The Preparation And Application Of Multi-Responsive Hydrogel With Multiple Shape Memory

Hydrogel is a type of three-dimensional polymer,which could absorb a lot of water and has good biocompatibility.Shape memory hydrogels?SMPs?have the capability to fix temporary shapes and recover to original shapes under external stimuli,such as light,temperature,magnetism,pH and so on.However,the current shape memory hydrogels have limited stimulus response or limited number of temporary shape.In order to broaden the list of SMPs and expand the applications,we have prepared a hydrogel?SA-SH/PVA?with multi-responsive and quadruple shape memory.Rhodamine B was chosen as a model drug to study the behaviour of drug release of SA-SH/PVA hydrogel.The main contents of this paper are as follows:?1?Firstly,SA-SH was prepared by grafting cysteamine onto sodium alginate in the presence of DMTMM.The ¹H NMR spectrum and FTIR spectroscopy indicated that cysteamine was successfully grafted onto alginate.The developed SA-SH/PVA hydrogel was simply prepared by mixing cysteamine grafted alginate?SA-SH?and poly?vinyl alcohol??PVA?and then treated with freezing/thawing.The equilibrium water content?EWC?of SA-SH/PVA hydrogel was decreased with the increasing of freezing/thawing treatment time.?2?The dynamic interaction between alginate and Ca²⁺imparts hydrogel with Ca²⁺-responsive shape memory behaviour.The temporary shape of SA-SH/PVA hydrogel fixed by Ca²⁺could recover to original shape by immersing in EDTA.2Na or Na₂CO₃ solution respectively.The thiol-disulfide interchange reaction imparts hydrogel with redox-induced shape memory behaviour.The results of rheological test and SEM indicated the increase of crosslinking density of hydrogel by immersing in H₂O₂ solution.The SA-SH/PVA hydrogel also exhibited excellent shape memory behaviour triggered by heat.By combining two physical interactions of metal complexation and dynamic thiol-disulfide reaction,triple shape memory effect could be achieved in athermal condition.Moreover,using Ca²⁺,redox-,thermal as stimuli subsequently,SA-SH/PVA hydrogel could show programmed quadruple-shape memory behaviour.The results of SEM indicated the increase of crosslinking density of hydrogel during the programmed shape memory process and the decrease of crosslinking density during the programmed shape recovery process.?3?Rhodamine B was chosen as a model drug to study the behaviour of drug release from SA-SH/PVA hydrogel.Using the heat,reductant,complexing agent as stimuli subsequently to reduce the crosslinking density of hydrogel to release rhodamine B,and the release of rhodamine B was 4.66%,4.09%,9.67%,respectively.In order to exclude the diffusion effect of rhodamine B in solution,we set distilled water as control group,and the release of rhodamine B in control group was 1.67%,3.52%,9.48%,respectively.We also studied the swelling and drug release behaviour of SA-SH/PVA hydrogel in different pH solution.In pH=7.4 PBS buffer solution,the swelling ratio of hydrogel was 772%and the accumulative release of rhodamine B was 67.83%,both of which were higher than those in pH=1.2 HCl buffer solution.