Study Of W/O/W Emulsion-based Co-Delivery Systems Of Arbutin And Coumaric Acid As Well As Their Interfacial Behaviors

Phenolic compounds are secondary metabolites in plants,which attracted much attention due to their various bioactive functions.Arbutin is one kind of hydrophilic phenolic compound,while coumaric acid is one kind of hydrophobic phenolic compound.Both arbutin and coumaric acid exhibit whitening,anti-inflammatory,and anticancer activities,which are widely used in food,medicine,cosmetics,and other fields.However,arbutin is unstable at low pH,high temperature and UV irradiation;Coumaric acid shows low solubility in water and high sensitivity to environmental conditions.These shortcomings limit their application.The present study focused on the hydrophilic arbutin and hydrophobic coumaric acid.Based on the development of W/O/W emulsion for co-delivery of arbutin and coumaric acid,biological macromolecules,such as protein-polysaccharide complex and DNA origami,are applied to modify W/O/W emulsion,which greatly improved the stability of W/O、W emulsion and the release profiles of arbutin and coumaric acid.In addition,the intermolecular interaction between biological macromolecules and arbutin or coumaric acid was further measured to study the zero-order release properties of arbutin and coumaric acid.The main results were presented as follows:1.The co-delivery system of arbutin and coumaric acid based on W/O/W emulsion was developed,which could co-deliver hydrophilic arbutin and hydrophobic coumaric acid.The particle size,polydispersity index and zeta potential of W/O/W emulsion were 355.98 nm,0.12,and-44.10 mV,respectively,with high encapsulation efficiency of arbutin(75±3%)and coumaric acid(68±2%).Due to the barrier effect of external aqueous phase,arbutin and coumaric acid were slowly released to achieve controlled release under simulated oral and gastrointestinal digestion conditions and increase the bioaccessibility of arbutin and coumaric acid by 43%and 42%,respectively.At the same time,the W/O/W emulsion improved the stability of arbutin and coumaric acid under adverse conditions(low pH,high temperature and UV-C treatment).In addition,the W/O/W emulsion showed excellent stability in the Lactobacillus beverage.It could be concluded that the hydrophilic arbutin and hydrophobic coumaric acid were codelivered by W/O/W emulsion with increased bioaccessibility.2.The influences of whey protein concentrate(WPC),whey protein concentrategum arabic(WPC-GA)and whey protein concentrate-high methoxyl pectin(WPC-PEC)complex on W/O/W emulsion were investigated.The stability and rheology of the modified emulsions,as well as encapsulation efficiency,releasing kinetics,degradation kinetics of arbutin and coumaric acid were explored.The results showed that the viscosity and stability of WPC-PEC complex(at the ratio of 1:3)modified W/O/W emulsion were the highest,while the encapsulation efficiency of arbutin and coumaric acid were highest at 91.08%and 80.92%,respectively.The strong gel network of WPC-PEC(1:3)complex resulted in the largest particle size of 569.67 nm.In addition,the WPC-PEC(1:3)modified W/O/W emulsion presented sustained release of arbutin and coumaric acid under the simulated digestion conditions.The degradation rate constant of arbutin(7.99×10-4 under pH=1.2;4.19×10-4 under 90℃;7.52×10-4 under UV-C treatment)and coumaric acid(5.18×10-4 under pH=1.2;3.24×10-4 under 90℃;6.90×10-4 under UV-C treatment)revealed the degradation rate was decreased.These results indicated that WPC-PEC(1:3)complex modified W/O/W emulsion,which simultaneously improved the encapsulation efficiency and stability of arbutin and coumaric acid.3.The influences of WPC-PEC complex on the zero-order release profiles of arbutin and coumaric acid were studied.The structure of WPC-PEC was characterized by morphological analysis,and the binding properties of WPC-PEC with arbutin and coumaric acid were tested by fluorescence spectroscopy and molecular docking simulation.The pore diameter of porous WPC-PEC complex was 29.02 μm,which couldn’t affect the release.At 298 K,the binding constant of coumaric acid(8.71×104 L/mol)was arbutin(2.09×104 L/mol),resulting in priority of coumaric acid in the binding order.The major binding affinity for WPC-PEC and arbutin was van der Waals force and hydrogen bond,while for WPC-PEC and coumaric acid was hydrophobic interaction.Overall,the zero-order release properties of arbutin and coumaric acid were summaried,which were attributed to the balance between diffusion effect and competition effect.4.Programmable DNA origami brings great possibilities to customize nanostructures with controllable nano precision and configurable functions.The amphiphilic triangular DNA origami with a central nanopore was designed,which integrated the effects of stabilizing phase and controlled release.The interfacial tension was reduced by 80%using amphiphilic triangular DNA origami as the single surfactant to stabilize the W/O/W emulsion.Microscopic observations presented that DNA origami was attached to the W/O and O/W interfaces.The modification of DNA origami enhanced the shear and elastic modulus of W/O/W emulsion,which remained stable droplets at strain conditions.DNA origami-based W/O/W emulsion decreased melanin content in zebrafish by 66%under UV-B interference with no cardio or motor toxicity.These results indicated that the non-toxic amphiphilic triangular DNA origami could solely stabilize W/O/W emulsion as the co-delivery system of arbutin and coumaric acid.5.The influences of DNA origami on the zero-order release profiles of arbutin and coumaric acid were studied.The results showed that the 10 μmol/L of DNA origami not only stabilized the W/O/W emulsion,but also achieved the zero-order release of arbutin and coumaric acid.Fluorescence analysis presented that arbutin was mainly bound by hydrogen bond and van der Waals force,while coumaric acid was mainly bound by hydrophobic interaction,with only one binding site.At 298 K,the binding constant of DNA origami with arbutin and coumaric acid were 3.18×104 L/mol and 1.38×104 L/mol,respectively.The binding mode analysis indictaed that the binding site of arbutin and coumaric acid was in the groove of DNA origami.Molecular docking simulations showed DNA origami binded with with arbutin and coumaric acid at docking sites,which could be used as a gated material for affinity-controlled release system.These central nanopores exhibited molecular gated effect to transport arbutin and coumaric acid with a constant rate.In summary,based on the development of W/O/W emulsion for co-delivery of arbutin and coumaric acid,biological macromolecules,such as protein-polysaccharide complex and DNA origami,are applied to modify W/O/W emulsion,which greatly improved the stability of W/O/W emulsion and the release profiles of arbutin and coumaric acid.In addition,the intermolecular interactions of biological macromolecules with arbutin and coumaric acid were revealed,and the zero-order release properties of arbutin and coumaric acid were clarified,which also provided a theoretical foundation for the design of zero-order release delivery system in the future.