Study Of Halloysite Supramolecular Gels And Halloysite Hybrid Materials On Promoting Osteogenic Differentiation

Halloysite nanotubes(HNTs)are aluminosilicates,which are a kind of natural one-dimensional nanomaterial with a hollow tubular nanostructure.Their unique nanostructure and surface properties can expand their applications in many aspects.In this paper,St@HNT supramolecular gel composed of HNTs and styrene(St)was prepared by electron transfer reaction between HNTs and conjugated molecules.Nano hydroxyapatite with biocompatibility and osteogenic activity was loaded on the surface of HNTs by hydrothermal reaction.The application potentiality of modified HNTs and its chitosan composite in tissue engineering scaffolds was studied.Specifically:(1)Under the action of ultrasound,St@HNT supramolecular gel could be formed by HNTs and St at a certain mass ratio.The agglomerated HNTs were uniformly dispersed in St under ultrasonic treatment.Then,electron transfer reactions occured between HNTs and St.The appearance of St@HNT gel(mass ratio St: HNTs = 100: 20)was light yellow and had a certain light transmittance.The polarized light microscope results of the gel and the microstructure of the dry gel showed that HNTs in the gel were distributed in clusters.The spaces between the HNT clusters were where St was in the gel.Ultrasound was the driving force for HNTs dispersing in St.At the same ultrasonic power,the ultrasonic time determined the dispersion level of HNT in St.There was no chemical reaction between HNTs and St.The results of electron paramagnetic resonance proved that free radicals existed in the mixing process of HNTs and St,which indicated that there was electron transfer reactions between HNTs and St.HNTs played a role as electron acceptors,while St played a role as electron donors.The electrons on St were transferred to the aluminum atoms and iron ions of HNTs through the crystal edges of HNTs.The formed St cation radicals or polycations carried a positive charge,which could interact strongly with HNTs that had a negative charge on its surface.Under this effect,enough St was adsorbed on the HNT clusters.The HNT clusters that had adsorbed a St liquid layer accumulate under the action of gravity,forming St@HNT supramolecular gel.(2)Hydroxyapatite(HAP)was synthesized outside HNTs by hydrothermal method.HAP@HNT hybrid materials with different proportions were prepared.HAPnanoparticles prepared by hydrothermal had obvious crystal structure,and the crystal of HNTs had no change during the hydrothermal process.In the microstructure of hybrid materials,HAP nanoparticles were mainly distributed outside the tubes of halloysite.When the proportion of HAP nanoparticles in the hybrid material was large,excess HAP would cause the specific surface area of HAP@HNT hybrid material to decrease,and its corresponding pore volume and adsorption performance would also decrease.The particle size distribution of HAP@HNTs was between that of HAP and HNTs.HNTs reduced the agglomeration of HAP.Using mouse skull osteoblasts(MC3T3-E1)as a cell model,HAP@HNTs successfully promoted MC3T3-E1 cell proliferation and differentiation.HAP@HNTs showed good biocompatibility and osteogenic induction of the cells.Therefore,HAP@HNTs was able to be used to construct bone tissue engineering scaffolds in bone tissue engineering.(3)Hybrid materials HAP@HNTs and chitosan(CS)were prepared into CS/HAP@HNT composite films by solution casting method.Microscopically,HAP@HNT particles could be uniformly distributed in the CS matrix,and some particles of hybrid materials were exposed on the surface of the composite film.The electrostatic interaction and hydrogen bonding between HAP@HNTs and CS improved tensile mechanical properties of the composite film.Compared with CS films,the tensile strength and the elastic modulus of composite films were significantly improved.Using MC3T3-E1 cells as the evaluation model,HAP@HNTs improved the cell compatibility of the composite film.In addition,HAP@HNT hybrid materials promoted osteogenic differentiation of MC3T3-E1.HAP@HNT particles not only played a role in promoting osteogenic differentiation,but also enhanced mechanical properties in the composite film.CS and HAP@HNT hybrid materials can be used to prepare new bone tissue scaffold materials.