摘要：

Homeostasis can be achieved by adding a protein supplement; however, an appropriate vector is required to deliver the protein into the cell because of the low stability of proteins in the blood and low cell membrane permeability. Here we report an easy one-step method of encapsulating proteins into liposomes for delivery. We used negatively charged superoxide dismutase (SOD) and a polycation liposome as protein and liposome models, respectively. Liposome-encapsulated SOD was prepared by freeze鈥搕hawing the SOD鈥搇iposome complex (lipoplexes). The amount of immobilized SOD within the lipoplex significantly increased on freeze鈥搕hawing. Surprisingly, subjecting the single-layered lipoplexes to freeze鈥搕hawing produced multilayered liposomes with SOD localized between the lipid layers. The amount of SOD delivered intracellularly significantly increased by freeze鈥搕hawing compared with that delivered by lipoplexes without freeze鈥搕hawing. SOD, liposomes, and endosomes were separately localized in the cells. The freeze鈥搕hawed lipoplex-encapsulated SOD samples were intravenously injected in mice. The SOD biodistribution was dramatically changed compared with the injection of free SOD or lipoplex. SOD was detached from the lipoplex in the bloodstream after the injection of non-freeze鈥搕hawed lipoplex, whereas the encapsulation of SOD in the liposomes upon freeze鈥搕hawing enabled the stable circulation of SOD with the liposomes in the bloodstream. This work paves the way for the application of the freeze鈥搕hawing technology for the easy one-step encapsulation of proteins into liposomes for protein delivery.

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