Stimuli Responsive PUA/PSS Layer By Layer Assembly Vehicles For Smart Drug Delivery

The pH-/thermal-responsive drug delivery systems made of aliphatic poly(urethane-amine)(PUA) and sodium poly(styrene sulfonate)(PSS) were successfully fabricated via Layer by Layer (LbL) self-assembly technique in the present research. The biocompatible and pH-/thermal-responsive PUA was employed to fabricate the LbL materials at the first time. The multilayer structure not only enriched the method of the construct multilayer systems but also it had a great potential in the smart drug delivery filed.Firstly, the fabrication and characterization of the CaCO3(PSS)-(PUA/PSS)4core shell microparticles prepared by LbL method were conducted. The ζ-potential and FTIR results demonstrated that the electrostatic interaction and hydrogen bonding under weak-acid condition between aliphatic PUA and PSS contribute to the formation of the multilayer polyelectrolytes. Doxorubicin hydrochloride (DOX), a water-soluble anticancer drug was employed as model drug. DOX release behaviors indicate that PUA/PSS multilayers could assuage the initial burst release of the DOX significantly and reduce the release rate effectively. In addition, the DOX releases of the multilayer-coated CaCO3microparticles are pH-/thermal-dual responsive. The release rate of the DOX was higher at pH2.1than that at pH7.4for dissolution of the CaCO3core at acid condition and the release rate was higher at55℃than that at37℃owing to the shrinkage of aliphatic PUA above its LCST. The mechanism of the pH-and thermal-responsive drug release of the hybrid microparticles was analyzed by plotting the cumulative release data versus time by fitting to the following empirical equation:Mt/M∞=Ktn. The results suggested that the release mechanism of the multilayer-coated CaCO3microparticles was Anomalous Diffusion at pH2.1and the release mechanism was Fickian Diffusion at pH7.4.Then the fabrication and the characterization PUA/PSS multilayer hollow capsules prepared via LbL method were conducted. TEM and EDX results demonstrated the successfully preparation of the hollow microcapsules. FESEM results indicated that the obvious variation of the hollow multilayer microcapsules in response to changes in temperature and pH value. At the lower pH, the swelled porous microcapsules were formed owing to the weakness of the interaction between PUA and PSS polyelectrolytes layers caused by the electrostatic repulsion between positive charges of the protonated PUA. The shrunk microcapsules were obtained due to the precipitation and the shrinkage of the PUA chains above its LCST. Besides, the DOX release of the hollow microcapsules is pH-/thermal-dual responsive. DOX release behaviors suggested that the drug release increased upon decreasing of the pH value Moreover, the DOX release was higher at55℃than that at37℃for the sake of the strongly shrinkage of the PUA chains.