Rapid and quantitative detection of zoonotic influenza A virus infection utilizing coumarin-derived dendrimer-based fluorescent immunochromatographic strip test (FICT)

Cysteamine-Gold Coated Carboxylated Fluorescent Nanoparticle Mediated Point-of-Care Dual-Modality Detection of the H5N1 Pathogenic Virus

Globally, point-of-care testing (POCT) is the most preferable on-site technique for disease detection and includes a rapid diagnostic test (RDT) and fluorescent immunochromatographic strip test (FICT). The testing kits are generally insufficient in terms of signal enhancement, which is a major drawback of this approach. Sensitive and timely on-site POCT methods with high signal enhancement are therefore essential for the accurate diagnosis of infectious diseases. Herein, we prepare cysteamine-gold coated carboxylated europium chelated nanoparticle (Cys Au-EuNPs)-mediated POCT for the detection of the H5N1 avian influenza virus (AIV). Commercial nanoparticles were used for comparison. The spectral characteristics, surface morphologies, functional groups, surface charge and stability of the Cys AuNPs, EuNPs, and Cys Au-EuNPs were confirmed by UV-visible spectrophotometry, fluorescence spectrometry, transmission electron microscope with Selected area electron diffraction (TEM-SAED), Fourier-transform infrared spectroscopy (FTIR) and zeta potential analysis. The particle size distribution revealed an average size of ~130 ± 0.66 nm for the Cys Au-EuNPs. The Cys Au-EuNP-mediated RDT (colorimetric analysis) and FICT kit revealed a limit of detection (LOD) of 10 HAU/mL and 2.5 HAU/mL, respectively, for H5N1 under different titer conditions. The obtained LOD is eight-fold that of commercial nanoparticle conjugates. The photo luminance (PL) stability of ~3% the Cys Au-EuNPs conjugates that was obtained under UV light irradiation differs considerably from that of the commercial nanoparticle conjugates. Overall, the developed Cys Au-EuNPs-mediated dual-mode POCT kit can be used as an effective nanocomposite for the development of on-site monitoring systems for infectious disease surveillance.

Development of a Rapid Fluorescent Diagnostic System for Early Detection of the Highly Pathogenic Avian Influenza H5 Clade 2.3.4.4 Viruses in Chicken Stool

Rapid diagnosis is essential for the control and prevention of H5 highly pathogenic avian influenza viruses (HPAIVs). However, highly sensitive and rapid diagnostic systems have shown limited performance due to specific antibody scarcity. In this study, two novel specific monoclonal antibodies (mAbs) for clade 2.3.4.4 H5Nx viruses were developed by using an immunogen from a reversed genetic influenza virus (RGV). These mAbs were combined with fluorescence europium nanoparticles and an optimized lysis buffer, which were further used for developing a fluorescent immunochromatographic rapid strip test (FICT) for early detection of H5Nx influenza viruses on chicken stool samples. The result indicates that the limit of detection (LoD) of the developed FICT was 40 HAU/mL for detection of HPAIV H5 clade 2.3.4.4b in spiked chicken stool samples, which corresponded to 4.78 × 10⁴ RNA copies as obtained from real-time polymerase chain reaction (RT-PCR). An experimental challenge of chicken with H5N6 HPAIV is lethal for chicken three days post-infection (DPI). Interestingly, our FICT could detect H5N6 in stool samples at 2 DPI earlier, with 100% relative sensitivity in comparison with RT-PCR, and it showed 50% higher sensitivity than the traditional colloidal gold-based rapid diagnostic test using the same mAbs pair. In conclusion, our rapid diagnostic method can be utilized for the early detection of H5Nx 2.3.4.4 HPAIVs in avian fecal samples from poultry farms or for influenza surveillance in wild migratory birds.

Application of dendrimer-based nanosensors in immunodiagnosis

Conventional immunoassays such as ELISA and FLISA have been used for clinical diagnosis for a long time. These assays are complex, time-consuming, and uneconomical. They have been overwhelmed with newer and more efficient methods such as electrochemical and electrochemiluminescent immunosensors that are cost-effective and require less time. Immunosensor is a biosensor that consists of a signal transducer and a biologically interactive system such as antigen and antibody interaction. Recent advances in nanotechnology have seen numerous efforts towards the usage of nanoparticles such as dendrimers in immunoassays. Dendrimers are highly branched structures with a high density of active peripheral groups, expanding their wide range of applications in immunoassays. A vast number of peripheral groups enrich the sensitivity of the immunosensor by governing the orientation of the antibody on the sensor surface. The current review highlights recent progress and developments in applying dendrimers for different immunoassays and their applicability in analyzing various biomarkers in clinical disease diagnosis.

