touch finger operation without extra manipulations. The μPADs realized to simultaneously detect glucose and lactic acid in the detection area to produce chromogenic agents and analyzed by the self-programed RGB application (APP) in smartphones. The HMN microfluidic paper-based chip provides a point-of-care platform for accurate detection of biomolecules in ISF, holding great promise in the development of wearable device.

Recent Advances in Molecular and Immunological Diagnostic Platform for Virus Detection: A Review

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused an ongoing coronavirus disease (COVID-19) outbreak and a rising demand for the development of accurate, timely, and cost-effective diagnostic tests for SARS-CoV-2 as well as other viral infections in general. Currently, traditional virus screening methods such as plate culturing and real-time PCR are considered the gold standard with accurate and sensitive results. However, these methods still require sophisticated equipment, trained personnel, and a long analysis time. Alternatively, with the integration of microfluidic and biosensor technologies, microfluidic-based biosensors offer the ability to perform sample preparation and simultaneous detection of many analyses in one platform. High sensitivity, accuracy, portability, low cost, high throughput, and real-time detection can be achieved using a single platform. This review presents recent advances in microfluidic-based biosensors from many works to demonstrate the advantages of merging the two technologies for sensing viruses. Different platforms for virus detection are classified into two main sections: immunoassays and molecular assays. Moreover, available commercial sensing tests are analyzed.

Paper-based analytical devices for point-of-need applications

Paper-based analytical devices (PADs) are powerful platforms for point-of-need testing since they are inexpensive devices fabricated in different shapes and miniaturized sizes, ensuring better portability. Additionally, the readout and detection systems can be accomplished with portable devices, allying with the features of both systems. These devices have been introduced as promising analytical platforms to meet critical demands involving rapid, reliable, and simple testing. They have been applied to monitor species related to environmental, health, and food issues. Herein, an outline of chronological events involving PADs is first reported. This work also introduces insights into fundamental parameters to engineer new analytical platforms, including the paper type and device operation. The discussions involve the main analytical techniques used as detection systems, such as colorimetry, fluorescence, and electrochemistry. It also showed recent advances involving PADs, especially combining optical and electrochemical detection into a single device. Dual/combined detection systems can overcome individual barriers of the analytical techniques, making possible simultaneous determinations, or enhancing the devices' sensitivity and/or selectivity. In addition, this review reports on distance-based detection, which is also considered a trend in analytical chemistry. Distance-based detection offers instrument-free analyses and avoids user interpretation errors, which are outstanding features for analyses at the point of need, especially for resource-limited regions. Finally, this review provides a critical overview of the practical specifications of the recent analytical platforms involving PADs, demonstrating their challenges. Therefore, this work can be a highly useful reference for new research and innovation.

Self-assembly of protein-DNA superstructures for alkaline phosphatase detection in blood

We designed a paper-based analytical device by integrating horseradish peroxidase (HRP)-encapsulated 3D DNA for visual detection of alkaline phosphatase (ALP). This device allows on-paper sample pre-treatment, target recognition and signal readout, enabling simple (without additional pre-treatment of blood samples) and rapid (within 23 min) determination of ALP in clinical samples.

Device integration of electrochemical biosensors

Electrochemical biosensors incorporate a recognition element and an electronic transducer for the highly sensitive detection of analytes in body fluids. Importantly, they can provide rapid readouts and they can be integrated into portable, wearable and implantable devices for point-of-care diagnostics; for example, the personal glucose meter enables at-home assessment of blood glucose levels, greatly improving the management of diabetes. In this Review, we discuss the principles of electrochemical biosensing and the design of electrochemical biosensor devices for health monitoring and disease diagnostics, with a particular focus on device integration into wearable, portable and implantable systems. Finally, we outline the key engineering challenges that need to be addressed to improve sensing accuracy, enable multiplexing and one-step processes, and integrate electrochemical biosensing devices in digital health-care pathways.

Current Advancements and Future Road Map to Develop ASSURED Microfluidic Biosensors for Infectious and Non-Infectious Diseases

Better diagnostics are always essential for the treatment and prevention of a disease. Existing technologies for detecting infectious and non-infectious diseases are mostly tedious, expensive, and do not meet the World Health Organization's (WHO) ASSURED (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free, and deliverable to end user) criteria. Hence, more accurate, sensitive, and faster diagnostic technologies that meet the ASSURED criteria are highly required for timely and evidenced-based treatment. Presently, the diagnostics industry is finding interest in microfluidics-based biosensors, as this integration comprises all qualities, such as reduction in the size of the equipment, rapid turnaround time, possibility of parallel multiple analysis or multiplexing, etc. Microfluidics deal with the manipulation/analysis of fluid within micrometer-sized channels. Biosensors comprise biomolecules immobilized on a physicochemical transducer for the detection of a specific analyte. In this review article, we provide an outline of the history of microfluidics, current practices in the selection of materials in microfluidics, and how and where microfluidics-based biosensors have been used for the diagnosis of infectious and non-infectious diseases. Our inclination in this review article is toward the employment of microfluidics-based biosensors for the improvement of already existing/traditional methods in order to reduce efforts without compromising the accuracy of the diagnostic test. This article also suggests the possible improvements required in microfluidic chip-based biosensors in order to meet the ASSURED criteria.

