Biodegradable Chimaeric Polymersomes Mediate Highly Efficient Delivery Of Exogenous Proteins Into Cells

In this thesis, poly(ethylene glycol)-b-poly(ε-caprolactone)-b-poly(2-(diethylamino)ethyl methacrylate) (PEG-PCL-PDEA) triblock copolymers were facilely synthesized via RAFT Polymerization using PEG-PCL-CPANDN as macroRAFT agent and AIBN as radical source. These tri-block copolymers have predetermined molocular weight and narrow distribution. For these tri-block copolymers, the moleculear weight of PEG, PCL and PDEA blocks are 5000 Da,18200 Da and 1100~4100 Da, respectively. Using film hydration method, polymersomes with a size of 60-150 nm and PDI of 0.1-0.2 were readily prepared via the self assembly processs in aqueous solution. The polymersome structure was confirmed by using TEM and CLSM technique. Especially, via 2D 1H NOESY NMR and zeta potential measurements, we can draw the conclusion that the polymersomes formed have an asymmetric membrane, with PDEA preferably located in the inner side of the polymersome membrane and PEG on the otter side of the polymersome membrane. MTT assay showed that these polymersomes were nontoxic in the concentration range of this study (<0.5 mg/mL). Remarkably, these asymmetric polymersomes could load proteins (including BSA, cytochrome C, lysozyme, ovalbumin and IgG) with very high loading efficiency (up to 100%) and high loading content (up to 56 wt. %). The loaded proteins can be released under a controlled manner, and cytochrome C released from the polymersomes maintained its bioactivity. Most importantly, these protein loaded polymersomes could escape from the endosome after endocytosis, and release the proteins into the cytosol. Furthermore, hydrophobic anticancer drug doxorubicin can be loaded into the same polymersome membrane, and was delivered into cells.Thus, these multifunctional chimaeric polymersomes are exceptional in that (1) longer PEG block (Mn = 5 kDa) oriented at the polymersome outlayer may offer excellent biocompatibility and stability in the circulation; (2) shorter cationic PDEA block (Mn = 1.1, 2.7 and 4.1 kDa, respectively) located inside the polymersomes on one hand facilitates efficient encapsulation and stabilization of proteins and on the other hand may assist polymersomes escaping from endosomes via"proton sponge effect", resulting in efficient cytoplasmic delivery of proteins; (3) protein loading is straightforward and free of organic solvents; (4) PCL block conveys good biodegradability; and (5) these polymersomes capable of simultaneously delivering proteins and hydrophobic anticancer drugs such as doxorubicin for combined therapy of cancer .