Nanoparticle PCR: nanogold-assisted PCR with enhanced specificity.

The polymerase chain reaction (PCR) revolutionized molecular genetics and has become one of the most popular techniques in modern biological and medical sciences. Owing to the exponential amplification ability of PCR, one could start from even a single copy of target DNA to produce large amounts of DNA copies for sequencing, molecular diagnosis, or genetic analysis. This remarkable amplification ability is critical in many circumstances, such as earlystage diagnosis of HIV or cancers. Given the rapidly increasing interest in optoelectronic DNA biosensors, the extremely high detection sensitivity of PCR has not been surpassed until now. However, the specificity of PCR does not match its unparalleled sensitivity. It is well known that even with sophisticated optimization, PCR specificity is not always satisfactory (e.g. in multiple-round PCR or multiplex PCR). Herein, we report a novel PCRmethod that employs inexpensive gold nanoparticles to effectively avoid nonspecific PCR reactions. Gold nanoparticles have found broad and important applications in biology; for example, a variety of ultrasensitive biosensor strategies have been reported which take advantage of gold nanoparticles. 11–14] Gold nanoparticles are nontoxic, biocompatible nanomaterials that can be either obtained from commercial sources or conveniently produced in laboratories, and owing to the availability of versatile chemistry for functionalization at their surface as well as their unique optoelectronic properties 11] gold nanoparticles provide a particularly useful platform for attachment of biomolecules. However, to the best of our knowledge, the use of gold nanoparticles to improve the performance of PCR has not been reported. Herein, we employed an error-prone two-round PCR as our model system. Amplification of very low quantities of copies of target genes usually increases the possibility of amplifying nonspecific sequences. In the first round, we amplified a 283-bp sequence using a l-DNA template with 35 PCR cycles; in the second round PCR, this 283-bp DNAwas employed as the template for the other 35-cycle PCR amplification sequence. Nonspecific PCR products tend to accumulate after two rounds of PCR, as manifest by a broad molecular size distribution of amplified products in agarose gel electrophoresis (Figure 1). Strikingly, in the presence of