Fabrication Of Quercetin-loaded Zein Composite Nanoparticles:Antioxidant Activity

In this study,we prepared zein-caseinate/κ-carrageenan composite nanoparticles as an oral delivery system for quercetin by used an antisolvent precipitation/electrostatic deposition method.Condition for the preparation of nanoparticles were determined by morphological structure,particle size,zeta-potential and loading characteristics.Investigating the effects of p H,ionic strength and temperature on the stability of nanoparticles.The biological activity of encapsulated quercetin in zein/caseinate-carrageenan nanoparticles were explored by the in vitro free radical scavenging test,in vitro simulated gastrointestinal digestion test and intracellular reactive oxygen scavenging test.The results were as follows:1.The concentration of carrageenan and the dispersion volume ratio of zein/caseinate nanoparticles can affect the p H stability of zein/caseinate-carrageenan nanoparticles.When the concentration of carrageenan was 0.04%and the dispersion ratio was 3:1（carrageenan solution:zein/caseinate nanoparticle dispersion）,the stable nanoparticles in the range of p H 2.0 to 8.0 could be formed.The average diameter of the zein/caseinate-carrageenan nanoparticles was about 110 nm with a PDI of0.175 and the zeta potential was-40.28 m V.The morphology of nanoparticles appeared uniform and smooth spherical shape by scanning electron microscope（SEM）and atomic force microscope（AFM）.2.There is an electrostatic interaction betweenκ-carrageenan and caseinate,which can form an outer layer with strong negative charge for the zein nanoparticles.Carrageenan-coated zein/caseinate nanoparticles were stabled by electrostatic repulsion and spatial repulsion.The nanoparticles were stable to aggregate at a wide p H range from 2.0 to 8.0.In particular,the nanoparticles also remained steady near the isoelectric point（p H 6.2）of zein and without aggregation and precipitation.Stability experiments at p H 6.40and p H 4.0,showed that at high Na⁺ionic strengths（2.0 M）,the nanoparticles had good stability.The nanoparticles solution also had good stability when exposed to high Ca²⁺ionic strengths（≤70 m M Ca Cl₂）.At 90℃heating for120 min,the distribution of nanoparticles was more uniform and stable.The freeze-dried nanoparticles had good water-dispersibility.3.When the mass ratio of zein to quercetin was 7:1,the content of quercetin in the nanoparticles was 5.56%,and the particle yield and the quercetin loading efficiency were 95.20%and 75.7%,respectively.The average diameter of the nanoparticles was about 147.8 nm with a PDI of 0.148and the zeta potential was-32.95 m V.The morphology of quercetin nanoparticles appeared uniform and smooth spherical shape by scanning electron microscope（SEM）and atomic force microscope（AFM）.The encapsulated quercetin was an amorphous form as determined by X–ray diffraction（XRD）.The nanoparticle dispersion was stable when subjected to p H 2.0 to 8.0 and to Na⁺ionic strengths 0 M to 2.0 M.At high Ca²⁺ionic strengths（≤70 m M Ca Cl₂）,the quercetin nanoparticles solution also had good stability.After heating at 90℃for 120 min,the particle size and surface morphology did not change,and the particle distribution was more uniform.The freeze-drying and redispersion process would not change the particle size and surface morphology of the quercetin nanoparticles.4.The encapsulated quercetin in zein-caseinate/κ-carrageenan nanoparticles had a higher in vitro antioxidant activity than free quercetin and ascorbic acid as determined by DPPH·or ABTS·⁺scavenging ability.The SC₅₀values of quercetin nanoparticles for scavenging DPPH·free radicals was only 30%of ascorbic acid,and the SC₅₀values of quercetin nanoparticles for scavenging ABTS·⁺free radicals equaled 40%of ascorbic acid.The release rate of the quercetin nanoparticles was higher than free quercetin and the physical mixture in vitro simulated digestion,and the zein-caseinate/κ-carrageenan nanoparticles could protect the quercetin from degradation during digestion.The cell viability rate of three digestion fluids（quercetin in nanoparticles,quercetin in mixture,and free quercetin）increased with the increase of dilution factor at the same treatment time.Thereinto,the quercetin nanoparticle digestive juice had the strongest inhibitory effect on Hep G2 cells,and had prominent antioxidant capacity for remove the intracellular ROS levels.To sum up,these results suggested that the zein-caseinate/κ-carrageenan nanoparticles could be an effective oral delivery system for quercetin,which had the potential to be used in dietary supplements and drug synergy therapy.