New rapid detection test with a combination of polymerase chain reaction and immunochromatographic assay for Mycobacterium tuberculosis complex

Synthesis, Chemical-Physical Characterization, and Biomedical Applications of Functional Gold Nanoparticles: A Review

Relevant properties of gold nanoparticles, such as stability and biocompatibility, together with their peculiar optical and electronic behavior, make them excellent candidates for medical and biological applications. This review describes the different approaches to the synthesis, surface modification, and characterization of gold nanoparticles (AuNPs) related to increasing their stability and available features useful for employment as drug delivery systems or in hyperthermia and photothermal therapy. The synthetic methods reported span from the well-known Turkevich synthesis, reduction with NaBH4 with or without citrate, seeding growth, ascorbic acid-based, green synthesis, and Brust-Schiffrin methods. Furthermore, the nanosized functionalization of the AuNP surface brought about the formation of self-assembled monolayers through the employment of polymer coatings as capping agents covalently bonded to the nanoparticles. The most common chemical-physical characterization techniques to determine the size, shape and surface coverage of AuNPs are described underlining the structure-activity correlation in the frame of their applications in the biomedical and biotechnology sectors.

Gold Nanoparticles for DNA/RNA-Based Diagnostics

The remarkable physicochemical properties of gold nanoparticles (AuNPs) have prompted development in exploring biomolecular interactions with AuNPs-containing systems, pursuing biomedical applications in diagnostics. Among these applications, AuNPs have been remarkably useful for the development of DNA/RNA detection and characterization systems for diagnostics, including systems suitable for point of need. Here, emphasis will be on available molecular detection schemes of relevant pathogens and their molecular characterization, genomic sequences associated with medical conditions (including cancer), mutation and polymorphism identification, and the quantification of gene expression.

Detection of influenza virus using a lateral flow immunoassay for amplified DNA by a microfluidic RT-PCR chip

Influenza virus RNA was amplified by a continuous-flow polydimethylsiloxane microfluidic RT-PCR chip within 15-20 min. The amplified influenza virus RNA was observed with the naked eye, as the red color at the test line, using a lateral flow immunoassay within 1 min.

Development of a method for the detection of infectious myonecrosis virus by reverse-transcription loop-mediated isothermal amplification and nucleic acid lateral flow hybrid assay

We report the development of a reverse-transcription loop-mediated isothermal amplification and nucleic acid lateral flow method (RT-LAMP-NALF) for detection of infectious myonecrosis virus (IMNV). The RT-LAMP-NALF method combines simplified nucleic acid extraction, a reverse-transcription loop-mediated isothermal amplification platform, and one-step visual colorimetric confirmation of the IMNV amplified sequences using a generic NALF qualitative detection test strip. The sensitivity of RT-LAMP (using two and three primer pairs) and nested RT-LAMP (using three primer pairs) was compared by real-time reverse-transcription-polymerase chain reaction (RT-PCR) using TaqMan probe. The detection of RT-LAMP (three primer pairs) products was accomplished by using a NALF-test strip. The RT-LAMP-NALF showed equivalent sensitivity to RT-LAMP (using three primer pairs), and it was found to be 100 and 10 times more sensitive than one-step RT-PCR and RT-LAMP (two primer pairs), respectively. On the other hand, the RT-LAMP-NALF was 10 and 100 times less sensitive than nested RT-PCR and real-time RT-PCR, respectively. The simplified RNA extraction method ranged from 4.4 x 10(6) to 2.2 x 10(8) IMNV copy numbers microL(-1) RNA, and it was similar with the standard RNA extraction (from 1.2 x 10(6) to 6.3 x 10(7) IMNV copy numbers microL(-1) RNA). These results clearly demonstrate that the RT-LAMP-NALF method is specific, sensitive, can shorten the time for analysis, and has potential application for IMNV diagnosis in resource-poor diagnostic settings.

Diagnostic accuracy of in-house PCR for pulmonary tuberculosis in smear-positive patients: meta-analysis and metaregression

In-house PCR (hPCR) could speed differential diagnosis between tuberculosis (TB) and nontuberculous mycobacterial disease in patients with positive smears and pulmonary infiltrates, but its reported accuracy fluctuates across studies. We conducted a systematic review and meta-analysis of hPCR sensitivity and specificity for smear-positive TB diagnosis, using culture as the reference standard. After searching English language studies in MEDLINE and EMBASE, we estimated cumulative accuracy by means of summary receiver operating characteristic analysis. The possible influence of hPCR procedures and study methodological features on accuracy was explored by univariate metaregression, followed by multivariate adjustment of items selected as significant. Thirty-five articles (1991 to 2006) met the inclusion criteria. The pooled estimates of the diagnostic odds ratio, sensitivity, and specificity (random-effect model) were, respectively, 60 (confidence interval [CI], 29 to 123), 0.96 (CI, 0.95 to 0.97), and 0.81 (CI, 0.78 to 0.84), but significant variations (mainly in specificity) limit their clinical applicability. The quality of the reference test, the detection method, and real-time PCR use explained some of the observed heterogeneity. Probably due to the limited study power of our meta-analysis and to the wide differences in both laboratory techniques and methodological quality, only real-time PCR also displayed a positive impact on accuracy in the multivariate model. Currently, hPCR can be confidently used to exclude TB in smear-positive patients, but its low specificity could lead to erroneous initiation of therapy, isolation, and contact investigation. As the inclusion of samples from treated patients could have artificially reduced specificity, future studies should report mycobacterial-culture results for each TB and non-TB sample analyzed.

The use of gold nanoparticles in diagnostics and detection

The widespread use of gold nanoparticles (GNPs) as labels in diagnostics and detection is due to a unique combination of chemical and physical properties that allow biological molecules to be detected at low concentrations. In this critical review detection methods based on GNPs are divided up and discussed based on the way in which signals are generated in response to specific target molecules. Particular attention is devoted to methods that allow target molecules to be detected with the unaided eye because these, more than any other, harness the full range of properties that make GNPs unique. Methods that are discussed include those in which specific target molecules induce a visible colour change, chromatographic methods that allow non-specialized users to perform sophisticated tests without additional equipment and methods in which trace amounts of GNPs are rendered visible to the unaided eye by catalytic deposition of a metal such as silver. The use of metal deposition as a means of enhancing the signal for optical and electrical detection is also reviewed. The other detection methods included in this review are based on interactions between GNPs and molecules located in close proximity to their surface. These include methods in which light emission from such molecules is enhanced (surface enhanced Raman scattering) or quenched (fluorescence), and methods in which the accumulation of specific target molecules induce subtle changes in the extinction spectra of GNPs that can be followed in real time with inexpensive equipment (166 references).

One step visual detection of PCR products with gold nanoparticles and a nucleic acid lateral flow (NALF) device

Specific PCR products are detected with an antibody-free lateral-flow device by sandwiching them between reporter oligonucleotides covalently attached to gold nanoparticles (GNPs) and capture oligonucleotides covalently attached to a nitrocellulose chromatographic strip.