Preparation And Properties Of Bioactive Glass/Sodium Alginate/Gelatin Composite Hydrogels

Finding a wound repair material that can quickly repair skin damage is an urgent problem for clinical and scientific researchers.In this paper,an oxidized sodium alginate/gelatin hydrogel（OSA/Gelatin）with self-healing properties was synthesized based on dynamic imine bonds,and bioactive glass was prepared by doping bioactive glass（BG）with different particle sizes.Oxidized sodium alginate/gelatin（BG/OSA/Gelatin）hydrogel.Sodium alginate with different degrees of oxidation was prepared by adjusting the molar ratio of sodium periodate to sodium alginate structural units,and the microscopic morphology,viscoelastic properties,swelling properties,self-healing properties of BG/OSA/Gelatin hydrogels were investigated properties,degradation properties and mechanical properties.The main work is as follows:Three kinds of bioactive glasses with amorphous structure were prepared by sol-gel method,namely BG-1,BG-2,and BG-3,respectively.The obtained compositions were BG-1（62%Si O₂,34%Ca O,4%P₂O₅）,BG-2（65%Si O₂,35%Ca O）,BG-3（53%Si O₂,26%Ca O,21%P₂O₅）,and the particle sizes are 94nm,403nm,and 1115nm,respectively.Because BG-1 has better dispersion effect and smaller average particle size,the bioactive glass used in the following experiments are all BG-1,but in order to ensure the comparison of the experiments,BG-3 with larger particle size is selected for comparative experiments.Using sodium periodate as the oxidant,the sodium alginate was modified.By studying the oxidation degree of sodium alginate,the reaction temperature,the molar ratio of sodium periodate and sodium alginate structural units and the reaction time were three factors influencing factors.,taking the degree of oxidation as the response value,a response surface analysis experiment with three factors and three levels was designed to obtain the optimal synthesis conditions:the temperature was 35°C,the molar ratio of sodium periodate and sodium alginate structural units was 0.6,and the reaction time was5h,the prepared sodium alginate had the highest oxidation degree.The oxidation degree of sodium alginate was measured by hydroxylamine hydrochloride-chromogenic titration method.Comparing the IR and H NMR spectra of sodium alginate before and after oxidation showed that sodium periodate successfully oxidized the molecular chain of sodium alginate.The Schiff base（Schiff base）reaction between oxidized sodium alginate and gelatin at 37°C generates covalently cross-linked hydrogels.It can be seen from the infrared spectrum that the C=O of the aldehyde group of the oxidized sodium alginate is transformed into the C=N of the Schiff base structure,which can reduce the potential physiological toxicity of the aldehyde group.Thus,the structure of sodium alginate was changed,and the aldehyde group obtained after oxidation reacted with the amino group on the gelatin chain with Schiff base to produce a C=N double bond.The incorporation of BG with different particle sizes into the gelatin/oxidized sodium alginate hydrogel system was studied.It can be seen by SEM that the higher the degree of oxidation of sodium alginate,the denser the network formed by the Schiff base reaction with gelatin.,the water absorption of the denser network hydrogels decreased by swelling ratio measurement.The BG/OSA/Gelatin hydrogel can achieve self-healing within 24h without external stimulation.Under simulated physiological conditions,the lower the oxidation degree of sodium alginate,the faster the degradation rate.Among them,the degradation rate of hydrogel 2 is the fastest,and the mass loss in one day is about 43%of the total mass,while the degradation rate of hydrogel 3 is the fastest.slowest.Both sodium alginate with high degree of oxidation and bioactive glass with smaller particle size and better dispersion can improve the mechanical properties of hydrogels,so the tensile and compressive strengths of hydrogels 3 and 4 are significantly higher than those of hydrogels 1,2.The measurement of WVTR of the four composite hydrogels shows that the hydrogels have good moisturizing ability.When used as wound dressings,they can ensure the gas exchange between the wound and the outside world,keep the wound moist,and promote wound recovery.The WVTR value of glue 3 was 2563.44 g/m²/day.