Biodistribution of long-circulating PEG-liposomes in a murine model of established subcutaneous abscesses

The biodistribution of long-circulating PEG-liposomes in a subcutaneous mouse model of established mixed infection abscesses was investigated to assess their possible role as drug carriers in the treatment of small, undrainable intra-abdominal abscesses. There was a 10-30-fold greater localisation of ⁶⁷Ga-labelled PEG-liposomes in abscesses compared to uninfected normal skin samples. Over 3% of the injected dose (ID) of liposomes was present in the abscesses 24 h after liposome administration in contrast to 0.1% in normal skin sections. The percentage ID present in the liver, spleen and kidneys was 17%, 4% and 2% per organ respectively. Five days after liposome injection, 2% ID could still be recovered from the abscesses. Using colloidal gold-labelled PEG-liposomes, it was shown that there was a 4-fold greater density of liposome clusters in the subcutaneous tissue surrounding the capsule than in the core of the abscesses. The clusters within the abscesses were distributed evenly. We conclude that PEG-liposomes localise to a significant degree at the infection focus in our mouse model and may provide a new approach to the antimicrobial treatment of intra-abdominal abscesses.