Recent advances in nanoparticle-based SERS imaging have led to better diagnoses of diseases such as cancer and improvements in image-guided tumor surgeries.
Since the discovery of x-rays over a century ago, the rapid development of radiological diagnostics has ushered in a new era for medical imaging. Through new innovative technologies, not only have we improved imaging performance, but we have also improved our diagnostic level, which means our ability to visualize in detail the structure of tissues, morphology and function of organs. The result is that current practices of early diagnosis, and therefore disease prevention, use powerful, non-invasive methods to save countless lives.
One such method is called surface enhanced Raman scattering (SERS), an extremely sensitive medical imaging technique based on a phenomenon called Raman scattering, which is based on the scattering of light. Since its discovery by CV Raman in 1928, it has become an ideal analytical method for biological applications because it allows researchers to easily determine which chemical groups are present in a molecule. Although this is a promising platform, Raman has low scattering intensity, which has limited its application.
In 1974, three scientists from the University of Southampton accidentally discovered enhanced Raman scattering, which occurred on the surface of a rough silver electrode. This led them to discover an enhanced Raman scattering phenomenon on special metal surfaces, which we call SERS. Since then, SERS has been widely used as a very sensitive analytical tool in food analysis and bacteria detection, for example.
With the explosion of nanotechnology in the 1990s, the capabilities of SERS were also improved, demonstrating better diffusion on the surface of nanoparticles. As a result of unremitting research efforts in biomedical applications of nanoparticles over the past 30 years, SERS can now be applied to in vivo imaging, including cancer diagnosis, image-guided surgery and theranostics of cancer.
It should be emphasized that SERS imaging can be used not only for pre-treatment diagnosis (like other imaging techniques), but also for imaging guided therapy due to its non-invasive nature, sensitivity high and its non-toxic side effects. The SERS nanoparticles are first injected intravenously and localized in the tumor tissue using the biological properties of the nanoparticles. Then, portable SERS devices can be used to perform real-time scanning to guide the surgeon in removing lesions. Previous studies have shown that SERS imaging can also be used to identify microscopic lesions, which are often overlooked by traditional imaging techniques.
To increase the capabilities of intraoperative SERS imaging, further research will focus on the preparation of SERS nanoparticles with greater sensitivity and biocompatibility, as well as the development of rapid, practical and multifunctional SERS devices. This includes new morphologies and the use of plasmonic nanomaterials, such as semiconductors, graphene, quantum dots and hybrid nanomaterials to improve the imaging accuracy of SERS nanoparticles and increase their biocompatibility.
While this is a promising strategy and some SERS nanoparticles are already receiving FDA approval, it is still a young field and there are limits that must be overcome. Experts are confident that developments will be made to extend the performance of current SERS nanoparticles and gain broader clinical approval to help improve patient outcomes and no doubt save countless lives.
Reference: Zhen Du, et al. Recent advances in the applications of nanoparticles in in vivo imaging SERS. WIREs Nanomedicine and Nanobiotechnology (2020). DOI: 10.1002 / wnan.1672