Portable biosensing devices for point-of-care diagnostics: Recent developments and applications

Emergence of infectious diseases and role of advanced nanomaterials in point-of-care diagnostics: a review

Infectious outbreaks are the foremost global public health concern, challenging the current healthcare system, which claims millions of lives annually. The most crucial way to control an infectious outbreak is by early detection through point-of-care (POC) diagnostics. POC diagnostics are highly advantageous owing to the prompt diagnosis, which is economical, simple and highly efficient with remote access capabilities. In particular, utilization of nanomaterials to architect POC devices has enabled highly integrated and portable (compact) devices with enhanced efficiency. As such, this review will detail the factors influencing the emergence of infectious diseases and methods for fast and accurate detection, thus elucidating the underlying factors of these infections. Furthermore, it comprehensively highlights the importance of different nanomaterials in POCs to detect nucleic acid, whole pathogens, proteins and antibody detection systems. Finally, we summarize findings reported on nanomaterials based on advanced POCs such as lab-on-chip, lab-on-disc-devices, point-of-action and hospital-on-chip. To this end, we discuss the challenges, potential solutions, prospects of integrating internet-of-things, artificial intelligence, 5G communications and data clouding to achieve intelligent POCs.

Development and validation study of compact biophotonic platform for detection of serum biomarkers

The application of advances in personalized medicine requires the support of in vitro diagnostic techniques aimed at the accurate, fast, sensitive, and precise determination of selected biomarkers. Herein, a novel optical centrifugal microfluidic device is developed for clinical analysis and point-of-care diagnostics. Based on compact disc technology, the integrated biophotonic system enables multiple immunoassays in miniaturized mode. The disposable microfluidic discs are made in cyclic olefin copolymer (COP), containing arrays of immobilized probes. In the developed approach, up to six patient samples can each be tested simultaneously. A portable instrument (<2 kg) controls the assay and the high-sensitive reproducible optical detection in transmission mode. Also, the instrument incorporates specific functionalities for personalized telemedicine. The device (analytical method, disc platform, reader, and software) has been validated to diagnose IgE-mediated drug allergies, such as amoxicillin and penicillin G. The total and specific IgE to β-lactam antibiotics were determined in human serum from patients (25 μL). The excellent analytical performances (detection limit 0.24 ng/mL, standard deviation 7-20 %) demonstrated that the developed system could have the potential for a broader impact beyond the allergy field, as it applies to other IVD tests.

Deep Learning-Assisted Smartphone-Based Electrochemiluminescence Visual Monitoring Biosensor: A Fully Integrated Portable Platform

A novel, portable deep learning-assisted smartphone-based electrochemiluminescence (ECL) cost-effective (~10$) sensing platform was developed and used for selective detection of lactate. Low-cost, fast prototyping screen printing and wax printing methods with paper-based substrate were used to fabricate miniaturized single-pair electrode ECL platforms. The lab-made 3D-printed portable black box served as a reaction chamber. This portable platform was integrated with a smartphone and a buck-boost converter, eliminating the need for expensive CCD cameras, photomultiplier tubes, and bulky power supplies. This advancement makes this platform ideal for point-of-care testing applications. Foremost, the integration of a deep learning approach served to enhance not just the accuracy of the ECL sensors, but also to expedite the diagnostic procedure. The deep learning models were trained (3600 ECL images) and tested (900 ECL images) using ECL images obtained from experimentation. Herein, for user convenience, an Android application with a graphical user interface was developed. This app performs several tasks, which include capturing real-time images, cropping them, and predicting the concentration of required bioanalytes through deep learning. The device's capability to work in a real environment was tested by performing lactate sensing. The fabricated ECL device shows a good liner range (from 50 µM to 2000 µM) with an acceptable limit of detection value of 5.14 µM. Finally, various rigorous analyses, including stability, reproducibility, and unknown sample analysis, were conducted to check device durability and stability. Therefore, the developed platform becomes versatile and applicable across various domains by harnessing deep learning as a cutting-edge technology and integrating it with a smartphone.

A smartphone-enabled colorimetric platform based on enzyme cascade amplification strategy for detection of Staphylococcus aureus in milk

Staphylococcus aureus is a pathogenic bacterium contaminating milk and dairy foods causing food poisoning and foodborne pathogens. In this work, a smartphone-enabled enzyme cascade-triggered colorimetric platform was constructed using a cascade bio-nanozyme formed by immobilized glucose oxidase (GOx) on Fe3O4@Ag for rapid detection of S. aureus. Benefiting from reasonable experimental design, a bio-nanozyme cascade-triggered reaction was achieved through H2O2 produced by GOx oxidation of glucose, followed by in situ catalysis of 3,3',5,5'-tetramethylbenzidine (TMB) by the inherent peroxidase-like activity of Fe3O4@Ag to produce color signals. Staphylococcus aureus detection could be performed through naked-eye observation and smartphone measurement, and the developed assay can achieve quantitative and qualitative detection of S. aureus. The on-site nanoplatform had satisfactory specificity and sensitivity with a low detection limit of 6.9 cfu·mL-1 in 50 min. Moreover, the nanoplatform has good practicality in the detection of S. aureus in milk samples. Therefore, the assay has potential application prospects in food safety inspection.

Portable all-in-one microfluidic system for CRISPR-Cas13a-based fully integrated multiplexed nucleic acid detection

Point-of-care testing of "sample in, answer out" is urgently needed for communicable diseases. Recently, rapid nucleic acid tests for infectious diseases have been developed for use in resource-limited areas, but they require types of equipment in central laboratories and are poorly integrated. In this work, a portable centrifugal microfluidic testing system is developed, integrated with magnetic bead-based nucleic acid extraction, recombinase-assisted amplification and CRISPR-Cas13a detection. The system, with the advantage of its power-supplied active rotating chip and highly programable flow control through integrated addressable active thermally-triggered wax valves, has a rapid turnaround time within 45 min, requiring only one user step. All reagents are preloaded into the chip and can be automatically released. By exploiting a multichannel chip, it is capable of simultaneously detecting 10 infectious viruses with limits of detection of 1 copy per reaction and 5 copies per reaction in plasmid samples and mock plasma samples, respectively. The system was used to analyse clinical plasma samples with good consistency compared to laboratory-based molecular testing. Moreover, the generalizability of our device is reported by successfully testing nasopharyngeal swabs and whole blood samples. The portable device does not require the operation of professional technicians, making it an excellent assay for on-site testing.

