Multifocal Raman Spectrophotometer for Examining Drug-Induced and Chemical-Induced Cellular Changes in 3D Cell Spheroids

Abstract

Cell spheroids offer alternative in vitro cell models to monolayer cultured cells because they express complexities similar to those of in vivo tissues, such as cellular responses to drugs and chemicals. Raman spectroscopy emerged as a powerful analytical tool for detecting chemical changes in living cells because it nondestructively provides vibrational information regarding a target. Although multiple iterations are required in drug screening to determine drugs to treat cell spheroids and assess the inter-spheroid heterogeneity, current Raman applications used in spheroids analysis allow the observation of only a few spheroids owing to the low throughput of Raman spectroscopy. In this study, we developed a multifocal Raman spectrophotometer that enables simultaneous analysis of multiple spheroids in separate wells of a regular 96-well plate. By utilizing 96 focal spots excitation and parallel signal collection, our system can improve the throughput by approximately 2 orders of magnitude compared to a conventional single-focus Raman microscope. The Raman spectra of HeLa cell spheroids treated with anticancer drugs and HepG2 cell spheroids treated with free fatty acids were measured simultaneously, and concentration-dependent cellular responses were observed in both studies. Using the multifocal Raman spectrophotometer, we rapidly observed chemical changes in spheroids, and thus, this system can facilitate the application of Raman spectroscopy in analyzing the cellular responses of spheroids.

Innovative Approaches for Drug Discovery: Quantifying Drug Distribution and Response with Raman Imaging

“…An adaptation of the multiwell RS system was used in 2023 to examine drug-induced cellular changes in 3D cell spheroids. 154 They investigated biochemical changes of HeLa and HepG2 spheroids subjected to Actinomycin D (ActD) and free fatty acid (FFA) treatments, respectively. In ActD-treated HeLa spheroids, Raman spectra revealed dose-dependent changes with a significant increase in the Raman intensity at 1485 cm −1 , and a decrease in the Raman intensity at 1585 cm −1 was observed with ActD treatment at a concentration range of 0.3−10 μM (Figure 5c.i−iii).…”

“…The authors applied this system to study drug polymorphism and alkyne-tag screening, and also demonstrated the capability for mapping relatively large samples. An adaptation of the multiwell RS system was used in 2023 to examine drug-induced cellular changes in 3D cell spheroids . They investigated biochemical changes of HeLa and HepG2 spheroids subjected to Actinomycin D (ActD) and free fatty acid (FFA) treatments, respectively.…”