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Posted: August 21, 2007

Detergents, eye rinses and other products with an on/off switch

(Nanowerk News) Researchers in Australia have developed a “switchable” detergent with a wide range of potential applications — from a laundry detergent that hardly needs a rinse cycle to a non-irritating eye rinse to increasing the amount of oil that companies can extract from a well.
The unusual product, described here today at the 234th national meeting of the American Chemical Society, is a biological detergent or surfactant, called a Pepfactant® because it is made from peptides, the building blocks of proteins.
Switchable detergent
The tube on the left shows the original emulsion, while the one on the right shows the rapid separation of the emulsion into oil and water after a newly developed "switchable" detergent is added. (Image: Annette Dexter, the University of Queensland)
“One of the possible applications that we are aware of is a surfactant that would switch between the wash cycle and rinse cycle during clothes washing, which would mean you could remove visible suds without having to use as large a quantity of water,” said biochemist Annette Dexter, Ph.D., of the Australian Institute for Bioengineering and Nanotechnology at The University of Queensland. Dexter is a co-inventor of pepfactants, along with Queensland colleague Anton Middelberg, a chemical engineer.
The unique aspect of the pepfactant is that it can be “switched on” or “switched off” depending on its intended application. For example, in laundry detergents there is a built-in pH change that occurs between the wash and rinse cycles. Pepfactants that are designed to respond to that pH change could be added to the detergent to reduce the rinse time, Dexter noted.
During the wash cycle, the pepfactant would be in the “on” position, allowing the detergent to clean soiled clothes. During the rinse cycle when the pH changes, the pepfactant switches “off,” allowing the suds to be removed with much less water than conventional detergents. Similarly, the pepfactants can be used to help separate oil from water and increase the number of barrels of oil that can be extracted from a well. “Currently, as little as one-third of the oil present underground is actually extracted from a well,” Dexter said.
Compared to conventional surfactants, which cost about $10 per kilogram (2.2 pounds), biologically synthesized pepfactants are expensive, according to Dexter, about $500 per kilogram. But, she added, “We are trying to bring that down by an order of magnitude.”
Despite the cost, the enormous potential that pepfactants offer has prompted inquiries from industry. There has been some commercial interest from detergent manufacturers, Dexter said, but she feels the more near-term application could be in the personal care area such as a shampoo, conditioner, skin cream or hand wash. There also could be potential applications for eye drops, she added.
“Chemical surfactants generally are very irritating to biological tissue. We could use our peptide surfactants in that context because they are extremely mild, so they could be used directly as a cleaning application.”
“They also could be used in drug delivery,” Dexter said. “Some companies have products in clinical trials that could deliver antibiotics to the eye, which are not water soluble. They are delivering those as an emulsion. So there’s something we could do with pepfactants, with the additional angle that we could then have that emulsion respond to the pH of the eye so that it would spread across the eye and not be washed away by the tears.”
The potential applications of pepfactants are so broad that it’s difficult to say which application might be the first to reach the market, according to Dexter. There has been some commercial interest, she said, and hopes that something in the personal care area might be available within the next 18 months.
Source: American Chemical Society
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