Alcohol-Induced Simple Coacervation Behavior Of Gelatin And Collagen Hydrolysate

Collagen has received widely attention due to the excellent biocompatibility,hydrophilicity,biodegradability and low immunogenicity.Gelatin and collagen hydrolysates are the products from collagen hydrolysis and denaturation.Their amino sequences and types in structure are similar with collagen.However,their processing and applications are more feasible since their good solubility in water media.Simple coacervation is considered as a facile pathway to construct polymer-based materials.In this dissertation,the simple coacervation behaviors of gelatin and collagen hydrolysates triggered by alcohol agent were investigated.The influences on coacervations and the coacervation mechanism were also discussed.Ethanol was used to induce coacervation in aqueous solution of gelatin.Coacervation in gelatin solution resulted from phase separation driven by ethanol as poor solvent,which has a significant effect on the aggregation and rearrangement of gelatin chains.Static coacervations were performed to investigate the influence on the coacervate morphology.Gelatin concentration and ethanol temperature had significant influence on the morphologies of the gelatin coacervates.High-concentration gelatin solution?>4.8 wt.%?was treated with lower temperature ethanol?<25°C?,tending to form a network morphology.Low-concentration gelatin solution?<4.8 wt.%?was treated with ethanol at near room temperature,tending to form a morphology with nanosphere aggregations.Dispersive nanospheres could be obtained after treating with higher temperature ethanol??45°C?.By stirring the mixture of gelatin solution and ethanol,individually dispersive nanospheres could be obtained.The size of the nanospheres could be adjusted by changing V_Gel:V_{Et OH} and the gelatin concentration.Turbidity and absorbance measurements were carried out to further investigate the coacervation dynamics.The coacervation system finally reached a dynamic equilibrium and a stable stage according to the V_Gel:V_{Et OH},suggesting that this was mainly accomplished by phase separation and molecular arrangement.DLS tests were applied to reveal that the ethanol-induced gelatin coagulation system is temperature-sensitive,and the particle size of the gelatin coacervates could be periodically changed with heating and cooling cycles.The changes of R_g and fractal dimension of gelatin coacervates in gelatin-ethanol system were investigated by SAXS.The results showed that the ethanol-induced gelatin coagulation system was a polydisperse system,and the size of the gelatin coacervates could be adjusted by changing V_Gel:V_{Et OH} and the gelatin concentration.This work provides useful information for constructing gelatin-based materials using a facile coacervation method.Coacervation resulted from phase separation was triggered by ethanol as poor solvent which has a significant effect on the aggregation and rearrangement of collagen hydrolysate?CH?macromolecules.Static coacervation was performed to investigate the influence on coacervates morphology.CH concentration and ethanol temperature had a significant influence on coacervates morphology.Treatment for the CH solution of high concentration by lower temperature ethanol?<25??tended to form a microspheres morphology.High temperature ethanol was not conducive to CH coacervation,while enhanced the CH solubilization in water-ethanol.By directly mixing under agitation,dispersed nanospheres could be successfully obtained.The turbidity and absorbance tests were carried out to further investigate the CH coacervation behaviors.The stability of milky suspension induced by ethanol was evaluated by self-built light transmittance measurement.The result showed that the absorbance and turbidity of CH suspension increased with increasing the V_{Et OH} ratio and CH concentration.The milky suspension with high V_{Et OH} would turn clear gradually due to the CH solubilization in water-alcohol.The maximum absorbance presented at p H around 7 where the charges of CH molecules were negative.The coacervation behavior of CH was very different from that of collagen and gelatin,owing to the lower molecular weight.