The coronavirus SARS-CoV-2 causes the current outbreak of the respiratory disease COVID-19. Testing for the active disease usually involves detecting the genetic material of the virus. The currently widely used test kits rely on a reverse transcription polymerase chain reaction (RT-PCR) to multiply the virus RNA from patient samples. However, this process has a fairly long processing time, which limits the testing throughput. It can also give false negatives in some stages of the infection, which hampers the control of the pandemic.
Jing Wang, Swiss Federal Institute of Technology (ETH) Zurich, and Swiss Federal Laboratories for Materials Science and Technology (Empa), Dübendorf, both Switzerland, and colleagues have developed a dual-functional plasmonic biosensor as an alternative approach for COVID-19 testing. The team used gold nanoislands, which were prepared from a gold nanofilm by thermal annealing and self-assembled on a glass surface. The surface of the gold nanoislands was then functionalized with DNA that is complementary to a partial sequence of SARS-CoV-2 RNA.
The sensor combines localized surface plasmon resonance (LSPR) and the plasmonic photothermal (PPT) effect. When virus RNA from SARS-CoV-2 is added to this system, it can bind to the DNA on the gold nanoislands. LSPR sensing can then detect this interaction by measuring changes in the refractive index at the surface. The binding between the DNA and RNA strands is dependent on the temperature. The PPT effect generates heat near the nanoparticles when the material is irradiated by a laser. This heat can inhibit the binding of nonmatching RNA sequences, whose interaction with the DNA is weaker overall due to mismatching base pairs. This increases the selectivity of the test.
The team found that their system can detect the SARS-CoV-2 virus quickly and selectively with a high sensitivity. The test accurately discriminates between genes from SARS-CoV-2 and from the similar SARS-CoV. The method has a low detection limit, down to 0.22 pM. After this proof-of-concept study, the test still needs to be validated using patient samples.
- Dual-Functional Plasmonic Photothermal Biosensors for Highly Accurate Severe Acute Respiratory Syndrome Coronavirus 2 Detection,
Guangyu Qiu, Zhibo Gai, Yile Tao, Jean Schmitt, Gerd A. Kullak-Ublick, Jing Wang,
ACS Nano 2020.
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