Fabrication of a low-cost benchtop optical imager for quantum dot microarray-based stress biomarker detection

We report on a simplified optical imager to detect the presence of a stress biomarker protein, namely the Heat shock protein 90 (Hsp90). The imager consists of two elements the optical unit and the sensor, which is a custom-made biochip. Measurement is based on the masking of the streptavidin conjugated quantum dot's (Sav-QDs) fluorescence when Hsp90 attaches to it via biotinylated antibodies (Ab). The masking effect was directly proportional to the Hsp90 concentration. The cost-efficient benchtop imager developed comprises a CMOS sensor, standard optical lenses, and a narrow bandpass filter for optically eliminating background fluorescence. This approach is promising for the realization of cheap, robust, and reliable point-of-care detection systems for various biomarker analyses.

Mobile Diagnostic Clinics

This article reviews the revolutionary impact of emerging technologies and artificial intelligence (AI) in reshaping modern healthcare systems, with a particular focus on the implementation of mobile diagnostic clinics. It presents an insightful analysis of the current healthcare challenges, including the shortage of healthcare workers, financial constraints, and the limitations of traditional clinics in continual patient monitoring. The concept of "Mobile Diagnostic Clinics" is introduced as a transformative approach where healthcare delivery is made accessible through the incorporation of advanced technologies. This approach is a response to the impending shortfall of medical professionals and the financial and operational burdens conventional clinics face. The proposed mobile diagnostic clinics utilize digital health tools and AI to provide a wide range of services, from everyday screenings to diagnosis and continual monitoring, facilitating remote and personalized care. The article delves into the potential of nanotechnology in diagnostics, AI's role in enhancing predictive analytics, diagnostic accuracy, and the customization of care. Furthermore, the article discusses the importance of continual, noninvasive monitoring technologies for early disease detection and the role of clinical decision support systems (CDSSs) in personalizing treatment guidance. It also addresses the challenges and ethical concerns of implementing these advanced technologies, including data privacy, integration with existing healthcare infrastructure, and the need for transparent and bias-free AI systems.

Multiarmed DNA jumper and metal-organic frameworks-functionalized paper-based bioplatform for small extracellular vesicle-derived miRNAs assay

Small extracellular vesicle-derived microRNAs (sEV-miRNAs) have emerged as promising noninvasive biomarkers for early cancer diagnosis. Herein, we developed a molecular probe based on three-dimensional (3D) multiarmed DNA tetrahedral jumpers (mDNA-Js)-assisted DNAzyme activated by Na+, combined with a disposable paper-based electrode modified with a Zr-MOF-rGO-Au NP nanocomplex (ZrGA) to fabricate a novel biosensor for sEV-miRNAs Assay. Zr-MOF tightly wrapped by rGO was prepared via a one-step method, and it effectively aids electron transfer and maximizes the effective reaction area. In addition, the mechanically rigid, and nanoscale-addressable mDNA-Js assembled from the bottom up ensure the distance and orientation between fixed biological probes as well as avoid probe entanglement, considerably improving the efficiency of molecular hybridization. The fabricated bioplatform achieved the sensitive detection of sEV-miR-21 with a detection limit of 34.6 aM and a dynamic range from100 aM to 0.2 µM. In clinical blood sample tests, the proposed bioplatform showed results highly consistent with those of qRT-PCRs and the signal increased proportionally with the NSCLC staging. The proposed biosensor with a portable wireless USB-type analyzer is promising for the fast, easy, low-cost, and highly sensitive detection of various nucleic acids and their mutation derivatives, making it ideal for POC biosensing.

A commentary on the development and use of smartphone imaging devices

Current-age smartphones are known for their wide array of functionality and are now being utilized in the field of healthcare and medicine due to their proven capabilities as smartphone imaging devices (SIDs). Recent technical advancements enabled the integration of special add-on lenses with smartphones to transform them into SIDs. With the rising demand for efficient point-of-care (PoC) devices for better diagnostic applications, SIDs will be a one-stop solution. Additionally, portability, user-friendliness and low-cost make it accessible for all even at remote locations. Furthermore, improvements in resolution, magnification and field-of-view (FOV) have attracted the scientific community to use SIDs in various biomedical applications such as disease diagnosis, food quality control and pathogen detection. SIDs can be arranged in various combinational setups by using different illumination sources and optics to achieve suitable contrast and visibility of the specimen under study. This Commentary illustrates the various illumination sources used in SID and also spotlights their design and applications.

Addressing Signal Drift and Screening for Detection of Biomarkers with Carbon Nanotube Transistors

Electrical biosensors, including transistor-based devices (i.e., BioFETs), have the potential to offer versatile biomarker detection in a simple, low-cost, scalable, and point-of-care manner. Semiconducting carbon nanotubes (CNTs) are among the most explored nanomaterial candidates for BioFETs due to their high electrical sensitivity and compatibility with diverse fabrication approaches. However, when operating in solutions at biologically relevant ionic strengths, CNT-based BioFETs suffer from debilitating levels of signal drift and charge screening, which are often unaccounted for or sidestepped (but not addressed) by testing in diluted solutions. In this work, we present an ultrasensitive CNT-based BioFET called the D4-TFT, an immunoassay with an electrical readout, which overcomes charge screening and drift-related limitations of BioFETs. In high ionic strength solution (1X PBS), the D4-TFT repeatedly and stably detects subfemtomolar biomarker concentrations in a point-of-care form factor by increasing the sensing distance in solution (Debye length) and mitigating signal drift effects. Debye length screening and biofouling effects are overcome using a poly(ethylene glycol)-like polymer brush interface (POEGMA) above the device into which antibodies are printed. Simultaneous testing of a control device having no antibodies printed over the CNT channel confirms successful detection of the target biomarker via an on-current shift caused by antibody sandwich formation. Drift in the target signal is mitigated by a combination of: (1) maximizing sensitivity by appropriate passivation alongside the polymer brush coating; (2) using a stable electrical testing configuration; and (3) enforcing a rigorous testing methodology that relies on infrequent DC sweeps rather than static or AC measurements. These improvements are realized in a relatively simple device using printed CNTs and antibodies for a low-cost, versatile platform for the ongoing pursuit of point-of-care BioFETs.

