Supramolecular Crosslinks Enable PIC Micelles With Tuneable Salt Stability And Diverse Properties

Polyion complex micelles(PIC micelles)is a soft matter material formed by electrostatic self-assembly of oppositely charged polyions.Due to its unique properties and biocompatibility,PIC micelles are widely used in different fields such as drug delivery,bioimaging and catalysis.In recent years,a series of research progress has been achieved regarding to the controllable preparation,functionalization and application of PIC micelles.However,due to its charge assembly characteristics,the salt stability of PIC micelles is generally low,that is,increasing the salt concentration can screen the charge interaction between polyions,resulting in the decomposition of micelles.Most PIC micelles hardly tolerate physiological salt concentration which strongly limits their applications.In this paper,a new method for improving the salt stability of PIC micelles by constructing molecular cross-link to is established.We synthesized bis-ligands and tri-ligands with pyridinedicarboxyl(DPA)as the coordination group.By controlling different metal and ligand combinations,anionic coordination polymers with controlled crosslinking degree were prepared.Further assembly with polycation-neutral diblock polymer,stable and functional PIC micelles were obtained.The study found that the salt stability of PIC micelles increased linearly with the increase of crosslinking degree of coordination polyions.At the same time,the functional coordination structure endows PIC micelles with different fluorescence and nuclear magnetic relaxation properties,and as well as the regulation of the coordination structure and corresponding properties Therefore,building molecular crosslinks can regulate both the stability and function of micelles.This strategy is suitable for different combinations of metals and ligands,demonstrating a general method to prepare stable and functional PIC micelles,which lays the foundation for the applications of such soft nanocarriers.The research content is as follows:(1)Using a combination of divalent transition metals and trivalent lanthanide metals to build up stable PIC micelles with different core crosslinking degrees.The transition metal has 6 coordination sites,which can coordinate with the bis-ligand L2 to form a linear coordination polymer,and the lanthanide metal has 9 coordination sites,which can form a cross-linked coordination polymer with the L2 ligand.In this study,the doping ratio of the two metals is controlled to control the degree of crosslink of the coordination polymers.The structure,morphology,stability and function of PIC micelles with different crosslinking degrees are studied.(2)Using the combination of bis-ligand L2 and tri-ligand L3 to construct stable PIC micelles with different core crosslinkdegree.The introduction of the tri-ligand L3 allows the micelle core to form crosslinked coordination polyions.In this study,PIC micelles with different core cross-linking degrees were obtained through the doping ratio of multidirectional ligands L2 and L3.The structure and stability of PIC micelles have been studied by DLS and TEM.(3)The hydrophobicity of the micellar care has been investigated based on a fluorescent probe.And the the functionality of micelles,such as fluorescence properties and nuclear magnetic properties,are tested as well.