SINGAPORE: Discarded durian husks could soon have a second life – as antibacterial hydrogel bandages.
The bandages, created by Nanyang Technological University (NTU) scientists, were developed in line with Singapore's push towards zero waste, said Professor William Chen on Thursday (Mar 25).
Prof Chen, the director of NTU's Food Science and Technology Programme, is the scientist behind the durian husk project.
“Twelve million durians are consumed every year. However, most of the durian fruit is discarded,” he said.
The husk, which comprises about 60 per cent of the durian, is usually discarded and incinerated, “posing an environmental issue”, said NTU in a media release.
The low-cost bandage is both biodegradable and non-toxic, which means it has a smaller environmental footprint than conventional synthetic bandages, the university said.
MAKING THE BANDAGE
Prof Chen and his team created the bandages by extracting high-quality cellulose from the durian husks. They converted the husks into cellulose powder through slicing, freeze-drying and ball-milling, before removing impurities.
This is a “significant reduction” in cost compared to traditional methods of using enzymes, said Prof Chen. The traditional method costs about S$27,000 per kg, while Prof Chen’s method costs about S$120 per kg to extract the same amount of cellulose.
After extracting the cellulose, researchers combined the extract with glycerol – a waste by-product from the biodiesel and soap industry – to make a soft gel. The gel, which is similar to silicon sheets, can be cut into bandages of various shapes and sizes.
The scientists then added organic molecules produced from baker’s yeast, making the bandages deadly to bacteria.
The bandages remain functional in extreme weather conditions, added Prof Chen.
He estimates that he can extract 200g of husk powder from a 3kg durian, of which 40g is pure cellulose. This 40g is enough to make 66 pieces of 7cm by 7cm hydrogel, which is enough material for about 1,600 plasters measuring 1cm by 2cm each.
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There are various applications for hydrogels, including wound dressing and wearable electronics, said Prof Chen.
About 80 to 90 per cent of hydrogel is water, said Associate Professor Andrew Tan, who was invited to Thursday’s media briefing as an independent expert. He is vice dean (faculty) at NTU’s Lee Kong Chian School of Medicine.
It is “well-established” in many clinical trials that hydrogel helps wounds to heal, added Assoc Prof Tan. For instance, the water keeps the wound area cool and moist, accelerating healing. Hydrogel also reduces scarring.
While durians were not the only possible choice to make these bandages, Prof Chen said he chose the fruit as there was “sustainable supply” and it was high in fibre content.
However, he noted that this was platform technology, and the method of extracting cellulose can be used on other materials.
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CHEAPER THAN CONVENTIONAL HYDROGEL PATCHES
According to Prof Chen, conventional hydrogel patches on the market are made of synthetic materials. Those with antimicrobial properties use metallic compounds like silver or copper ions.
These materials make conventional hydrogel patches more costly than Prof Chen’s hydrogel, which is made from natural waste materials.
A typical hurdle for university research to market is scalability and cost-reduction, said Prof Chen. So it was important to keep the process simple, low-cost and green, he added.
The durian husks are low in cost and Prof Chen’s extraction method – which uses environmentally friendly detergent – is simple, so the project could be scaled up for production, he said.
Although currently just a proof of concept, if cellulose can be extracted in a sustainable and cost-effective way, then there is “great potential” for the durian husk-based hydrogel to replace current hydrogels already on the market, Prof Chen said.