The First Discovery of a Microstructure in Black Plaster and Its Performance Characterization

BACKGROUND: Black plaster is one of the classic dosage forms of traditional Chinese medicine for external use and has been widely utilized since the Tang and Song Dynasties. In this paper, we take Goupi Gao as the research object and discuss the scientific characteristics of the black plaster dosage form. Goupi Gao ointment is a plaster for external use of traditional Chinese medicine. METHODS: Methods for the morphological and quantitative characterization of black plaster’s microstructure, based on FESEM-IPP (Field Emission Scanning Electron Microscope IPP Image Processing) technology, were established. According to the actual operating temperature of Goupi Gao, three temperatures were selected: 28°C, 35°C, and 45°C. A UPLC analysis method was applied to the cinnamaldehyde and eugenol in Goupi Gao, and the release behavior of Goupi Gao from three samples at three temperatures was investigated using the paddle over disk method. Preparation of rabbit model of knee osteoarthritis of cold blood stasis type by cold stimulation combined with drug induction. RESULTS: In terms of morphology, Goupi Gao and the blank black plaster matrix both formed a double continuous phase system with a thicker vegetable oil phase and crossed “branched” soap crystal fibers. Based on the IPP image quantification parameters, the pore area (A) was highly positively correlated with temperature. After the 28 °C treatment, A(1) = (216.8±59.5) μm(2); after the 35 °C treatment, A(2) = (259.7±52.8) μm(2); after the 45 °C treatment, A(3) = (408.0±57.7) μm(2), and there were no significant differences in other pore parameters. CONCLUSION: The black plaster matrix’s unique structure makes it highly applicable in numerous medications; it exhibits slow-release and performs well in extreme temperatures, with good adhesion and peeling properties.