Radionuclide imaging of liposomal drug delivery.

INTRODUCTION: Ever since their discovery, liposomes have been radiolabeled to monitor their fate in vivo. Despite extensive preclinical studies, only a limited number of radiolabeled liposomal formulations have been examined in patients. Since they can play a crucial role in patient management, it is of importance to enable translation of radiolabeled liposomes into the clinic. AREAS COVERED: Liposomes have demonstrated substantial advantages as drug delivery systems and can be efficiently radiolabeled. Potentially, radiolabeled drug-loaded liposomes form an elegant theranostic system, which can be tracked in vivo using single-photon emission computed tomography (SPECT) or positron emission tomography (PET) imaging. In this review, we discuss important aspects of liposomal research with a focus on the use of radiolabeled liposomes and their potential role in drug delivery and monitoring therapeutic effects. EXPERT OPINION: Radiolabeled drug-loaded liposomes have been poorly investigated in patients and no radiolabeled liposomes have been approved for use in clinical practice. Evaluation of the risks, pharmacokinetics, pharmacodynamics and toxicity is necessary to meet pharmaceutical and commercial requirements. It remains to be demonstrated whether the results found in animal studies translate to humans before radiolabeled liposomes can be implemented into clinical practice.