Ultraviolet, Did the Cell See It from the Side or the Bottom? Assessment and Modeling of UV Effects on Cultured Cells Using the CL-1000 UV-Crosslinker

Numerous natural extracts and compounds have been evaluated for their ability to mitigate the adverse effects of ultraviolet (UV) overexposure. However, variability in the UV doses that trigger biological responses across studies likely arises from inconsistencies in UV exposure standardization. We hypothesize that these discrepancies are due to variations in culture plates and dishes. The UV dose (D) required to reduce cell viability by 50% differed by a factor of ten between 3.5 cm dishes and 96-well plates. Similarly, the EC₅₀ dose for IL-6 release (<i>D</i>_1/2) varied, potentially correlating with the surface area (S). UV exposure to wells with increasing height in 3.5 cm dishes resulted in a decrease in IL-6 release, suggesting that the greater the well height, the more it may influence UV exposure through reflection or shielding effects, thereby contributing to the physiological effects on the cells. To compare these differences among plates, we defined the height-to-diameter ratio (r). Analysis revealed a linear correlation between <i>D</i>_1/2 and S in a log-log plot, and between <i>D</i>_1/2 and r in a semi-log plot. From this, we defined two empirical indices <i>σ</i> and ρ for UV dose adjustment. A deductive model was also developed to derive a D' value that adjusts UV doses without requiring training. As with σ and ρ, the UV dose D was effectively adjusted using D' as well. These attempts suggest that D' offers a foundational framework for evaluating UVB effects on cultured cells.