Visual DNA microarrays for simultaneous detection of human immunodeficiency virus type-1 and Treponema pallidum coupled with multiplex asymmetric polymerase chain reaction

A repertoire of biomedical applications of noble metal nanoparticles

The emerging properties of noble metal nanoparticles are attracting huge interest from the translational scientific community. In this feature article, we highlight recent advances in the adaptation of noble metal nanomaterials and their biomedical applications in therapeutics, diagnostics and sensing.

A Multiplex Asymmetric Reverse Transcription-PCR Assay Combined With an Electrochemical DNA Sensor for Simultaneously Detecting and Subtyping Influenza A Viruses

The reliable and rapid detection of viral pathogens that cause respiratory infections provide physicians several advantages in treating patients and managing outbreaks. The Luminex respiratory virus panel (RVP) assay has been shown to be comparable to or superior to culture/direct fluorescent-antibody assays (DFAs) and nucleic acid tests that are used to diagnose respiratory viral infections. We developed a multiplex asymmetric reverse transcription (RT)-PCR assay that can simultaneously differentiate all influenza A virus epidemic subtypes. The amplified products were hybridized with an electrochemical DNA sensor, and the results were automatically acquired. The limits of detection (LoDs) of both the Luminex RVP assay and the multiplex RT-PCR-electrochemical DNA sensor were 101 TCID50 for H1N1 virus and 102 TCID50 for H3N2 virus. The specificity assessment of the multiplex RT-PCR-electrochemical DNA sensor showed no cross-reactivity among different influenza A subtypes or with other non-influenza respiratory viruses. In total, 3098 respiratory tract specimens collected from padiatric patients diagnosed with pneumonia were tested. More than half (43, 53.75%) of the specimens positive for influenza A viruses could not be further subtyped using the Luminex RVP assay. Among the remaining 15 specimens that were not subtyped, not degraded, and in sufficient amounts for the multiplex RT-PCR-electrochemical DNA sensor test, all (100%) were H3N2 positive. Therefore, the sensitivity of the Luminex RVP assay for influenza A virus was 46.25%, whereas the sensitivity of the multiplex RT-PCR-electrochemical DNA sensor for the clinical H1N1 and H3N2 specimens was 100%. The sensitivities of the multiplex RT-PCR-electrochemical DNA sensor for the avian H5N1, H5N6, H9N2, and H10N8 viruses were 100%, whereas that for H7N9 virus was 85.19%. We conclude that the multiplex RT-PCR-electrochemical DNA sensor is a reliable method for the rapid and accurate detection of highly variable influenza A viruses in respiratory infections with greater detection sensitivity than that of the Luminex xTAG assay. The high mutation rate of influenza A viruses, particularly H3N2 during the 2014 to 2016 epidemic seasons, has a strong impact on diagnosis. A study involving more positive specimens from all influenza A virus epidemic subtypes is required to fully assess the performance of the assay.

Development of a novel protein biochip enabling validation of immunological assays and detection of serum IgG and IgM antibodies against Treponema pallidum pathogens in the patients with syphilis

In this study, we developed a novel protein biochip methodology that was characterized by dithiobis (succinimidyl undecanoate) (DSU) and specialized for detection of serum IgG and IgM antibodies against Treponema pallidum pathogens in the patients with syphilis, respectively. The biochips were validated by a dimension of atomic force microscope (AFM). The visualized detection limit of IgG antibody on the biochip was 0.39μg/ml. Finally, 286 serum samples from the patients with syphilis were simultaneously tested on the rTpN15-17-47 coated biochips. The results were evaluated in comparison with the assays of T. pallidum particle agglutination (TPPA) and the toluidine red unheated serum test (TRUST). The result demonstrated that the relative positive rate in the 286 patients by biochip was 99.0%, similar to that by TPPA (97.9%, P>0.05) and higher than that by TRUST, (76.2%, P<0.01). The detection specificities were 100% for the biochip and the TPPA and 97.0% for the TRUST. Thus, the protein biochip would provide a useful platform not only for enabling concurrent detection of the infectious antibodies directed against T. pallidum on a larger scale, but also for monitoring therapy modality of the disease.

Development of a Multiplex Real-Time PCR Assay for the Detection of Treponema pallidum, HCV, HIV-1, and HBV

Treponema pallidum, hepatitis C virus (HCV), human immunodeficiency virus (HIV)-1, and hepatitis B virus (HBV) are major causes of sexually transmitted diseases passed through blood contact. The development of a sensitive and efficient method for detection is critical for early diagnosis and for large-scale screening of blood specimens in China. This study aims to establish an assay to detect these pathogens in clinical serum specimens. We established a TaqMan-locked nucleic acid (LNA) real-time polymerase chain reaction (PCR) assay for rapid, sensitive, specific, quantitative, and simultaneous detection and identification. The copy numbers of standards of these 4 pathogens were quantified. Standard curves were generated by determining the mean cycle threshold values versus 10-fold serial dilutions of standards over a range of 10(6) to 10(1) copies/μL, with the lowest detection limit of the assay being 10(1) copies/μL. The assay was applied to 328 clinical specimens and compared with enzyme-linked immunosorbent assay (ELISA) and commercial nucleic acid testing (NAT) methods. The assay identified 39 T. pallidum-, 96 HCV-, 13 HIV-1-, 123 HBV-, 5 HBV/HCV-, 1 T. pallidum/HBV-, 1 HIV-1/HCV-, and 1 HIV-1/T. pallidum-positive specimens. The high sensitivity of the assay confers strong potential for its use as a highly reliable, cost-effective, and useful molecular diagnostic tool for large-scale screening of clinical specimens. This assay will assist in the study of the pathogenesis and epidemiology of sexually transmitted blood diseases.

