Preparation And Tunable Properties Of Sodium Alginate-based Composite Hydrogels

Sodium alginate(SA)is a natural polymer material which is characterized by nontoxic,biodegradable and biocompatible properties.However,the application is limited in the field of drug controlled release due to the shortcomings such as rigidity,fragility and poor mechanical properties.In this paper,sodium alginate/cellulose nanocrystals(SA/CNC)composite hydrogels and sodium alginate/polyvinyl alcohol(SA/PVA)freeze-dried film are prepared,respectively.The microstructure,swelling behavior,mechanical properties and drug release behavior are investigated,which can provide the experiment data for controlling the properties of composite hydrogels as drug release material.SA/CNC composite hydrogels were prepared by physical crosslinking using CaCl2 as crosslinking agent.The effects of crystal forms and content of CNC on the properties of composite hydrogels were studied.SEM and swelling tests showed that both the mesh size and the swelling ratio of SA/CNC composite gels decreased with the increase of CNC content.The swelling ratio of SA/CNC in different pH solution was changed significantly,indicating the pH sensitivity.The Fick simulation showed that the characteristic index n increased and the swelling rate decreased with the addition of CNC.And the characteristic index n changed with the increase of pH.The mechanical tests showed that the tensile strength of SA/CNC I was high,it can reach the maximum value of 0.27 MPa when the content of CNC I was 0.5%.While compression strength of SA/CNC II was high,it can reach the maximum value of 0.41 MPa when the content of CNC II was 1%.SA/PVA lyophilized membrane was prepared by two-step method.The results of FT-IR showed that the interaction between SA and PVA increased with the content of PVA increasing.SEM results showed that when the mass ratio of SA/PVA was 2:8,the membrane structure was uniform and the pore size was small.While with more SA in SA/PVA,it was difficult to disperse uniformly and the phase separation can be observed.The swelling ratio of SA/PVA decreased gradually with the increasing PVA.When the content of PVA was high,the toughness of SA/PVA was excellent,and tensile strength reached the maximum value at the mass ratio of 4: 6.The drug release behavior of SA/CNC composite hydrogels and SA/PVA lyophilized membrane was studied using chloramphenicol as model drug.The results showed that the drug loading of SA/CNC system was lower than that of pure SA,and the key factor that affected the drug loading was the swelling ratio.The buffer solution with pH=7 was more suitable for the release of drug than water.By changing the crystal forms and the content of CNC,the drug release rate and release amount can be controlled within a certain range.The release rate of SA/PVA lyophilized membrane with different mass ratio was changed slightly,and the release amount was mainly affected by the content of SA,the more the SA was,the smaller the drug released.