Optimization of preparation procedures for nano-sponges of flavonoids fromGlycyrrhizae Radix et Rhizoma by Box-Behnken response surface methodology based on CRITIC weighted evaluation

Abstract

In this paper, nano-sponges of flavonoids from Glycyrrhizae Radix et Rhizoma (LF-NSP) were prepared by agitation-freeze drying method. Box-benhnken design and response surface method based on the single factor experiment was used to optimize the preparation process, with the stirring temperature as well as stirring time and speed as the independent variables, while with drug loading, particle size and the generalized "normalized value" as the response values. In addition, the nano-sponges were characterized by scanning electron microscope (SEM), infraredspectroscopy (FT-IR) and differential scanning calorimetry (DSC), and its release in vitro was also investigated. The results showed that the optimum preparation conditions for glycyrrhizin nano-sponges were as follows：The proportion of main drug and auxiliary drug was 1:2; the proportion of crosslinking agent DPC and β-CD was 4:1; stirring temperature 45 °C for 4.8 h at 245 r·min⁻¹. The comprehensive score of LF-NSP prepared under these conditions was 94.78. FT-IR and DSC results indicated the formation of Glycyrrhiza flavonoids nano-sponges, and SEM showed that they were spherical particles in shape. In release experiment in vitro, the cumulative release of glycyrrhizin flavonoids nano-sponges for 240 min was 81.8%, while that of crude drug was only 31.5%. Nano-sponges can significantly improve the dissolution of flavonoids from Glycyrrhizae Radix et Rhizoma.