Hydrogen-Bond-Selective Phase Transfer of Nanoparticles across Liquid/Gel Interfaces

摘要

An important defense mechanism for organisms are the various interfaces between fluids and cellular layers, which act as biological barriers to prevent foreign substances from reaching targets in a larger mass fraction. However, this mechanism also suppresses the efficiency of targeting and imaging in vivo. Despite extensive studies of biomedical use, the use of colloidal nanoparticles (NPs) for crossing biological barriers has been little addressed. Mimicking the interfacial transport of molecules with NPs should offer new insights into imaging translocation pathways within extrava-scular spaces and delivering drugs across biological barriers. Thermodynarnically, colloidal NPs prefer to attach to inter-faces, but they will not cross an interface readily because their surface wettability is not easy to change and they have the solvation energies much higher than small molecules. Procedures to transfer hydrophobic NPs from the oil phase to the water phase have been reported, namely, phase transfer and ligand exchange with the aid of amphiphilic molecules, but these methods are obviously not practical for crossing biological barriers. We have recently succeeded in transferring NPs from a salt-water phase to an oil phase by relying on the stimuli response of the polymer brushes anchored on them. Once transferred into the oil phase, however, further environmental change drove the NPs to attach to the water/ oil interface but not to cross it. On the other hand, the water/ oil interface is not a proper model for biological barriers composed of different cellular layers. Herein we demonstrate a hydrogen-bond-selective method to direct hydrophobic NPs, coated with a mixture of polylactide (PLA) and poly(ethylene glycol) (PEG) brushes, to transfer from the organic to the aqueous phase during PLA degradation across not only water/oil but also liquid/gel interfaces: that is, the water/organogel and the oil/hydrogel interface.