The use of gold and silver in medicine

Prof. Dr. Fabian Mohr researches the medical effect of precious metals in inorganic chemistry

Silver and gold are more than just chemical elements, while identified as atomic numbers 47 and 79 in the periodic table. The University of Hanover is working on novel surfaces for medical devices such as ear tubes or bladder catheters that reduce the risk of infection in hospitals. Special coatings release ions that kill bacteria in a moist environment. Nanomedical scientists see potential in the anti-inflammatory effect of precious metals to develop therapies. Gold is already being used to treat pathological obesity, blood sugar and lipometabolic disorders. Scientists at the Georgia Institute of Technology in Atlanta (USA) are working on new approaches to tumour therapy for leukaemia patients. Golden nanocomponents are supposed to improve the uptake of medicinal substances into the cells as transport vehicles. Thus, precious metals play an important role in modern medicine.
At the University of Wuppertal, chemist Prof. Dr. Fabian Mohr has been working on so-called metal complexes with biological activity for years, and can confirm the medical effect of gold and silver.

Unusual reactivity and new medications

Mohr, whose scientific career developed in Australia, Canada, the USA and Spain, has been Professor of Inorganic Chemistry in the Faculty of Mathematics and Natural Sciences since 2014. "As scientists, we are curious people that want to understand systems," he says, and in the case of gold and silver, it is particularly interesting when metal atoms of these two systems come very close to each other. Then, amazing effects such as light phenomena or unusual reactivity occur. "The second research direction is more application-oriented. It is specifically about discovering new medicines." Gold and silver have long been used to treat various cancers and even exotic tropical diseases such as malaria can be treated with them due to their antibiotic effect. The issue of resistant bacteria, which are resistant to conventional antibiotics and make work in hospitals difficult, challenge the scientist. "It is important to develop new structures, new structural motifs, in order to somehow kill these resistant germs.

A book on the most important aspects of gold chemistry

A few years ago, the book "Gold Chemistry" was published, in which Mohr, as the editor, presents a comprehensive overview of the most important aspects of gold chemistry. Additionally, current and future applications of gold compounds are presented in a variety of fields. One part of this book deals particularly with the possible applications of gold compounds as potential agents against arthritis, tumours and HI viruses in medicine.
"As medications, gold and silver have a very, very long tradition," he explains. "In ancient China, gold powder was used to disinfect wounds. In the European Middle Ages, so-called drinking gold (aurum potabile) came on the market as a panacea, which, depending on where it was purchased, sometimes contained more gold or sometimes none at all." Since the 1970s, gold existed in the form of a medicine against arthrosis. And the antibacterial effect of silver was already known to the ancient Romans. This property is also used today and various silver salts are used on large burns to reduce the risk of infection. "Many people have silver burn ointment in their first aid kits at home. The World Health Organisation even has a list of so-called Essential Medicines that actually includes this silver compound, silver sulphadiazine."

Gold and silver in colloidal form

In medicine, so-called colloidal gold or silver is used often. Mohr explains: "You have to imagine a colloidal solution or a colloid itself as a dispersion of very fine particles in a liquid. In the USA, colloidal gold used to be successfully used to treat addictions and depression, as it has an activating and harmonising effect on the glandular system and the life energy, and calms the nervous system. Silver colloid, on the other hand, was successfully used to fight all kinds of pathogens such as fungi and bacteria. The precious metals are so fine that one also speaks of nanosilver or nanogold, because their proportion is only one billionth. The solutions are usually transparent, so they are not perceptible to the eye. The expert knows, that colloidal visible forms also exist. "You might know this from ruby glass at home. Ruby glass is in fact nothing more than a dispersion of colloidal gold, i.e. fine gold particles in a glass. That gives a red colour. And depending on how big the particles are, you can produce this colour spectrum from light pink to dark purple. That is a very characteristic property of small particles that are nanometre-sized."

Antibacterial effect of silver

Mohr knows that a lot of research is still being done in this field, even though the antibacterial effect of silver has been known for a long time. A future pioneering example could be the antibacterial coating of glass touchscreens. "Innovative research dealt with coating by silver nanoparticles," he says. "The glass is then still transparent but has a self-disinfecting surface." Places of application for these new possibilities would include automated teller machines, which, due to the new coating, would always self-disinfect. And in advertising, too, substances with a share of silver are sometimes a topic in shampoos or clothing.
The preservation of drinking water due to the germicidal effect of silver was also practised in the times of the ancient Romans. ". Water stored in a silver jug was more germ-free than water stored in tin or wooden vessels. And indeed, silver vessels have been found in the houses of rich Romans, where drinking water was stored for a dry period of time and remained fresher there." But using these precious metals can be costly. Today, a kilo of gold costs the equivalent of 48,000 euros, while silver is an outright bargain at a price per kilo of around 700 euros. In terms of usable quantity, however, there are alternatives today, because, Mohr says, "compared to other substances that are used on a large scale, especially in crop protection, the costs are simply far too high. There are other means that are more economical."

Gold therapy

In the 1930s, the French doctor Jacques Forestier successfully treated patients who had rheumatoid arthritis with gold compounds. Until the late 1980s, gold therapy was the medication of choice for severe rheumatism. "It js actually one of the longest-used gold-based medications," Mohr knows, "especially the auranofin, which was sold under the name Ridaura, was very effective against joint pain." But side effects during long term usage, especially in the gastrointestinal tract, led to the discontinuation of this medication. "However, there are new studies showing that the same substance is also active against the HI virus." Research in Brazil, where AIDS remains widespread, showed that these gold compounds can help. Cancer diseases can also be treated with this compound. "Very recent studies even show efficacy against covid viruses," and perhaps, Mohr speculates, "this medication will be taken out of the drawer at some point again against another disease."

Precious metals for modern medicine

"Precious metals, and not only gold and silver, have a great significance in medicine," Mohr says. "Platinum is also used in cancer therapy. A platinum medication has really cured many people of cancer, and further developments are hoped for in the future. In particular, a lot is expected from the gold nanoparticles. One future avenue is, among other things, photodynamic therapy. This is a method of treating tumours and tissue changes by combining light with a light-activated substance. "Such gold nanoparticles develop local heat, when they come into contact with light of a certain energy. One would like to exploit this by, for example, administering these non-toxic golden nanoparticles to cancer patients and then targeting specific energy of individual organs or organ parts with a beam of light. There, the nanoparticles become hot, the heat kills the cancer cells and a healing process occurs."

Accordingly, Fabian Mohr's conclusion is clear. "There will certainly be happening a lot in this field in the next few years. And I think that metals will play an ever greater role in medicine than they already do now."

Uwe Blass (Interview on June 21, 2021)

Prof. Dr. Fabian Mohr studied chemistry in Melbourne (Australia) and received his doctorate there. After working in Canada, the USA and Spain, he came to the University of Wuppertal as a junior professor in 2006. He has been Professor of Inorganic Chemistry in the Faculty of Mathematics and Natural Sciences since 2014.