Electron spin resonance spectroscopy for the study of nanomaterial-mediated generation of reactive oxygen species

Abstract

Many of the biological applications and effects of nanomaterials are attributed to their ability to facilitate the generation of reactive oxygen species (ROS). Electron spin resonance (ESR) spectroscopy is a direct and reliable method to identify and quantify free radicals in both chemical and biological environments. In this review, we discuss the use of ESR spectroscopy to study ROS generation mediated by nanomaterials, which have various applications in biological, chemical, and materials science. In addition to introducing the theory of ESR, we present some modifications of the method such as spin trapping and spin labeling, which ultimately aid in the detection of short-lived free radicals. The capability of metal nanoparticles in mediating ROS generation and the related mechanisms are also presented.

Use of fluorescent probes for ROS to tease apart Type I and Type II photochemical pathways in photodynamic therapy

“…Due to the short half-life and high reactivity of the ROS themselves, spin traps are generally employed to transform them to stable or long-lived detectable spin-active species with a distinctive line splitting pattern [26-28]. Several substances have been used as spin-trapping agents, and can be classified in three groups: compounds with nitrone, nitroso and piperidine/pyrrolidine groups [29]. Nitrones such as 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) and 5-ethoxycarbonyl-5-methyl-1-pyrroline N- oxide (EMPO) have been extensively used for trapping hydroxyl and superoxide anion radicals in biochemical and biological systems, forming distinguishable adducts depending on the structure of the trapped radical [30].…”

Predicting the environmental impact of nanosilver

“…Zero-valent Ag has a relatively low redox potential and can participate in a Fenton-like reaction involving hydrogen peroxide (H 2 O 2 ) at acidic pH (i.e. H + ), leading to the formation of a hydroxyl radical ( • OH) and dissolution of AgNPs (He et al, 2014). AgNPs can also generate ROS via surface plasmon enhancement.…”

“…•− ), which can be converted to other ROS (He et al, 2014). From a biological perspective AgNP-mediated generation of ROS is more likely to occur via surface plasmon resonance rather than Fenton-like reaction since the latter requires an acidic pH and most biological systems operate within pH ∼7 to 8.…”

Predicting and identifying reactive oxygen species and electrons for photocatalytic metal sulfide micro–nano structures

“…Fluorescent probes can be easily used to detect O 2 ÀÅ , Å OH, and 1 O 2 , but interference from other oxidants frequently requires additional HPLC analyses to definitively identify the reactive oxygen species [12]. Electron spin resonance spectroscopy (ESR) together with spin trapping is the most reliable and direct method for identification and quantification of short-lived free radicals and reactive oxygen species [13,14]. However, the lack of a standardized and systematic approach can lead to inaccurate identification of reactive oxygen species.…”