Development of a Rapid Fluorescent Diagnostic System to Detect Subtype H9 Influenza A Virus in Chicken Feces

The circulation of the H9N2 virus results in significant economic losses in the poultry industry, and its zoonotic transmission highlights the need for a highly sensitive and rapid diagnostic and detection system for this virus. In this study, the performance of lateral flow test strips for a fluorescent immunochromatographic test (FICT) was optimized for the diagnosis of H9N2 virus-infected animal samples. The novel monoclonal antibodies (McAbs) against influenza A H9 viruses were developed, and two categories of McAbs with linear and conformational epitopes were compared for the performance of rapid diagnostic performance in the presence of feces sample at different time points (2, 4, and 6 days) post-infection (dpi). The limit of detection (LOD) of FICT and Kd values were comparable between linear and conformational epitope McAbs. However, superior performance of linear epitope McAbs pairs were confirmed by two animal studies, showing the better diagnostic performance showing 100% relative sensitivity in fecal samples at 6 dpi although it showed less than 80% sensitivity in early infection. Our results imply that the comparable performance of the linear epitope McAbs can potentially improve the diagnostic performance of FICT for H9N2 detection in feces samples. This highly sensitive rapid diagnostic method can be utilized in field studies of broiler poultry and wild birds.

Avian Influenza in Wild Birds and Poultry: Dissemination Pathways, Monitoring Methods, and Virus Ecology

Avian influenza is one of the largest known threats to domestic poultry. Influenza outbreaks on poultry farms typically lead to the complete slaughter of the entire domestic bird population, causing severe economic losses worldwide. Moreover, there are highly pathogenic avian influenza (HPAI) strains that are able to infect the swine or human population in addition to their primary avian host and, as such, have the potential of being a global zoonotic and pandemic threat. Migratory birds, especially waterfowl, are a natural reservoir of the avian influenza virus; they carry and exchange different virus strains along their migration routes, leading to antigenic drift and antigenic shift, which results in the emergence of novel HPAI viruses. This requires monitoring over time and in different locations to allow for the upkeep of relevant knowledge on avian influenza virus evolution and the prevention of novel epizootic and epidemic outbreaks. In this review, we assess the role of migratory birds in the spread and introduction of influenza strains on a global level, based on recent data. Our analysis sheds light on the details of viral dissemination linked to avian migration, the viral exchange between migratory waterfowl and domestic poultry, virus ecology in general, and viral evolution as a process tightly linked to bird migration. We also provide insight into methods used to detect and quantify avian influenza in the wild. This review may be beneficial for the influenza research community and may pave the way to novel strategies of avian influenza and HPAI zoonosis outbreak monitoring and prevention.

Recent Advances in Functional Polymers Containing Coumarin Chromophores

Natural and synthetic coumarin derivatives have gained increased attention in the design of functional polymers and polymer networks due to their unique optical, biological, and photochemical properties. This review provides a comprehensive overview over recent developments in macromolecular architecture and mainly covers examples from the literature published from 2004 to 2020. Along with a discussion on coumarin and its photochemical properties, we focus on polymers containing coumarin as a nonreactive moiety as well as polymer systems exploiting the dimerization and/or reversible nature of the [2πs + 2πs] cycloaddition reaction. Coumarin moieties undergo a reversible [2πs + 2πs] cycloaddition reaction upon irradiation with specific wavelengths in the UV region, which is applied to impart intrinsic healability, shape-memory, and reversible properties into polymers. In addition, coumarin chromophores are able to dimerize under the exposure to direct sunlight, which is a promising route for the synthesis and cross-linking of polymer systems under "green" and environment-friendly conditions. Along with the chemistry and design of coumarin functional polymers, we highlight various future application fields of coumarin containing polymers involving tissue engineering, drug delivery systems, soft robotics, or 4D printing applications.

