Development of a colloidal gold-based immunochromatographic test strip for screening of microalbuminuria

Lateral Flow Assay: A Summary of Recent Progress for Improving Assay Performance

Lateral flow tests are one of the most important types of paper-based point-of-care (POCT) diagnostic tools. It shows great potential as an implement for improving the rapid screening and management of infections in global pandemics or other potential health disorders by using minimally expert staff in locations where no sophisticated laboratory services are accessible. They can detect different types of biomarkers in various biological samples and provide the results in a little time at a low price. An important challenge regarding conventional LFAs is increasing their sensitivity and specificity. There are two main approaches to increase sensitivity and specificity, including assay improvement and target enrichment. Assay improvement comprises the assay optimization and signal amplification techniques. In this study, a summarize of various sensitivity and specificity enhancement strategies with an objective evaluation are presented, such as detection element immobilization, capillary flow rate adjusting, label evolution, sample extraction and enrichment, etc. and also the key findings in improving the LFA performance and solving their limitations are discussed along with numerous examples.

Spot tests: past and present

Microchemistry, i.e., the chemistry performed at the scale of a microgram or less, has its roots in the late eighteenth and early nineteenth centuries. In the first half of the twentieth century a wide range of spot tests have been developed. For didactic reasons, they are still part of the curriculum of chemistry students. However, they are even highly important for applied analyses in conservation of cultural heritage, food science, forensic science, clinical and pharmacological sciences, geochemistry, and environmental sciences. Modern pregnancy tests, virus tests, etc. are the most recent examples of sophisticated spot tests. The present ChemTexts contribution aims to provide an overview of the past and present of this analytical methodology.

Point-of-care cancer diagnostic devices: From academic research to clinical translation

Early and timely diagnosis of cancer plays a decisive role in appropriate treatment and improves clinical outcomes, improving public health. Significant advances in biosensor technologies are leading to the development of point-of-care (POC) diagnostics, making the testing process faster, easier, cost-effective, and suitable for on-site measurements. Moreover, the incorporation of various nanomaterials into the sensing platforms has yielded POC testing (POCT) platforms with enhanced sensitivity, cost-effectiveness and simplified detection schemes. POC cancer diagnostic devices provide promising platforms for cancer biomarker detection as compared to conventional in vitro diagnostics, which are time-consuming and require sophisticated instrumentation, centralized laboratories, and experienced operators. Current innovative approaches in POC technologies, including biosensors, smartphone interfaces, and lab-on-a-chip (LOC) devices are expected to quickly transform the healthcare landscape. However, only a few cancer POC devices (e.g. lateral flow platforms) have been translated from research laboratories to clinical care, likely due to challenges include sampling procedures, low levels of sensitivity and specificity in clinical samples, system integration and signal readout requirements. In this review, we emphasize recent advances in POC diagnostic devices for cancer biomarker detection and discuss the critical challenges which must be surmounted to facilitate their translation into clinical settings.

Point-of-care biosensors in medicine: a brief overview of our achievements in this field based on the conducted research in EMRI (endocrinology and metabolism research Institute of Tehran University of medical sciences) over the past fourteen years

The growing demand of diagnostic tools with enhanced analytical characteristics in term of sensitivity, selectivity, and low response time has encouraged researches to conduct their research towards development of point-of-care (POC) biosensors. POC diagnostic devices are powerful tools for detection, diagnosis, and monitoring of diseases at its initial stage. The above characteristics encouraged us to conduct active multidisciplinary and collaborative research oriented towards the design and development of POC sensing systems. Here, we present a brief overview of our recent achievement in the field of biomedical POC devices implemented in paper based microfluidic and screen printing electrodes and discuss the critical limitations that need to be surmounted to facilitate their translation into clinical practice in the future.

Combined Mini-Parasep SF and Nanogold Immunoassay Show Potential in Stool Antigen Immunodetection for Giardiasis Diagnosis

