ABSTRACT
Objective: To determine the prescription technology of gastrodin starch microsphere and investigate its nasal mucoadhesion and in vitro release characteristics. Methods: Gastrodin starch microspheres were prepared by compound emulsion crosslinking method. According to the particle diameter, drug loading efficiency (DLE), and entrapment efficiency (EE), the best prescription technology was selected by using single-factor investigation and uniform design. Using toad palate mucosa as model and average residence time as indicator, mucoadhesion of gastrodin starch microsphere was evaluated. Using gastrodin API as a control, paddle method was applied to in vitro release test of gastrodin starch microspheres. The content of gastrodin was determined to calculate the cumulative release percentage. In addition, the curve of drug release in vitro was fitted with different release model to analyze the in vitro release characteristics of gastrodin starch microsphere in nasal cavity, synthetically. Results: The optimum prescription and preparation technology of gastrodin starch microsphere were as follows: gastrodin 2.0 g, starch 4.5 g, liquid paraffin 100.0 mL, Span80 3.5 g, ECH 5.1 mL, preparation temperature 40℃, and rotational speed 1000 r/min. The particle diameter of gastrodin starch microsphere was (47.69±1.92) μm, the DLE and EE of microsphere were (9.78±0.70)% and (35.72±3.28)%, respectively. It was about (176.92±23.25) s that in adhesive powder resided in nasal cavity, which translated into human nasal residence time was just 20-30 min, while the average residence time of gastrodin starch microspheres was extended to (944.33±68.29) s, translated into human nasal residence time was about 3 h. The cumulated release percent of gastrodin starch microspheres was more than 90% in 3 h. Compared with other in vitro release models, Weibull model was the fittest model to gastrodin starch microspheres, the t50 of gastrodin starch microspheres was 40.08 min, and t90 was 245.73 min. Conclusion: Gastrodin starch microspheres prepared with optimum prescription technology have uniform particle diameter, high DLE and EE. Microspheres have good mucoadhesion and sustained release, ensure that gastrodin release gently and completely during the nasal retention period.