A rapid and quantitative fluorescent microsphere immunochromatographic strip test for detection of antibodies to porcine reproductive and respiratory syndrome virus

A fluorescent microsphere-based immunochromatographic strip test (FICT) was developed for the rapid, sensitive, and quantitative detection of porcine reproductive and respiratory syndrome virus (PRRSV) antibodies at the pen-side. The assay was based on the formation of a sandwich immune-complex (anti-pig IgG-PRRSV antibodies-NSP7/N), which was validated by a comparison with IDEXX-ELISA using 3325 clinical specimens. The diagnostic specificity, sensitivity, and accuracy of FICT were 97.28, 93.41, and 94.95%, respectively. FICT showed a good correlation with the virus neutralization assay. Overall, a promising pen-side diagnostic tool was developed for the rapid and quantitative detection of PRRSV antibodies within 15 min.

Developing Gold Nanoparticles-Conjugated Aflatoxin B1 Antifungal Strips

Lateral flow immunochromatographic assays are a powerful diagnostic tool for point-of-care tests, based on their simplicity, specificity, and sensitivity. In this study, a rapid and sensitive gold nanoparticle (AuNP) immunochromatographic strip is produced for detecting aflatoxin B1 (AFB1) in suspicious fungi-contaminated food samples. The 10 nm AuNPs were encompassed by bovine serum albumin (BSA) and AFB1 antibody. Thin-layer chromatography, gel electrophoresis and nuclear magnetic resonance spectroscopy were employed for analysing the chemical complexes. Various concentrations of AFB1 antigen (0-16 ng/mL) were tested with AFB1 antibody-BSA-AuNPs (conjugated AuNPs) and then analysed by scanning electron microscopy, ultraviolet-visible spectroscopy, and Zetasizer. The results showed that the AFB1 antibody was coupled to BSA by the N-hydroxysuccinimide ester method. The AuNPs application has the potential to contribute to AFB1 detection by monitoring a visible colour change from red to purple-blue, with a detection limit of 2 ng/mL in a 96-well plate. The lateral flow immunochromatographic strip tests are rapid, taking less than 10 min., and they have a detection capacity of 10 ng/g. The smartphone analysis of strips provided the results in 3 s, with a detection limit of 0.3 ng/g for AFB1 when the concentration was below 10 ng/g. Excellent agreement was found with AFB1 determination by high-performance liquid chromatography in the determination of AFB1 among 20 samples of peanuts, corn, rice, and bread.

Rapid and Ultrasensitive Quantification of Multiplex Respiratory Tract Infection Pathogen via Lateral Flow Microarray based on SERS Nanotags

Respiratory tract infections (RTIs) are severe acute infectious diseases, which require the timely and accurate identification of the pathogens involved so that the individual treatment plan can be selected, including optimized use of antibiotics. However, high throughput and ultrasensitive quantification of multiple nucleic acids is a challenge in a point of care testing (POCT) device.

Methods: Herein, we developed a 2×3 microarray on a lateral flow strip with surface enhanced Raman scattering (SERS) nanotags encoding the nucleic acids of 11 common RTI pathogens. On account of the signal magnification of encoded SERS nanotags in addition to the high surface area to volume ratio of the nitrocellulose (NC) membrane, rapid quantification of the 11 pathogens with a broad linear dynamic range (LDR) and ultra-high sensitivity was achieved on one lateral flow microarray.

Results: The limit of detection (LOD) for influenza A, parainfluenza 1, parainfluenza 3, respiratory syncytial virus, coxiella burnetii, legionella pneumophila, influenza B, parainfluenza 2, adenovirus, chlamydophila pneumoniae, and mycoplasma pneumoniae were calculated to be 0.031 pM, 0.030 pM, 0.038 pM, 0.038 pM, 0.040 pM, 0.039 pM, 0.035 pM, 0.032 pM, 0.040 pM, 0.039 pM, and 0.041 pM, respectively. The LDR of measurement of the target nucleic acids of the eleven RTI pathogens were 1 pM-50 nM, which span 5 orders of magnitude.

Conclusions: We anticipate this novel approach could be widely adopted in the early and precise diagnosis of RTI and other diseases.

