Babies and small children are prone to middle ear infections, which typically have to be treated with orally administered antibiotics. A new fast-acting topical gel could soon replace such drugs, however, potentially reducing unpleasant side effects.
One of the challenges with middle ear infections lies in the fact that the infected area is located behind the ear-canal-spanning tympanic membrane (aka the eardrum). This means that medicated ointments can't be applied directly to the area, due to the fact that they can't reach it.
Instead, children have to take the required antibiotics orally. Because those drugs end up getting distributed throughout the body, the dosage has to be relatively high in order for enough of the medication to make its way to the ear. Such high doses not only cause negative side effects such as upset stomachs, they also contribute to the development of antibiotic-resistant bacteria.
Seeking a solution to this problem, Assoc. Prof. Rong Yang and colleagues at Cornell University looked to spherical microscopic structures known as liposomes.
Previous research indicated that when liposomes are positively charged, they're able to pass through skin and similar biological barriers. Therefore, if those liposomes are loaded up with an antibiotic payload, they can essentially "smuggle" that payload through the skin to an otherwise-unreachable target.
In the course of their research, however, the scientists discovered that positively-charged liposomes could not pass through infected eardrum tissue. If those liposomes were negatively charged, however, they were taken up by immune cells in the infected tissue, allowing them to get through.
With this finding in mind, Yang's team encapsulated the antibiotic ciprofloxacin in negatively-charged liposomes. Those liposomes were then added to a temperature-sensitive hydrogel, which was applied to the eardrums of chinchillas with middle ear infections. Chinchillas were chosen because their middle ear structure is similar to that of humans.
In all of the animals treated with that version of the gel, just a single application completely cured the infection within 24 hours.
Such was not the case with a couple of control groups of chinchillas, one of which received a gel containing non-encapsulated ciprofloxacin, and the other of which got a gel in which the antibiotic was encapsulated in positively-charged liposomes. Even after seven days of treatment, just 25% of the animals in the first group were cured, and just 50% in the second group.
"A single-dose treatment for middle ear infections represents a significant step forward toward reducing the burden on families and improving outcomes for young children," says Yang. "I am most excited about the next stage of translating this technology from the lab to the clinic, as it has the potential to improve patient compliance, reduce antibiotic resistance, and ultimately transform how children receive antibiotics."
The research is described in a paper that was recently published in the journal ACS Nano.
Source: American Chemical Society
