Background
Therapeutic interventions for infectious and inflammatory diseases are becoming increasingly challenging in terms of therapeutic resistance and side-effects. Theranostic systems to ameliorate diagnosis and therapy are therefore highly warranted. The pathophysiological changes in inflammatory lesions provide an attractive basis for extravasation and accumulation of PEGylated liposomes. The objective of this study was to provide direct quantitative information on the theranostic potential of radiolabeled liposome for accumulation in inflammatory models using position emission tomography (PET).

Method
Preclinical murine models of inflammation (turpentine and LPS), infection (Staphylococcus aureus) and collagen-induced arthritis (CIA) was established and monitored using bioluminescence imaging (BLI). Across all models PET imaging using radiolabeled PEGylated liposomes (64Cu-liposomes) were performed and evaluated in terms of accumulation properties in inflammatory and infectious lesions.

Results
BLI demonstrated that the inflammatory and infectious models were successfully established and provided information on lesion pathology. Activity of 64Cu-liposomes were increased in inflammatory and infectious lesions between early (10-minute or 3-hour) and late (24-hour) PET scans, which validates that a continuous extravasation and accumulation of long circulation PEGylated liposomes occurs.

Conclusion
The theranostic potential of long circulating PEGylated radiolabeled liposomes was shown in multiple preclinical models. Impressive accumulation was seen in both inflammatory and infectious lesions. These results are encouraging towards advancing PEGylated liposomes as imaging and drug delivery systems in inflammatory and infectious diseases.