Integrated Point-of-Care Immune Cell Analyzer with Rapid Blood Sample Reaction and Wide Field-of-View Detection

The development of affordable, reliable, and rapid diagnostic devices is crucial for monitoring immunological responses using a drop of blood. However, conventional automated diagnostic devices typically involve expensive and impractical robotic fluid-handling approaches. Herein, we developed an integrated cell analyzer comprising a cylindrical sample cartridge connected to a direct current motor and a compact fluorescence imaging module. Sample mixing and loading are performed automatically by a programmable sequence of single motor rotation controlled by an Android application. Two distinct stained immune cell samples can be identified by using two types of fluorescence imaging modes. The effectiveness of mixing performance in antigen-antibody (Ag-Ab) reactions was assessed through a compound objective lens that collects weak fluorescence emitted by the cell membrane. Active mixing with bidirectional rotation of the cartridge in a confined space shortened the Ag-Ab reaction time by a factor of 3.3 and achieved cell counting with higher accuracy while reducing reagent consumption by 4 times compared to the conventional incubation method. High-intensity fluorescence images of cells labeled with a nucleic acid stain were acquired through a single-lens-based fluorescence imaging module with a large field of view (FOV) in an unconventional detection chamber with a curved substrate. Compared with a flat chamber, the curved detection chamber reduces the effects of field curvature and provides aberration-free wide-FOV images, even with a simple lens. Our integrated cell analyzer thus offers a practical and cost-effective solution for monitoring patient immune responses in point-of-care settings.

Ceria-Based Nanozymes in Point-of-Care Diagnosis: An Emerging Futuristic Approach for Biosensing

In recent years, there has been a notable increase in interest surrounding nanozymes due to their ability to imitate the functions and address the limitations of natural enzymes. The scientific community has been greatly intrigued by the study of nanoceria, primarily because of their distinctive physicochemical characteristics, which include a variety of enzyme-like activities, affordability, exceptional stability, and the ability to easily modify their surfaces. Consequently, nanoceria have found extensive use in various biosensing applications. However, the impact of its redox activity on the enzymatic catalytic mechanism remains a subject of debate, as conflicting findings in the literature have presented both pro-oxidant and antioxidant effects. Herein, we creatively propose a seesaw model to clarify the regulatory mechanism on redox balance and survey possible mechanisms of multienzyme mimetic properties of nanoceria. In addition, this review aims to showcase the latest advancements in this field by systematically discussing over 180 research articles elucidating the significance of ceria-based nanozymes in enhancing, downsizing, and enhancing the efficacy of point-of-care (POC) diagnostics. These advancements align with the ASSURED criteria established by the World Health Organization (WHO). Furthermore, this review also examines potential constraints in order to offer readers a concise overview of the emerging role of nanoceria in the advancement of POC diagnostic systems for future biosensing applications.

Development of a C-reactive protein quantification method based on flow rate measurement of an ink solution pushed out by oxygen gas generated by catalase reaction

A novel determination method for protein biomarkers based on on-chip flow rate measurement was developed using a microchip with organic photodiodes (OPDs). This quantitative method is based on the flow rate measurement of an ink solution pushed out by oxygen gas generated through catalase reaction. The amount of oxygen gas generated in the sample reservoir is dependent on the concentration of the analyte; therefore, the flow rate of the ink solution is also dependent on the concentration of the analyte. The concentration of the analyte can thus be estimated by measurement of the ink solution flow rate. The ink solution flow rate was estimated by measuring the migration time of the ink solution between two points using two OPDs placed below the microchannel. The principle of this method was demonstrated by the measurement of catalase using the microchip. In addition, the developed method was applied to the determination of C-reactive protein (CRP), a biomarker of inflammation, based on a catalase-linked immunosorbent assay (C-LISA). The limit of detection for CRP was 0.20 µg/mL. The method was also applied to the determination of CRP in human serum, and the quantitative values obtained by this method were in excellent agreement with those obtained by the conventional enzyme-linked immunosorbent assay (ELISA) method. The developed method does not require a photodetector with high sensitivity and is thus capable of downsizing; therefore, this will be useful for on-site analyses such as point-of-care testing and field measurements.

Smartphone-integrated paper-based biosensor for sensitive fluorometric ethanol quantification

The development of fluorometric paper-based analytical devices (fPADs) integrated with smartphone for fluorometric quantification of ethanol in an instrument-free and portable setup is described. The NAD+-dependent alcohol dehydrogenase immobilized within chitosan modified paper substate was utilized as a bio-recognition element and enzymatically generated NADH was used as a fluorescent probe. 3D-printed imaging setup which houses a paper chip holder and UV-light emitting device (LED) was developed for rapid, accurate capture of the fluorescent images. The biocompatible chitosan layer covering the paper provides a feasible environment for enzyme immobilization and enhances the fluorescence signal. The developed fPADs exhibited high sensitivity for ethanol detection and has a linear range for ethanol detection from 17 µM to 8.75 mM (R2 =0.99). Additionally, the fPADs were applied to quantify ethanol in four different wine samples including red, white, rose, and sparkling wines successfully. Moreover, the fPADs produce reproducible signals without loss of enzyme activity for at least 14 days and ~80% activity remained till 28 days. Thus, the proposed approach can provide a facile, affordable, portable, and instrument-free tool for the onsite quantification of ethanol in real samples and is applicable for food quality controls.

Surface functionalized 3D printed metal structures as next generation recyclable SERS substrates

Combining the design flexibility and rapid prototyping capabilities of additive manufacturing with photocatalytic and plasmonic functionalities is promising for the development of next-generation SERS applications such as point of care diagnostics and in situ monitoring of chemical reactions in fuels and chemical processing. Laser powder bed fusion (LPBF) is a well-matured additive manufacturing technique which generates metallic structures through localised melting and joining of metal powders using a laser. LPBF reduces material wastage during manufacturing, is applicable to a wide range of metals and alloys, and allows printing of complex internal structures. This feature article elaborates the use of soot templating, chemical vapour deposition and electroless plating techniques for grafting plasmonic and semiconductor nanoparticles on the surface of LPBF manufactured metallic substrates. The capability to fabricate different types of intricate metallic lattices using additive manufacturing is demonstrated and technical challenges in their adequate functionalization are elaborated. The developed methodology allows tailoring of the substrate structure, composition, morphology, plasmonic and photocatalytic activities and thus unveils a new class of recyclable SERS substrates.

Smart and Multifunctional Materials Based on Electroactive Poly(vinylidene fluoride): Recent Advances and Opportunities in Sensors, Actuators, Energy, Environmental, and Biomedical Applications

From scientific and technological points of view, poly(vinylidene fluoride), PVDF, is one of the most exciting polymers due to its overall physicochemical characteristics. This polymer can crystalize into five crystalline phases and can be processed in the form of films, fibers, membranes, and specific microstructures, being the physical properties controllable over a wide range through appropriate chemical modifications. Moreover, PVDF-based materials are characterized by excellent chemical, mechanical, thermal, and radiation resistance, and for their outstanding electroactive properties, including high dielectric, piezoelectric, pyroelectric, and ferroelectric response, being the best among polymer systems and thus noteworthy for an increasing number of technologies. This review summarizes and critically discusses the latest advances in PVDF and its copolymers, composites, and blends, including their main characteristics and processability, together with their tailorability and implementation in areas including sensors, actuators, energy harvesting and storage devices, environmental membranes, microfluidic, tissue engineering, and antimicrobial applications. The main conclusions, challenges and future trends concerning materials and application areas are also presented.

