| In the rapidly developing field of biomaterials, pharmaceutical, biochemistry and polymer science, amphiphilic block copolymers have exhibited various interesting properties such as surface activity, aggregate formation and so on, which have made them as potential candidates in advanced materials formation and engineering applications.A novel type of amphiphilic tri-block copolymers with both pH and temperature sensitiveness:poly (ethylene glycol)-poly (dimethylamino ethyl methacrylate)-poly (ε-caprolactone)(PEG-PDMA-PCL) was synthesized via sequential oxyanionic polymerization of macromolecules. The structures of the polymers were confirmed by using1H-NMR spectroscopy and gel permeation chromatography (GPC). The self-assembly behavior of the tri-block copolymers in aqueous solution was studied with laser light scattering (LLS) and transmission electron microscopy (TEM). By comparing with di-block copolymer PDMA-PCL, we found the tri-block copolymer could keep the first-order aggregation in the aqueous solution during the changing of pH and temperature. Moreover, based on the NMR and LLS measurements at different temperatures, the results showed the micelles formed by the tri-block copolymer PEG-PDMA-PCL changed both core and shell sizes at different temperatures, which made them the potential candidates as structure templates and drug carrier.The anti-cancer drug of doxorubicin (DOX) was chosen as a model drug to investigate the potential application of this triblock copolymer in drug controlled release. The results indicated the important roles of the PCL block for drug loading, the PDMA block for pH-responsive release, and PEG block for good bio-affinity. Cell cytotoxicity tests showed that the DOX-loaded PEG-PDMA-PCL micelles were pharmaceutically active to suppress the growth of SKOV-3cells. This novel stimuli-responsive block copolymer is an attractive candidate as the "smart" pH-responsive carrier for intracellular delivery of hydrophobic drugs. |
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