Advances in Raman Spectroscopy for Life Science Research

Comments

Michael Scott Long received his Ph.D. in analytical chemistry from Penn State. Nature, the Washington State Academy of Sciences, and many others have published his scientific writing and science journalism. He lives in Richland, Washington.

February 29, 2024

Raman spectroscopy is an invaluable life science research technique—for interrogating the intestinal microbiome (Lee et al., 2021), diagnosing oral cancer (Zhang et al., 2022), serving as a compliment to conventional biopsies (Qi et al., 2023), and more. Because it’s non-destructive and rapid, analyses can be conducted on living cells in real time, such as for identifying antimicrobial resistance profiles (Rebrosova et al., 2022). Furthermore, in Raman microspectroscopy applications, subcellular resolution is possible for many eukaryotes. The pertinence of Raman spectroscopy is perhaps best indicated by its global market size: estimated as over $0.8 billion in 2023, and predicted to reach over $1.1 billion by 2028 (MarketsAndMarkets, 2023).

Search Raman spectrometers
Search Now Search our directory to find the right raman spectrometer for your research needs.

How can Raman spectroscopy advance your research program? Here, we provide an overview of basic principles and biochemically pertinent considerations, representative commercial instrumentation, as well as recent applications to cell biology and microbiology.

Overview and biological utility

A biomolecule is Raman-active if the polarizability of at least one of its molecular bonds changes during laser-induced, vibration-associated electronic transitions. Raman spectra are unique to the substance; a “fingerprint.” Four facts render Raman spectroscopy especially useful in life science research (Lee et al., 2021; Pezzotti, 2021):

1. Raman signals arise from electron-rich functional groups that are common in biology, such as C=O.

2. Molecular vibrations can be readily detected from only a few atoms that nevertheless correspond to e.g., unfolding of a large protein.

3. Because Raman signals from small molecules tend to be weak, Raman spectroscopy is essentially transparent to water—unlike infrared spectroscopy.

4. Cryogenic or vacuum conditions are unnecessary—unlike in cryogenic electron microscopy or nanoscale secondary ion mass spectrometry.

Industry perspectives: Tools and trends

What tools can best serve your Raman spectroscopy needs? Teledyne Princeton Instruments offers its LS-785 series Raman and near-infrared spectrometers. “The LS-785 has been a crucial tool helping in applications such as optical cell classification, optical measurement of glucose concentration, in vivo identification of cancerous tissue, and diagnosis of neonatal brain injury,” says Sebastian Remi, Application Scientist. “Combined with our ultra-high sensitivity cameras and detectors, the high throughput of the LS-785 helps increase signal detectability as well as shortens observation time and decreases potentially damaging exposure to cells and tissue.”

What current analysis trends should be on a life scientist’s radar, and how is Raman spectroscopy ideal in such contexts? Chris Brown, Chief Product Officer and Co-Founder of 908 Devices, says: “Process analytical technologies (PATs) are evolving quickly, particularly given the pharmaceutical industry’s focus on Biopharma 4.0—enabling data-driven descriptive, predictive, and prescriptive control to optimal endpoints in yield, quality, and efficiency. PAT has historically involved significant capital investment, and substantial expertise from dedicated PAT teams to support scale-up, pilot, and production implementation. But we’ve seen a lot of increasing demand in much earlier phases of biopharmaceutical development for simple but high-powered tools to facilitate rapid screening/selection of cell lines, process conditions/parameters and process models, and digital twins.

“MAVERICK is a great example of a highly lauded PAT technology—Raman spectroscopy—being productized for efficiency and end-use simplicity in the hands of a non-PAT expert. Raman has traditionally required a lot of time, expert manual intervention, and investment. But with MAVERICK early-phase process development scientists can leverage highly sophisticated turn-key analytics and control strategies for mammalian cell culture process development. At the same time, the systems are logging richly detailed Raman data for advanced process modeling initiatives,” Brown adds.

Next, we present representative life science research that heavily relied on Raman spectroscopy.

Artificial intelligence in cancer research

Raman spectra are sensitive indicators of the biochemical composition of cells and tissue—and thus in principle are an ideal data source in biopsies. In fact, researchers have long known the specific biochemical changes that correspond to the Raman spectral shifts seen in various malignant tumors (Chang et al., 2024). However, Raman spectra are often broad and overlapping, which can hinder interpretation. Artificial intelligence (AI) can help solve this data analysis challenge by identifying subtle yet critical details that are otherwise challenging to detect and decipher. Nevertheless, how to choose an appropriate AI classification model remains an open question.

In a preprint, Chen et al. (2023) studied five representative Raman datasets (such as melanoma cells) that differ in terms of various data characteristics, such as tissue sites and Raman shift range. They identified the AI technologies that performed the best under which data characteristics. For example, regarding melanoma screening, they substantially improved AI model accuracy (from 89.3% to 99.7%) and identified six diagnostic Raman shifts (such as for iron-containing protein), which is consistent with previous findings.

Diagnosing urinary tract infections

Urinary tract infections (UTIs) are the most common outpatient infection: 50% to 60% of adult women have at least one in their lifetime (Medina et al., 2019). A critical parameter for treating such infections is the quantity of live pathogens. The standard method of determining this UTI parameter remains urine culture, which unfortunately requires more than 18 hours to complete. Rendering Raman spectroscopy compatible with rapidly determining live pathogen number would facilitate UTI patient treatment.

Wang et al. (2023) improved on single-cell Raman–deuterium isotope probing for UTI diagnosis. Conventionally, this technique has required a few hours to complete, and in the meantime the bacteria multiply—obviating determination of pathogen count. The researchers’ improvement here was to add sodium acetate to the cell culture medium, which did not harm the bacteria but prevented cell division and proliferation. In only three hours with urine samples that had been seeded with E. coli cells, they determined pathogen counts that were highly consistent with each other and within the same order of magnitude as the much longer urine culture method. Validation on clinical UTI samples remains to be completed.

Raman spectroscopy has wide-ranging applications, throughout cell biology and microbiology, in basic research and clinical work. Affordable, portable Raman instruments can even be made by students as a laboratory exercise (Emmanuel et al., 2021). Although data analysis can be challenging in complex matrices such as biological tissue, tools are available for simplifying the task for non-specialists. Speak with a Raman instrumentation manufacturer to choose the technology that is most appropriate for your application.