Impedimetric DNA Sensors for Epirubicin Detection Based on Polythionine Films Electropolymerized from Deep Eutectic Solvent

An electrochemically active polymer, polythionine (PTN), was synthesized in natural deep eutectic solvent (NADES) via multiple potential scans and characterized using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). NADES consists of citric acid monohydrate, glucose, and water mixed in the molar ratio of 1:1:6. Electrodeposited PTN film was then applied for the electrostatic accumulation of DNA from salmon sperm and used for the sensitive detection of the anticancer drug epirubicin. Its reaction with DNA resulted in regular changes in the EIS parameters that made it possible to determine 1.0-100 µM of epirubicin with the limit of detection (LOD) of 0.3 µM. The DNA sensor developed was successfully applied for the detection of epirubicin in spiked samples of artificial and natural urine and saliva, with recovery ranging from 90 to 109%. The protocol of the DNA sensor assembling utilized only one drop of reactants and was performed with a minimal number of steps. Together with a simple measurement protocol requiring 100 µL of the sample, this offers good opportunities for the further use of the DNA sensor in monitoring the drug level in biological samples, which is necessary in oncology treatment and for the pharmacokinetics studies of new antitumor drugs.

4D-printed needle panel meters coupled with enzymatic derivatization for reading urea and glucose concentrations in biological samples

On-site analytical techniques continue being developed with advances in modern technology. To demonstrate the applicability of four-dimensional printing (4DP) technologies in the direct fabrication of stimuli-responsive analytical devices for on-site determination of urea and glucose, we used digital light processing three-dimensional printing (3DP) and 2-carboxyethyl acrylate (CEA)-incorporated photocurable resins to fabricate all-in-one needle panel meters. When adding a sample having a value of pH above the pKa of CEA (ca. 4.6-5.0) into the fabricated needle panel meter, the [H+]-responsive layer of the needle, printed using the CEA-incorporated photocurable resins, swelled as a result of electrostatic repulsion among the dissociated carboxyl groups of the copolymer, leading to [H+]-dependent bending of the needle. When coupled with a derivatization reaction (urease-mediated hydrolysis of urea to decrease [H+]; glucose oxidase-mediated oxidization of glucose to increase [H+]), the bending of the needle allowed reliable quantification of urea or glucose when referencing pre-calibrated concentration scales. After method optimization, the method's detection limits for urea and glucose were 4.9 and 7.0 μM, respectively, within a working concentration range from 0.1 to 10 mM. We verified the reliability of this analytical method by determining the concentrations of urea and glucose in samples of human urine, fetal bovine serum, and rat plasma with spike analyses and comparing the results with those obtained using commercial assay kits. Our results confirm that 4DP technologies can allow the direct fabrication of stimuli-responsive devices for quantitative chemical analysis, and that they can advance the development and applicability of 3DP-enabling analytical methods.

Rapid electrical impedance detection of sickle cell vaso-occlusion in microfluidic device

Sickle cell disease is characterized by painful vaso-occlusive crises, in which poorly deformable sickle cells play an important role in the complex vascular obstruction process. Existing techniques are mainly based on optical microscopy and video processing of sickle blood flow under normoxic condition, for measuring vaso-occlusion by a small fraction of dense sickle cells of intrinsic rigidity but not the vaso-occlusion by the rigid, sickled cells due to deoxygenation. Thus, these techniques are not suitable for rapid, point-of-care testing. Here, we integrate electrical impedance sensing and Polydimethylsiloxane-microvascular mimics with controlled oxygen level into a single microfluidic chip, for quantification of vaso-occlusion by rigid, sickled cells within 1 min. Electrical impedance measurements provided a label-free, real-time detection of different sickle cell flow behaviors, including steady flow, vaso-occlusion, and flow recovery in response to the deoxygenation-reoxygenation process that are validated by microscopic videos. Sensitivity of the real part and imaginary part of the impedance signals to the blood flow conditions in both natural sickle cell blood and simulants at four electrical frequencies (10, 50, 100, and 500 kHz) are compared. The results show that the sensitivity of the sensor in detection of vaso-occlusion decreases as electrical frequency increases, while the higher frequencies are preferable in measurement of steady flow behavior. Additional testing using sickle cell simulants, chemically crosslinked normal red blood cells, shows same high sensitivity in detection of vaso-occlusion as sickle cell vaso-occlusion under deoxygenation. This work enables point-of-care testing potentials in rapid, accurate detection of steady flow and sickle cell vaso-occlusion from microliter volume blood specimens. Quantification of sickle cell rheology in response to hypoxia, may provide useful indications for not only the kinetics of cell sickling, but also the altered hemodynamics as obseved at the microcirculatory level.

Low-Cost Microfluidic Systems for Detection of Neglected Tropical Diseases

Neglected tropical diseases (NTDs) affect tropical and subtropical countries and are caused by viruses, bacteria, protozoa, and helminths. These kinds of diseases spread quickly due to the tropical climate and limited access to clean water, sanitation, and health care, which make exposed people more vulnerable. NTDs are reported to be difficult and inefficient to diagnose. As mentioned, most NTDs occur in countries that are socially vulnerable, and the lack of resources and access to modern laboratories and equipment intensify the difficulty of diagnosis and treatment, leading to an increase in the mortality rate. Portable and low-cost microfluidic systems have been widely applied for clinical diagnosis, offering a promising alternative that can meet the needs for fast, affordable, and reliable diagnostic tests in developing countries. This review provides a critical overview of microfluidic devices that have been reported in the literature for the detection of the most common NTDs over the past 5 years.

