Variation of Strand Break Yield for Plasmid DNA Irradiated with High-ZMetal Nanoparticles

Abstract

Using agarose gel electrophoresis, we measured the effectiveness of high-Z metal particles of different sizes on SSB and DSB yields for plasmid DNA irradiated with 160 kVp X rays. For plasmid samples prepared in Tris-EDTA buffer, gold nanoparticles were shown to increase G'(SSB) typically by a factor of greater than 2 while G'(DSB) increased by a factor of less than 2. Similar dose-modifying effects were also observed using gold microspheres. Addition of 10(-1) M DMSO typically decreased damage yields by a factor of less than 0.5. Plasmid samples prepared in PBS showed significantly different damage yields compared to those prepared in Tris-EDTA (P < 0.001) with G'(SSB) and G'(DSB) increasing by factors of 100 and 48, respectively. Furthermore, addition of gold nanoparticles to samples prepared in PBS decreased G'(SSB) and G'(DSB) by factors of 0.2 and 0.3, respectively. The results show plasmid damage yields to be highly dependent on differences in particle size between the micro- and nanometer scale, atomic number (Z) of the particle, and scavenging capacity of preparation buffers. This study provides further evidence using a plasmid DNA model system for the potential of high-Z metal nanoparticles as local dose-modifying agents.

Gold nanoparticles as novel agents for cancer therapy

“…The DNA plasmid model is a relatively simple system that allows the study of radiation-induced DNA damage and chemical-free radical effects [56]. Plasmid DNA refers to double stranded extrachromosomal DNA which ranges from a few hundred to a few thousand base pairs in length and is normally present in bacteria.…”

“…Butterworth et al [56] examined the impact of size and scavenging conditions on radiosensitisation. A dose enhancement factor (DEF) of 2 was noted for SSB and DSB with 50 mg ml -1 of 5-nm GNP in a 10-mM TRIS buffer with 160-kVp X-rays.…”

Cold atmospheric pressure plasma jet interactions with plasmid DNA

“…16 Plasmid DNA pCDNA3.1 ͑Invitrogen͒ was purified using Qiagen plasmid maxi kits after propagation in E. coli. 17 The DNA concentration was determined spectroscopically. Subsequently, the DNA was diluted to a concentration of 14 ng/ l in 10 mM phosphate buffered saline ͑PBS͒ and 10 mM tris-EDTA.…”

“…The results for exposure to plasmid DNA in water solution ͑not shown͒ reveal quantitatively very similar results to 10 mM PBS; this is in contrast to x-ray irradiation. 17 In order to investigate the role of radical damage to the plasmid DNA, 10 mM tris-EDTA-a substance known to be a much stronger radical scavenger than PBSwas used as a buffer solution. 100 mM tris-EDTA mimics the radical scavenging environment found in cells in protecting DNA from damage.…”

Model for electron emission of high-Z radio-sensitizing nanoparticle irradiated by X-rays

“…One of them explains this increase of cancerous cells death by the nanoparticles emission of electrons. These electrons, released by the interaction of X-rays with nanoparticles, are supposed to be more efficient in the destruction of cancerous cells than the electrons released in water (or tissue) by the interaction of the same X-rays [3,17,4]. But this electron emission is not well known and consequently nanoparticle critical parameters such as size or composition are often chosen following others criteria than electron emission: biocompatibility [20,18], commercial availabilities, production methods.…”