Preparation and characterization of salvianolic acids-tanshinones composite powder for inhalation via co-micronized method

Abstract

Salvianolic acids and tanshinones are main hydrophilic and lipophilic extracts from Salvia Miltiorrhiza with significant anti-pulmonary fibrosis effects. The aim of this study was to prepare a co-micronized salvianolic acids-tanshinones composite powder for inhalation using a planetary ball mill. The micronization process parameters were optimized by central composite design (CCD) and response surface methodology (RSM). Treatment time, rotation speed and the ball/sample weight ratio were selected as the independent variables, and the volume fraction of particle size in 1-5 μm was taken as the dependent variable. The powder properties were evaluated by scanning electron microscopy (SEM), laser diffraction and X-ray powder diffraction (XRPD). The powder flow and hygroscopicity were determined with repose angle, compressibility index and critical relative humidity(CRH). According to the results, the salvianolic acids-tanshinones composite powder produced in optimal conditions had a narrow and unimodal particle size distribution and a smaller D₅₀ of 2.33 μm. The volume fraction of particle size in 1-5 μm was 80.82%. The repose angle was (50.60±1.13) °, and the critical relative humidity is about 77%. After being micronized, the particle size significantly reduced, and the number of amorphous substances slightly increased, with no significant changes in powder flow and hygroscopicity. These findings indicate that the grinding method with a planetary ball mill can be used to co-micronize various components with different properties and prepare composite drug powders for dry powder inhalation.