Paper-based tuberculosis diagnostic devices with colorimetric gold nanoparticles

A novel flow through assay and smartphone application based prototype for point-of-care diagnosis of tuberculosis

Affordable point-of-care test sensors with automated result recording are essential for reducing undetected tuberculosis cases in remote, resource-limited areas. Therefore, this study addresses this need with three key aims. First, we aimed to lower the costs of a patented flow-through assay (Kit and method: WO2016/024116A1) by developing an in-house method for producing antibody-coated gold nanoparticles (anti-IgG-AuNPs). These anti-IgG-AuNPs demonstrated specific binding with performance comparable to existing antibody-capped gold nanoparticles. The second aim was to transform the flow-through assay into a multi-disease screening tool by incorporating multiple antigen test spots. A newly designed wax-printed background allows for simultaneous testing of up to five antigens, delivering results within 15 min at the point-of-care, while also reducing assay costs by 70 %. Lastly, we developed a smartphone application (RAP-TBS) to provide quantitative analysis of the flow-through assay results. This user-friendly app requires no additional hardware and addresses the limitations of subjective visual interpretation.

Multiple signal amplification strategy for ultrasensitive sensing of Mycobacterium bovis based on 8-17 DNAzyme and CRISPR-Cas13a

Bovine tuberculosis caused by Mycobacterium bovis is not only responsible for economic losses but can also seriously jeopardize human health. Therefore, for the ultra-sensitive detection of M. bovis, a novel triple-cycle amplification system was developed based on 8-17 deoxyribozyme (DNAzyme), clustered regularly interspaced short palindromic repeats-associated protein 13a (CRISPR-Cas13a)-mediated cleavage cycles and the catalytic hairpin assembly (CHA) reaction (termed as DzCCR). In the presence of the target, the A-sequence containing 8-17 DNAzyme fragments was released from A-B using a strand displacement reaction, which could specifically cleave the HX-gRNA probe, releasing the sequence of gRNA and H and realizing the first signal amplification. Then, the released gRNA could bind to the Cas13a-g complex and activate the trans-cutting ability of Cas13a to re-cut RNA bulge sequences in HX-gRNAs, achieving the second signal amplification. Moreover, the H-sequence generated by the upstream 8-17 DNAzyme and Cas13a cleavage reaction further triggered the CHA, allowing the G-quadruplex dimer to be exposed, realizing signal output by adding thioflavin T (THT), and thereby achieving the third signal amplification. Benefiting from the triple signal amplification, the DzCCR system could quantitatively detect the M. bovis target down to a concentration of 0.5 fM with a linear calibration range from 1 to 500 fM. Furthermore, we investigated the ability of this system to detect M. bovis in real samples by standard addition method, the recovery ranged from 92.6% to 107.5%, and the relative standard deviations (RSD) ranged from 1.9% to 4.1%. Owing to the constant temperature and high sensitivity, the proposed strategy could be used as a new approach for the detection of M. bovis.

Recent advances in gold nanoparticles-based biosensors for tuberculosis determination

Tuberculosis (TB) is one of the major killer diseases affecting lung parenchymal tissues. Mycobacterium tuberculosis (Mtb) is the bacterium that causes it. It most commonly affects the lungs, although it can affect any part of the body, including the stomach, glands, bones, and nervous system. Although anti-mycobacterial drugs are available, it remains a major threat to public health due to the rise of drug-resistant strains, and early and accurate diagnosis is very important. Currently, research science and medical communities are focusing on the use of cost-effective biosensors to manage human biological processes and assess accurate health diagnostics. Due to their high sensitivity in chemical and biological assays, nanomaterials have been considered in the field of biosensors for better diagnosis, and among them, gold nanoparticles (AuNPs) can play an important role in accelerating the diagnosis of TB. Superior biocompatibility, conductivity, catalytic properties, high surface-to-volume ratio, and high density enable their widespread use in the fabrication of biosensors. This review evaluates the diagnostic accuracy of AuNP-based biosensors for the detection of Mtb. According to different transducers of biosensors, their structure, performance, advantages and limitations are summarized and compared. Moreover, the upcoming challenges in their analytical performance have been highlighted and the strategies to overcome those challenges have been briefly discussed.

Diagnosis of extra pulmonary tuberculosis: An update on novel diagnostic approaches

Tuberculosis (TB) remains a major global public health problem worldwide. Though Pulmonary TB (PTB) is mostly discussed, one in five cases of TB present are extrapulmonary TB (EPTB) that manifests conspicuous diagnostic and management challenges with respect to the site of infection. The diagnosis of EPTB is often delayed or even missed due to insidious clinical presentation, pauci-bacillary nature of the disease, and lack of laboratory facilities in the resource limited settings. Culture, the classical gold standard for the diagnosis of tuberculosis, suffers from increased technical and logistical constraints in EPTB cases. Other than culture, several other tests are available but their feasibility and effciacy for the detection of EPTB is still the matter of interest. We need more specific and precise test/s for the various forms of EPTB diagnosis which can easily be applied in the routine TB control program is required. A test that can contribute remarkably towards improving EPTB case detection reducing the morbidity and mortality is the utmost requirement. In this review we described the scenario of molecular and other noval methods available for laboratory diagnosis of EPTB, and also discussed the challenges linked with each diagnostic method. This review will make the readers aware of new emerging diagnostic techniques in the field of EPTB diagnosis. They can make an informed decision to choose the appropriate one according to the test availability, their clinical settings and financial considerations.

