The antibiotic gentamicin can be encapsulated into liposomes, allowing for more accurate use in situations such as wound treatment, according to new research presented at the recent Letters in Applied Microbiology ECS Research Symposium.

lipsomes

Liposomes containing gentamicin can be produced with the use of three different types of phospholipids offering high encapsulation efficiency, low polydispersity and adequate size for targeted use, said Vikas Nariapara from the University of the West of England.

“Wound recovery is often impeded by infections, requiring the use of antibiotics. However, due to antimicrobial resistance and a lack of new antibiotics, the supply of suitable antibiotics is dwindling,” he told The Microbiologist.

“An alternative to producing new antibiotics could be to reconsider how we administer them to improve their effectiveness. The aim of this project was to identify if gentamicin could be encapsulated within a suitable phospholipid to produce liposomes that could be implemented for targeted wound delivery.”

Liposome self-assembly

The UWE team encapsulated gentamicin sulphate in three different types of phospholipid (DMPC, DSPS & DPPC), using a novel liposome production method known as microfluidics. Utilising liposome self-assembly, one aqueous solution containing gentamicin sulphate and another ethanol solution containing the phospholipid with cholesterol was passed through a microfluidics chip. 

Following production, the quantity of the drug successfully enclosed within the liposomes known as encapsulation efficiency (EE) was identified. This was done by centrifuging the liposomes and quantifying the concentration of gentamicin sulphate remaining in the supernatant via spectrophotometry. 

Finally, the physiochemical characteristics of the liposomes were identified. Size and polydispersity (PdI) were measured using dynamic lighting scattering and zeta potential by measuring the velocity of the liposomes in applied electric fields. 

Well dispersed

“The resulting liposomes had an average EE of 97%, suggesting the majority of the drug was encapsulated. The size of all three phospholipid liposomes remained in the 50-200nm range desired for drug delivery allowing for potential targeting. The PdI remained below 0.3 for all liposomes, indicating liposomes are homogeneous and well dispersed,” Mr Nariapara said.

The team were surprised by just how high the encapsulation efficiency (EE) was - while current methods achieve EEs of around 70%, their method produced an EE averaging 97%.

“This means gentamicin can successfully be encapsulated into liposomes for targeted therapies, allowing for more accurate use in situations such as wound treatment,” Mr Nariapara said.

Better efficacy

“In addition, liposomal forms of antibiotics have been found to have greater efficacy. Therefore lower concentrations of antibiotics are needed for minimum inhibitory and bactericidal effect. 

“Encapsulated antibiotics are also better tolerated by the body, reducing nephrotoxicity and allowing greater maximum tolerated doses.”

He added that he would like to see more phospholipids used for encapsulation, with varying flow rate ratios of the solutions being passed through the microfluidics chip. 

“More antibiotics need to be encapsulated, especially those that have increasing rates of resistance or poorly tolerated ones with high effectiveness,” he said.

Dr Alexandros Stratakos led the study, and Mr Nariapara was supported by PhD student  Miss Jessica Ghodke whose assistance kept the project moving swiftly. “I was also motivated by a fantastic research group that creates a pleasant laboratory environment,” he said.

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