Researchers have created a topical antibiotic gel which they say cured middle ear infection within 24 hours of being applied once in the ears of chinchilla rodents.
The scientists encapsulated the antibiotic ciprofloxacin within liposomes which interacted with the cell structure of the tympanic membrane (eardrum) to facilitate uptake of the drug,
They said these infections occurred behind the eardrum, a structure that was impervious to most drugs, but the liposomes were better able to deliver the drug across infected intact eardrums.
The scientists from Cornell University’s School of Chemical and Biomedical Engineering in the US reported findings in ACS Nano on 28 March 2025.
“I often receive emails from parents asking when our formulation will be available, and I share their hope for a solution,” said Assistant Professor Rong Yang, one of the research team leaders.
“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.”
A/Prof Yang said oral antibiotics, which were often prescribed to treat the condition in humans, could trigger side-effects that disrupted treatment, lead to infection recurrence and antibiotic resistance.
Applying an antibiotic directly to the infected area rather than taking it orally could reduce side effects such as candida and upset stomach, she said.
The scientists said liposomes had been used for delivery of other drugs because they interacted with the cell structure of membranes and skin to facilitate uptake.
While positively charged liposomes were widely considered better than negatively charged ones at transporting drugs across multilayered tissues such as skin, their study found that negatively charged liposomes were better able to deliver drugs across infected eardrums.
Using mouse cells, they found this was because of the uptake of the liposomes by immune cells responding to the infection.
The team encapsulated ciprofloxacin in negatively charged liposomes and added them to a temperature-sensitive hydrogel to form an antibiotic salve.
They then conducted experiments with chinchillas because the animal’s ears are similar to human ears in response to middle ear infections and treatment.
They applied one of three formulations to the eardrums of infected chinchillas: ciprofloxacin in negatively charged liposomes in gel, ciprofloxacin in positively charged liposomes in gel, or ciprofloxacin in gel.
Salve solidified for sustained release
After the gel solidified for sustained release, the antibiotic moved across the eardrum from the outer ear to the middle ear, they said.
They found all infected chinchillas receiving gel containing ciprofloxacin encapsulated in negatively charged liposomes were infection-free within 24 hours. These animals showed no eardrum inflammation or recurrence of infection during seven days of treatment.
“Our results indicate that negatively charged liposomes outperformed positively charged ones, successfully eradicating 100% of AOM cases,” they wrote.
“We attributed this to interactions between the negatively charged liposomes and the immune response to infection. Specifically, the complement activation, which triggers neutrophils’ phagocytosis, is enhanced in response to the negatively charged liposomes.”
In comparison, after seven days, only a portion of the animals receiving gel formulations with either free antibiotic (25%) or antibiotic encapsulated in positively charged liposomes (50%) were cleared of infection, and their eardrum inflammation was similar to that of untreated animals.
The researchers suggested that a single dose of treatment for middle ear infections could improve patient compliance and potentially reduce paediatric antibiotic usage, thereby improving patient care.
“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,” A/Prof Yang said.
The National Institute on Deafness and Other Communication Disorders, part of the National Institutes of Health, and the Hartwell Foundation funded the research.
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