Covalent loading or directional binding of biomolecules on gold nanoparticles (AuNPs) could lead to better results than simple direct adsorption for an enhanced ELISA application. The use of Mini-Parasep solvent-free (SF) without ether or ethyl acetate for the clean and efficient concentration of protozoa cysts, it is a single-use device for in vitro diagnostic use only. In this work, we used Mini-Parasep SF for the detection of giardia cysts in comparison to direct smear and Merthiolate-Iodine Formaldehyde Concentration (MIFC) technique in addition to its use in antigen detection by AuNPs biomolecule loading using rabbit polyclonal antibodies (pAb) against purified Giardia antigen (PGA). As a result, Mini-Parasep SF was the most effective method for Giardia cyst detection and regarding optimization of Mini-Parasep antigen detection, our data showed increased sensitivity and specificity of nano-sandwich ELISA to 92% and 94% respectively and increased positive predictive value (PPV) and negative predictive value (NPV) to 88.64% and 95.91% respectively. In conclusion, this research provides that Mini-Parasep SF concentrator enhanced Giardia cyst detection and improved antigen preparation for AuNPs sandwich ELISA in giardiasis diagnosis. The advantages of this method are the short assay time and the raised accuracy of antigen detection providing concentrated samples without the risk of solvent use and being a disposable Mini-Parasep it helps in giardia antigen purification as well as raising the sensitivity and specificity of ELISA through binding AuNPs.

Preparation of an anti-isoprocarb monoclonal antibody and its application in developing an immunochromatographic strip assay

In this study, a carboxyl group was introduced into the isoprocarb molecule to obtain an isoprocarb hapten, which was then coupled with a protein to obtain an artificial antigen. Three monoclonal antibody cell lines, 1D11, 6E6 and 1B5, were finally obtained by mouse immunization, cell fusion and subcloning, and the antibody produced by cell line 1B5 had the best affinity and sensitivity. The monoclonal antibody was highly sensitive and specific for isoprocarb, with an IC₅₀ of 2.09 ng/ml and a cross-reactivity rate of <0.21%. By optimizing the indirect competitive (ic)-ELISA, the optimal conditions were determined to be pH 7.4, 0% methanol and 0.8% NaCl, the limit of detection value was 0.23 ng/ml, and the linear range of the ic-ELISA was 0.46-9.62 ng/ml. The recovery rate of the isoprocarb cucumber sample was 97-99% for the ic-ELISA method. In addition, we successfully developed an immunochromatographic test strip for the detection of isoprocarb residues. The cutoff values in phosphate-buffered saline and cucumber extract were 10 and 25 ng/ml, respectively. Both methods met the requirements for isoprocarb residue detection in agricultural products, and can be used for semiquantitative and qualitative analysis of isoprocarb in vegetables.

Rapid visual sensing and quantitative identification of duck meat in adulterated beef with a lateral flow strip platform

A novel high-sensitivity authentication method has been demonstrated for the rapid visual detection of adulterated meat based on both the lateral flow strip (LFS) platform and on polymerase chain reaction (PCR). After the rapid extraction of genomic components from meat, the on-site amplification of the target DNA of adulterated duck meat is carried out with the rationally designed functional FITC- and biotin-modified primer set, thereby producing numerous double-stranded DNA (dsDNA) products dually labelled with FITC and biotin. The FITC-labelled terminal end of the products binds to the pre-immobilized FITC antibody on the test line of the strip, and the biotin-labelled terminal end binds to the streptavidin-conjugated gold nanoparticles, resulting in a visible test line on the LFS for the rapid identification of duck meat in adulterated beef. After optimization, an adulteration ratio as low as 0.05% can be easily measured, which is more sensitive than other common adulteration authentication methods and is even comparable to instrumental methods. Moreover, 22 commercial processed meat samples were tested with this new strategy, and 4 adulterated samples were successfully identified by both the classic method and our method. In essence, the present authentication method is simple in design, convenient in operation, and can be easily extended to the identification of other adulteration components just by replacing the modified primers.

A novel detection method of Cryptosporidium parvum infection in cattle based on Cryptosporidium parvum virus 1

Cryptosporidium parvum is an important zoonotic parasite that causes significant economic loss in the animal husbandry industry, especially the cattle industry. As there is no specific vaccine or drug against Cryptosporidium, a rapid and accurate method for the detection of C. parvum is of great significance. In this study, colloidal gold strips were developed based on Cryptosporidium parvum virus 1 (CSpV1) for the detection of C. parvum infection in cattle fecal samples. The colloidal gold solution was prepared by reducing trisodium citrate and the CSpV1 #5 monoclonal antibody was labeled with colloidal gold. A polyclonal antibody against the CSpV1 capsid protein and an anti-mouse IgG antibody were coated on the colloidal gold strips for use in the test and control lines, respectively. Our results showed that the detection sensitivity in fecal samples was up to a 1:64 dilution. There was no cross-reaction with Cryptosporidium andersoni or Giardia in the fecal samples. The different preservation conditions (room temperature, 4°C, and 37°C) and preservation time (7, 30, 60, and 90 days) were analyzed. The data showed that the strips could be preserved for 90 days at 4°C and for 60 days at room temperature or 37°C. The colloidal gold strips were used to detect the samples of 120 clinical fecal in Changchun, China. The results indicated that the rate of a positive test was 5% (6/120). This study provides a rapid and accurate method for detecting C. parvum infection in cattle and humans.

