Role of Immersion Refractometry for Investigating Laser Induced Effects in Cells

摘要

The broad background of scattered light observed in spectra of cell suspensionsis reduced by factors of up to twenty by immersion refractometry allowing for improved spectroscopic determination of the absorption properties of cells in the 325 to 820 nm range. Refractive-index matched spectra of E.coli Cla exhibit a set of resonant features near 422, 561, and 582 nm. Exposure wavelengths are chosen based on this spectrum and cell viability is investigated in E.coli suspensions exposed to 350, 400, 422, 440, and 700 nm radiation delivered in nanosecond pulses with total doses from 500 millijoules to 60 Joules. We observe a loss in cell viability for doses greater than 1 Joule at 422 nm and for all doses at other wavelengths; exposures of less than 1 Joule at 422 nm enhance growth. Excluding exposures at wavelengths within the resonant feature, longer wavelengths are less effective at reducing the viability of E. coli Cla. This indicates the occurrence of at least two absorption processes.