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

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 H2O2 (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.

Imaging short‐lived reactive oxygen species (ROS) with endogenous contrast MRI

“…[8][9][10][11][12][13] Instead of developing an MRI technique with submicrosecond temporal resolution to study its MRI properties, we alternatively established an imaging platform that sustainably produces ROS. Fresh egg white treated with H 2 O 2 prolongs ROS production for hours, with quantifiable ROS concentrations over time.…”

“…Based on this simple model, we estimated the detection sensitivity of ROS MRI is at the pM level under the assumption of a 1 ls lifetime for hydroxyl radicals. [8][9][10][11][12][13] Under shorter lifetimes (eg, 1 ns), the detection sensitivity will be proportionally higher (eg, 10 23 pM level). Given that the physiological concentrations of ROS is in the lM level 14 and their concentration can be elevated by over 100 times under conditions such as inflammation or stroke and reperfusion, 14,31,32 the pM detection sensitivity provides the capability to detect ROS under both physiological and pathological conditions.…”

“…For example, the lifetime of singlet oxygen, superoxide, and hydroxyl radical in aqueous solutions is within the ls regime. [8][9][10][11][12][13] In addition, The power of MRI resides in providing superb softtissue structural contrast for clinical diagnosis. In addition to the anatomical information provided by MRI, molecular information may also be obtained.…”

“…According to Rosen criteria, requiring CNR >5, the detection sensitivity of ROS imaging was around 10 pM assuming a lifetime of 1 ls for the hydroxyl radicals. [8][9][10][11][12][13] With the estimated ROS concentrations over time and the corresponding T 1 relaxation times, the T 1 relaxivity of ROS was computed to be 3.4 3 10 7 s 21 ÁmM 21 , which is much larger than that of Gd-DTPA (0.9 s 21 ÁmM 21 ) (Fig. 5).…”

“…For example, the lifetime of singlet oxygen, superoxide, and hydroxyl radical in aqueous solutions is within the ls regime. [8][9][10][11][12][13] In addition, the in vivo concentration of ROS is generally low (lM level), 14 making the detection more challenging. In order to measure ROS, several methods have been developed including optical redox scanning 15 and exogenous contrast magnetic resonance imaging (MRI)-based methods.…”