Preparation And Characterization Of Cationized β-lactoglobulin-pectin-loaded Curcumin Nanoparticles

In the nature,almost all naturally active substances have poor solubility,instability and low biological potency.Fortunately,the protein can effectively improve these bad properties by form nanocomposites with the active substances,and promote the application in functional foods.In the protein transport the active substances studies,theβ-lactoglobulin（BLG）widely used as a delivery vector and effectively improved the bioavailability of active substances,due to the anti-digestion in gastric environment and easy degradation in intestinal environment.However,there are few reports about BLG composite with active substances after modified.Therefore,this study modified the BLG by limited cationization with polyethyleneimine（PEI）,and established two systems about transport active substances,which were the CBLG-curcumin nanocomplex and CBLG-pectin complex coacervation microencapsulated curcumin.The main contents of the study as follows:（1）CBLG was produced by cationic modification of BLG,via using branched polyimide（PEI）,which properties and structure was characterized.These results showed that theζ-potential of BLG increased from-8.6 mv to+6.1 mv,and the surface hydrophobicity（H₀）of BLG increased from 110.6 to 398.1.The structural melting temperature（T_m）of BLG changed as detected by differential scanning calorimetry,which increased from 93.3°C to 105.9°C.The secondary structure and functional groups of BLG were analyzed by Fourier Transform Infrared Spectroscopy（FTIR）and Circular Dichroism,original BLG and after modification.The results showed that the cationic modification changes the characteristic groups and the proportion of secondary structure in BLG.5（2）The CBLG nanocomplex（C-C）was produced and then characterized the appearance,structure,surface properties,stability and bioavailability.The appearance results showed that the nanocomplex solution has good dispersibility and stability,and the dry powder of nanocomplex showed smooth and round particles and the particle size is less than 100 nm.The fluorescence spectrum results present a H₀ change,the H₀of CBLG decreased from 398.1to 126.8 after the complexed with curcumin.The results of X-diffraction and DSC analysis indicated that,curcumin was combined with CBLG in an amorphous state,and T_m of C-C decreased from 105.9°C to 88.3°C.After curcumin complexed with CBLG,the retention rate of curcumin in the nanocomplex solution was still more than 50%after 4 hours of water bath at 80°C,which suggested the curcumin stability was enhanced.The in vitro digestion simulation results presented the bioavailability changes,the curcumin in B-C complex was58.1%,higher than 22%of C-C complex.（3）The influence of mixing ratio,temperature and ionic strength about the CBLG-pectin complex coacervation system was studied using turbidity titration（600 nm）.We optimized the complex coacervation conditions and characterized the interaction about CBLG and pectin by FTIR.Specifically,we prepared the complex coacervation polymer with a high yield of83.5%and average particle size of 274.2 nm,and the optimized complex coacervation conditions as follows:CBLG with pectin mixed as the ratio 2:1（w/w）,temperature at 25°C,the sodium chloride concentration 0 m M and adjusted the p H to 9.0.The FTIR results indicated that,the complex coacervation reaction between CBLG and pectin,the electrostatic interaction between molecules is the mainly effect,and the complex condensation reaction process with no chemical bond change.（4）The microcapsules（C-P-C）were prepared and encapsulated curcumin by complex coacervation of CBLG with pectin.The microcapsules were characterized by appearance,crystal characteristic,thermal stability and bioavailability of curcumin.The results as follow:C-P-C has good dispersibility in aqueous solution,and the dry powder particles of C-P-C presented smooth spherical shape with the size of 1-10μm.DSC result indicated that the T_mof C-P-C microcapsules was 80.99°C,lower than 88.29°C of C-C complex,which suggested the structure stability of CBLG was reduced by the composite condensation.However,the thermal stability result showed a high stability of curcumin in C-P-C,the retention of curcumin in C-P-C aqueous solution up to 85%after storage at 80°C for 4 hours,which significantly higher the curcumin retention 51.3%of C-C nanocomplexes.The in vitro digestion simulation results suggested,the CBLG and pectin complex coacervation significantly improved the stability and bioavailability of curcumin in digestive system,compared to the C-C nanocomplex.