Colorimetric biosensing of pathogens using gold nanoparticles

Rapid detection of pathogens is crucial to minimize adverse health impacts of nosocomial, foodborne, and waterborne diseases. Gold nanoparticles are extremely successful at detecting pathogens due to their ability to provide a simple and rapid color change when their environment is altered. Here, we review general strategies of implementing gold nanoparticles in colorimetric biosensors. First, we highlight how gold nanoparticles have improved conventional genomic analysis methods by lowering detection limits while reducing assay times. Then, we focus on emerging point-of-care technologies that aim at pathogen detection using simpler assays. These advances will facilitate the implementation of gold nanoparticle-based biosensors in diverse environments throughout the world and help prevent the spread of infectious diseases.

Competitive reporter monitored amplification (CMA)--quantification of molecular targets by real time monitoring of competitive reporter hybridization

Background

State of the art molecular diagnostic tests are based on the sensitive detection and quantification of nucleic acids. However, currently established diagnostic tests are characterized by elaborate and expensive technical solutions hindering the development of simple, affordable and compact point-of-care molecular tests.

Methodology and Principal Findings

The described competitive reporter monitored amplification allows the simultaneous amplification and quantification of multiple nucleic acid targets by polymerase chain reaction. Target quantification is accomplished by real-time detection of amplified nucleic acids utilizing a capture probe array and specific reporter probes. The reporter probes are fluorescently labeled oligonucleotides that are complementary to the respective capture probes on the array and to the respective sites of the target nucleic acids in solution. Capture probes and amplified target compete for reporter probes. Increasing amplicon concentration leads to decreased fluorescence signal at the respective capture probe position on the array which is measured after each cycle of amplification. In order to observe reporter probe hybridization in real-time without any additional washing steps, we have developed a mechanical fluorescence background displacement technique.

Conclusions and Significance

The system presented in this paper enables simultaneous detection and quantification of multiple targets. Moreover, the presented fluorescence background displacement technique provides a generic solution for real time monitoring of binding events of fluorescently labelled ligands to surface immobilized probes. With the model assay for the detection of human immunodeficiency virus type 1 and 2 (HIV 1/2), we have been able to observe the amplification kinetics of five targets simultaneously and accommodate two additional hybridization controls with a simple instrument set-up. The ability to accommodate multiple controls and targets into a single assay and to perform the assay on simple and robust instrumentation is a prerequisite for the development of novel molecular point of care tests.

Molecular and nanotechnologic approaches to etiologic diagnosis of infectious syndromes

Infectious diseases are a major global public health problem. Multiple agents are now recognized to cause indistinguishable illnesses. The term 'syndrome' applies to such situations, for which early and rapid diagnosis of the infecting agent would enable prompt and appropriate therapy. Public health physicians would also get timely information on the specific etiology of the infectious syndrome, facilitating intervention at the community level in the face of outbreaks or epidemics. A variety of molecular techniques have been evaluated for rapid diagnosis of infectious syndromes. These techniques include real-time multiplex PCR, DNA microarray, loop-mediated isothermal amplification, and other similar assays. This review surveys such state-of-the-art technologies.

Rapid and simultaneous detection of Ureaplasma parvum and Chlamydia trachomatis antibodies based on visual protein microarray using gold nanoparticles and silver enhancement

Based on gold-labeled silver stain (GLSS) method, we developed the visual protein microarray for simultaneous, sensitive, and specific detection of Ureaplasma parvum and Chlamydia trachomatis using N-terminus multiple-banded antigen (NMBA) of U. parvum and major outer membrane protein of C. trachomatis. The specific antigens were immobilized on glass surface that was treated with 3-glycidoxypropyltrimethoxysilane, and they were used as the capturing probes to recognize the complementary target antibodies binding to the detecting probes of Nano-gold-Staphylococcal protein A (SPA). In the "sandwich" format, Nano-gold-SPA probe was used as an indicator and GLSS was applied to amplify the detection signals and produce black image on array spots, which were visible with naked eyes. In our model arrays, the detection limit of protein microarray was as low as 2 ng/mL, and the lowest titer of detectable antibody was 1:128; thus, this sensitivity was comparable to the fluorescent detection method. The visual simultaneous protein microarrays were used to detect total 186 clinical samples, which had been determined by enzyme-linked immunosorbent assay (ELISA) and fluorescence quantitative real-time polymerase chain reaction; the results were identical and no distinct difference (P > 0.05) existed between them. Our results demonstrate that we have developed the visual protein microarray technique, which is of high sensitivity and high specificity, and it may have potential in clinical applications.