Preparation and structure characterization of short glucan chain-curcumin nano-emulsion

Abstract: In order to solve the problem of curcumin's low biological value in food and drug, the helical space structure of the short glucan chains with a short DP (degree of polymerization) was induced to embed the water insolubility curcumin and to enhance its biological value. This article introduced a way how to make short glucan chains and use short glucan chains to encapsulate with curcumin to make inclusion complexes and nano-emulsions. Short glucan chains were obtained by pullanase's enzymatic hydrolysis, which came out successfully by the verification of XRD (X-ray diffraction) results. The inclusion complexes were made by mixing, but its poor encapsulation efficiency and loading content were about 28.46% and 1.27%, separately. Short glucan chain-curcumin nano-emulsions were produced by emulsification and shearing to improve the embedding rate and drug loading, using the Hi-shear dispersing emulsifier with D-speed shearing solution for 5 min to get SGC-CUR nano-emulsion, and the nano-homogenizer was used to homogenize the sheared emulsion twice under a pressure of 50 MPa to prepare the emulsion. High embedding rate and drug loading were produced by making curcumin-short glucan chain into nano-emulsions, and we got a good result of embedding rate and drug loading: 71.11% and 12.07%, respectively. Popular methods as SEM (scanning electron microscopy), TGA (thermogravimetric analysis), Zeta etc. were measured to analysis stability, water solubility and structure characterization. Curcumin's solubility was not only increased by adding emulsifier but also by interaction behaviors between short glucan chains and curcumin, which stop crystal's growing and kept amorphous state to enhance its solubility. From SEM we knew that the short glucan chain-curcumin had rough surface because of the enzymatic hydrolysis, partially cracked and stuck together, this phenomenon was almost the same with former studies that starch nanoparticles were adhered. As for nano-emulsions' Zeta potential were below 20 mV which means it has a low stability and has a room to improve, this result was same with the picture showed at the 7th day that the emulsion slowly began to stratify. The nano-emulsion particle size changed from 238.33 to 170.87 nm when fewer emulsifier were added, probably because of more water/oil interface had produced, which supported the formation of smaller droplets. The PDI (particle size distribution index) of nano-emulsions was all less than 0.3, which means the particle size distribution followed a uniform distribution pattern. The process greatly improved the solubility of curcumin, increased the stability of curcumin, and provided a suitable way for the medical field to find better embedding of curcumin wall materials.