Development of a smartphone-based rapid dual fluorescent diagnostic system for the simultaneous detection of influenza A and H5 subtype in avian influenza A-infected patients

Accurate and rapid diagnosis of highly pathogenic avian influenza A H5N1 is of critical importance for the effective clinical management of patients. Here, we developed a rapid and simultaneous detection toolkit for influenza A H5 subtype viruses in human samples based on a bioconjugate of quantum dots (QDs) assembly and a smartphone-based rapid dual fluorescent diagnostic system (SRDFDS). Methods: Two types of QDs were assembled on a latex bead to enhance the detection sensitivity and specificity of influenza A infection (QD580) and H5 subtype (QD650). The dual signals of influenza A and H5 subtype of H5N1-infected patients were detected simultaneously and quantified separately by SRDFDS equipped with two emission filters. Results: Our results showed a high sensitivity of 92.86% (13/14) and 78.57% (11/14), and a specificity of 100% (38/38, P < 0.0001) and 97.37% (37/38) for influenza A and H5 subtype detection, respectively. Conclusion: Therefore, our multiplex QD bioconjugates and SRDFDS-based influenza virus detection toolkit potentially provide accurate and meaningful diagnosis information with improved detection accuracies and sensitivities for H5N1 patients.

Clinical evaluation of rapid fluorescent diagnostic immunochromatographic test for influenza A virus (H1N1)

Rapid diagnostic tests (RDTs) have been developed to detect influenza A virus for the swift diagnosis and management of patients. However, despite the simplicity and convenience, the low sensitivity of RDTs remains a limitation for their use in point of care testing (POCT). In this study, we developed a rapid fluorescent immunochromatographic strip test (FICT) and the performance of FICT was confirmed by the real-time reverse transcription-polymerase chain reaction (rRT-PCR) of H1N1, compared with that of RDT. The limit of detection (LOD) of FICT was improved by 16-fold compared to RDT. FICT showed 85.29% sensitivity (29/34) (95% Confidence Interval [95% CI]: 68.94 to 95.05), 100% specificity (26/26) (95% CI: 86.78 to 100.00), and a strong correlation (kappa; 0. 92) compared with rRT-PCR (20 ≤ Ct ≤ 36). In contrast, RDT (Standard Diagnostics [SD] BIOLINE Influenza Ag A/ B/ A(H1N1) Pandemic) showed 55.88% sensitivity (19/34) (95% CI: 37.87 to 72.82), 100% specificity (26/26) (95% CI: 77.07 to 100), and had a fair correlation with rRT-PCR (kappa; 0. 75). FICT had better sensitivity than RDT (P < 0.01; McNemar’s test). Therefore, FICT has the potential to improve the quality of current rapid POCT for the diagnosis of influenza A/H1N1 infection.

In vitro selection of electrochemical peptide probes using bioorthogonal tRNA for influenza virus detection

An electrosensitive peptide probe has been developed from an in vitro selection technique using biorthogonal tRNA prepared with an electroreactive non-natural amino acid, 3,4-ethylenedioxythiophene-conjugated aminophenylalanine. The selected probe quantitatively detected the influenza virus based on a signal "turn-on" mechanism. The developed strategy could be used to develop electrochemical biosensors toward a variety of targets.

Effective Bioactivity Retention of Low-Concentration Antibodies on HFBI-Modified Fluorescence ICTS for Sensitive and Rapid Detection of PSA

Nowadays, increasing analytical sensitivity is still a big challenge in constructing membrane-based fluorescence immunochromatography test strips (FICTS). However, the bioactivity of antibody (Ab) immobilized on the test line (T line) of porous nitrocellulose membrane (PNM), which directly influences the analytical sensitivity, is less studied. In this work, a novel amphiphilic hydrophobin (HFBI) protein was introduced to modify the T line to effectively retain the Abs' bioactivity. The results indicated that HFBI could self-assemble on the PNM and immobilize the Abs in the "stand-up" orientation. Compared with the conventional FICTS, the HFBI-modified FICTS with only 0.2 mg/mL of monoclonal Abs on T line enable more accurate quantitative detection and better sensitivity (0.06 ng/mL for prostate specific antigen), which is more than 2 orders of magnitude lower than that of the conventional FICTS with the same concentration of monoclonal Abs on T line. Furthermore, the accuracy of this HFBI-modified FICTS was investigated by testing 150 clinical serum samples and the detection results were coincident with those by electrochemiluminescence immunoassay. Our results provide a novel and promising strategy of Ab immobilization on FICTS for near-patient and point-of-care application.

