Autofluorescence spectroscopy for determining cell confluency

The essentials

• Manufacturing cells in multiple batches of small volumes is essential for patient-specific therapies
• New non-destructive modalities of cell monitoring must be developed to ensure comparable end products and constant monitoring
• Optical spectroscopy was used for the first time to determine cell confluency in a study by Derrick Yong et al.
• The team exploited the autofluorescence properties of molecules found natively within cells and applied spectral decomposition on the acquired autofluorescence spectra to discern the relative contributions of different molecules, namely flavin adenine dinucleotide (FAD) and reduced nicotinamide adenine dinucleotide (NADH)
• This was quantifiable as redox ratios (RR) that represent the extent of oxidation to reduction based upon optically measured quantities of FAD and NADH
• Results showed that RR was significantly higher for lower confluencies ($\leq$50$\%$), which could be attributed to different metabolic requirements as cells switch from individual survival to concerted proliferation
• The relationship between RR and confluency was validated through bio-chemical assays and autofluorescence imaging with negligible effects on cell viability confirmed through a live-dead study
• This study highlights the potential use of optical spectroscopy in non-destructive monitoring of cell culture processes for patient-specific therapies, providing an effective tool for quality control during manufacturing processes.

Key points written by AI: they may contain errors, check them against the paper.