Chemical Enhancement by Nanomaterials under X-ray Irradiation

Abstract

We report here a new phenomenon of dynamic enhancement of chemical reactions by nanomaterials under hard X-ray irradiation. The nanomaterials were gold and platinum nanoparticles, and the chemical reaction employed was the hydroxylation of coumarin carboxylic acid. The reaction yield was enhanced 2000 times over that predicted on the basis of the absorption of X-rays only by the nanoparticles, and the enhancement was found for the first time to depend on the X-ray dose rate. The maximum turnover frequency was measured at 1 × 10(-4) s(-1) Gy(-1). We call this process chemical enhancement, which is defined as the increased yield of a chemical reaction due to the chemical properties of the added materials. The chemical enhancement described here is believed to be ubiquitous and may significantly alter the outcome of chemical reactions under X-ray irradiation with the assistance of nanomaterials.

Actual questions raised by nanoparticle radiosensitization

“…To quantify precisely these radicals production by NP, coumarin (Sicard-Roselli et al, 2014) and 3 carboxy-coumarin (Cheng et al, 2012) were used as specific and quantitative probes. Sicard-Roselli et al…”

Gold Nanoparticles for Imaging and Radiotherapy

“…There is some suggestion that this behaviour is linked to the production of free radicals which can then diffuse through the aqueous medium to cause DNA strand breaks. 17 This conclusion is also supported by radiochemistry experiments, 18,19 which suggest that catalytic effects might be at work. However, absolute quantitative experiments on OH production have not been published to date, so definitive predictions of the importance of this effect in a radiotherapeutic setting are still not available.…”

The synergistic radiosensitizing effect of tirapazamine-conjugated gold nanoparticles on human hepatoma HepG2 cells under X-ray irradiation

“…The radiation enhancements of PEG-AuNPs and TPZs-AuNPs in solutions were evaluated by hydroxyl radical production using 3-CCA as probe following the procedure presented by Cheng et al 32 The fluorescence intensity of irradiated solution increased along with the radiation dose ( Figure S2). The radiation enhancement ratio could be calculated using the equation E r = F i /F 0 , where E r , F i , and F 0 stand for enhancement ratio, fluorescence intensity of the irradiated solution with or without AuNPs, and fluorescence intensity of the nonirradiated 3-CCA solution without AuNPs (control), respectively.…”

“…31 Following Cheng et al's procedure, 32 3-CCA was dissolved in PBS (pH 7.4). The solution was filtered by a 0.22 µm membrane filter, and DMSO was added to yield a 3-CCA/DMSO solution, which was then diluted ten times with PBS.…”