Background Among nanodrugs, PEGylated nanoliposomes loaded with an active agent are of major importance. In this paper we studied the structures and morphology of PEGylated nanoliposomes before and after remote loading with doxorubicin. Methods High-resolution structures were obtained by solution X-ray scattering combined with our advanced analysis tools. We studied the PEGylated liposomal doxorubicin (PLD) product Doxil®, and its generics, where remote doxorubicin loading is performed by a gradient of ammonium sulfate, and LC100, a novel PLD under development, where remote loading was done by a gradient of ammonium methanesulfonate. The PLD structures were compared with drug-free nanoliposomes having identical composition. Results We determined the membrane electron density profiles of the empty and loaded PLDs, the thickness and density of the PEG layers, and the structure of the drug inside the liposomes. Conclusions The liposomal membranes had the same structure for both ammonium salts. We found that the drug formed crystals inside PLDs loaded by ammonium sulfate, whereas it had an amorphous morphology in the PLD loaded by ammonium methanesulfonate. The variations of the drug's structural parameters between the generics of Doxil® are similar to the variations between batches of the same product, suggesting that all these products were structurally similar. General significance This paper demonstrates that solution X-ray scattering, when combined with our powerful analysis tools, can determine the high-resolution structure of complex non-crystallized nanoparticle dispersions used in nanomedicine, thereby providing useful physical insights into their functions.
Bibliographical noteFunding Information:
We are grateful to Einav Raviv for creating the illustration in Fig. 8 . Financial support from the Israel Science Foundation (grant 1372/13 ), US–Israel Binational Science Foundation (grant 2009271 ), and the FTA-Hybrid Nanomaterials program of the Planning and Budgeting Committee of the Israel Council of Higher Education , and the Barenholz Research Fund is acknowledged. The Barenholz Research Fund was established by Professor Barenholz from royalties obtained from various Barenholz licensed patents. These funds are dedicated to support research in the Barenholz Lab). Y.S. thanks the Israel Ministry of Science for a fellowship. We thank the Rudin, Wolfson, and Safra foundations for supporting our laboratory.
© 2015 Published by Elsevier B.V.
- Drug delivery
- Generic drugs
- Liposomal doxorubicin
- PEGylated liposomes