Synthesis of an amphiphilic hyperbranched polymer as a novel pH-sensitive drug carrier

An amphiphilic hyperbranched polymer containing large amounts of pH sensitive bonds was synthesized by our group. The hydrophobic chains are hyperbranched polyacetals (HBPAs) and the hydrophilic chains are polyethylene glycols. Polyethylene glycols are attached to the hyperbranched polyacetals by the hydrazone bonds. The amphiphilic hyperbranched polymer could be assembled into micelles easily by the dialysis method. The micelles containing large amounts of pH sensitive bonds were quite fragile in pH 5.0 buffer solution but very stable in pH 7.4 buffer solution. DOX-loaded micelles were also prepared by the dialysis method. The sizes of the blanked micelle and DOX-loaded micelle were 30 nm and 35 nm, respectively. The increase of the diameter confirmed that DOX was successfully loaded into the micelle. Drug loading content and drug loading efficiencies were 2.34% and 23.4%, respectively, which was detected by the UV-VIS at the wavelength of 482 nm. The drug release behavior demonstrated that DOX was released faster in pH 5.0 buffer solution than in pH 7.4 buffer solution.