Sustainable futures
Grain to graphene
Countless millions of tonnes of rice husks are discarded by farmers throughout Asia. Researchers at the University of Nottingham Ningbo China ask: what if these grains could be turned into a ‘wonder material’ and deliver new cancer treatments?
Rice and corn husks and wheat stalks are left to rot in fields worldwide by farmers as they harvest their crops. Such agricultural waste can be turned into high-value, sustainable products including graphene, the wonder material with remarkable properties that has the potential for transformative applications in healthcare.
Professor Cheng Heng Pang and colleagues University of Nottingham Ningbo China’s Department of Chemical and Environmental Engineering have developed techniques that turn such agricultural waste into graphene. Made up of a single layer of carbon atoms, among graphene’s many curious properties is its great surface area – if one gram of graphene were to be opened, it would cover six basketball courts. That amount of surface makes graphene an ideal candidate for binding on to anti-cancer agents – whether it be chemotherapy drugs, proteins or antibodies – so that they can be delivered very precisely into the body.
Graphene also absorbs specific wavelengths of light, including near-infra-red (NIR) radiation. If graphene can be made to bind to cancer cells, it can be specifically heated until those cells die. This form of treatment – called photothermal therapy – has been shown to be effective.
Professor Pang said: “We can make all this from waste. Previously, most agricultural waste had just been incinerated for heating, or put to other low-value uses. But every gram of the graphene we make can sell for around £250.”
The UNNC team turns waste into graphene through a thermo-chemical process that involves heating the waste and applying chemical treatments to reorganise the carbon atoms, before shaping the new material into the required dimensions. Mostly this is in the form of two-dimensional sheets, but the team has also successfully produced single dots of graphene. These glow with a specific colour when they are irradiated with certain wavelengths of light, and so can be used in bio-imaging. These are more valuable still, selling for £6,500 per gram.
Professor Pang said agricultural waste was a good choice for producing graphene: the removal of such waste biomass was often good for the environment and the process did not require harsh chemicals. Biomass from certain plants also contains useful trace elements, such as zinc or selenium, which can be inherited in the graphene, making it more effective in some medical applications.
Professor Pang and the UNNC team have published multiple papers and established patents and are now working to make their process greener and faster, incorporating AI technology whilst using materials that are both environmentally sustainable and (since they will end up in the human body) biocompatible. The aim is to see how the process might be scaled-up to industrial level, with materials being made of the quality needed for biomedical applications.