Robust determination of adherent and suspended cancer cell concentration using optical density

Optical density is commonly used as a simple and rapid indirect measurement method to estimate biomass concentration in liquid cultures. However, the object of optical density detection is often algae cells, colonies, and other microorganisms，few studies adopt optical density to quantitatively measure the concentration of cancer cells. In this paper, different liquid media and cancer cells were used to implement a full-wavelength spectral analysis by microplate reader to find the corresponding robust wavelength. According to the experimental results, we suggest measuring cell concentration at near-infrared wavelengths, such as 850 nm, to facilitate the subsequent unification of protocols applicable to different cell types and culture conditions. Meanwhile, a portable flow cell sensor based on optical density is demonstrated. The calibration curves under various experimental conditions have high regression coefficient R² values, all greater than 0.99, which are expected to be used for online real-time measurement of cell concentration in biological reaction processes. This study provides the feasibility of using the optical density method as a quick and easy way for indirect quantitative measurement of cancer cell concentration.