| Protein polysaccharide natural polymer nano-self-assembled particles have been widely used in the delivery of bio-active substances because of their wide sources,green safety,mild preparation conditions,good bio-compatibility and biodegradability.In addition,there are many active groups in the natural polymer nanoparticle system,which can interact with many bioactive components or drug molecules strongly.The nano-dimension endows the natural polymer nanoparticle system with the excellent characteristics of large specific surface area and high mechanical strength.The application of nano-drug-loading system has many advantages,so it has broad application prospects in the field of bio-pharmaceutical and functional food.Natural food-grade biopolymer proteins and polysaccharides have been widely used to prepare nanoparticles with different structures,and to construct safe and efficient delivery carriers for active ingredients and oral delivery systems for phytochemicals.In this paper,OVA and CMC were used as protein and polysaccharide models to prepare nanoparticles,and their assembly conditions were optimized.The effects of preparation conditions,such as pH value,temperature,salt concentration,and mass ratio of protein to polysaccharide were discussed.Stability was evaluated and applied to the encapsulation and transportation of functional components of curcumin.The main research results are as follows:1、Protein-polysaccharide nanoparticles were prepared by self-assembly of natural OVA and CMC.The optimum preparation conditions were as follows:0.5 mg/ml of ovalbumin and CMC sodium solution were prepared,the volume ratio was 1:2,pH was adjusted to 2.6,heated for 30 min in a water bath at 80 ℃,and cooled to form core-shell nanoparticles with a hydrated radius of 180 nm.At the same time,the interaction and phase separation behavior between OVA and CMC under different conditions were studied by turbidimetry.The zeta potential and particle size of protein-polysaccharide complex were analyzed.The results showed that with the decrease of pH,the opposite charges existed between OVA and CMC,and through electrostatic interaction attract compound condensation.Meanwhile,At the same time,there are four different phase regions(co-solution region,complex insoluble region,soluble complex region,co-solution region).Heating enhances the hydrophobic interaction between molecules after protein denaturation,resulting in the formation of more stable nanoparticles.It was found that the particle size of the composite aggregates changed slightly at the four ratios between 25-80 ℃,indicating that the prepared nanoparticles had good thermal stability.The nanoparticles formed after heating at 80 ℃for 30 min could tolerate high concentration of salt ions,and no dissociation and aggregation occurred after three months in the refrigerator at 4 0C.It shows that the nanoparticles prepared by this experiment have good stability and have certain bacteriostatic effect.2.The surface morphology and structure of nanoparticles were characterized,and the force of forming nanoparticles and maintaining the stability of nanoparticles were clarified.The self-assembly mechanism of nanoparticles was discussed.The results showed that CMC and OVA formed spherical particles with nano-scale by self-assembly,and the internal and external contrast of nanoparticles was not significant.The particles show a certain core-shell structure.Hydrophobic regions in nano nuclei can be used to entrapped hydrophobic materials.UV and fluorescence spectra showed that the addition of polysaccharides affected the spatial conformation of proteins.The interaction between OVA and CMC changed the microenvironment around the proteins.More tyrosine groups were exposed to hydrophilic environment,while tryptophan moved to more hydrophobic environment.n addition,at three different ratios(OVA:CMC = 1:1,1:2,2:1),the molecular forces that promote the formation of nanoparticles are mainly hydrogen bonding and hydrophobic interaction.But the molecular force to maintain nanoparticle stability is different.When OVA:CMC=1:1,hydrogen bond,ionic bond and hydrophobic interaction contribute partially to the stability of polymer nanoparticles;and when OVA:CMC=1:2,with the increase of CMC,ionic bond and hydrophobic interaction contribute greatly to the stability of biopolymer nanoparticles.when OVA:CMC=2:1,ionic bond contributes greatly to the stability of biopolymer nanoparticles;The stability of rice particles has no contribution,and hydrogen bond and hydrophobic interaction have a small contribution.With the increase of temperature,the nanoparticles become denser and denser.The topological structure of nanoparticles at 70 ℃ is very close to hollow spheres.The topology of nanoparticles at 85 ℃is closer to the homogeneous sphere.So the OVA-CMC composite solution heated at 80 ℃ is more advantageous to the preparation of nanoparticles as carriers of bio-active substances.3.Under the optimum preparation conditions,the highest encapsulation efficiency(95.4%)and encapsulation capacity(36.4%)were obtained when the quality of OVA-CMC sodium nanoparticles was 1:2:1.OVA-CMC sodium nanoparticles were highly loaded with curcumin.Good dispersion and stability effectively improved the problem of low water solubility of curcumin.When OVA:CMC was 1:2,the df value of the nanoparticles changed from 1.024 to 2.022,and the topological structure changed from 0.88 to 0.79,indicating that curcumin was successfully embedded in the nanoparticles.Some curcumin in the particles was precipitated with the increase of temperature.When the high temperature was restored to room temperature,the free curcumin was re-precipitated into the nanoparticles.This temperature reversibility and temperature sensitivity provided a good reference for the future practical application in food.According to the UV kinetic spectra at different temperatures,the total enthalpy change-H/R=1753.19,the external enthalpy change-H0/R=-1068,the curcumin concentration in the nanoparticles changed with temperature to dlnC*/d(1/T)=-2821.45,and the activation energy Ea=-5776.16.At the same time,the nanoparticles containing curcumin showed very significant antioxidant activity.Curcumin exists in three states in the system,that is,it is free in solution,adheres to the shell of particles,and is embedded in the nucleus of nanoparticles. |
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