Bacteriophages: an overview of the control strategies against multiple bacterial infections in different fields

Bacteriophages (phages/viruses) need host bacteria to replicate and propagate. Primarily, a bacteriophage contains a head/capsid to encapsidate the genetic material. Some phages contain tails. Phages encode endolysins to hydrolyze bacterial cell wall. The two main classes of phages are lytic or virulent and lysogenic or temperate. In comparison with antibiotics, to deal with bacterial infections, phage therapy is thought to be more effective. In 1921, the use of phages against bacterial infections was first demonstrated. Later on, in humans, phage therapy was used to treat skin infections caused by Pseudomonas species. Furthermore, phages were successfully employed against infections in animals - calves, lambs, and pigs infected with Escherichia coli. In agriculture, for instance, phages have successfully been used e.g., Apple blossom infection, caused by Erwinia amylovora, was effectively catered with the use of bacteriophages. Bacteriophages were also used to control E. coli, Salmonella, Listeria, and Campylobacter contamination in food. Comparatively, phage display is a recently discovered technology, whereby, bacteriophages play a significant role. This review is an effort to collect almost recent and relevant information regarding applications and complications associated with the use of bacteriophages.

A novel electrochemical nanobiosensor for the ultrasensitive and specific detection of femtomolar-level gastric cancer biomarker miRNA-106a

Gastric cancer (GC) is the second leading cause of cancer-related deaths all over the world. miR-106a is a circulatory oncogenic microRNA (miRNA), which overexpresses in various malignancies, especially in GC. In this study, an ultrasensitive electrochemical nanobiosensor was developed for the detection of miR-106a using a double-specific probe methodology and a gold-magnetic nanocomposite as tracing tag. The successful modification of the electrode and hybridization with the target miRNA were confirmed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. Differential pulse voltammetry (DPV) was used for quantitative evaluation of miR-106a via recording the reduction peak current of gold nanoparticles. The electrochemical signal had a linear relationship with the concentration of the target miRNA ranging from 1 × 10^-3 pM to 1 × 10³ pM, and the detection limit was 3 × 10^-4 pM. The proposed miRNA-nanobiosensor showed remarkable selectivity, high specificity, agreeable storage stability, and great performance in real sample investigation with no pretreatment or amplification. Consequently, our biosensing strategy offers such a promising application to be used for clinical early detection of GC and additionally the screen of any miRNA sequence.

Paper-based point-of-care testing for diagnosis of dengue infections

Dengue endemic is a serious healthcare concern in tropical and subtropical countries. Although well-established laboratory tests can provide early diagnosis of acute dengue infections, access to these tests is limited in developing countries, presenting an urgent need to develop simple, rapid, and robust diagnostic tools. Point-of-care (POC) devices, particularly paper-based POC devices, are typically rapid, cost-effective and user-friendly, and they can be used as diagnostic tools for the prompt diagnosis of dengue at POC settings. Here, we review the importance of rapid dengue diagnosis, current dengue diagnostic methods, and the development of paper-based POC devices for diagnosis of dengue infections at the POC.

Rapid detection of Enterobacter cloacae by immunomagnetic separation and a colloidal gold-based immunochromatographic assay

This is the first study of detection of Enterobacter cloacae via combined immunomagnetic separation and a colloidal gold-based immunochromatographic assay.

Synthesis, characterization and in vitro biocompatibility study of Au/TMC/Fe3O4 nanocomposites as a promising, nontoxic system for biomedical applications

The unique properties and applications of iron oxide and Au nanoparticles have motivated researchers to synthesize and optimize a combined nanocomposite containing both. By using various polymers such as chitosan, some of the problems of classic core-shell structures (such as reduced saturation magnetization and thick coating) have been overcome. In the present study, chitosan and one of its well-known derivatives, N-trimethylchitosan (TMC), were applied to construct three-layer nanocomposites in an Au/polymer/Fe3O4 system. It was demonstrated that replacement of chitosan with TMC reasonably improved the properties of the final nanocomposites including their size, magnetic behavior and thermal stability. Moreover, the results of the MTT assay showed no significant cytotoxicity effect when the Au/TMC/Fe3O4 nanocomposites were applied in vitro. These TMC-containing magnetic nanoparticles are well-coated by Au nanoparticles and have good biocompatibility and can thus play the role of a platform or a label in various fields of application, especially the biomedical sciences and biosensors.

