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.