Colorimetric Detection of Plasmodium vivax in Urine Using MSP10 Oligonucleotides and Gold Nanoparticles

Rapid Detection of Neisseria gonorrhoeae Genomic DNA Using Gold Nanoprobes Which Target the Gonococcal DNA Uptake Sequence

The rapid spread of antimicrobial resistant Neisseria gonorrhoeae continues to pose a serious threat to global health. To successfully treat and control gonococcal infections, rapid diagnosis is critical. Currently, nucleic acid amplification tests are the recommended diagnostic, however, these are both technically demanding and time consuming, making them unsuitable for resource-poor clinics. Consequently, there is a substantial need for an affordable, point-of-care diagnostic to use in these settings. In this study, DNA-functionalised gold nanoparticles (gold nanoprobes), with the ability to specifically detect the DNA Uptake Sequence (DUS) of Neisseria gonorrhoeae, were prepared. Using complementary annealing, the gold nanoprobes were shown to hybridise to genomic gonococcal DNA, causing a significant shift in their salt stability. By exploiting the shift in nanoprobe stability under the presence of target DNA, a solution-based colorimetric diagnostic for gonococcal DNA was prepared. Detection of purified genomic DNA was achieved in under 30 minutes, with a detection limit of 15.0 ng. Significantly, testing with DNA extracted from an off-target control organism suggested specificity for Neisseria. These results highlight the potential of DUS-specific gold nanoprobes in the rapid point-of-care diagnosis of gonococcal infections.

Biosensor Based Immunoassay: A New Approach for Serotyping of Toxoplasma gondii

Toxoplasmosis is the most reported parasitic zoonosis in Europe, with implications in human health and in the veterinary field. There is an increasing need to develop serotyping of Toxoplasma gondii (T. gondii) in view of greater sensitivity and efficiency, through the definition of new targets and new methodologies. Nanotechnology is a promising approach, with impact in the development of point-of-care devices. The aim of this work was to develop a simple but highly efficient method for Toxoplasma gondii serotyping based on gold nanoparticles. A simple colorimetric method was developed using gold nanoparticles modified with the synthetic polymorphic peptide derived from GRA6 antigen specific for type II T. gondii. The method of preparation of the gold nanoprobes and the experimental conditions for the detection were found to be critical for a sensitive discrimination between positive and negative sera. The optimized method was used to detect antibodies anti-GRA6II both in mice and human serum samples. These results clearly demonstrate that a biosensor-based immunoassay using AuNPs conjugated with polymorphic synthetic peptides can be developed and used as a serotyping device

Nano Based Approach for the Treatment of Neglected Tropical Diseases

Neglected tropical diseases (NTDs) afflict more than one billion peoples in the world’s poorest countries. The World Health Organization (WHO) has recorded seventeen NTDs in its portfolio, mainly caused by bacterial, protozoal, parasitic, and viral infections. Each of the NTDs has its unique challenges on human health such as interventions for control, prevention, diagnosis, and treatment. Research for the development of new drug molecules against NTDs has not been undertaken by pharmaceutical industries due to high investment and low-returns, which results in limited chemotherapeutics in the market. In addition, conventional chemotherapies for the treatment of NTDs are unsatisfactory due to its low efficacy, increased drug resistance, short half-life, potential or harmful fatal toxic side effects, and drug incompetence to reach the site of parasite infection. In this context, active chemotherapies are considered to be re-formulated by overcoming these toxic side effects via a tissue-specific targeted drug delivery system. This review mainly emphasizes the recent developments of nanomaterial-based drug delivery systems for the effective treatment of NTDs especially sleeping sickness, leishmaniasis, chagas disease, soil-transmitted helminthiasis, african trypanosomiasis and dengue. Nanomaterials based drug delivery systems offer enhanced and effective alternative therapy through the re-formulation approach of conventional drugs into site-specific targeted delivery of drugs.