Engineering Innovative Interfaces for Point-of-Care Diagnostics

The ongoing Coronavirus disease 2019 (COVID-19) pandemic illustrates the need for sensitive and reliable tools to diagnose and monitor diseases. Traditional diagnostic approaches rely on centralized laboratory tests that result in long wait times to results and reduce the number of tests that can be given. Point-of-care tests (POCTs) are a group of technologies that miniaturize clinical assays into portable form factors that can be run both in clinical areas --in place of traditional tests-- and outside of traditional clinical settings --to enable new testing paradigms. Hallmark examples of POCTs are the pregnancy test lateral flow assay and the blood glucose meter. Other uses for POCTs include diagnostic assays for diseases like COVID-19, HIV, and malaria but despite some successes, there are still unsolved challenges for fully translating these lower cost and more versatile solutions. To overcome these challenges, researchers have exploited innovations in colloid and interface science to develop various designs of POCTs for clinical applications. Herein, we provide a review of recent advancements in lateral flow assays, other paper based POCTs, protein microarray assays, microbead flow assays, and nucleic acid amplification assays. Features that are desirable to integrate into future POCTs, including simplified sample collection, end-to-end connectivity, and machine learning, are also discussed in this review.

Sensitive Small Molecule Aptasensing based on Hybridization Chain Reaction and CRISPR/Cas12a Using a Portable 3D-Printed Visualizer

Next-generation biosensing tools based on CRISPR/Cas have revolutionized the molecular detection. A number of CRISPR/Cas-based biosensors have been reported for the detection of nucleic acid targets. The establishment of efficient methods for non-nucleic acid target detection would further broaden the scope of this technique, but up to now, the concerning research is limited. In the current study, we reported a versatile biosensing platform for non-nucleic acid small-molecule detection called SMART-Cas12a (small-molecule aptamer regulated test using CRISPR/Cas12a). Simply, hybridization chain reaction cascade signal amplification was first trigged by functional nucleic acid (aptamer) through target binding. Then, the CRISPR/Cas system was integrated to recognize the amplified products followed by activation of the trans-cleavage. As such, the target can be ingeniously converted to nucleic acid signals and then fluorescent signals that can be readily visualized and analyzed by a customized 3D-printed visualizer with the help of a home-made App-enabled smartphone. Adenosine triphosphate was selected as a model target, and under the optimized conditions, we achieved fine analytical performance with a linear range from 0.1 to 750 μM and a detection limit of 1.0 nM. The satisfactory selectivity and recoveries that we have obtained further demonstrated this method to be suitable for a complex sample environment. The sample-to-answer time was less than 100 min. Our work not only expanded the reach of the CRISPR-Cas system in biosensing but also provided a prototype method that can be generalized for detecting a wider range of analytes with desirable adaptability, sensitivity, specificity, and on-site capability.

Simultaneous determination of procalcitonin and interleukin-6 in human serum samples with a point-of-care biosensing device

The simultaneous determination of two inflammatory diseases biomarkers, namely procalcitonin (PCT) and interleukin-6 (IL-6), in human serum samples employing a Point-of-Care device based on Multi Area Reflectance Spectroscopy is presented. Dual-analyte detection was achieved using silicon chips with two silicon dioxide areas of different thickness, one functionalized with an antibody specific for PCT and the other with an antibody specific for IL-6. The assay included reaction of immobilized capture antibodies with mixtures of PCT and IL-6 calibrators with the biotinylated detection antibodies, streptavidin and biotinylated-BSA. The reader provided for the automated execution of the assay procedure, as well as for the collection and processing of the reflected light spectrum, the shift of which is correlated to analytes concentration in the sample. The assay was completed in 35 min and the detection limits for PCT and IL-6 were 2.0 and 0.01 ng/mL respectively. The dual-analyte assay was characterized by high reproducibility (the intra- and inter-assay coefficients of variation were less than 10% for both analytes) and accuracy (the percent recovery values ranged from 80 to 113% for both analytes). Moreover, the values determined for the two analytes in human serum samples with the assay developed were in good agreement with the values determined for the same samples by clinical laboratory methods. These results support the potential of the proposed biosensing device application for inflammatory biomarkers determination at the Point-of-Need.

MicroLED biosensor with colloidal quantum dots and smartphone detection

A fluorescence sensor with the capability for spatially multiplexed measurements utilizing smartphone detection is presented. Bioconjugated quantum dots are used as the fluorescent tag and are excited using a blue-emitting microLED (µLED). The 1-dimensional GaN µLED array is butt-coupled to one edge of the glass slide to take advantage of total internal reflection fluorescence (TIRF) principles. The bioassays on the top surface of the glass waveguide are excited and the resultant fluorescence is detected with the smartphone. The red, green, and blue channels of the digital image are utilized to spectrally separate the excitation light from the fluorescence for analysis. Using a biotin-functionalized glass slide as proof of principle, we have shown that streptavidin conjugated quantum dots can be detected down to a concentration of 8 nM.

Reshaping de Novo Protein Switches into Bioresponsive Materials for Biomarker, Toxin, and Viral Detection

De novo designed protein switches are powerful tools to specifically and sensitively detect diverse targets with simple chemiluminescent readouts. Finding an appropriate material host for de novo designed protein switches without altering their thermodynamics while preserving their intrinsic stability over time would enable the development of a variety of sensing formats to monitor exposure to pathogens, toxins, and for disease diagnosis. Here, a de novo protein-biopolymer hybrid that maintains the detection capabilities induced by the conformational change of the incorporated proteins in response to analytes of interest is generated in multiple, shelf-stable material formats without the need of refrigerated storage conditions. A set of functional demonstrator devices including personal protective equipment such as masks and laboratory gloves, free-standing films, air quality monitors, and wearable devices is presented to illustrate the versatility of the approach. Such formats are designed to be responsive to human epidermal growth factor receptor (HER2), anti-hepatitis B (HBV) antibodies, Botulinum neurotoxin B (BoNT/B), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This combination of form and function offers wide opportunities for ubiquitous sensing in multiple environments by enabling a large class of bio-responsive interfaces of broad utility.

The development of microfluidic-based western blotting: Technical advances and future perspectives

Over the past two decades significant technical advancement in the field of western blotting has been made possible through the utilization of microfluidic technologies. In this review we provide a critical overview of these advancements, highlighting the advantages and disadvantages of each approach. Particular attention is paid to the development of now commercially available systems, including those for single cell analysis. This review also discusses more recent developments, including algorithms for automation and/or improved quantitation, the utilization of different materials/chemistries, use of projection electrophoresis, and the development of triBlots. Finally, the review includes commentary on future advances in the field based on current developments, and the potential of these systems for use as point-of-care devices in healthcare.

