Encapsulation Of IgY By Sodium Alginate-based Composite Hydrogels And Study On Its Release Properties

Specific egg yolk antibody?IgY? can treat intestinal diseases caused by bacteria or viruses,and has the advantages of low cost,non-toxicity,no drug resistance,etc.However,IgY can be easily inactivated by gastric acid and pepsin after orally adiministration.In this thesis,sodium alginate?ALG? was used as main wall materials to encapsulate IgY by inject-gelation method.The aim was to reduce the activity loss of IgY in stomach.The properties of hydrogel beads,the interaction between the core material and wall materials,and the swelling release kinetics of the hyrogel beads were investigated.Firstly,the optimal preparation process of IgY-calcium alginate hydrogel beads was investigated according to encapsulation efficiency,loading efficiency and activity retention rate The results indicated that when IgY concentration was 10 mg/g,ALG concentration was 1.5%,CaCl₂ concentration was 0.1 mol/L,the crosslinking solution pH was 5.0,and dried at 50? for 3 h,IgY-calcium alginate hydrogel beads exhibited best performance.Under these conditions,the encapsulation efficiency was 52.26%,the loading efficiency was 28.24 mg/100mg hydrogel beads,the hydrogel beads were in good spherity and had smooth surface,and the gentle preparation process didn't affect the IgY activity.At the same time,the physical properties of the hydrogel beads were investigated.Most of the IgY-alginate calcium hydrogel beads had a diameter of 2.5 to 2.7 mm and a hardness over 2000 g.After 2 h in simulated gastric fluid?SGF?or 0.5 h in simulated intestinal fluid?SIF?,the mass of hydrogel beads were about 2?3 times or 15 times of the initial dry weight,and the cumulative release ratio of IgY were about 30% and 60%respectively.And after 2 h in SIF,the mass of hydrogel beads was more than 25 times of the initial dry weight and most of the IgY released.Secondly,due to the hydrogel beads prepared by sodium alginate as a single wall material have the problems of low encapsulation efficiency,high IgY release ratio and activity loss when incubated in SGF.Kappa-carrageenan?CG? was chosen as a composite wall material by viscosity and encapsulation experiments to improve the performance of the alginate hydrogel beads.When the CG concentration was 0.45%,the best IgY-CG-calcium alginate hydrogel beads were made.The encapsulation efficiency reach 63.01% and the IgY activity retention rate after 2 h digestion in stomach increased by 35.41%,there is nearly no activity loss.The loading efficiency decreased slightly,but there was still 26.54 mg/100 mg hydrogel beads.In addition,there was nearly no IgY release in stomach according to the swell-release experiment.Through observation of macroscopic and microscopic morphology,it was found that after the addition of CG,the whole hydrogel beads became denser.Thirdly,the interaction between the core material and wall materials were further explored by potential analysis,turbidity analysis and thermodynamic analysis.The isoelectric point?PI?of IgY was between pH 5.0 and 6.0.So when the pH was lower than the PI,there were electrostatic attractions between the positively charged IgY and negatively charged ALG or CG.The turbidity test found that the complex solution of ALG,CG and IgY had higher turbidity than the single solution,indicating that there were certain electrostatic interactions between polysaccharides and IgY.The results of DSC test showed that ALG could slightly increase the denaturation temperature of IgY.Finally,the swell-release kinetics of the hydrogel beads were investigated.It was found that the IgY-CG-calcium alginate hydrogel beads prepared in this experiment did not show“over-swelling”phenomenon when swelled in SGF,and the swelling in SIF followed Schott second-order swelling kinetics?r²>0.99?.Futher investigation of IgY release mechanism found that the release of IgY from the hydrogel beads mainly accorded with the first-order release model.In addition,the Ritger-Peppas release model analysis indicated that when CG concentration?0.15%,the release mechanism was Fick diffusion and it changed into irregular diffusion when CG concentration was above 0.30%.The optimal hydrogel bead preparation process obtained in this thesis provided basic theoretical research for the development of intestinal delivery system for IgY,and the exploration of its release rule lays a foundation for its further application.