A novel approach to low-cost, rapid and simultaneous colorimetric detection of multiple analytes using 3D printed microfluidic channels

This research paper presents an inventive technique to swiftly create microfluidic channels on distinct membrane papers, enabling colorimetric drug detection. Using a modified DIY RepRap 3D printer with a syringe pump, microfluidic channels (µPADs) are crafted on a flexible nylon-based substrate. This allows simultaneous detection of four common drugs with a single reagent. An optimized blend of polydimethylsiloxane (PDMS) dissolved in hexane is used to create hydrophobic channels on various filter papers. The PDMS-hexane mixture infiltrates the paper's pores, forming hydrophobic barriers that confine liquids within the channels. These barriers are cured on the printer's hot plate, controlling channel width and preventing spreading. Capillary action drives fluid along these paths without spreading. This novel approach provides a versatile solution for rapid microfluidic channel creation on membrane papers. The DIY RepRap 3D printer integration offers precise control and faster curing. The PDMS-hexane solution accurately forms hydrophobic barriers, containing liquids within desired channels. The resulting microfluidic system holds potential for portable, cost-effective drug detection and various sensing 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.

Rapid Colorimetric Detection of Wound Infection with a Fluidic Paper Device

Current procedures for the assessment of chronic wound infection are time-consuming and require complex instruments and trained personnel. The incidence of chronic wounds worldwide, and the associated economic burden, urge for simple and cheap point-of-care testing (PoCT) devices for fast on-site diagnosis to enable appropriate early treatment. The enzyme myeloperoxidase (MPO), whose activity in infected wounds is about ten times higher than in non-infected wounds, appears to be a suitable biomarker for wound infection diagnosis. Herein, we develop a single-component foldable paper-based device for the detection of MPO in wound fluids. The analyte detection is achieved in two steps: (i) selective immunocapture of MPO, and (ii) reaction of a specific dye with the captured MPO, yielding a purple color with increasing intensity as a function of the MPO activity in infected wounds in the range of 20–85 U/mL. Ex vivo experiments with wound fluids validated the analytic efficiency of the paper-based device, and the results strongly correlate with a spectrophotometric assay.

Biorecognition and detection of antigens from Mycobacterium tuberculosis using a sandwich ELISA associated with magnetic nanoparticles

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is one of the 10 leading causes of death worldwide, especially in low-income areas. A rapid, low-cost diagnostic assay for TB with high sensitivity and specificity is not currently available. Bio-functionalized magnetic nanoparticles (MNPs) which are able to efficiently detect and concentrate biomolecules from complex biological samples, allows improving the diagnostic immunoassays. In this way, a proof-of-concept of MNP-based sandwich immunoassay was developed to detect various MTB protein antigens. The superficial and secretory antigenic proteins considered in this research were: CFP10, ESAT6, MTC28, MPT64, 38 kDa protein, Ag85B, and MoeX. The proteins were cloned and expressed in an E. coli system. Polyclonal antibodies (ab) against the recombinant antigens were elicited in rabbits and mice. Antibodies were immobilized on the surface of amine-silanized nanoparticles (MNP@Si). The functionalized MNP@Si@ab were tested in a colorimetric sandwich enzyme-linked immunosorbent assay (sELISA-MNP@Si@ab) to recognize the selected antigens in sputum samples. The selected MTB antigens were successfully detected in sputum from TB patients in a shorter time (~ 4 h) using the sELISA-MNP@Si@ab, compared to the conventional sELISA (~15 h) standardized in home. Moreover, the sELISA-MNP@Si@ab showed the higher sensitivity in the real biological samples from infected patients.

Novel mesoporous silica nanocarriers containing gold; a rapid diagnostic tool for tuberculosis

Tuberculosis (TB) is major health concern and reason of deaths from decades to current date. Even though with a lot of advancements, diagnostic techniques, and discovery of standard antibiotics TB remains crucial challenge and can create worst scenario for human health in near future. Nanoparticles play emerging role in diagnosis and treatment of TB. In this study, we developed mesoporous silica nanoparticles containing gold (MSNs@GNPs) for rapid diagnosis and treatment of TB. The physicochemical characterization revealed effective surface morphology and particles diameter, that is applicable for in vitro applications. The in vitro antimicrobial analysis revealed that the designed MSNs@GNPs has retained significantly lower minimal inhibitory concentration (MIC) values and can effectively demolish mycobacterium tuberculosis (Mtb). Furthermore, the diagnosis efficiency of the MSNs@GNPs was evaluated by calorimetric analysis. Which demonstrates that MSNs@GNPs can be used for rapid diagnosis of the tuberculosis when applied on in vitro culture of the Mtb. The current study needs further verification on human's clinical samples from tuberculosis patients. However, MSNs@GNPs can be a versatile clinical approach for the rapid diagnosis and clinical treatment of the tuberculosis.