A Self-Assembled Coumarin-Anchored Dendrimer for Efficient Gene Delivery and Light-Responsive Drug Delivery

The assembly of low molecular weight polymers into highly efficient and nontoxic nanostructures has broad applicability in gene delivery. In this study, we reported the assembly of coumarin-anchored low generation dendrimers in aqueous solution via hydrophobic interactions. The synthesized material showed significantly improved DNA binding and gene delivery, and minimal toxicity on the transfected cells. Moreover, the coumarin moieties in the assembled nanostructures endow the materials with light-responsive drug delivery behaviors. The coumarin substitutes in the assembled nanostructures were cross-linked with each other upon irradiation at 365 nm, and the cross-linked assemblies were degraded upon further irradiation at 254 nm. As a result, the drug-loaded nanoparticle showed a light-responsive drug release behavior and light-enhanced anticancer activity. The assembled nanoparticle also exhibited a complementary anticancer activity through the codelivery of 5-fluorouracil and a therapeutic gene encoding tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). This study provided a facile strategy to develop light-responsive polymers for the codelivery of therapeutic genes and anticancer drugs.

Hierarchical Nanogold Labels to Improve the Sensitivity of Lateral Flow Immunoassay

Lateral flow immunoassay (LFIA) is a widely used express method and offers advantages such as a short analysis time, simplicity of testing and result evaluation. However, an LFIA based on gold nanospheres lacks the desired sensitivity, thereby limiting its wide applications. In this study, spherical nanogold labels along with new types of nanogold labels such as gold nanopopcorns and nanostars were prepared, characterized, and applied for LFIA of model protein antigen procalcitonin. It was found that the label with a structure close to spherical provided more uniform distribution of specific antibodies on its surface, indicative of its suitability for this type of analysis. LFIA using gold nanopopcorns as a label allowed procalcitonin detection over a linear range of 0.5-10 ng mL^-1 with the limit of detection of 0.1 ng mL^-1, which was fivefold higher than the sensitivity of the assay with gold nanospheres. Another approach to improve the sensitivity of the assay included the silver enhancement method, which was used to compare the amplification of LFIA for procalcitonin detection. The sensitivity of procalcitonin determination by this method was 10 times better the sensitivity of the conventional LFIA with gold nanosphere as a label. The proposed approach of LFIA based on gold nanopopcorns improved the detection sensitivity without additional steps and prevented the increased consumption of specific reagents (antibodies).

Smartphone-Based Dual-Modality Imaging System for Quantitative Detection of Color or Fluorescent Lateral Flow Immunochromatographic Strips

Nowadays, lateral flow immunochromatographic assays are increasingly popular as a diagnostic tool for point-of-care (POC) test based on their simplicity, specificity, and sensitivity. Hence, quantitative detection and pluralistic popular application are urgently needed in medical examination. In this study, a smartphone-based dual-modality imaging system was developed for quantitative detection of color or fluorescent lateral flow test strips, which can be operated anywhere at any time. In this system, the white and ultra-violet (UV) light of optical device was designed, which was tunable with different strips, and the Sobel operator algorithm was used in the software, which could enhance the identification ability to recognize the test area from the background boundary information. Moreover, this technology based on extraction of the components from RGB format (red, green, and blue) of color strips or only red format of the fluorescent strips can obviously improve the high-signal intensity and sensitivity. Fifty samples were used to evaluate the accuracy of this system, and the ideal detection limit was calculated separately from detection of human chorionic gonadotropin (HCG) and carcinoembryonic antigen (CEA). The results indicated that smartphone-controlled dual-modality imaging system could provide various POC diagnoses, which becomes a potential technology for developing the next-generation of portable system in the near future.

Advanced nanotechnologies in avian influenza: Current status and future trends - A review

In the last decade, the control of avian influenza virus has experienced many difficulties, which have caused major global agricultural problems that have also led to public health consequences. Conventional biochemical methods are not sufficient to detect and control agricultural pathogens in the field due to the growing demand for food and subsidiary products; thus, studies aiming to develop potent alternatives to conventional biochemical methods are urgently needed. In this review, emerging detection systems, their applicability to diagnostics, and their therapeutic possibilities in view of nanotechnology are discussed. Nanotechnology-based sensors are used for rapid, sensitive and cost-effective diagnostics of agricultural pathogens. The application of different nanomaterials promotes interactions between these materials and the virus, which enables researchers to construct portable electroanalytical biosensing analyser that should effectively detect the influenza virus. The present review will provide insights into the guidelines for future experiments to develop better techniques to detect and control influenza viruses.