Flexible Label-Free Platinum and Bio-PET-Based Immunosensor for the Detection of SARS-CoV-2

The demand for new devices that enable the detection of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) at a relatively low cost and that are fast and feasible to be used as point-of-care is required overtime on a large scale. In this sense, the use of sustainable materials, for example, the bio-based poly (ethylene terephthalate) (Bio-PET) can be an alternative to current standard diagnostics. In this work, we present a flexible disposable printed electrode based on a platinum thin film on Bio-PET as a substrate for the development of a sensor and immunosensor for the monitoring of COVID-19 biomarkers, by the detection of L-cysteine and the SARS-CoV-2 spike protein, respectively. The electrode was applied in conjunction with 3D printing technology to generate a portable and easy-to-analyze device with a low sample volume. For the L-cysteine determination, chronoamperometry was used, which achieved two linear dynamic ranges (LDR) of 3.98-39.0 μmol L-1 and 39.0-145 μmol L-1, and a limit of detection (LOD) of 0.70 μmol L-1. The detection of the SARS-CoV-2 spike protein was achieved by both square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) by a label-free immunosensor, using potassium ferro-ferricyanide solution as the electrochemical probe. An LDR of 0.70-7.0 and 1.0-30 pmol L-1, with an LOD of 0.70 and 1.0 pmol L-1 were obtained by SWV and EIS, respectively. As a proof of concept, the immunosensor was successfully applied for the detection of the SARS-CoV-2 spike protein in enriched synthetic saliva samples, which demonstrates the potential of using the proposed sensor as an alternative platform for the diagnosis of COVID-19 in the future.

Compact Camera Fluorescence Detector for Parallel-Light Lens-Based Real-Time PCR System

The polymerase chain reaction is an important technique in biological research. However, it is time consuming and has a number of disadvantages. Therefore, real-time PCR technology that can be used in real-time monitoring has emerged, and many studies are being conducted regarding its use. Real-time PCR requires many optical components and imaging devices such as expensive, high-performance cameras. Therefore, its cost and assembly process are limitations to its use. Currently, due to the development of smart camera devices, small, inexpensive cameras and various lenses are being developed. In this paper, we present a Compact Camera Fluorescence Detector for use in parallel-light lens-based real-time PCR devices. The proposed system has a simple optical structure, the system cost can be reduced, and the size can be miniaturized. This system only incorporates Fresnel lenses without additional optics in order for the same field of view to be achieved for 25 tubes. In the center of the Fresnel lens, one LED and a complementary metal-oxide semiconductor camera were placed in directions that were as similar as possible. In addition, to achieve the accurate analysis of the results, image processing was used to correct them. As a result of an experiment using a reference fluorescent substance and double-distilled water, it was confirmed that stable fluorescence detection was possible.

After Theranos: Using point-of-care testing to advance measures of health biomarkers in human biology research

OBJECTIVES

The rise and fall of the health technology startup Theranos is emblematic of the promise and peril of point-of-care testing (POCT). Instruments that deliver immediate results from minimally invasive samples at the location of collection can provide powerful tools to deliver health data in clinical and public health contexts. Yet, POCT availability is driven largely by market interests, which limits the development of inexpensive tests for diverse health conditions that can be used in resource-limited settings. These constraints, combined with complex regulatory hurdles and substantial ethical challenges, have contributed to the underutilization of POCT in human biology research.

METHODS

We evaluate current POCT capabilities and limitations, discuss promising applications for POCT devices in resource-limited settings, and discuss the future of POCT.

RESULTS

As evidenced by publication trends, POCT platforms have rapidly advanced in recent years, gaining traction among clinicians and health researchers. We highlight POCT devices of potential interest to population-based researchers and present specific examples of POCT applications in human biology research.

CONCLUSIONS

Several barriers can limit POCT applications, including cost, lack of regulatory approval for non-clinical use, requirements for expensive equipment, and the dearth of validation in remote field conditions. Despite these issues, we see immense potential for emerging POCT technology capable of analyzing new sample types and used in conjunction with increasingly common technology (e.g., smart phones). We argue that the fallout from Theranos may ultimately provide an opportunity to advance POCT, leading to more ethical data collection and novel opportunities in human biology research.

Passivation Strategies for Enhancing Solution-Gated Carbon Nanotube Field-Effect Transistor Biosensing Performance and Stability in Ionic Solutions

Interest in point-of-care diagnostics has led to increasing demand for the development of nanomaterial-based electronic biosensors such as biosensor field-effect transistors (BioFETs) due to their inherent simplicity, sensitivity, and scalability. The utility of BioFETs, which use electrical transduction to detect biological signals, is directly dependent upon their electrical stability in detection-relevant environments. BioFET device structures vary substantially, especially in electrode passivation modalities. Improper passivation of electronic components in ionic solutions can lead to excessive leakage currents and signal drift, thus presenting a hinderance to signal detectability. Here, we harness the sensitivity of nanomaterials to study the effects of various passivation strategies on the performance and stability of a transistor-based biosensing platform based on aerosol-jet-printed carbon nanotube thin-film transistors. Specifically, non-passivated devices were compared to devices passivated with photoresist (SU-8), dielectric (HfO2), or photoresist + dielectric (SU-8 followed by HfO2) and were evaluated primarily by initial performance metrics, large-scale device yield, and stability throughout long-duration cycling in phosphate buffered saline. We find that all three passivation conditions result in improved device performance compared to non-passivated devices, with the photoresist + dielectric strategy providing the lowest average leakage current in solution (~2 nA). Notably, the photoresist + dielectric strategy also results in the greatest yield of BioFET devices meeting our selected performance criteria on a wafer scale (~90%), the highest long-term stability in solution (<0.01% change in on-current), and the best average on/off-current ratio (~104), hysteresis (~32 mV), and subthreshold swing (~192 mV/decade). This passivation schema has the potential to pave the path toward a truly high-yield, stable, and robust electrical biosensing platform.

Surface Wrinkling for Flexible and Stretchable Sensors

Recent advances in nanolithography, miniaturization, and material science, along with developments in wearable electronics, are pushing the frontiers of sensor technology into the large-scale fabrication of highly sensitive, flexible, stretchable, and multimodal detection systems. Various strategies, including surface engineering, have been developed to control the electrical and mechanical characteristics of sensors. In particular, surface wrinkling provides an effective alternative for improving both the sensing performance and mechanical deformability of flexible and stretchable sensors by releasing interfacial stress, preventing electrical failure, and enlarging surface areas. In this study, recent developments in the fabrication strategies of wrinkling structures for sensor applications are discussed. The fundamental mechanics, geometry control strategies, and various fabricating methods for wrinkling patterns are summarized. Furthermore, the current state of wrinkling approaches and their impacts on the development of various types of sensors, including strain, pressure, temperature, chemical, photodetectors, and multimodal sensors, are reviewed. Finally, existing wrinkling approaches, designs, and sensing strategies are extrapolated into future applications.

