'We have developed a process that is inherently non-toxic - we do not make use of any chemicals at all, except for a commercially available gold precursor,' Kattesh Katti, the researcher leading the team, told Chemistry World. The scientists, based at the University of Missouri, have patented their discovery and created a company to develop the technology further.
Current methods of gold nanoparticle production require a variety of reagents such as hydrazine, sodium borohydride and dimethyl formamide. This makes the process costly and potentially toxic, making it awkward to produce nanoparticles that are suitable for medical applications.
The new process uses ordinary soybeans, commonly used to make soymilk or tofu, added to water. Soybeans are known to be a 'superfood', containing a wide variety of beneficial non-toxic chemicals. These naturally active 'phytochemicals' leach out into the water and when gold salts are added, they reduce the gold ions in the solution to nanoparticles. Different phytochemicals then stabilise the nanoparticles, preventing from fusing together into a larger gold metallic structure.
'This process produces uniform nanoparticles that are an ideal size for biomedical use,' Katti added. However, he would not comment further on the chemicals involved or how the nanoparticles were made and stabilised.
Katti's team became interested in using plants to make nanoparticles when they discovered last year that gum arabic, a common food additive taken from the acacia tree, was able to form a coating around gold nanoparticles that makes them stable and nontoxic.1
Ravi Saraf, at the University of Nebraska-Lincoln, US, uses gold nanoparticles in his research into bacteria. 'We need to be careful - although no chemicals are being used, reducing gold can still produce potentially toxic compounds,' he warned. 'However, if this process does prove to be environmentally-friendly throughout, then it will be a big thing. There are new applications for gold nanoparticles emerging all the time.'