Acid-sensitive charge-reversal co-assembled polyurethane nanomicelles as drug delivery carriers

In order to obtain drug delivery carriers with good stability in blood and high cellular uptake efficiency, carboxyl groups and tertiary amine groups were respectively introduced into polyurethane to synthesize two kinds of amphiphilic polyurethanes with opposite charges (PUC and PUN). Their structures were characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (¹H NMR) spectroscopy and gel permeation chromatography (GPC). PUC-PUN co-assembled nanomicelles were prepared by electrostatic interaction between PUC and PUN micelles, which showed acid-sensitive property. When the pH of the solution was decreased from 7.4 to 6.5, PUC-PUN-1 micelles showed negative-to-positive charge-reversal property among these micelles. The results of stability and cell experiments demonstrated that PUC-PUN-1 micelles not only had excellent stability in simulated normal physiological environment but also could obviously enhance the cellular uptake efficiency. PUC-PUN-1 micelles had low cytotoxicity against SGC-7901 and MGC-803 cells, whereas PUC-PUN-1/DOX micelles had higher cytotoxicity compared to pure DOX and PUN-1/DOX micelles. Moreover, the results of in vivo antitumor activity experiments showed that PUC-PUN-1/DOX micelles had better tumor inhibition ability and safety than pure DOX. In addition, the results of in vitro drug release experiments indicated that PUC-PUN-1/DOX micelles had almost no burst release or leakage of drugs in pH 7.4 environment. However, the drug release was accelerated in pH 5.0, which followed Fickian diffusion mechanism.