Tungsten particles have long been used as microcarriers in biolistic bombardment because of their cost-effectiveness compared to alternative gold particles—even if the former have several drawbacks, including their DNA-degrading activity. We characterized tungsten-induced DNA degradation to assess the value of this metal particle and to improve tungsten-based biolistic bombardment. Alkaline pH, low temperature, and high salt concentration were found to diminish tungsten-induced DNA breakdown. The pH was the most influential factor in this phenomenon, both in aqueous solutions and on the particles. Furthermore, alkaline pH greater than 9.4 of an adsorption mixture was found to be essential for DNA binding to metal particles. Based on these findings, we propose a new formula of DNA/tungsten adsorption by using TE buffers that keep alkaline pH (>9.4) of the mixture, in which tungsten-bound plasmid DNA cleavage was suppressed to half the level of that in the conventional DNA-binding condition.