Advances in phage display technology for drug discovery

INTRODUCTION

Over the past decade, several library-based methods have been developed to discover ligands with strong binding affinities for their targets. These methods mimic the natural evolution for screening and identifying ligand-target interactions with specific functional properties. Phage display technology is a well-established method that has been applied to many technological challenges including novel drug discovery.

AREAS COVERED

This review describes the recent advances in the use of phage display technology for discovering novel bioactive compounds. Furthermore, it discusses the application of this technology to produce proteins and peptides as well as minimize the use of antibodies, such as antigen-binding fragment, single-chain fragment variable or single-domain antibody fragments like VHHs.

EXPERT OPINION

Advances in screening, manufacturing and humanization technologies demonstrate that phage display derived products can play a significant role in the diagnosis and treatment of disease. The effects of this technology are inevitable in the development pipeline for bringing therapeutics into the market, and this number is expected to rise significantly in the future as new advances continue to take place in display methods. Furthermore, a widespread application of this methodology is predicted in different medical technological areas, including biosensing, monitoring, molecular imaging, gene therapy, vaccine development and nanotechnology.

Development of a colloidal gold immunochromatographic strip for the rapid detection of soft-shelled turtle systemic septicemia spherical virus

A colloidal gold immunochromatographic strip (ICS) test based on a competitive format was developed for the rapid detection of soft-shelled turtle systemic septicemia spherical virus (STSSSV) in turtle and fecal samples. Specific egg yolk antibodies (IgY) against STSSSV were labeled with colloidal gold and used as probes in the one-step test strip. Antigen (STSSSV) and goat anti-chicken IgY were drawn on the nitrocellulose membrane as the test line and control line, respectively. When STSSSV standard samples (0-100μg/mL) were detected by the strips, the visual limit of detection (LOD) was found to be 50.0μg/mL. The ICS test showed high stability; the strips were stable for at least 3 months at 4°C without significant loss of activity. There was no obvious cross-reactivity with other aquatic pathogens. The assay can be performed within 5-10min. Analysis of STSSSV in turtle samples revealed that data obtained from the ICS test were in a good agreement with those obtained by ELISA. The positive results of fecal samples suggested that this method could be used to detect STSSSV while protecting the animals' welfare. The ICS assay does not need specialized equipment or a technician and can be used as a reliable, rapid, cost-effective and convenient qualitative tool for on-site diagnosis.

Development of enzyme-linked immunosorbent assay for estimation of urinary albumin

Yearly estimation of urinary albumin is a prerequisite for predicting renal status in Diabetes Type II patients with negative dipstick results for overt proteinuria. A simple, sensitive, and cost-effective enzyme linked immunosorbent assay (ELISA) for urinary albumin has been developed using human serum albumin antiserum (HSA-antiserum), HSA-biotin, and streptavidin-horseradish peroxidase (SA-HRP) conjugates. To the antibody-coated wells, 100 μL of HSA standards followed by 1:100 diluted urine samples in duplicate were added and then 50 μL of HSA-biotin conjugates was added in all the wells. 100 μL of SA-HRP was added after washing. Bound enzyme activity was measured by adding 100 μL TMB/H2O2. The analytical sensitivity and ED50 of the developed method was found to be 0.01 μg/mL and 0.35 μg/mL, respectively. The percent recovery of the HSA from exogenously spiked urine pools were in the range of 98.13-100.29%. The intra- and inter-assay coefficient of variation (CVs) ranged from 3.38-10.32 % and 4.22-11.01%, respectively. The antibody showed 4.4% and 3.2% cross reactivity with monkey and horse serum albumin, respectively. There was no cross reaction with human β2-microglobulin, γ-globulin, and haemoglobulin.

New analytical applications of gold nanoparticles as label in antibody based sensors

Gold nanoparticles (AuNPs) with optical and electrochemical distinctiveness as well as biocompatibility characteristics have proven to be powerful tools in nanomedicinal application. This review article discusses recent advances in the application of AuNPs as label in bioanalytical devices, especially electrochemical immunosensors, rapid and point-of-care (PoC) tests. A crucial assessment regarding implementation of different formats of antibodies allowing rapid and sensitive analysis of a range of analytes is also provided in this study. In addition to this, different approaches to minimize antibodies into Fab, scFv or even single-domain antibody fragments like VHHs will be reviewed. Given the high level of target specificity and affinity, such biomolecules are considered to be excellent elements for on-site or PoC analysis.