Functionalizing liposomes could pave the way to personalised medicine

Liposomes are successful drug delivery vehicles prescribed for several types of cancer but also for treatment of fungal infections or pain management. Now researchers from the Medical University of Vienna show a straightforward method to functionalize liposomes for specific targeting, potentially paving the way for personalised medicine. 

The new study by Dr Anna Ohradanova-Repic and colleagues from the Institute for Hygiene and Applied Immunology, Center for Pathophysiology, Infectiology and Immunology of the Medical University of Vienna in collaboration with the University of Minho, Braga, Portugal, shows not only a smart but also easy way for liposome functionalization.

Researchers linked the small specific fragment of the antibody, called Fab, by gene technology with a hydrophobic anchor. Through this hydrophobic anchor, the Fab fragment got naturally inserted into the hydrophobic liposomal membrane part during liposomal preparation. "It was quite fascinating to see how easy the liposome functionalization was. We tested two different Fab fragments and they both worked very well. We observed specific targeting not only to the antigen-positive cells in the lab dish but also in mice, where our liposomes precisely recognised human tumours that we had implanted.", says Dr Ohradanova-Repic.

Dr Hannes Stockinger, the senior author of the study, adds: "If we coupled this delivery method with screening of patient’s tumours for the presence of a unique surface protein, which we can target with the Fab fragment-functionalized liposomes, we might be able to treat tumours more efficiently and decrease the side effects of the delivered anti-cancer drugs substantially. I foresee this as a personalised medicine of the future. Yet, a lot of work is ahead of us to implement this treatment strategy in clinical practice."

The concept of liposomal drug delivery has revolutionised the pharmaceutical field and came into praxis some 20 years ago when the first liposomal formulation of the anti-cancer drug doxorubicin was approved for clinical use.

Liposomes, <200 nm phospholipid vesicles, are longer retained in blood circulation and accumulate at pathological sites, leading to higher efficacy and lower systemic toxicity compared to the free drugs they encapsulate.

To target liposomes to certain tissues or cells, such as tumour cells, a specific binder of a unique protein (an antigen) on the targeted cell, known as a monoclonal antibody, must be linked to the liposome surface. This coupling is called the functionalization of the liposome and done chemically, often at the final stages of liposome production and can potentially damage the liposome or by targeting antibody.

The study has now been published in Nanomedicine-Nanotechnology, Biology, and Medicine.