Multidrug resistant tuberculosis - Diagnostic challenges and its conquering by nanotechnology approach - An overview

One of the leading killer diseases that target the parenchymal tissues of lungs is Tuberculosis. Although antimycobacterial drugs are available, there are increased incidences of drug resistance encountered in Mycobacterium sp. They have been categorized into MDR (Multidrug resistant) and XDR (Extensively drug-resistant) strains exhibiting resistance toward successive treatment regimen. This situation threatens the futuristic containment of TB with the dearth of anti-TB drugs. Nanotechnology, the emerging multidisciplinary science has presented an excellent opportunity for timely and accurate diagnosis and discrimination of Mycobacteria via its unique physio-chemical and optical characteristics. The delayed and misdiagnosis of TB and lack of sensitive diagnostic method(s) has seen a paradigm shift toward nanoparticulate system for improved diagnosis, drug delivery and reduced treatment frequency. This review article highlights the evolution of tuberculosis and its transformation to multidrug resistant strain. Further, the conventional methods for diagnosing TB and the challenges encountered in their analytical performance have been highlighted and the strategies to overcome those challenges have been briefly discussed. Smart approaches encompassing metal nanoparticles, Quantum Dots (QDs) and Field Effect Transistors (FET) based biosensor for accurate diagnosis have been critically reviewed. A decade long state-of-the-art knowledge on TB nanodiagnostics, fabrication concepts and performance characteristics has been reviewed.

Nucleic Acids Analysis

Nucleic acids are natural biopolymers of nucleotides that store, encode, transmit and express genetic information, which play central roles in diverse cellular events and diseases in living things. The analysis of nucleic acids and nucleic acids-based analysis have been widely applied in biological studies, clinical diagnosis, environmental analysis, food safety and forensic analysis. During the past decades, the field of nucleic acids analysis has been rapidly advancing with many technological breakthroughs. In this review, we focus on the methods developed for analyzing nucleic acids, nucleic acids-based analysis, device for nucleic acids analysis, and applications of nucleic acids analysis. The representative strategies for the development of new nucleic acids analysis in this field are summarized, and key advantages and possible limitations are discussed. Finally, a brief perspective on existing challenges and further research development is provided.

Rapid and sensitive detection of Mycobacterium tuberculosis based on strand displacement amplification and magnetic beads

Tuberculosis is one of the main infectious diseases threatening public health, and the development of simple, rapid, and cost-saving methods for tuberculosis diagnosis is of profound importance for tuberculosis prevention and treatment. The bacterium Mycobacterium tuberculosis (MTB) is the pathogen that causes tuberculosis, and assaying for MTB is the only criterion for tuberculosis diagnosis. A new enzyme-free method based on strand displacement amplification and magnetic beads was developed for simple, rapid, and cost-saving MTB detection. Under optimum conditions, a good linear relationship could be observed between fluorescence and MTB specific DNA concentration ranging from 0.05 to 150 nM with a correlation coefficient of 0.993 (n = 8) and a detection limit of 47 pM (3σ/K). The present method also distinguished a one base mismatch from MTB specific DNA, showing great promise for MTB genome single base polymorphism analysis. MTB specific DNA content in polymerase chain reaction samples was successfully detected using the new method, and recoveries were 97.8-100.8%, indicating that the present method had high accuracy and shows good potential for the early diagnosis of tuberculosis.

Colorimetric-based detection of Ureaplasma urealyticum using gold nanoparticles

Ureaplasma urealyticum (uu) is one of the most common agents of urogenital infections and is associated with complications such as infertility, spontaneous abortion and other sexually transmitted diseases. Here, a DNA sensor based on oligonucleotide target-specific gold nanoparticles (AuNPs) was developed, in which the dispersed and aggregated states of oligonucleotide-functionalised AuNPs were optimised for the colorimetric detection of a polymerase chain reaction (PCR) amplicon of U. urealyticum DNA. A non-cross-linking approach utilising a single Au-nanoprobe specific of the urease gene was utilised and the effect of a PCR product concentration gradient evaluated. Results from both visual and spectral analyses showed that target-Au-nanoprobe hybrids were stable against aggregation after adding the inducer. Furthermore, when a non-target PCR product was used, the peak position shifted and salt-induced aggregation occurred. The assay's limit of detection of the assay was 10 ng with a dynamic range of 10-60 ng. This procedure provides a rapid, facile and low-cost detection format, compared to methods currently used for the identification of U. urealyticum.

Long-term stabilization of hydrogen peroxide by poly(vinyl alcohol) on paper-based analytical devices

Stabilizing reagents that can be deposited onto paper is an important issue for researchers who depend on paper-based analytical devices (PADs), because long-term stability of the devices is essential in point-of-care testing. Here, we found that poly(vinyl alcohol) (PVA) would stabilize hydrogen peroxide placed on a paper substrate following exposure to air. Horseradish peroxidase was employed as a sample in colorimetric measurements of PADs after hydrogen peroxide and 3,3',5,5'-tetramethylbenzidine were deposited as substrates in an enzymatic reaction. The addition of PVA to hydrogen peroxide significantly suppressed its degradation. Concentrations of PVA that ranged from 0.5 to 2%, increased the duration of the stability of hydrogen peroxide, and the results for a PVA concentration of 1% approximated those of 2% PVA. Storage of the PADs at 4 °C in a refrigerator extended the stability of the hydrogen peroxide containing 2% PVA by as much as 30 days. The stability of hydrogen peroxide without PVA was degraded after one day under room temperature.

