Evaluation of 18F-labeled targeted perfluorocarbon-filled albumin microbubbles as a probe for microUS and microPET in tumor-bearing mice

Objective: In this study, albumin-shelled, targeted MBs (tMBs) were first demonstrated with the expectation of visualization of biodistribution of albumin-shelled tMBs. The actual biodistribution of albumin-shelled tMBs is of vital importance either for molecular imaging or for drug delivery.

Motivation: Recently, albumin microbubbles (MBs) have been studied for drug and gene delivery in vitro and in vivo through cavitation. Targeted lipid-shelled MBs have been applied for ultrasound molecular imaging and conjugated with radiolabeled Antibodies for whole-body biodistribution evaluations. The novelty of the work is that, in addition to the lipid tMBs, the albumin tMBs was also applied in biodistribution detection.

Methods: Multimodality albumin-shelled, (18)F-SFB-labeled VEGFR2/KDR/Flk-1 tMBs were synthesized, and their characteristics in mice bearing MDA-MB-231 human breast Cancer were investigated with micro-positron-emission tomography (microPET) and high-frequency ultrasound (microUS).

Results: Albumin-shelled MBs can be labeled with (18)F-SFB directly and conjugated with Antibodies for dual molecular imaging. The albumin-shelled tMBs show a lifetime in 30min in the blood pool and a highly specific adherence to tumor vessels in mice bearing human breast Cancer.

Conclusions: From the evaluations of whole-body biodistribution, the potential of the dual molecular imaging probe for drug or gene delivery in animal experiments with albumin shelled MBs has been investigated.