Changes in Human Hair Induced by UV- and Gamma Irradiation

The effect of UV- and 137Cs gamma radiation on the structural and chemical integrity of human hair was studied to determine the feasibility of using human hair as a non-invasive biomarker of radiation exposure to ionized gamma- and non-ionized UV-radiation. Steady state tryptophan (Trp) fluorescence and chemical analytical methods were used to evaluate the molecular integrity of Trp fluorophores and SH-groups in hair proteins and to assess the radiation induced damage quantitatively. It was found that human hair fibers were progressively damaged by exposure to both UV- and ionized gamma radiation. Damage to the hair was evidenced by a decrease in the fluorescence intensity as a result of observed depletion of the amino acid tryptophan as well as significant reduction in a number of free SH-groups in hair proteins. Hair damage was dose-dependent for exposures between 0 and 10.0 Gy and 0 - 20 J/cm2 of UV-radiation. Additional results demonstrate that hair-fibers exposed to gamma rays, with much higher quantum energy than UV, undergo a smaller extent of changes in Trp fluorescence than when exposed to lower or equal energy of UV-irradiation. The stable Trp fluorophore appears to be extremely sensitive to UV-radiation in contrast to the ionized gamma radiation whose damage is originated from the reaction of free radicals and direct deposition of energy. We conclude that fluorescence spectroscopy represents a useful tool in the quantitative evaluation of the radiation exposure and could also be used for the rapid and non-invasive assessment of radiation dose i.e. biodosimeter. The approach is simple, non-invasive and appears to have considerable potential that enables quantitative evaluation of radiation dose exposure in a single hair fiber.

Chip-scale broadband spectroscopic chemical sensing using an integrated supercontinuum source in a chalcogenide glass waveguide

On-chip spectroscopic sensors have attracted increasing attention for portable and field-deployable chemical detection applications. So far, these sensors largely rely on benchtop tunable lasers for spectroscopic interrogation. Large footprint and mechanical fragility of the sources, however, preclude compact sensing system integration. In this paper, we address the challenge through demonstrating, for the first time to our knowledge, a supercontinuum source integrated on-chip spectroscopic sensor, where we leverage nonlinear Ge_(22)Sb_(18)Se_(60) chalcogenide glass waveguides as a unified platform for both broadband supercontinuum generation and chemical detection. A home-built, palm-sized femtosecond laser centering at 1560 nm wavelength was used as the pumping source. Sensing capability of the system was validated through quantifying the optical absorption of chloroform solutions at 1695 nm. This work represents an important step towards realizing a miniaturized spectroscopic sensing system based on photonic chips.