Non-crosslinking gold nanoprobes for detection of nucleic acid sequence-based amplification products.

Lack of an appropriate detection method for isothermal RNA amplification technique, known as nucleic acid sequence-based amplification (NASBA), is considered as a major defect for its vast applications. In that regard, novel detection methods as fast, specific, and sensitive as the gold nanoprobe detection technique are highly demanded and non-crosslinking gold nanoprobes are regarded as the ideal choice. In this study, we attempted to integrate these two techniques (RNA amplification and nanoprobe detection) into a single detection-associated amplification method. In that line, essential adjustments such as amplicon dilution, disturbing reagent extraction, ion adjustment, and modification of the hybridization protocol were needed due to the ribonucleic acid nature of NASBA products and the presence of some interfering reagents in the amplification reaction environment. The adjustments successfully resulted in the gold nanoparticle-based detection of NASBA products with naked eyes in a whole operational time of less than 3.5h (including nucleic acid extraction, amplification, and detection). Furthermore, the developed assay was successfully applied to detect dnaK messenger RNA of Salmonella typhimurium. The developed colorimetric method facilitated the detection step of NASBA leading to an ideal methodology for rapid assays and serves as an ideal alternative to the highly expensive reverse transcription polymerase chain reaction (RT-PCR) approach.