Enzyme Nanosheet-Based Electrochemical Aspartate Biosensor for Fish Point-of-Care Applications

Bacterial infections in marine fishes are linked to mass mortality issues; hence, rapid detection of an infection can contribute to achieving a faster diagnosis using point-of-care testing. There has been substantial interest in identifying diagnostic biomarkers that can be detected in major organs to predict bacterial infections. Aspartate was identified as an important biomarker for bacterial infection diagnosis in olive flounder (Paralichthys olivaceus) fish. To determine aspartate levels, an amperometric biosensor was designed based on bi-enzymes, namely, glutamate oxidase (GluOx) and aspartate transaminase (AST), which were physisorbed on copolymer reduced graphene oxide (P-rGO), referred to as enzyme nanosheets (GluOx-ASTENs). The GluOx-ASTENs were drop casted onto a Prussian blue electrodeposited screen-printed carbon electrode (PB/SPCE). The proposed biosensor was optimized by operating variables including the enzyme loading amount, coreactant (α-ketoglutarate) concentration, and pH. Under optimal conditions, the biosensor displayed the maximum current responses within 10 s at the low applied potential of -0.10 V vs. the internal Ag/AgCl reference. The biosensor exhibited a linear response from 1.0 to 2.0 mM of aspartate concentrations with a sensitivity of 0.8 µA mM^-1 cm^-2 and a lower detection limit of approximately 500 µM. Moreover, the biosensor possessed high reproducibility, good selectivity, and efficient storage stability.

Smartphone-Based Multiplexed Biosensing Tools for Health Monitoring

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

Point-of-Care Diagnostics for Farm Animal Diseases: From Biosensors to Integrated Lab-on-Chip Devices

Zoonoses and animal diseases threaten human health and livestock biosecurity and productivity. Currently, laboratory confirmation of animal disease outbreaks requires centralized laboratories and trained personnel; it is expensive and time-consuming, and it often does not coincide with the onset or progress of diseases. Point-of-care (POC) diagnostics are rapid, simple, and cost-effective devices and tests, that can be directly applied on field for the detection of animal pathogens. The development of POC diagnostics for use in human medicine has displayed remarkable progress. Nevertheless, animal POC testing has not yet unfolded its full potential. POC devices and tests for animal diseases face many challenges, such as insufficient validation, simplicity, and portability. Emerging technologies and advanced materials are expected to overcome some of these challenges and could popularize animal POC testing. This review aims to: (i) present the main concepts and formats of POC devices and tests, such as lateral flow assays and lab-on-chip devices; (ii) summarize the mode of operation and recent advances in biosensor and POC devices for the detection of farm animal diseases; (iii) present some of the regulatory aspects of POC commercialization in the EU, USA, and Japan; and (iv) summarize the challenges and future perspectives of animal POC testing.

Point-of-Care and Label-Free Detection of Porcine Reproductive and Respiratory Syndrome and Swine Influenza Viruses Using a Microfluidic Device with Photonic Integrated Circuits

Swine viral diseases challenge the sector’s sustainability by affecting productivity and the health and welfare of the animals. The lack of antiviral drugs and/or effective vaccines renders early and reliable diagnosis the basis of viral disease management, underlining the importance of point-of-care (POC) diagnostics. A novel POC diagnostic device utilizing photonic integrated circuits (PICs), microfluidics, and information and communication technologies for the detection of porcine reproductive and respiratory syndrome virus (PRRSV) and swine influenza A (SIV) was validated using spiked and clinical oral fluid samples. Metrics including sensitivity, specificity, accuracy, precision, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were calculated to assess the performance of the device. For PRRSV, the device achieved a sensitivity of 83.5%, specificity of 77.8%, and DOR values of 17.66, whereas the values for SIV were 81.8%, 82.2%, and 20.81, respectively. The POC device and PICs can be used for the detection of PRRSV and SIV in the field, paving the way for the introduction of novel technologies in the field of animal POC diagnostics to further optimize livestock biosecurity.

A Comprehensive Review on Water Quality Monitoring Devices: Materials Advances, Current Status, and Future Perspective

Water quality monitoring has become more critical in recent years to ensure the availability of clean and safe water from natural aquifers and to understand the evolution of water contaminants across time and space. The conventional water monitoring techniques comprise of sample collection, preservation, preparation, tailed by laboratory testing and analysis with cumbersome wet chemical routes and expensive instrumentation. Despite the high accuracy of these methods, the high testing costs, laborious procedures, and maintenance associated with them don't make them lucrative for end end-users and field testing. As the participation of ultimate stakeholders, that is, common man for water quality and quantity can play a pivotal role in ensuring the sustainability of our aquifers, thus it is essential to develop and deploy portable and user-friendly technical systems for monitoring water sources in real-time or on-site. The present review emphasizes here on possible approaches including optical (absorbance, fluorescence, colorimetric, X-ray fluorescence, chemiluminescence), electrochemical (ASV, CSV, CV, EIS, and chronoamperometry), electrical, biological, and surface-sensing (SPR and SERS), as candidates for developing such platforms. The existing developments, their success, and bottlenecks are discussed in terms of various attributes of water to escalate the essentiality of water quality devices development meeting ASSURED criterion for societal usage. These platforms are also analyzed in terms of their market potential, advancements required from material science aspects, and possible integration with IoT solutions in alignment with Industry 4.0 for environmental application.

Gires-Tournois Immunoassay Platform for Label-Free Bright-Field Imaging and Facile Quantification of Bioparticles

Bright-field imaging of nanoscale bioparticles is a challenging task for optical microscopy because the light-matter interactions of bioparticles are weak on conventional surfaces due to their low refractive index and small size. Alternatively, advanced imaging techniques, including near-field microscopy and phase microscopy, have enabled visualization and quantification of the bioparticles, but they require assistance of sophisticated/customized systems and post-processing with complex established algorithms. Here, a simple and fast immunoassay device, Gires-Tournois immunoassay platform (GTIP) is presented, which provides unique color dynamics in response to optical environment changes and thus enables the label-free bright-field imaging and facile quantification of bioparticles using conventional optical microscopy. Bioparticles on GTIP slow down the velocity of reflected light, leading to vivid color change according to the local particle density and maximizing chromatic contrast for high spatial distinguishability. The particle distribution and density on the surface of the resonator are readily analyzed through 2D raster-scanning-based chromaticity analysis. GTIP offers multiscale sensing capability for target analytes that possess different refractive indices and sizes.

