Development of a cell-subculture bell (C-Bell) device using low-cost RGB color sensors.

Monitoring cell culture status is fundamental in biological and biotechnological research to ensure experimental reproducibility and reliability. However, existing subculturing methods, based on manual observation of cell morphology and media color, are time-consuming, labor-intensive, and prone to variability due to subjective interpretation. In this study, we developed and validated C-Bell, a non-invasive, low cost, Arduino-based automated monitoring system that measures and analyzes color changes in cell culture media in real time. This system uses an integrated RGB color sensor to quantitatively detect pH-dependent media color changes associated with cell metabolic activity, converting the data into a standardized index, the C-Bell Index. To evaluate the performance of the C-Bell device, we first used control and acidified media to verify the RGB sensor’s ability to detect and quantify color changes. Furthermore, we applied the system to lung cancer cell lines seeded at various densities, measuring and analyzing media acidification under actual cell culture conditions using the C-Bell Index. The C-Bell index-based real-time cell culture media analysis results were cross-validated using microscopic observations. The C-Bell device enables continuous automated monitoring of culture plates in a CO₂ incubator, eliminating the need for labor-intensive and subjective manual inspections. It reduces experimenter bias, lowers labor demands, and enhances experimental reproducibility. The modular and scalable design of C-Bell enables adaptation to diverse culture conditions and laboratory environments, providing a practical, reliable tool for automated cell culture monitoring in basic and translational research.