CARS based label‐free assay for assessment of drugs by monitoring lipid droplets in tumour cells

Abstract

Coherent anti-Stokes Raman scattering (CARS) is becoming an established tool for label-free multi-photon imaging based on molecule specific vibrations in the sample. The technique has proven to be particularly useful for imaging lipids, which are abundant in cells and tissues, including cytoplasmic lipid droplets (LD), which are recognized as dynamic organelles involved in many cellular functions. The increase in the number of lipid droplets in cells undergoing cell proliferation is a common feature in many neoplastic processes [1] and an increase in LD number also appears to be an early marker of drug-induced cell stress and subsequent apoptosis [3]. In this paper, a CARS-based label-free method is presented to monitor the increase in LD content in HCT116 colon tumour cells treated with the chemotherapeutic drugs Etoposide, Camptothecin and the protein kinase inhibitor Staurosporine. Using CARS, LDs can easily be distinguished from other cell components without the application of fluorescent dyes and provides a label-free noninvasive drug screening assay that could be used not only with cells and tissues ex vivo but potentially also in vivo.Series of CARS images of HCT 116 cells after treatment at the specified times after drug treatment.

Cellular transformations in near‐infrared light‐induced apoptosis in cancer cells revealed by label‐free CARS imaging

“…Therefore, in addition to fluorescence labeling, we employed the second, label‐free imaging method of CARS microscopy to examine PBM‐induced apoptosis in more detail, and to monitor and characterize the changes in proteins/lipids distribution and organization in HeLa cells irradiated with low doses of NIR light. CARS microscopy is known as a powerful label‐free bio‐imaging tool that enables both selective probing of specific biomolecules and their long‐term observations . The effectiveness of this approach for monitoring macromolecular transformations of major types of biomolecules during apoptosis has been demonstrated by Prasad's group previously .…”

Raman spectroscopy and coherent anti-Stokes Raman scattering imaging: prospective tools for monitoring skeletal cells and skeletal regeneration

“…Raman spectroscopy provides information from the intrinsic vibrations of molecules in their native state, without the need for an exogenous label and has been explored as a label-free method for biological and biomedical applications [24][25][26]. Fourier transform infrared (FTIR) spectroscopy, a technique which provides complementary information to Raman spectroscopy, has also been applied to biological samples in order to study their vibrational profile.…”

Modern trends in biophotonics for clinical diagnosis and therapy to solve unmet clinical needs

“…Their intracellular distributions were visualized time‐ and concentration‐dependent in live cells for up to 48 hours of exposure. A CARS assay was presented to monitor the lipid droplet content in colon tumor cells treated with chemotherapeutic drugs . The increase in the number of lipid droplets in cells undergoing cell proliferation is a common feature in many neoplastic processes and an increase in LD number also appears to be an early marker of drug‐induced cell stress and subsequent apoptosis.…”