Nucleic acid testing, which aims to test related pathogenic bacteria and viruses, is an important method for disease diagnosis, food safety control and environmental monitoring.

Traditional nucleic acid testing depends on polymer chain reactions, or PCR, to exponentially amplify target nucleotide sequences, and has been widely used in laboratories and clinics.

The thermal cycle is a key part of PCR and decides its testing speed, but the heat cycle efficiency of traditional PCR instruments is generally and comparatively low. It takes personnel several hours to do one test. It is difficult to satisfy the increasing need for nucleic acid testing, especially during large-scale pandemics (such as COVID-19 and SARS).

To realize fast nucleic acid amplification testing, it is necessary to adopt high-efficiency heating/cooling methods when performing the heat cycle.

Targeting this issue, researchers developed several kinds of plasma photothermic circulatory systems based on gold nanostructures (like gold nanorod, gold bicone and gold film) for rapid nucleic acid amplification.

These systems can realize high heating rates under laser radiation and thus obviously reduce amplification time. Yet nano-particles in high concentrations needed by the systems may restrain the amplification efficiency, and the cooling velocity has not been improved.

Currently, the need for ultrafast heat cycle methods with higher efficiency and faster heating/cooling rates has not yet been satisfied.

The Bioinspired Engineering and Biomechanics Center at XJTU’s School of Life Science and Technology recently cooperated with the soft nanomaterials lab from Washington University in St. Louis. They put forward a way of using the plasma photothermal effect of gold nanorods to form ultrafast thermal circulation systems, making the rate of temperature rise and fall faster than 104 degrees Celsius per second.

This method restricts heating volume at the aL level and thus realizes rapid temperature responses. Quantifying and adjusting the nano-localized temperature field in the process is an important challenge.

The research combines experimental measurements and numerical simulation and puts forward a way of indirectly measuring surface temperature of nanogold for the first time.

Researchers also studied the relationship between the surface temperature and concentration of nanogold and laser intensity. They combined it with thermal diffusion simulation and created a method to accurately regulate and control the nano-localized temperature field. They successfully realized isothermal amplification of mediate double strands specificity nuclease through regulation and control.

The quantification and adjustment method is suitable for diverse nanostructures of precious metals with photothermal effects, and can help to promote the development of the nano-localized biochemical reaction field.

A related study was released in Small Methods with the subject of “Quantifying and Adjusting Plasmon-Driven Nano-Localized Temperature Field around Gold Nanorods for Nucleic Acids Amplification”, and was chosen as the cover article.

The article’s first author is You Minli, assistant professor at the School of Life Science and Technology of Xi'an Jiaotong University and its corresponding authors are Professor Srikanth Singamaneni from Washington University in St. Louis and Professor Xu Feng from Xi'an Jiaotong University.

Joint authors are XJTU’s doctoral students Jia Pengpeng and Ren Yulin, vice-professors He Xiaocong and Feng Shangsheng, assistant professors Li Zedong and Cao Lei, Wang Zheyu, a doctoral student from Washington University in St. Louis, Gao Bin, chief physician from Tangdu Hospital, and Yao Chunyan, chief physician from Southwest Hospital.

The Bioinspired Engineering and Biomechanics Center is the paper’s first author and corresponding organization.

The work has been subsidized by the National Key R&D Program of China, the National Natural Science Foundation of China and Shaanxi’s scientific and technological innovation team project.

Link to the paper:

https://onlinelibrary.wiley.com/doi/abs/10.1002/smtd.202001254