Polyelectrolyte Constructed Functional Carriers And Their Applications

Polyelectrolyte is widely existed in biological system and plays an important role in supporting the activities of life.Arising from the understanding on biomaterials,researchers have constructed a series of functional objects from either natural or artificial polyeletrolyte materials for finding attractive applications,including drug delivery and biomimetics.In this work,chitosan-based thermosensitive polymer micelles and pH sensitive hydrogels were designed and prepared as drug carriers for controlling drug release.Moreover,densely grafted poly(acrylic acid)(PAA)brushes were prepared as catalytic substrates to direct the supramolecular self-assembly through accelerating the formation of self-assemblers.Details of these works are described below:1.A thermosensitive amphiphilic copolymer(PHCS-g-PNVCL)was synthesized by grafting thermosensitive polymer PNVCL onto the backbone of phthalic anhydride modified chitosan(PHCS).Based on the nanoprecipitation method,PHCS-g-PNVCL could self-assemble into polymer micelles in aqueous solution with a diameter of 210 nm.Interestingly,transmission electron microscopy characterization indicated that these polymer micelles showed an unexpected pod-like structure.The structure of this pod-like micelle was further revealed by the in situ characterization of polarizing microscope.Furthermore,the drug loading and control release performance of these polymer micelles were explored by using meloxicam(MLX)as a model drug.The results suggested that PHCS-g-PNVCL micelles could effectively load the model drug and control the release rate by adjusting the ambient temperature.2.A macromolecular crosslinker(CSMAH)was obtained by grafting maleic anhydride(MAH)onto the backbone of chitosan.Based on this kind of crosslinker,a series of pH sensitive hydrogels were prepared by initiating the copolymerization of CSMAH with acylic acid(AA)monomers.Rheological mearements indicated that these hydrogels had stable mechanical performance,and the mechanical strength increased effectively with the increase of CSMAH.Scanning electron microscopy characterization showed that these hydrogels were constructed by well-organized three dimensional networks.The subsequent swelling tests demonstrated that these hydrogels presented significant responsive to pH.The controllability of these hydrogels over drug release were investigated using MLX and amoxicillin as model drugs.The in vitro drug release experiments suggested that it was feasible to control the drug release from the hydrogel by controlling pH.A numerical simulation based on Korsemeyer-Peppas and Weibull functions indicated that the drugs were released from the hydrogels undergoing a combined mechanism of drug diffusion and relaxation of hydrogel network.3.Directed formation of supramolecular gel was achieved based on a proton catalyzed supramolecular self-assembly system,in which the formation of gelator molecules can be promoted under the catalysis of proton.It has been demonstrated that densely grafted PAA brush can locally lower the pH at the brush surface.In this context,a series of micropatterned PAA brushes were prepared to direct the supramolecular gel formation through locally accelerating the formation of gelator molecules.The micropatterned PAA brushes were prepred by immobilizing ATRP initiators onto glass surface using microcontact printing following a surface initiated ATRP of AA from the glass surface.From the characterization of confocal laser scanning microscopy,we found that these micropatterned PAA brushes can spatially direct the formation of supramolecular gel through promoting the local formation of gelators.Additionally,the spatial dimensions can be controlled by changing the grafting density of PAA brush.4.In this work,the directed formation of supramolecular gel fibers were extended to nanoscale using nano spherical PAA brushes as catalyst.The spherical PAA brushes were prepared through in situ initiated polymerization of AA monomers from the surface of polystyrene nanoparticles with a diameter of 100 nm.The prepared spherical PAA brush had a hydrodynamic diameter of 340 nm.The results suggested that the gelation process could be effectively accelerated by spherical PAA brush,showing catalysis effect of spherical PAA brush on the gel formation.Cryo-transmission electron microscopy revealed that the self-assembled supramolecular gel fibers were specifically located in the vicinity of the spherical PAA brush due to the local catalysis of PAA brush on the gelators formation.