Salt/pH dual-responsive supramolecular brush copolymer micelles with molecular recognition of nucleobases for drug delivery

Abstract

A new type of salt/pH dual-responsive micelles based on supramolecular amphiphilic brush copolymers, poly(2-hydroxyethyl metharylate)-g-(poly(ε-caprolactone)-adenine:uracil-poly(ethylene glycol)) (PHEMA-g-(PCL-A:U-PEG)) was developed for the anticancer drug delivery owing to the fact that the tumor tissues show low pH and high salt concentration. The supramolecular structure of brush copolymer was confirmed by variable-temperature ¹H NMR and Fourier transform infrared spectroscopy (FTIR). Doxorubicin (DOX) as a model anticancer drug was efficiently loaded into the supramolecular micelles (up to 70%) due to the compact structure of brush polymer. The cumulative release profile of the DOX-loaded micelles showed a low level of drug release (about 20 wt% in 25 h) at pH 7.4 with a low salt concentration, and was significantly accelerated at a lower pH (5.0) and a high salt concentration (over 70 wt% in 6 h), exhibiting an salt/pH dual-responsive controlled drug release capability. Methyl tetrazolium (MTT) assay showed that DOX-loaded micelles had high anticancer efficacy against Hela cancer cells and blank micelles had a very low cytotoxicity. These supramolecular brush copolymer micelles possess many favorable traits, such as low cytotoxicity and excellent biodegradability, adequate drug loading capacity, and rapid drug release in response to the intracellular level of pH and salt concentration, which endow them as a promise candidate for delivering anticancer drugs.