Plasmonic-based platforms for diagnosis of infectious diseases at the point-of-care

Infectious diseases such as HIV-1/AIDS, tuberculosis (TB), hepatitis B (HBV), and malaria still exert a tremendous health burden on the developing world, requiring rapid, simple and inexpensive diagnostics for on-site diagnosis and treatment monitoring. However, traditional diagnostic methods such as nucleic acid tests (NATs) and enzyme linked immunosorbent assays (ELISA) cannot be readily implemented in point-of-care (POC) settings. Recently, plasmonic-based biosensors have emerged, offering an attractive solution to manage infectious diseases in the developing world since they can achieve rapid, real-time and label-free detection of various pathogenic biomarkers. Via the principle of plasmonic-based optical detection, a variety of biosensing technologies such as surface plasmon resonance (SPR), localized surface plasmon resonance (LSPR), colorimetric plasmonic assays, and surface enhanced Raman spectroscopy (SERS) have emerged for early diagnosis of HIV-1, TB, HBV and malaria. Similarly, plasmonic-based colorimetric assays have also been developed with the capability of multiplexing and cellphone integration, which is well suited for POC testing in the developing world. Herein, we present a comprehensive review on recent advances in surface chemistry, substrate fabrication, and microfluidic integration for the development of plasmonic-based biosensors, aiming at rapid management of infectious diseases at the POC, and thus improving global health.

Toxicological Behavior of Gold Nanoparticles on Various Models: Influence of Physicochemical Properties and Other Factors

Potential applications of gold nanoparticles in biomedicine have increasingly been reported on account of the ease of synthesis, bioinert characteristics, optical properties, chemical stability, high biocompatibility, and specificity. The safety of these particles remains a great concern, as there are differences among toxicity study protocols used. This article focuses on integrating results of research on the toxicological behavior of gold nanoparticles. This can be influenced by the physicochemical properties, including size, shape, surface charge, and other factors, such as methods used in the synthesis of gold nanoparticles, models used, dose, in vivo route of administration, and interference of gold nanoparticles with in vitro toxicity assay systems. Several researchers have reported toxicological studies with regard to gold nanoparticles, using various in vitro, in vivo, and in ovo models. The conflicting results concerning the toxicity of gold nanoparticles should thus be addressed to justify the safe use of gold nanoparticles in biomedicine.

Recent developments of aptasensors expedient for point-of-care (POC) diagnostics

Aptamers are nucleic acid-based molecular recognition elements that are specific and have high binding affinity against their respective targets. On account of their target recognition capacity, aptamers are widely utilized in a number of applications including diagnostics. This review aims to highlight the recent developments of aptasensors expedient for point-of-care (POC) diagnostics. Significant focus is given on the primary assay formats of aptamers such as fluorescence, electrochemical, surface plasmon resonance (SPR) and colorimetric assays. A potpourri of platforms such as paper-based device, lateral flow assay, portable electrodes, portable SPR and smart phones expedient for point-of-care (POC) diagnostics are discussed. Emphasis is also given on the technicalities and assay configurations associated with the sensors.

Nanoparticle-based Point of Care Immunoassays for in vitro Biomedical Diagnostics

In resource-limited settings, the availability of medical practitioners and early diagnostic facilities are inadequate relative to the population size and disease burden. To address cost and delayed time issues in diagnostics, strip-based immunoassays, e.g. dipstick, lateral flow assay (LFA) and microfluidic paper-based analytical devices (microPADs), have emerged as promising alternatives to conventional diagnostic approaches. These assays rely on chromogenic agents to detect disease biomarkers. However, limited specificity and sensitivity have motivated scientists to improve the efficiency of these assays by conjugating chromogenic agents with nanoparticles for enhanced qualitative and quantitative output. Various nanomaterials, which include metallic, magnetic and luminescent nanoparticles, are being used in the fabrication of biosensors to detect and quantify biomolecules and disease biomarkers. This review discusses some of the principles and applications of such nanoparticle-based point of care biosensors in biomedical diagnosis.

Detection of chikungunya virus-specific IgM on laser-cut paper-based device using pseudo-particles as capture antigen

The incidence of arbovirus infections has increased dramatically in recent decades, affecting hundreds of millions of people each year. The Togaviridae family includes the chikungunya virus (CHIKV), which is typically transmitted by Aedes mosquitoes and causes a wide range of symptoms from flu-like fever to severe arthralgia. Although conventional diagnostic tests can provide early diagnosis of CHIKV infections, access to these tests is often limited in developing countries. Consequently, there is an urgent need to develop efficient, affordable, simple, rapid, and robust diagnostic tools that can be used in point-of-care settings. Early diagnosis is crucial to improve patient management and to reduce the risk of complications. A glass-fiber laser-cut microfluidic device (paper-based analytical device [PAD]) was designed and evaluated in a proof of principle context, for the analysis of 30 µL of patient serum. Biological raw materials used for the functionalization of the PAD were first screened by MAC-ELISA (IgM capture enzyme-linked immunosorbent assay) for CHIKV Immunoglobulin M (IgM) capture and then evaluated on the PAD using various human samples. Compared with viral lysate traditionally used for chikungunya (CHIK) serology, CHIKV pseudo-particles (PPs) have proven to be powerful antigens for specific IgM capture. The PAD was able to detect CHIKV IgM in human sera in less than 10 minutes. Results obtained in patient sera showed a sensitivity of 70.6% and a specificity of around 98%. The PAD showed few cross-reactions with other tropical viral diseases. The PAD could help health workers in the early diagnosis of tropical diseases such as CHIK, which require specific management protocols in at-risk populations.

