Raman technique spots early-stage viruses

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In the laboratory, scientists and clinicians have come to rely on Raman spectroscopy because of its ability to provide chemically specific information about biospecimens. A variation on conventional methods, called coherent anti-Stokes Raman scattering (CARS) — in which femtosecond laser pulses cause molecules to vibrate in unison — has been used for identifying anthrax and mold spores, among other applications. Now, in the age the COVID-19 pandemic, the combination of plasmon resonance and Raman scattering is allowing for a practical approach to detecting the presence of virus particles.

While conventional Raman techniques are restricted by the Abbe limit, near-field optical techniques can be applied for greater contrast, and features that are smaller than the limit can be illuminated. A laser beam can both excite the molecule in question and reveal information contained within specific Raman signals.

These concepts led a research team at Texas A&M University to develop a technique with a catchy name, FAST CARS. FAST stands for the femtosecond adaptive spectroscopic technique. In the cover story here, the team explains that the combination of plasmon enhancement with lateral resolution has been applied to various specimens, and it has the capacity to capture a variety of signals before the immune system has begun producing antibodies to fight the illness.

Elsewhere in this issue, Rajagopal Srinivasan relates how devices that utilize light sensors have the potential to monitor urinary tract infections — for which dipstick colorimetric readings are often unreliable — at the bedside. Two recently developed device prototypes, one of which features a spectroscopic camera, capture spectral data in seconds from body fluids that have not been contaminated with outside elements, and they may allow early — and more importantly, correct — diagnoses. Learn more here.

In another feature article, Raluca Borlan, Monica Focsan, Simion Astilean, and Patriciu Achimas-Cadariu point out that near-infrared fluorophores contained within nanoparticles have the ability to image the boundaries of cancer tumors. In a clinical setting, a surgeon could receive this information in real time, reducing the need for invasive resections that could harm the patient. See what the future may hold here.

Finally, Emma McCarthy discusses how advancements in camera technology have produced effective in vivo imaging, based on factors including detector sensitivity, spatial resolution, and reduced noise, which could have a dramatic impact on the outcomes of diagnosis and treatment of a variety of conditions. Technologies such as NIR probes are enabling imaging at deeper depths with higher resolution to monitor the effects of treatment and allow doctors to change course as necessary. Read about the status of these advancements here.

And in “Biopinion,” Jose Pozo asserts that government regulation and the biomedical photonics community’s tendency to be territorial may hinder the arrival of a variety of optical approaches in the medical market. But the unified effort to effectively analyze and treat COVID-19 has cut across barriers in industry and academia, as participants have worked toward common goals. Pozo calls for the community to continue this momentum as the world confronts other public health challenges. See more of his point of view here.

Enjoy the issue!

Published: September 2021

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