Multifunctional liposomes for multi-modality near-infrared fluorescent, MR, and nuclear imaging of drug delivery and disease treatment

Objectives Multi-modality imaging can integrate distinct information provided by each modality and have synergistic advantages over any single modality imaging in diagnosis, monitoring of disease treatment, and evaluation of drug in vivo behaviors. Herein, we report the development and characterization of a multifunctional lipid nanoparticle (liposome) drug delivery system that can be non-invasively monitored for their in vivo behavior with multi-modality near-infrared (NIR) fluorescent, MR, and SPECT or PET imaging.

Methods DSPE lipid-conjugated functional compounds, DOTA-DSPE, Gd(III)DOTA-DSPE, and IRDye-DSPE were synthesized in house. Liposomes, composed of Gd(III)DOTA-DSPE/DOTA-DSPE/DSPC/Cholesterol and having ammonium sulfate/pH gradient, were prepared by lipid film hydration and extrusion. IRDye-DSPE was then incorporated into liposomes by post-insertion method. The prepared liposomes were labeled with ^99mTc or ⁶⁴Cu for SPECT or PET imaging, respectively. The obtained multifunctional liposomes were intratumorally injected into squamous cell carcinoma of head and neck tumor xenografts in nude rats. Their in vivo distributions were obtained with the use of NIR fluorescent, MR, SPECT and PET imaging.

Results The synthesized products were confirmed by mass spectroscopy. The prepared 100-nm liposomes could be effectively labeled with ^99mTc or ⁶⁴Cu and showed high in vitro stability. Both the nuclear and in vivo NIR fluorescent images clearly showed the retention and distribution of liposomes inside the tumor. MR imaging obtained 3-D high resolution micro-intratumoral distribution of the liposomes.

Conclusions Liposomes containing IRDye-DSPE, Gd(III)DOTA-DSPE, DOTA-DSPE and having ammonium sulfate/pH gradient with radiolabeling are promising as drug carriers allowing non-invasive multi-modality imaging of their in vivo behavior with NIR fluorescence, MRI, SPECT and PET