Detecting Biothreat Agents: From Current Diagnostics to Developing Sensor Technologies

Although a fundamental understanding of the pathogenicity of most biothreat agents has been elucidated and available treatments have increased substantially over the past decades, they still represent a significant public health threat in this age of (bio)terrorism, indiscriminate warfare, pollution, climate change, unchecked population growth, and globalization. The key step to almost all prevention, protection, prophylaxis, post-exposure treatment, and mitigation of any bioagent is early detection. Here, we review available methods for detecting bioagents including pathogenic bacteria and viruses along with their toxins. An introduction placing this subject in the historical context of previous naturally occurring outbreaks and efforts to weaponize selected agents is first provided along with definitions and relevant considerations. An overview of the detection technologies that find use in this endeavor along with how they provide data or transduce signal within a sensing configuration follows. Current "gold" standards for biothreat detection/diagnostics along with a listing of relevant FDA approved in vitro diagnostic devices is then discussed to provide an overview of the current state of the art. Given the 2014 outbreak of Ebola virus in Western Africa and the recent 2016 spread of Zika virus in the Americas, discussion of what constitutes a public health emergency and how new in vitro diagnostic devices are authorized for emergency use in the U.S. are also included. The majority of the Review is then subdivided around the sensing of bacterial, viral, and toxin biothreats with each including an overview of the major agents in that class, a detailed cross-section of different sensing methods in development based on assay format or analytical technique, and some discussion of related microfluidic lab-on-a-chip/point-of-care devices. Finally, an outlook is given on how this field will develop from the perspective of the biosensing technology itself and the new emerging threats they may face.

Paper-Based Analytical Methods for Smartphone Sensing with Functional Nanoparticles: Bridges from Smart Surfaces to Global Health

In this Feature, the most recent developments as well as "pros and cons" in smartphone sensing, which have been developed using various functional nanoparticles in paper-based sensing systems, will be discussed. Additionally, smart phone sensing and POC combination as a potential tool that opens a gate for knowledge flow "from lab scale data to public use" will be evaluated.

Paper-Based Sensors: Emerging Themes and Applications

Paper is a versatile, flexible, porous, and eco-friendly substrate that is utilized in the fabrication of low-cost devices and biosensors for rapid detection of analytes of interest. Paper-based sensors provide affordable platforms for simple, accurate, and rapid detection of diseases, in addition to monitoring food quality, environmental and sun exposure, and detection of pathogens. Paper-based devices provide an inexpensive technology for fabrication of simple and portable diagnostic systems that can be immensely useful in resource-limited settings, such as in developing countries or austere environments, where fully-equipped facilities and highly trained medical staff are absent. In this work, we present the different types of paper that are currently utilized in fabrication of paper-based sensors, and common fabrication techniques ranging from wax printing to origami- and kirigami-based approaches. In addition, we present different detection techniques that are employed in paper-based sensors such as colorimetric, electrochemical, and fluorescence detection, chemiluminescence, and electrochemiluminescence, as well as their applications including disease diagnostics, cell cultures, monitoring sun exposure, and analysis of environmental reagents including pollutants. Furthermore, main advantages and disadvantages of different types of paper and future trends for paper-based sensors are discussed.

A Simple Imaging Device for Fluorescence-Relevant Applications

This article unveiled the development of an inexpensive, lightweight, easy-to-use, and portable fluorescence imaging device for paper-based analytical applications. We used commercial fluorescent dyes, as proof of concept, to verify the feasibility of our fluorescence imaging device for bioanalysis. This approach may provide an alternative method for nucleotide detection and semen analysis, using a miniaturized fluorescence reader that is more compact and portable than conventional analytical equipment.

Policy Considerations for Mobile Biosensors

Meeting policy requirements is essential for advancing molecular diagnostic devices from the laboratory to real-world applications and commercialization. Considering policy as a starting point in the design of new technology is a winning strategy. Rapid developments have put mobile biosensors at the frontier of molecular diagnostics, at times outpacing policymakers, and therefore offering new opportunities for breakthroughs in global health. In this Perspective we survey influential global health policies and recent developments in mobile biosensing in order to gain a new perspective for the future of the field. We summarize the main requirements for mobile diagnostics outlined by policy makers such as the World Health Organization (WHO), the World Bank, the European Union (EU), and the Food and Drug Administration (FDA). We then classify current mobile diagnostic technologies according to the manner in which the biosensor interfaces with a smartphone. We observe a trend in reducing hardware components and substituting instruments and laborious data processing steps for user-friendly apps. From this perspective we see software application developers as key collaborators for bridging the gap between policy and practice.

