A new study calls into question spider silk's medicinal properties. Photo courtesy of Simon Fruergaard
Oct. 5 (UPI) -- The supposed healing properties of spider silk may have no basis in science, according to the authors of a study published Tuesday by iScience.
Earlier studies showing that extracts of spider silk, when applied to surgical sutures on skin, for example, can help protect against infection may have been compromised, the said.
In their analysis of silk from seven different spider species, the researchers said there was no evidence of antimicrobial activity, or the ability to prevent bacteria or fungi from causing infections.
Although this does not rule out that some spider silk, from species not included in the study, may have medicinal properties, it casts doubt on previous reports, they said.
"We were unable to detect antimicrobial activity of social spider silk, regardless of method or microbe, and this made us curious about why other studies were able to," co-author Trine Bilde said in a press release.
"We then started scrutinizing the papers reporting antimicrobial activity in fine detail and became aware of methodological shortcomings," said Bilde, a professor of biology at Aarhus University in Denmark.
Since the age of the Roman empire, spider silk has been used as a remedy to treat everything from skin lesions to warts, according to researchers at Utah State University.
Historically, doctors covered open wounds in cobwebs or advised patients to place cocoons on infected teeth, and synthetic forms of the material may also have technological applications.
Spiders use their silk to protect their eggs, which offer high nutritional content to microbes, Bilde and her colleagues said.
However, instead of warding off microbial threats with intrinsic antimicrobial activity, the silk casing around the eggs might function only as a physical barrier, she said.
"Spider silk has always been admired and almost has a mythical status," Bilde said.
However, "it's one of these myths that seems to have become 'established' by 'belief' and not by strong empirical support," she said.
In addition to testing the silk from seven spider species themselves, Bilde and her colleagues reviewed data from 15 previous studies designed to assess the antimicrobial activity of the material.
Three of the included studies found no evidence of antimicrobial activity in spider silk, and those that did failed to account for the risk for bacterial contamination of their samples, the researchers said.
Some of the studies may have inadvertently measured the effect of solvents such as acetone or ethyl acetate used to extract the spider silk instead of the spider silk itself, they suggested.
"Rather than assuming that spider silk is antimicrobial, we should now assume that it isn't," Bilde said.
"We can still test the idea in new species and with new organisms, but with a more cautious starting point," she said.