Generation mechanism of hydroxyl radical species and its lifetime prediction during the plasma-initiated ultraviolet (UV) photolysis

TLDR

The study is situated in plasma chemistry and medicine, where plasma‑initiated UV photolysis offers a novel approach. The authors aim to elucidate the mechanism of hydroxyl radical generation and measure its lifetime in biosolution. They used theoretical and semiempirical calculations, pH‑dependent current measurements, and apoptosis assays to model hydroxyl radical generation, lifetime, and interaction with cancer cells. Plasma‑initiated UV photolysis continuously produces hydroxyl radicals, which become the dominant reactive species, with density and lifetime inversely related to depth in the solution.

Abstract

Abstract Through this work, we have elucidated the mechanism of hydroxyl radicals (OH • ) generation and its life time measurements in biosolution. We observed that plasma-initiated ultraviolet (UV) photolysis were responsible for the continues generation of OH • species, that resulted in OH • to be major reactive species (RS) in the solution. The density and lifetime of OH • species acted inversely proportional to each other with increasing depth inside the solution. The cause of increased lifetime of OH • inside the solution is predicted using theoretical and semiempirical calculations. Further, to predict the mechanism of conversion of hydroxide ion (OH − ) to OH • or H 2 O 2 (hydrogen peroxide) and electron, we determined the current inside the solution of different pH. Additionally, we have investigated the critical criterion for OH • interaction on cancer cell inducing apoptosis under effective OH • exposure time. These studies are innovative in the field of plasma chemistry and medicine.