Improvement of a rapid diagnostic application of monoclonal antibodies against avian influenza H7 subtype virus using Europium nanoparticles

The development of a sensitive and rapid diagnostic test is needed for early detection of avian influenza (AI) H7 subtype. In this study, novel monoclonal antibodies (mAbs) against influenza A H7N9 recombinant hemagglutinin (rHA)1 were developed and applied to a Europium nanoparticle–based rapid fluorescent immunochromatographic strip test (FICT) to improve the sensitivity of the rapid diagnostic system. Two antibodies (2F4 and 6D7) exhibited H7 subtype specificity in a dot-FICT assay by optimization of the conjugate and the pH of the lysis buffer. The subtype specificity was confirmed by an immunofluorescence assay and Western blot analysis. The limit of detection of the FICT employing novel mAbs 31 ng/mL for H7N9 rHA1 and 40 hemagglutination units/mL for H7 subtype virus. Sensitivity was improved 25-fold using Europium as confirmed by comparison of colloidal gold-based rapid diagnostic kit using the 2F4 and 6D7 mAbs.

Direct and label-free influenza virus detection based on multisite binding to sialic acid receptors

A system to discriminate human or avian influenza A remains a highly sought-after tool for prevention of influenza pandemics in humans. Selective binding of the influenza A viral hemagglutinin (HA) to specific sialic acid (SA) receptors (Neu5Acα(2-6)Gal in humans, Neu5Acα(2-3)Gal in birds) is determined by the genotype of the HA and neuraminidase (NA) segments, making it one of the key characteristics that distinguishes human or avian influenza A virus. Here we demonstrate the direct detection of whole H1N1 influenza A virus using 6′-sialyllactose (Neu5Acα(2-6)Galβ(1-4)Glc, 6SL)-immobilized gold electrodes as biosensing surfaces. The sensitivity was higher than that of conventional immunochromatographic technique (ICT) for influenza virus and not restricted by genetic drift. The label-free detection technology via direct attachment of a whole virus using a chemically modified electrode is a promising means to provide a simple and rapid diagnostic system for viral infections.

A review of fluorescent signal-based lateral flow immunochromatographic strips

Fluorescent signal-based lateral flow immunochromatographic strips (FLFICS) have received great expectations since they combine the quantitative sensitivity of fluorescence analysis and the simplicity, rapidness, and portability of a common lateral flow immunochromatographic strip (LFICS).

Smartphone-Based Fluorescent Diagnostic System for Highly Pathogenic H5N1 Viruses

Field diagnostic tools for avian influenza (AI) are indispensable for the prevention and controlled management of highly pathogenic AI-related diseases. More accurate, faster and networked on-site monitoring is demanded to detect such AI viruses with high sensitivity as well as to maintain up-to-date information about their geographical transmission. In this work, we assessed the clinical and field-level performance of a smartphone-based fluorescent diagnostic device with an efficient reflective light collection module using a coumarin-derived dendrimer-based fluorescent lateral flow immunoassay. By application of an optimized bioconjugate, a smartphone-based diagnostic device had a two-fold higher detectability as compared to that of the table-top fluorescence strip reader for three different AI subtypes (H5N3, H7N1, and H9N2). Additionally, in a clinical study of H5N1-confirmed patients, the smartphone-based diagnostic device showed a sensitivity of 96.55% (28/29) [95% confidence interval (CI): 82.24 to 99.91] and a specificity of 98.55% (68/69) (95% CI: 92.19 to 99.96). The measurement results from the distributed individual smartphones were wirelessly transmitted via short messaging service and collected by a centralized database system for further information processing and data mining. Smartphone-based diagnosis provided highly sensitive measurement results for H5N1 detection within 15 minutes. Because of its high sensitivity, portability and automatic reporting feature, the proposed device will enable agile identification of patients and efficient control of AI dissemination.

Addressing Barriers to the Development and Adoption of Rapid Diagnostic Tests in Global Health

Immunochromatographic rapid diagnostic tests (RDTs) have demonstrated significant potential for use as point-of-care diagnostic tests in resource-limited settings. Most notably, RDTs for malaria have reached an unparalleled level of technological maturity and market penetration, and are now considered an important complement to standard microscopic methods of malaria diagnosis. However, the technical development of RDTs for other infectious diseases, and their uptake within the global health community as a core diagnostic modality, has been hindered by a number of extant challenges. These range from technical and biological issues, such as the need for better affinity agents and biomarkers of disease, to social, infrastructural, regulatory and economic barriers, which have all served to slow their adoption and diminish their impact. In order for the immunochromatographic RDT format to be successfully adapted to other disease targets, to see widespread distribution, and to improve clinical outcomes for patients on a global scale, these challenges must be identified and addressed, and the global health community must be engaged in championing the broader use of RDTs.