Preparation And Properties Of Natural Polymer-based Composite Hydrogels

Both sodium alginate?SA?and cellulose are biocompatible and biodegradable,which are widely used in the fields of tissue engineering and pharmaceutical carriers.In this work,SA/cellulose nanocrystals?CNC?and SA/oxidized CNC composite hydrogels were prepared,respectively.The microstructure,morphology,swelling behavior,pH sensitivity,mechanical properties and drug release behavior of SA-based composite hydrogels were characterized by FT-IR,SEM,swelling kinetics,compression experiments,and so on.It can provide experimental data for the development of new drug carrier materials.Firstly,the influences of crystal form of CNC and initial state of hydrogels on the properties of SA composite hydrogel were investigated.FT-IR results showed that,compared with SA/CNC I,the interaction between SA and CNC II was strong.However,the effect of CNC on the morphology of SA was small.Adding CNC or soaking the hydrogels can all improve the swelling ratio of SA gel in the deionized water.The swelling mechanism was studied by Fick equation.It showed that the addition of CNC I did not change the swelling mechanism of SA in the deionized water,while CNC II changed it from Fick diffusion to non-Fick diffusion.Compared with the rinsed samples,the soaked ones showed the small characteristic index n and the high swelling ratio.And the pH sensitivity experiments proved that SA/CNC I had the high pH sensitivity.Then,the effects of degree oxidation?DO?of CNC and initial state of hydrogels on SA/oxidized CNC were studied.FT-IR results proved the interaction between oxidized CNC and SA.Moreover,the higher the DO of CNC,the stronger the interaction was.Compared with the pure SA,the pH sensitivity of SA/oxidized CNC increased significantly,and the greater the DO of CNC,the more sensitive the composite hydrogel to the variation of pH.The swelling ratio of the soaked gels in pH=2 and 7.4 buffer solution was larger than that of the rinsed ones.The effect of DO of CNC on the swelling ratio was weakened for soaked gels,but the pH sensitivity was enhanced.Mechanical experiments confirmed that the addition of oxidized CNC improved the compressive strength,and made the elastic effective chain?_e of the gel increased,indicating that the oxidized CNC was involved in the formation of the crosslinking network by hydrogen bonds.Moreover,the gelation experiment proved that the oxidized CNC could complex with Ca²⁺,which might also contribute to the gel network.Finally,the drug release behavior of SA composite gel was studied with chloramphenicol as model drug.The drug release experiments in the deionized water showed that the addition of CNC I and II could increase the drug loading of SA gel and decrease the drug release rate and cumulative release rate.Compared with the rinsed samples,the soaked ones with the same composition had high drug loading and low cumulative release rate,which was related to the swelling ratio and pore size of the gel.SA/CNC II showed the high drug loading and low release rate,which was related to the high swelling ratio and strong interaction between gel and drugs.The drug release experiments both in pH=2 and 7.4 buffer solution showed that the cumulative release rate of SA gel was reduced after adding CNC.However,the cumulative release rate of soaked samples in the two kinds of pH environments was higher than that of rinsed ones.The gels with low crosslinking degree have high drug loading and cumulative release rate.The drying method to the drug-loaded gel also has an effect on its release behavior.Compared with oven drying,the gels obtained by freeze drying have a high cumulative release rate.