Much has been made in the past few years of the use of silver as a biocide and its use in hospitals, wound dressings and as a water purifier, but gold seems to have lagged behind in the medical stakes – that is perhaps until now! University of Missouri researchers have found that gold nanoparticles can be used in treatment for aggressive prostate cancers.

An article published on the University of Missouri’s website (www. Missouri.edu)  reports that University of Missouri scientists have found a more efficient way of targeting prostate tumours than using relatively toxic chemotherapy by using gold nanoparticles and a compound found in tea leaves. This new treatment would require doses that are thousands of times smaller than chemotherapy and do not travel through the body inflicting damage to healthy areas. The study is being published in the Proceedings of the National Academy of Science.

“In our study, we found that a special compound in tea was attracted to tumour cells in the prostate,” said Kattesh Katti, curators’ professor of radiology and physics in the School of Medicine and the College of Arts and Science and senior research scientist at the MU Research Reactor. “When we combined the tea compound with radioactive gold nanoparticles, the tea compound helped ‘deliver’ the nanoparticles to the site of the tumours and the nanoparticles destroyed the tumour cells very efficiently.”

Currently, doctors may treat prostate cancer by injecting hundreds of radioactive ‘seeds’ into the prostate. However, that treatment is not effective when treating an aggressive form of the cancer, said Cathy Cutler, research professor at the MU Research Reactor and co-author of the study. The size of the seeds and their inability to deliver effective doses hampers their ability to stop the aggressive form of prostate cancer.

However, in the MU study,  scientists created nanoparticles that are just the right size. Instead of hundreds of injections, the team only needed to use one or two injections, and the nanoparticles were more likely to stay very close to the tumour sites.

Cutler and Katti have been working with colleagues Raghuraman Kannan, Anandhi Upendran, Charles Caldwell as well as others in the Department of Radiology and at the MU Research Reactor to develop and design the nanoparticles to the correct shape and size. If the nanoparticles produced are too small, they can escape and spread; if they are made large enough, the nanoparticles will stay inside the tumour and treat it much more effectively than current methods.

 “Current therapy for this disease is not effective in those patients who have aggressive prostate cancer tumours,” Cutler said. “Most of the time, prostate cancers are slow-growing; the disease remains localized and it is easily managed. Aggressive forms of the disease spread to other parts of the body, and it is the second-leading cause of cancer deaths in U.S. men. However, we believe the gold nanoparticles could shrink the tumours, both those that are slow-growing and aggressive, or eliminate them completely.”

“This treatment is successful due to the inherent properties of radioactive gold nanoparticles,” Kannan said. “First, the gold nanoparticles should be made to the correct size, and second, they have very favourable radiochemical properties, including a very short half-life.”

With a half-life of only 2.7 days, the radioactivity from the gold nanoparticles is finished within three weeks.

“Because of their size and the compound found in tea, the nanoparticles remain at the tumour sites,” Upendran said. “This helps the nanoparticles maintain a high level of effectiveness, resulting in significant tumour volume reduction within 28 days of treatment.”

In the current study, the team tested the nanoparticles on mice. Prior to human trials, the scientists will study the treatment in dogs with prostate cancer. Prostate cancer in dogs is extremely close to the human form of the disease.

While this is indeed an interesting study from a medical point of view it is unfortunately unlikely to have anything but the minutest effect on gold demand given that gold nanoparticles by definition are of microscopic size.  However it does demonstrate that there is some continuing interest in gold in the medical sector.  Indeed the World Gold Council reports as follows:

“Throughout most of the 20th century gold compounds were investigated for a range of ailments. Medicines were marketed for the treatment of rheumatoid arthritis, with the most widely used being the oral drug Auranofin. Recent years have seen a resurgence of interest in gold compounds in the treatment of cancer, with many prominent academic and industrial labs active in the field.

“Gold offers a high degree of resistance to bacteria, making it the material of choice for implants at risk of infection, such as the inner ear. Gold has a tradition of use in this application and is considered a highly valuable metal in microsurgery of the ear.

“A recent treatment for prostate cancer uses grains of gold, approximately the size of a grain of rice. The surgical procedure involves inserting three gold grains into the prostate using ultrasound. The position of the gold grains can be detected using x-rays (gold is opaque to x-rays) allowing the doctors to accurately target the prostate position within one or two millimeters.

“Doctors also implant high purity gold (typically 99.99%) in the upper eyelid to treat facial nerve paralysis. The aim of the treatment is to help the patient’s upper eyelids to close when muscle paralysis is preventing this motion. Following the implantation of the gold device (typically a few grams in weight), the gravitational pull on the implant facilitates closure of the eyelid.”