Enhancing-effect of gold nanoparticles on DNA strand displacement amplifications and their application to an isothermal telomerase assay†
The exciting applications of gold nanoparticles (AuNPs) in bio-diagnostics are not limited to use as signal transduction probes; the fascinating effect of AuNPs on enhancing the reactions of nucleic acids has also been increasingly recognized. Herein, we explored the power of AuNPs and their enhancing effect on isothermal amplification reactions. The EXPIATR assay, based on a programmed path of isothermal strand displacement amplifications, has been proven to be a sensitive assay for telomerase activity. However, the assay is not applicable to the complex, protein-rich samples which more closely resemble real clinical specimens, since the abundant cellular proteins in the complex samples can impair the specificity of the amplification reactions. In the presence of AuNPs, the sensitivity of the detection of telomerase activity in complex samples is improved five-fold compared with the traditional assay, providing an efficient way to enhance the reliability of the EXPIATR assay to a new level. In addition to the situation of low-specificity caused by the external interference of cell lysates, it was further demonstrated that AuNPs showed a similar effect on improving the low-specificity caused by the polymerase, which implies that AuNPs affect the amplification reactions in a very fundamental way, presumably by enhancing the activity and stability of the amplification enzymes. By revealing and demonstrating the beneficial role of AuNPs in nucleic-acid reactions, this study provides a new avenue to promote the clinical applications of isothermal nucleic acid amplification.