Automatic diagnosis of tuberculosis disease based on Plasmonic ELISA and color-based image classification

Tuberculosis (TB) remains one of the most devastating infectious diseases and its treatment efficiency is majorly influenced by the stage at which infection with the TB bacterium is diagnosed. The available methods for TB diagnosis are either time consuming, costly or not efficient. This study employs a signal generation mechanism for biosensing, known as Plasmonic ELISA, and computational intelligence to facilitate automatic diagnosis of TB. Plasmonic ELISA enables the detection of a few molecules of analyte by the incorporation of smart nanomaterials for better sensitivity of the developed detection system. The computational system uses k-means clustering and thresholding for image segmentation. This paper presents the results of the classification performance of the Plasmonic ELISA imaging data by using various types of classifiers. The five-fold cross-validation results show high accuracy rate (>97%) in classifying TB images using the entire data set. Future work will focus on developing an intelligent mobile-enabled expert system to diagnose TB in real-time. The intelligent system will be clinically validated and tested in collaboration with healthcare providers in Malaysia.

Cure of tuberculosis using nanotechnology: An overview

Mycobacterium tuberculosis is the causative agent of tuberculosis (TB), a major health issue of the present era. The bacterium inhabits the host macrophage and other immune cells where it modulates the lysosome trafficking protein, hinders the formation of phagolysosome, and blocks the TNF receptor-dependent apoptosis of host macrophage/monocytes. Other limitations such as resistance to and low bioavailability and bio-distribution of conventional drugs aid to their high virulence and human mortality. This review highlights the use of nanotechnology-based approaches for drug formulation and delivery which could open new avenues to limit the pathogenicity of tuberculosis. Moreover phytochemicals, such as alkaloids, phenols, saponins, steroids, tannins, and terpenoids, extracted from terrestrial plants and mangroves seem promising against M. tuberculosis through different molecular mechanisms. Further understanding of the genomics and proteomics of this pathogenic microbe could also help overcome various research gaps in the path of developing a suitable therapy against tuberculosis.

Signal Amplified Gold Nanoparticles for Cancer Diagnosis on Paper-Based Analytical Devices

In this work, we report a highly sensitive colorimetric sensing strategy for cancer biomarker diagnosis using gold nanoparticles (AuNPs) labeled with biotinylated poly(adenine) ssDNA sequences and streptavidin-horseradish peroxidase for enzymatic signal enhancement. By adopting this DNA-AuNP nanoconjugate sensing strategy, we were able to eliminate the complicated and costly thiol-binding process typically used to modify AuNP surfaces with ssDNA. In addition, different antibodies can be introduced to the AuNP surfaced via electrostatic interactions to provide highly specific recognition sites for biomolecular sensing. Moreover, multiple, simultaneous tests can be rapidly performed with low sample consumption by incorporating these surface-modified AuNPs into a paper-based analytical device that can be read using just a smartphone. As a result of these innovations, we were able to achieve a detection limit of 10 pg/mL for a prostate specific antigen in a test that could be completed in as little as 15 min. These results suggest that the proposed paper platform possesses the capability for sensitive, high-throughput, and on-site prognosis in resource-limited settings.

Probing the modulated formation of gold nanoparticles-beta-lactoglobulin corona complexes and their applications

Understanding the interactions between proteins and nanoparticles (NPs) along with the underlying structural and dynamic information is of utmost importance to exploit nanotechnology for biomedical applications. Upon adsorption onto a NP surface, proteins form a well-organized layer, termed the corona, that dictates the identity of the NP-protein complex and governs its biological pathways. Given its high biological relevance, in-depth molecular investigations and applications of NPs-protein corona complexes are still scarce, especially since different proteins form unique corona patterns, making identification of the biomolecular motifs at the interface critical. In this work, we provide molecular insights and structural characterizations of the bio-nano interface of a popular food-based protein, namely bovine beta-lactoglobulin (β-LG), with gold nanoparticles (AuNPs) and report on our investigations of the formation of corona complexes by combined molecular simulations and complementary experiments. Two major binding sites in β-LG were identified as being driven by citrate-mediated electrostatic interactions, while the associated binding kinetics and conformational changes in the secondary structures were also characterized. More importantly, the superior stability of the corona led us to further explore its biomedical applications, such as in the smartphone-based point-of-care biosensing of Escherichia coli (E. coli) and in the computed tomography (CT) of the gastrointestinal (GI) tract through oral administration to probe GI tolerance and functions. Considering their biocompatibility, edible nature, and efficient excretion through defecation, AuNPs-β-LG corona complexes have shown promising perspectives for future in vitro and in vivo clinical settings.

Synthetic Biology-Based Point-of-Care Diagnostics for Infectious Disease

Infectious diseases outpace all other causes of death in low-income countries, posing global health risks, laying stress on healthcare systems and societies, and taking an avoidable human toll. One solution to this crisis is early diagnosis of infectious disease, which represents a powerful way to optimize treatment, increase patient survival rate, and decrease healthcare costs. However, conventional early diagnosis methods take a long time to generate results, lack accuracy, and are known to seriously underperform with regard to fungal and viral infections. Synthetic biology offers a fast and highly accurate alternative to conventional infectious disease diagnosis. In this review, we outline obstacles to infectious disease diagnostics and discuss two emerging alternatives: synthetic viral diagnostic systems and biosensors. We argue that these synthetic biology-based approaches may overcome diagnostic obstacles in infectious disease and improve health outcomes.

