Figure: A single-temperature method to amplify DNA via helicase. With the assistance of gold nanoparticles, genetic tests for biomarkers can be realized in low-cost settings.

A low-cost way to amplify DNA for genetic tests

The motivation – Helicase is an important enzyme involved in DNA amplification and biological cell replication. Together with several assisting proteins, helicase denatures double-stranded DNA to give single DNA strands, leading to the production of more strands, which are needed for cell replication. Inspired by this biological function, a DNA amplification method called helicase-dependent amplification (HDA) was designed for in vitro use by scientists; this method separates double-stranded DNA into the individual strands using helicases rather than heat, which is used in the conventional polymerase chain reaction amplification method. Unfortunately, this new method is limited because helicase denaturation under in vitro conditions is not very efficient compared with the strand separation that is achieved in the rich cellular environment, which includes proteins that assist in the denaturation process.

The discovery – Using a method called nanoHDA, the Li Group at Simon Fraser University (SFU) discovered that gold nanoparticles can play the role of a helicase assistant in denaturing the DNA, which is subsequently copied and amplified in the in vitro DNA amplification technique. The gold nanoparticles assist by binding to, and maintaining the status of, single-stranded DNA, which enhances the efficiency and specificity of the DNA amplification.

Its significance – The helicase-dependent amplification technique is conducted at a single temperature, whereas the conventional polymerase chain reaction amplification method cycles through three different temperatures, and thus requires an expensive thermocycler.  Helicase-dependent amplification provides the low-cost nucleic acid amplification needed for genetic tests to be conducted in point-of-care settings. The challenge posed by the HDA method is that it is not effective for amplifying long human DNA, though it is successful when used with short bacterial and viral DNA. The Li Group’s new nanoHDA method enables the use of a single-temperature amplification method to effectively amplify human genomic DNA for the detection of difficult biomarkers like point mutations in genetic tests.

Read the paper“NanoHDA: A nanoparticle-assisted isothermal amplification technique for genotyping assays” by Sedighi, A; Oberc, C; Whitehall, V; Li, PCH. Nano Research 10(1):12–21 (2017).  DOI: 10.1007/s12274-016-1262-z

Website article compiled by Jacqueline Watson with Theresa Kitos