Raman spectroscopy for virus detection

Surface-enhanced Raman spectroscopy (SERS) extends the application of Raman spectroscopy to include trace analysis of materials such as explosive residues, crime scene evidence, chemical agents, and pesticides. As a label-free technique, SERS is also well suited for biosensing, from blood sugar to diagnosis of diseases such as cancer, Alzheimer's and Parkinson's.

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A new variant of SERS, developed by a group at Jackson State University in Mississippi, USA, uses a hybrid probe composed of graphene oxide attached to popcorn-shaped gold nanoparticles to extremely sensitively detect DNA characteristics of HIV.

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SERS adsorbs the analyte to a metal substrate, enabling the detection of extremely low levels of the analyte by Raman spectroscopy. Localized surface plasmons are generated by the electromagnetic resonance effect between the substrate and the Raman excitation laser, and interact with the analyte to enhance the Raman emission by up to 1010 times.

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SERS can be performed on a matrix or use colloids suspended in solution. While metals such as gold, silver and copper are the most used materials for SERS, new options such as graphene, semiconductors and quantum dots are also being explored. Graphene oxide, a chemically treated version of graphene, has several properties that make it particularly suitable for biological applications.

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Unlike most SERS substrates, the enhanced Raman signals observed with graphene oxide substrates are thought to be due to chemical effects. By combining graphene oxide and more traditional gold nanoparticles into a hybrid SRS probe, the Jackson State University research team exploits both chemical and electromagnetic enhancing effects to target two particularly deadly pathogens: human immunodeficiency virus (HIV) and methicillin. Resistant St. aphylococcus aureus (MRSA).

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Although techniques such as polymerase chain reaction, or PCR, are the gold standard for virus detection, it has been demonstrated that viruses such as the coronavirus MERS-CoV can also be detected using Raman spectroscopy and SERS techniques. When tested in mass epidemic situations, the costs associated with Raman-based systems were more accessible than conventional PCR tests.