A new sunscreen ingredient has been developed in Oxfordshire using the revolutionary techniques of nanotechnology.

The ingredient, called Optisol, is now being evaluated by cosmetics companies.

It was developed by Oxford University spin-off company Oxonica, which uses pioneering chemical techniques to manipulate tiny particles, which are smaller than the width of a human hair.

Last year, Prince Charles expressed fears that nanotechnology could lead to new materials which could erode the Earth and eventually reduce it to a "grey goo".

But Oxonica chief executive Kevin Matthews said nanoparticles had been used in sunscreens for some time and were safer than conventional materials.

An EU report said the global market for nanotechnology, now worth £1bn, could grow tenfold within six years.

But Britain's top science institution, the Royal Society, last month discovered that only 29 per cent of people had ever heard of nanotechnology and only 19 per cent could offer a definition. Oxonica, based at the Begbroke Science Park, said its sunscreen absorbed dangerous ultraviolet rays without breaking up.

There have been warnings that conventional sunscreens react to sunlight by forming "free radicals" -- highly reactive chemicals linked to skin ageing and cell damage.

The company said sunscreen made with Optisol provided five-star performance, as measured by the Boots star rating system, for more than two hours.

While sunburn is mainly caused by UVB rays, scientists now believe that UVA rays may be just as important in causing some skin disorders.

David Browning, the company's executive vice-president for healthcare, said: "The synergy of Optisol with currently used sunscreen active components provides the opportunity to produce sunscreens delivering the highest levels of both UVB and UVA performance, consistently delivered over a number of hours."

Optisol is based on ultrafine titanium dioxide, already used in sunscreens, but includes in the crystal a small amount of manganese, which allows absorbed ultraviolet energy to be dissipated. It said this virtually eliminated free radicals.

The first products containing Optisol are expected to be on the market in 2006.