Ultrasensitive Electrochemical Detection of Mutated Viral RNAs with Single-Nucleotide Resolution Using a Nanoporous Electrode Array (NPEA)

The detection of nucleic acids and their mutation derivatives is vital for biomedical science and applications. Although many nucleic acid biosensors have been developed, they often require pretreatment processes, such as target amplification and tagging probes to nucleic acids. Moreover, current biosensors typically cannot detect sequence-specific mutations in the targeted nucleic acids. To address the above problems, herein, we developed an electrochemical nanobiosensing system using a phenomenon comprising metal ion intercalation into the targeted mismatched double-stranded nucleic acids and a homogeneous Au nanoporous electrode array (Au NPEA) to obtain (i) sensitive detection of viral RNA without conventional tagging and amplifying processes, (ii) determination of viral mutation occurrence in a simple detection manner, and (iii) multiplexed detection of several RNA targets simultaneously. As a proof-of-concept demonstration, a SARS-CoV-2 viral RNA and its mutation derivative were used in this study. Our developed nanobiosensor exhibited highly sensitive detection of SARS-CoV-2 RNA (∼1 fM detection limit) without tagging and amplifying steps. In addition, a single point mutation of SARS-CoV-2 RNA was detected in a one-step analysis. Furthermore, multiplexed detection of several SARS-CoV-2 RNAs was successfully demonstrated using a single chip with four combinatorial NPEAs generated by a 3D printing technique. Collectively, our developed nanobiosensor provides a promising platform technology capable of detecting various nucleic acids and their mutation derivatives in highly sensitive, simple, and time-effective manners for point-of-care biosensing.

Smartphone-based mobile biosensors for the point-of-care testing of human metabolites

Rapid, accurate, portable and quantitative profiling of metabolic biomarkers is of great importance for disease diagnosis and prognosis. The recent development in the optical and electric biosensors based on the smartphone is promising for profiling of metabolites with advantages of rapid, reliability, accuracy, low-cost and multi-analytes analysis capability. In this review, we introduced the optical biosensing platforms including colorimetric, fluorescent and chemiluminescent sensing, and electrochemical biosensing platforms including wired and wireless communication. Challenges and future perspectives desired for reliable, accurate, cost-effective, and multi-functions smartphone-based biosensing systems were also discussed. We envision that such smartphone-based biosensing platforms will allow daily and comprehensive metabolites monitoring in the future, thus unlocking the potential to transform clinical diagnostics into non-clinical self-testing. We also believed that this progress report will encourage future research to develop advanced, integrated and multi-functional smartphone-based Point-of-Care testing (POCT) biosensors for the monitoring and diagnosis as well as personalized treatments of a spectrum of metabolic-disorder related diseases.

Reversible photonic hydrogel sensors via holographic interference lithography

Continuous monitoring of physiological conditions and biomarkers via optical holographic sensors is an area of growing interest to facilitate the expansion of personalised medicine. Here, a facile laser-induced dual polymerization method is developed to fabricate holographic hydrogel sensors for the continuous and reversible colorimetric determination of pH variations over a physiological range in serum (pH 7-9). Readout parameters simulated through a Finite-difference time-domain Yee's algorithm retrieve the spectral response through expansion. Laser lithography of holographic hydrogel sensor fabrication is achieved via a single 355 nm laser pulse to initiate polymerization of ultrafine hydrogel fringes. Eliminating the requirement for complex processing of toxic components and streamlining the synthetic procedure provides a simpler route to mass production. Optimised pH-responsive hydrogels contain amine bearing functional co-monomers demonstrating reversible Bragg wavelength shifts of 172 nm across the entire visible wavelength range with pH variation from 7.0 to 9.0 upon illumination with broadband light. Photolithographic recording of information shows the ability to convey detailed information to users for qualitative identification of pH. Holographic sensor reversibility over 20 cycles showed minimal variation in replay wavelength supporting reliable and consistent readout, with optimised sensors showing rapid response times of <5 min. The developed sensors demonstrate the application to continuous monitoring in biological fluids, withstanding interference from electrolytes, saccharides, and proteins colorimetrically identifying bovine serum pH over a physiological range. The holographic sensors benefit point-of-care pH analysis of biological analytes which could be applied to the identification of blood gas disorders and wound regeneration monitoring through colorimetric readouts.

Smartphone-Based Biosensor Devices for Healthcare: Technologies, Trends, and Adoption by End-Users

Smart biosensors are becoming an important support for modern healthcare, even more so in the current context. Numerous smartphone-based biosensor developments were published in recent years, some highly effective and sensitive. However, when patents and patent applications related to smart biosensors for healthcare applications are analyzed, it is surprising to note that, after significant growth in the first half of the decade, the number of applications filed has decreased considerably in recent years. There can be many causes of this effect. In this review, we present the state of the art of different types of smartphone-based biosensors, considering their stages of development. In the second part, a critical analysis of the possible reasons why many technologies do not reach the market is presented. Both technical and end-user adoption limitations were addressed. It was observed that smart biosensors on the commercial stage are still scarce despite the great evolution that these technologies have experienced, which shows the need to strengthen the stages of transfer, application, and adoption of technologies by end-users.

Multiplex optical bioassays for food safety analysis: Toward on-site detection

Food safety analysis plays a significant role in controlling food contamination and supervision. In recent years, multiplex optical bioassays (MOBAs) have been widely applied to analyze multiple hazards due to their efficiency and low cost. However, due to the challenges such as multiplexing capacity, poor sensitivity, and bulky instrumentation, the further application of traditional MOBAs in food screening has been limited. In this review, effective strategies regarding food safety MOBAs are summarized, such as spatial-resolution modes performed in multi-T lines/dots strips or arrays of strip/microplate/microfluidic chip/SPR chip and signal-resolution modes employing distinguishable colorimetric/luminescence/fluorescence/surface plasma resonance/surface-enhanced Raman spectrum as signal tags. Following this, new trends on how to design engineered sensor architecture and exploit distinguishable signal reporters, how to improve both multiplexing capacity and sensitivity, and how to integrate these formats into smartphones so as to be mobile are summarized systematically. Typically, in the case of enhancing multiplexing capacity and detection throughput, microfluidic array chips with multichannel architecture would be a favorable approach to overcome the spatial and physical limitations of immunochromatographic assay (ICA) test strips. Moreover, noble metal nanoparticles and single-excitation, multiple-emission luminescence nanomaterials hold great potential in developing ultrasensitive MOBAs. Finally, the exploitation of innovative multiplexing strategy hybridized with powerful and widely available smartphones opens new perspectives to MOBAs. In future, the MOBAs should be more sensitive, have higher multiplexing capacity, and easier instrumentation.