Periodic table still poses puzzles while offering cures for researchers
Scientist who helps develop cures for cancer says not enough is known about some elements
The periodic table - that staple of the chemistry lesson - has 108 elements. They are the basis of the universe and all it contains.
But which of those elements are essential for human life - which ones can't we do without?
"There's a surprising amount that we don't yet know." said Peter Sadler, a professor of chemistry at the University of Warwick in the UK and the Mok Hing-Yiu distinguished visiting professor at the University of Hong Kong.
His work puts him at the point where inorganic chemistry, biology and medicine meet as he mines the periodic table to work out which elements we depend upon and which ones might help us overcome diseases. His expertise is in developing cures for cancer based on precious metals.
"There are about 18 elements that we know are definitely essential for life," said Sadler, who is working on a project at the University of Hong Kong. "These include not only the obvious candidates such as carbon, oxygen, and iron, but also less evident elements including manganese, cobalt and molybdenum."
It's also known that deficiencies of some elements can cause illness. "A lack of iron, or a lack of copper, causes anaemia. A lack of zinc during childhood will mean that the reproductive organs don't develop properly," Sadler says. But there are some elements about which scientists are uncertain.
"Fluorine causes confusion" says Sadler. "We know that it's good for strengthening the enamel in teeth but, although it's added to the water in Hong Kong and many other countries, we don't know much about what else it does in the body."
"Silicon is another example. We don't know if silicon is essential or not. It might affect bone formation but we're not sure. Then there's bromine, vanadium, and chromium, which are also unconfirmed. We've got a lot to learn."
When it comes to fighting cancer, the most common element used is platinum. "It's used in about 50 per cent of all chemotherapy treatments" says Sadler. "Platinum has proved very successful at treating certain forms, including testicular cancer." (Cyclist Lance Armstrong was cured of testicular cancer with platinum-based drugs).
When it's administered the platinum binds to a cell's DNA using two anchor points and bends it out of shape.
Cancer cells are usually unable to repair the damage and die.
However, Sadler cautions that there are a number of problems with the current generation of platinum-based drugs.
"They are notorious for their debilitating side effects. The platinum doesn't discriminate enough between cancer cells and healthy tissue. Although many healthy cells are able to fight off the platinum by using repair enzymes to remove it, others are damaged and acquire mutations in their DNA. Platinum can actually cause cancer, as well as cure it," he says.
Another issue is that some cancers are developing resistance. "The cancer cells have adapted their chemistry and are able to detoxify the platinum compound. They employ various defence mechanisms, using repair enzymes to cut the platinum out, then transport it out of the cells, or wrap it up so it's less harmful".
For those reasons there's a pressing need for new cures for cancer.
Sadler is conducting research into novel ways to use platinum to make it more effective at killing cancer cells while being less toxic to healthy tissues.
"We're trying to design photo-activated platinum compounds. We want to put them in cancer cells and activate them by irradiating them with light from fibre optic cables," he said.
"That way we could target cancer cells and do very little damage to normal cells."
He is also working to identify other precious metals that might work more efficiently and cause fewer side effects than platinum.
"Cancer cells have less defence strategies against these other metals because they attack in a totally different way to platinum. Take osmium - our highly active organo-osmium compounds don't attack the DNA," Sadler says. "Instead they attack the metabolic machinery that the cells use to make energy, so the cells die."
Sadler is optimistic about the medical riches the periodic table might one day reveal.
"Whether your interests lie in understanding the causes of conditions such as senile dementia and Alzheimer's, discovering new antibiotics to fight resistance or simply in healthy food and drink, we can expect research into the chemistry of the elements to have a major impact," Sadler says.