Naked-eye colorimetric detection of HCV RNA mediated by a 5' UTR-targeted antisense oligonucleotide and plasmonic gold nanoparticles

The increasing incidence of hepatitis C viral (HCV) infection worldwide is a major concern for causing liver cirrhosis and hepatocellular carcinoma, leading to increased morbidity and mortality. Currently, the prevalence of HCV infection is estimated to be in the range of ∼3%. According to the World Health Organization, antiviral drugs can cure more than 95% of the HCV infected cases, if timely diagnosis and treatment are provided. The gold standard RT-qPCR assay is expensive and requires a minimum turnaround time of 4 h. Hence, a rapid and cost-effective detection assay that can be used even in resource-limited settings would be highly beneficial for mass level screening. Herein, we present an Au NP based facile strategy for rapid, early-stage, and sensitive detection of HCV RNA in clinical samples which avoids thiol tagging to the antisense oligonucleotide and expensive infrastructure. This technique utilizes the hybridization of a short-chain antisense oligonucleotide from the 5' untranslated region (UTR) of the viral genome with the isolated HCV RNA samples. Using a specific sequence universal to all HCV genotypes-obtained through the NCBI BLASTn tool-the HCV positive samples have stabilized the citrate capped Au NPs against salt-induced aggregation, retaining their red color. On the other hand, negative controls, including HBV and HIV positive samples, do not stabilize the Au NPs, which results in purple coloration. Besides, the assay is successfully tested with a RNase A enzyme-treated HCV positive sample, which does not stabilize the Au NPs, thus confirming the role of the viral HCV RNA in this strategy. This Au NP based assay takes about 30 min using the viral RNA isolate and has high specificity with a detection limit of 100 IU mL^-1, which is ∼10 fold lower than the state-of-the-art Au NP based strategy.

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.

Design of a gold nanoprobe for the detection of Pseudomonas aeruginosa elastase gene (lasB)

In this study, a gold nanoparticle-based DNA diagnostic sensor that is sensitive to the aggregation states of gold nanoparticles was used to identify the amplified and non-amplified lasB gene.

Molluscicidal Activities of Curcumin-Nisin Polylactic Acid Nanoparticle (PLA) on Adult Snail Intermediate Hosts of Schistosomes and Fasciola spp

Digenetic trematode infections including schistosomiasis and fascioliasis have highly neglected statuses but are a menace to people in the poorest countries of the tropics, causing high morbidity and mortality in humans as well as great global losses in livestock production. This has neccesitated the widespread search for better control options for the snail vectors of these diseases. Hence, a novel drug - curcumin and nisin poly lactic acid (PLA) entrapped nanoparticles (CurNisNp) was screened for molluscicidal activity against the adults (> 2 months old) of Biomphalaria pfeifferi, Bulinus globosus and Lymnaea natalensis vector snails. Mortality was determined after 96-h of exposure at varying concentrations. The snails of the species L. natalensis were found to be the most susceptible to the molluscicide (LC50 323.6 ppm). This finding further supports the desirability of curcumin-nisin polylactic acid (PLA) nanoparticles as a molluscicide and therefore shows that it could be a good alternative to conventional molluscicides with prospects in the selective control of fascioliasis. However, more optimization of the drug could ensure a greater molluscicidal potency.

An Update on Malaria Rapid Diagnostic Tests

PURPOSE OF REVIEW

Modern advances in malaria rapid diagnostic test (RDT) technology have increased demand for low-cost, easy-to-use assays in areas endemic for malaria. Substantial developments in diagnostic sensitivity and specificity, improvements in non-falciparum RDTs, and novel biotechnological innovations are gradually aligning the performance of RDTs with reference-level diagnostics including PCR and expert microscopy gold standards.

RECENT FINDINGS

Trends have emerged in recent malaria RDT literature: (1) improvements in the sensitivity and specificity of RDTs for Plasmodium falciparum diagnosis, making them comparable to expert microscopic examination; (2) reduced false-positive and false-negative reactions with novel antibody development; (3) improved sensitivity and specificity capabilities of Plasmodium vivax-specific RDTs; (4) developing RDTs for co-endemic mixed infection differentiation; (5) significant improvements of RDTs for Plasmodium knowlesi; (6) a global push towards assessing and confronting the growing concerns of widespread pfhrp2 gene deletions; and (7) original innovation in loop-mediated isothermal amplification (LAMP) biotechnological RDT-like platforms that demonstrate promising performance characteristics for P. falciparum, P. vivax, and P. knowlesi infections. The past 5 years have been characterized by increasing demand for malaria RDTs, translating into meaningful improvements in performance and novel biotechnological innovation. Future work should facilitate the development of improved RDT platforms for Plasmodium ovale, P. knowlesi, and Plasmodium malariae, and surmount the issue of pfhrp2 gene deletions, while maintaining comparable performance to both PCR and expert microscopy reference standards.