Tungsten Particle-Induced Nicking of Supercoiled Plasmid DNA

Improvement of DNA/Metal Particle Adsorption in Tungsten-Based Biolistic Bombardment; Alkaline pH is Necessary for DNA Adsorption and Suppression of DNA Degradation

“…2 and 4). This finding is consistent with the previously reported pH dependency of tungsten-induced DNA nicking (Mazuś et al 2000). Furthermore, plasmid DNA degraded at pH of <3.0 without tungsten particles (Fig.…”

“…4). Our results apparently conflict with those of Buchowicz's group; their results show that tungsten particles cause only relaxation and linearization, but not fragmentation of plasmid ccDNA (Krysiak et al 1999a;Krysiak et al 1999b;Mazuś et al 2000). Although the causes to explain the different results have not been found yet, it might be due to the experimental conditions of the two laboratories: for instance, tungsten:DNA ratio (w/w; 5-50 in their study vs. 600 in our study), the buffer (TE and citrate buffers vs. TE), the incubation time (20 min vs. 30 min to 24 h), and incubation temperature (21°C vs. 4°C or 25°C).…”

“…However, this phenomenon has so far not been intensively studied. Only a few reports on tungsten-induced DNA cleavage have been published in the past decade (Krysiak et al 1999a;Krysiak et al 1999b;Mazuś et al 2000); the nicking and linearization of plasmid DNA were reported to occur during incubation with tungsten particles, and DNA nicking with tungsten depends on pH of the incubation buffer. Therefore, we investigated minutely the effect of tungsten particles on plasmid DNA degradation to evaluate the value of this metal element and to diminish the disadvantage of tungsten particles in biolistic bombardment.…”

A review of tungsten: From environmental obscurity to scrutiny

“…Genotoxic effects for various tungsten compounds, including tungsten carbide, sodium tungstate, tungsten(IV) oxide, tungsten(VI) chloride, and its products of microparticle decomposition, have been demonstrated in experiments with human cells [143,144]. However, the mechanism appears not to be related to DNA nicking [145]. Cemented carbides consisting of tungsten carbide and metallic cobalt were shown to be genotoxic in human lymphocytes and in type II pneumocytes producing DNA strand breaks and micronuclei directly associated with risk of lung cancer in occupational settings [146].…”

Genetic Transformation of Plants

“…On the other hand, the reaction rate is not inftuenced by free radical scavengers or ascorbate. No changes in plasmid DNA structure can be observed when tungsten particles are replaced by tungsten partide leachates or commercial tungsten compounds (Mazus et al 2000). Likewise, gold particles leave plasmid DNA intact.…”