Engineered Paper-Based Cell Culture Platforms

Paper is used in various applications in biomedical research including diagnostics, separations, and cell cultures. Paper can be conveniently engineered due to its tunable and flexible nature, and is amenable to high-throughput sample preparation and analysis. Paper-based platforms are used to culture primary cells, tumor cells, patient biopsies, stem cells, fibroblasts, osteoblasts, immune cells, bacteria, fungi, and plant cells. These platforms are compatible with standard analytical assays that are typically used to monitor cell behavior. Due to its thickness and porous nature, there are no mass transport limitations to/from the cells in paper scaffolds. It is possible to pattern paper in different scales (micrometer to centimeter), generate modular configurations in 3D, fabricate multicellular and compartmentalized tissue mimetics for clinical applications, and recover cells from the scaffolds for further analysis. 3D paper constructs can provide physiologically relevant tissue models for personalized medicine. Layer-by layer strategies to assemble tissue-like structures from low-cost and biocompatible paper-based materials offer unique opportunities that include understanding fundamental biology, developing disease models, and assembling different tissues for organ-on-paper applications. Paper-based platforms can also be used for origami-inspired tissue engineering. This work provides an overview of recent progress in engineered paper-based biomaterials and platforms to culture and analyze cells.

A Printed Multicomponent Paper Sensor for Bacterial Detection

We present a simple all-in-one paper-based sensor for E. coli detection using a composite ink made of a fluorogenic DNAzyme probe for bacterial recognition and signal generation, lysozyme that lyses whole bacterial cells, and pullulan/trehalose sugars that stabilize printed bioactive molecules. The paper sensor is capable of producing a fluorescence signal as a readout within 5 minutes upon contacting E. coli, can achieve a limit of detection of 100 cells/mL, in a variety of sample matrixes, without sample enrichment, and remains stable for at least 6 months when stored at ambient temperature. Therefore, this simple paper sensor provides rapid bacterial testing on site, and can be shipped and stored under ambient conditions to benefit users living in resource-limited regions.

A review on wax printed microfluidic paper-based devices for international health

Paper-based microfluidics has attracted attention for the last ten years due to its advantages such as low sample volume requirement, ease of use, portability, high sensitivity, and no necessity to well-equipped laboratory equipment and well-trained manpower. These characteristics have made paper platforms a promising alternative for a variety of applications such as clinical diagnosis and quantitative analysis of chemical and biological substances. Among the wide range of fabrication methods for microfluidic paper-based analytical devices (μPADs), the wax printing method is suitable for high throughput production and requires only a commercial printer and a heating source to fabricate complex two or three-dimensional structures for multipurpose systems. μPADs can be used by anyone for in situ diagnosis and analysis; therefore, wax printed μPADs are promising especially in resource limited environments where people cannot get sensitive and fast diagnosis of their serious health problems and where food, water, and related products are not able to be screened for toxic elements. This review paper is focused on the applications of paper-based microfluidic devices fabricated by the wax printing technique and used for international health. Besides presenting the current limitations and advantages, the future directions of this technology including the commercial aspects are discussed. As a conclusion, the wax printing technology continues to overcome the current limitations and to be one of the promising fabrication techniques. In the near future, with the increase of the current interest of the industrial companies on the paper-based technology, the wax-printed paper-based platforms are expected to take place especially in the healthcare industry.

Nanodiagnostics for tuberculosis detection

INTRODUCTION

Tuberculosis (TB) is a leading killer worldwide. End TB strategy aims at ending the TB epidemic by 2030. Early, accurate, and affordable diagnosis represents a cornerstone to achieve this goal. Innovative strategies for TB diagnostics have been introduced. However, the ideal assay is yet unavailable and conventional methods remain necessary for diagnosis. Unique properties of nanoparticles (NPs) have allowed their utilization in TB detection via targeting disease biomarkers. Area covered: Until now, around thirty-five TB NP-based assays have been partially or fully characterized. Accuracy, low-cost, and short time-to-result represent the common properties of proposed platforms. TB nanodiagnostics now encompass almost all clinical aspects of the disease including active TB, non-tuberculous mycobacteria, rifampicin resistant TB, TB/HIV co-infection, latent TB, and extra-pulmonary TB. This review summarizes state-of-the-art knowledge of TB nanodiagnostics for the last 10 years. Special consideration is given for fabrication concepts, detection strategies, and clinical performance using various clinical specimens. The potential of TB nanodiagnostics to fulfill the need for ideal MTB testing is assessed. Expert commentary: TB nanodiagnostics show promise to be ideal detection tools that can meet the rigorous demands to end the TB epidemic by 2030.

Technical aspects and challenges of colorimetric detection with microfluidic paper-based analytical devices (μPADs) - A review

Paper-based devices are a leading alternative among the main analytical tools for point-of-care testing, due to their portability, low-cost, and ease-of-use. Colorimetric readouts are the most common method of detection in these microfluidic devices, enabling qualitative, semi-quantitative and fully quantitative analysis of multiple analytes. There is a multitude of ways to obtain a colorimetric output in such devices, including nanoparticles, dyes, redox and pH indicators, and each has unique drawbacks and benefits. There are also multiple variables that impact the analysis of colorimetric reactions in microfluidic paper-based systems, including color homogeneity, image capture methods, and the data handling itself. Here, we present a critical review of recent developments and challenges of colorimetric detection on microfluidic paper-based analytical devices (μPADs), and present thoughts and insights towards future perspectives in the area to improve the use of colorimetric readouts in conjunction with μPADs.

