Design And Applications Of Functional Nanocarrier Of Natural Colorants

Natural colorants,which impart a vivid color to food and add additional health benefits,are favored over synthetic colorants;however,their applications are limited by their low solubility in water,sensitivity to the external environment and low bioavailability.Therefore,replacement of synthetic colors with natural alternatives remains an important challenge.Aims at the problems of natural colorants,First,a versatile microfluidic strategy is developed to incorporate natural colorants in shellac nanoparticles with controlled physicochemical properties.The solubility,stability and bioavailability of the natural colorants encapsulated in shellac nanoparticles are significantly improved.Then the mechanism of the co-precipitation of natural pigments and polymers is explored through fluid dynamic simulation and experiments,and the theoretical model of the co-precipitation process is summarized,which proves that the coprecipitation process is able to controlled by microfluidics.Finally,a nanoparticle-single crystal composite carrier is designed,which further improves the stability of the natural colorants and realized a unique dual-pH response mode,which expanded the application of natural colorants in the fields of food and medicine.The main content and innovation results obtained are as follows :(1)A robust,simple,versatile microfluidic strategy is developed to incorporate natural colorants in shellac nanoparticles.The co-precipitation of natural colorants and shellac is achieved by the rapid mixing of good solvent and poor solvent in the flow-focusing microfluidic device,and the hydrophobic natural colorants are successfully encapsulated in biocompatible shellac nanoparticles.By introducing molecular interactions,an extremely high encapsulation efficiency is achieved.The developed colorants-loaded shellac nanoparticles have shown various advantages,including controlled particle size,excellent dispersibility,enhanced stability,wide pH stability range and improved biocompatibility,which are well-suited for the development of functional foods,such as functional natural color drinks.(2)The mechanism of nano-coprecipitation in the microfluidic channel is explored,and the effect of mixing time on the coprecipitation process and the performance of nanoparticles is studied in depth and it is found that the mixing time had a great effect on the size of the nanoparticles and the encapsulation efficiency.Numerical simulation and calculation verify that the mixing time of ethanol with water in the microfluidic channel is shorter than the aggregation time of the unimers,and the vortex diffusion is dominant to enhance the mixing process so that the size of the nanoparticles is smaller and more uniform compared to traditional method.We demonstrate that the microfluidic technology could ensure rapid mixing of the solution and effectively control the mixing process,thereby regulate the performance of the nanoparticles.A three-step co-precipitation model of curcumin and shellac is established,which is then verified by experiments.(3)A new nanoparticle-single crystal composite carrier is designed.Chlorophyll is first loaded in shellac nanoparticles via co-precipitation with a high encapsulation efficiency,and then the chlorophyll-loaded nanoparticles are incorporated into calcite crystals grown from a gel media containing the nanoparticles.Under the protection of shellac nanoparticles and calcite crystals,chlorophyll shows excellent stability even under light.The nanoparticle-single crystal composite carrier also possesses a unique pH-triggered release mode,which mimics the pH change from acidic in the stomach to alkaline in the intestine and is thus well suited for controlled,targeted intestinal release.This work suggests that the crystal composites are an ideal delivery vehicle for the functional design of bioactive molecules.