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Imaging the cytosolic drug delivery mechanism of HDL-like nanoparticles.

Qiaoya Lin (1,2,3), Juan Chen (3), Kenneth K. Ng (3,4), Weiguo Cao (3,5), Zhihong Zhang (1,3)
Gang Zheng (2,3,4,6).

Pharm Res. 2014 Jun;31(6):1438-49.

1. Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics Huazhong University of Science & Technology, Wuhan, 430074, China.
2. Department of Medical Biophysics, University of Toronto, Toronto, Canada.
3. Ontario Cancer Institute Campbell Family Cancer Research Institute and Techna Institute UHN, Toronto, Canada.
4. Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada.
5. Department of Chemistry, Shanghai University, Shanghai, China.
6. University of Toronto, TMDT 5-363, 101 College Street, Toronto, Ontario, M5G 1L7, Canada.




Molecular therapeutics often require an effective nanoparticle-based delivery strategy to transport them to cytosolic organelles to be functional. Recently, a cytosolic delivery strategy based on the scavenger receptor class B type I (SR-BI) mediated pathway has shown great potential for the effective delivery of theranostics agents into the cytoplasm of cells without detrimental endosomal entrapment. This study elucidates this unique delivery mechanism for improving cytosolic drug delivery.


Multifluorophore-labeled HDL-mimicking peptide phospholipid scaffold (HPPS) nanoparticles were developed. Fluorescence imaging was utilized to examine HPPS transporting payloads into cells step by step through sequential inhibition studies.


HPPS specifically recognizes and binds to SR-BI, then interacts with SR-BI, which results in direct transport of payload molecules into the cell cytoplasm without entire particles internalization. The cytosolic transport of payloads occurred through a temperature- and energy-independent pathway, and was also different from actin- and clathrin-mediated endocytosis. Furthermore, this transport was significantly inhibited by disruption of lipid rafts using filipin or methyl-{Beta}-cyclodextrin.


The cytosolic delivery of payloads by HPPS via SR-BI targeting is predominately mediated through a lipid rafts/caveolae-like pathway. This cytosolic delivery strategy can be utilized for transporting molecular therapeutics that require their action sites to be within cytosolic organelles to enhance therapeutic effect.

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