Paper-based diagnostic devices for clinical paraquat poisoning diagnosis

This article unveils the development of a paper-based analytical device designed to rapidly detect and clinically diagnose paraquat (PQ) poisoning. Using wax printing technology, we fabricated a PQ detection device by pattering hydrophobic boundaries on paper. This PQ detection device employs a colorimetric sodium dithionite assay or an ascorbic acid assay to indicate the PQ level in a buffer system or in a human serum system in 10 min. In this test, colorimetric changes, blue in color, were observable with the naked eye. By curve fitting models of sodium dithionite and ascorbic acid assays in normal human serum, we evaluated serum PQ levels for five PQ-poisoned patients before hemoperfusion (HP) treatment and one PQ-poisoned patient after HP treatment. As evidenced by similar detection outcomes, the analytical performance of our device can compete with that of the highest clinical standard, i.e., spectrophotometry, with less complicated sample preparation and with more rapid results. Accordingly, we believe that our rapid PQ detection can benefit physicians determining timely treatment strategies for PQ-poisoned patients once they are taken to hospitals, and that this approach will increase survival rates.

Colorimetric detection based on localised surface plasmon resonance of gold nanoparticles: Merits, inherent shortcomings and future prospects

Localised surface plasmon resonance (LSPR) of gold nanoparticles (AuNPs) has been exploited for two decades in analytical science and has proven to be a powerful tool for the detection of various kinds of substances including small molecules, ions, macro biomolecules and microbes. Detection can be performed by visual colour change observations, photometry or resonance light scattering. A wide range of applications have been studied in the areas of environmental, pharmaceutical and biological analysis and clinical diagnosis. In this article, some fundamental aspects and important applications involving LSPR of AuNPs are reviewed. Several inherent shortcomings of these techniques and possible strategies to circumvent them are discussed.

Enhanced Analytical Performance of Paper Microfluidic Devices by Using Fe3O4 Nanoparticles, MWCNT, and Graphene Oxide

Spheres, tubes, and planar-shaped nanomaterials as Fe3O4 nanoparticles (MNPs), multiwalled carbon nanotubes (MWCNT), and graphene oxide (GO) were used for the first time to treat microfluidic paper-based analytical devices (μPADs) and create a biocompatible layer with high catalytic surface. Once glucose measurements are critical for diabetes or glycosuria detection and monitoring, the analytical performance of the proposed devices was studied by using bienzymatic colorimetric detection of this carbohydrate. The limit of detection values achieved for glucose with μPADs treated with MNPs, MWCNT, and GO were 43, 62, and 18 μM, respectively. The paper surface modification solves problems associated with the lack of homogeneity on color measurements that compromise the sensitivity and detectability levels in clinical diagnosis.

DNA templated self-assembly of gold nanoparticle clusters in the colorimetric detection of plant viral DNA using a gold nanoparticle conjugated bifunctional oligonucleotide probe

The DNA templated self-assembly of gold nanoparticles clustered in different configurations (nn = 2–∞) was investigated in the colorimetric detection of ToLCNDV DNA using a gold nanoparticle conjugated bifunctional oligonucleotide probe.

An approach to enhance self-compensation capability in paper-based devices for chemical sensing

This paper describes a simple design for increasing the tolerance of reagent dislocation on a paper-based platform using a combination of wax-treated paper and a vortex mixer. To date, massive budgetary funds are required in the biotechnological industry to develop new applications; a large part of that cost is attributable to the screening of specific chemical compounds. Here, we propose using a liquid-handling robot to automatically deposit selected reagents on a paper-based platform. We also present a preliminary concept approach for developing a reagent placing device with simple and inexpensive features. A defect of inaccuracy was observed between droplet location and test well location after viewing the performance of the liquid-handling robot on our paper-based platform. Because of dislocation error resulting from robotic reagent placement, we decided to apply an external, rotational force following droplet placement in order to compensate for the distance of reagent dislocation. Note, the largest distance of reagent dislocation was determined by examining the results of altering applied reagent volume, but not concentration, in volumes from 5 µL to 30 µL in a series of experiments. As a result of these experiments, we observed that dislocation was positively affected by an increase in applied volume. A colorimetric assay for nitrite detection was also performed to confirm the feasibility of this method. This work, we believe, can minimize the cost of chemical compound screening for the biotechnological industry.

Reprint of 'Evaluating organophosphate poisoning in human serum with paper'

This manuscript describes the development and clinical testing of a paper-based, metabolic assay designed for rapid, semi-quantitative measurement of organophosphate poisoning. Paper-based platforms, including point-of-care devices and 96-well plates, provided semi-quantitative information regarding the concentration of AchE (a biomarker for organophosphate poisoning). The paper-based 96-well-plate developed and implemented in this study was used to measure the level of organophosphate poisoning in three different clinical patients. Results were comparable to those obtained using conventional hospital methods currently considered the "gold standard". This diagnostic device offers several advantages over conventional methods, including short operating time (twice as fast as conventional methods), procedure simplicity, and reduced fabrication cost. With further commercialization efforts, the methods described in this manuscript could be applied to a wide range of potential diagnostic applications in the field.