Rapid and accurate nanoelectrokinetic diagnosis of drug-resistant bacteria

Increased antimicrobial resistance presents a major threat to public health, and it is a global health problem due to the rapid globalization and transmission of infectious diseases. However, fast and precise diagnosis tool is lacking, and inappropriate antibiotic prescription leads to the unforeseen production of drug-resistant bacteria. Here, we report a Rapid and Accurate Nanoelectrokinetic Diagnostic System (RANDx) for detecting drug-resistant bacteria, which cause a common infectious disease called Urinary Tract Infection (UTI), within 7 min. We develop nanoelectrokinetic paper-based analytic device (NEK-PAD) as a sample prep module of RANDx and obtain >100-fold post-wetting preconcentration by balancing between ion concentration polarization (ICP) and radial imbibition for a constant flow rate. Simultaneously with preconcentration, our cathodic nanochannel design enables NEK-PAD to extract drug-resistant enzymes without denaturation and accelerate enzyme-linked reactions under electrical spontaneous heating at approximately 37 °C. Finally, using a cell phone camera, we detect label-free drug-resistant bacteria as low as 10⁴ cfu/mL, which is higher than clinically required threshold (>10⁵ cfu/mL) by enhancing 1000 times of the limit of detection (LOD) of colorimetric nitrocefin assay. We believe that the RANDx will be an innovative precision medicine tool for UTI and other infectious diseases in limited remote settings.

A finger-driven disposable micro-platform based on isothermal amplification for the application of multiplexed and point-of-care diagnosis of tuberculosis

Tuberculosis (TB) remains the high-risk infectious pathogen that caused global pandemic and high mortality, particularly in the areas lack in health resources. Clinical TB screening and diagnosis are so far mainly conducted on limited types of commercial platforms, which are expensive and require skilled personnel. In this work, we introduced a low-cost and portable finger-driven microfluidic chip (named Fd-MC) based on recombinase polymerase amplification (RPA) for rapid on-site detection of TB. After injection of the pre-treated sample solution, the pre-packaged buffer was driven by the pressure generated by the finger-actuated operation to accomplish sequential processes of diagnosis in a fully isolated microchannel. An in-situ fluorescence strategy based on FAM-probe was implemented for on-chip results read-out though a hand-held UV lamp. Hence, the Fd-MC proved unique advantageous for avoiding the risk of infection or environmental contamination. In addition, the Fd-MC was designed for multiplexed detection, which is able to not only identify TB/non-TB infection, but also differentiate between human Mycobacterium tuberculosis and Mycobacterium bovis. The platform was verified in 37 clinical samples, statistically with 100% specificity and 95.2% sensitivity as compared to commercial real-time RPA. Overall, the proposed platform eliminates the need on external pumps and skilled personnel, holding promise to POC testing in the resource-limited area.

Microfluidic Paper-based Device for Medicinal Diagnosis

BACKGROUND

The demand for point-of-care testing (POCT) devices has rapidly grown since they offer immediate test results with ease of use, makingthem suitable for home self-testing patients and caretakers. However, the POCT development has faced the challenges of increased cost and limited resources. Therefore, the paper substrate as a low-cost material has been employed to develop a cost-effective POCT device, known as "Microfluidic paper-based analytical devices (μPADs)". This device is gaining attention as a promising tool for medicinal diagnostic applications owing to its unique features of simple fabrication, low cost, enabling manipulation flow (capillarydriven flow), the ability to store reagents, and accommodating multistep assay requirements.

OBJECTIVE

This review comprehensively examines the fabrication methods and device designs (2D/3D configuration) and their advantages and disadvantages, focusing on updated μPADs applications for motif identification.

METHODS

The evolution of paper-based devices, starting from the traditional devices of dipstick and lateral flow assay (LFA) with μPADs, has been described. Patterned structure fabrication of each technique has been compared among the equipment used, benefits, and drawbacks. Microfluidic device designs, including 2D and 3D configurations, have been introduced as well as their modifications. Various designs of μPADs have been integrated with many powerful detection methods such as colorimetry, electrochemistry, fluorescence, chemiluminescence, electrochemiluminescence, and SER-based sensors for medicinal diagnosis applications.

CONCLUSION

The μPADs potential to deal with commercialization in terms of the state-of-the-art of μPADs in medicinal diagnosis has been discussed. A great prototype, which is currently in a reallife application breakthrough, has been updated.

Paper-based analytical devices for virus detection: Recent strategies for current and future pandemics

The importance of user-friendly, inexpensive, sensitive, and selective detection of viruses has been highlighted again due to the recent Coronavirus disease 2019 (COVID-19) pandemic. Among the analytical tools, paper-based devices (PADs) have become a leading alternative for point-of-care (POC) testing. In this review, we discuss the recent development strategies and applications in nucleic acid-based, antibody/antigen-based and other affinity-based PADs using optical and electrochemical detection methods for sensing viruses. In addition, advantages and drawbacks of presented PADs are identified. Current state and insights towards future perspectives are presented regarding developing POC diagnosis platform for COVID-19. This review considers state-of-the-art technologies for further development and improvement in PADs performance for virus detection.

Using Stereolithographic Printing to Manufacture Monolithic Microfluidic Devices with an Extremely High Aspect Ratio

Stereolithographic printing (SL) is widely used to create mini/microfluidic devices; however, the formation of microchannels smaller than 500 μm with good inner surface quality is still challenging due to the printing resolution of current commercial printers and the z-overcure error and scalloping phenomena. In the current study, we used SL printing to create microchannels with the aim of achieving a high degree of dimensional precision and a high-quality microchannel inner surface. Extensive experiments were performed and our results revealed the following: (1) the SL printing of microchannels can be implemented in three steps including channel layer printing, an oxygen inhibition process, and roof layer printing; (2) printing thickness should be reduced to minimize the scalloping phenomenon, which significantly improves dimensional accuracy and the quality of inner microchannel surfaces; (3) the inclusion of an oxygen inhibition step is a critical and efficient approach to suppressing the z-overcure error in order to eliminate the formation of in-channel obstructions; (4) microchannels with an extremely high aspect ratio of 40:1 (4000 μm in height and 100 μm in width) can be successfully manufactured within one hour by following the three-step printing process.