| The shape memory polymer(SMP)is a new kind of functional polymer material.Compared with other shape memory materials,such as alloy,polymer hydrogel can respond with a larger response to a variety of stimuli,such as heat,light,electricity and solvents.Polyvinyl alcohol(PVA)hydrogel has good stability,easy processing,no irritation and good biocompatibility,and has been widely used in the biomedical field.Hydroxyapatite(HA)is a kind of calcium phosphate bioceramics,which is similar to the chemical composition and crystal structure of the natural bone.HA has good bioactivity and biocompatibility.Reduced graphene oxide(RGO)has excellent mechanical properties,high aspect ratio,no cytotoxicity and oxygen-containing functional groups.RGO can be used as reinforcement to improve the mechanical strength of the matrix.However,the low tensile strength,elastic modulus and elongation at break of PVA hydrogel are too poor,which limits its application in biomedical field.Thus,HA and RGO were added to the PVA matrix,which not only improved the mechanical strength of the composite material,but also made it have good biocompatibility.The application of PVA is broaden,not only in biomedical field.In this paper,the RGO/HA/PVA hydrogels was prepared successfully by in-situ growth method with adding HA and RGO into the PVA matrix.The structure and mechanical properties of RGO/HA/PVA hydrogels were investigated.The results show that the structure of RGO/HA/PVA hydrogels is uniform.The HA particles are uniformly dispersed in the PVA matrix.RGO/HA/PVA hydrogels have good thermal stability.Compared with pure PVA,the tensile strength of RGO/HA/PVA hydrogels increases by three times,and the elongation at break increases by about seven times.For results of shape memory test,RGO/HA/PVA hydrogels have good shape memory properties under the solvent(water and phosphate buffer solution)-thermally stimulus conditions,especially in the water at 70℃,the following is in PBS at 37℃ which is body temperature.The final deformation recovery rate of all hydrogels can reach 100%.However,the shape recovery of RGO/HA/PVA hydrogels was poor under the condition of thermal stimulation,and its recovery rate is only 82%.The effect of RGO addition on the structure,properties and shape recovery of RGO/HA/PVA hydrogels are also studied.Three kinds of RGO/HA/PVA composite hydrogels with different RGO content are prepared.The results show that the content of RGO do not affect the homogeneity of RGO/HA/PVA hydrogels.And the increase of RGO content could improve the thermal stability of RGO/HA/PVA hydrogels.When the content of RGO is 6.67wt%,the tensile strength and elongation at break of RGO/HA/PVA hydrogel are 0.18Mpa and 254%,respectively.For the shape memory test results,RGO/HA/PVA hydrogels with the different RGO content have good recovery effect under the solvent(water and PBS)-thermally stimulus conditions,and the final deformation recovery rate can reach 100%.When the RGO content is 6.67wt%,RGO/HA/PVA hydrogels have better shape memory properties.For different stimulus conditions,according to the shape memory effect of RGO/HA/PVA hydrogels to sort from high to low,The following is water at 70℃,PBS at 37℃,PBS at 70℃,water at 37℃ thermal.The addition of RGO is not conducive to the shape recovery of RGO/HA/PVA hydrogel induced by thermal.The cytocompatibility of HA/PVA and RGO/HA/PVA hydrogels was studied by co-culture with MC3T3-E1 cells in vitro,and the effects of different RGO contents on the RGO/HA/PVA hydrogels are investigated.The results show that the addition of HA and RGO could improve the cell compatibility of RGO/HA/PVA hydrogels and promote cell proliferation.The cell proliferation of RGO/HA/PVA hydrogels is better with the increase of RGO content.When RGO content is 6.67wt%,cell proliferation of RGO/HA/PVA hydrogels is the best.RGO/HA/PVA hydrogel is not conducive to cell activity,but the adverse effect decreases with the increase of RGO content,indicating that RGO is non-toxic. |
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