| To solve the low holding efficiencies and environmental pollution of the pesticides with emulsifiable concentrate (EC) formulation as well as the low maintain efficacy and frequent administration of anesthetic, the mixed formulation of microcapsules and emulsion for acetochlor and the formulation of microcapsules for ropivacain were prepared using solvent extraction and solvent evaporation method, respectively. The effects of processing conditions on the properties of products were investigated and the optimal conditions were obtained. The study was listed below in detail.1. The solvent extraction method was proposed to prepare the mixed formulation of aqueous microcapsule-suspension (CS) and the oil-in-water emulsion (EW) with acetochlor as the core material and poly (ε-caprolactone) (PCL) as the wall material. At the same time, the stability, encapsulation efficiency and drug loading efficiency, release kinetics, and size and morphology of the product were characterized and the effects of the stirring rate, temperature, surfactant, ratio of core to wall were investigated. The mixed formulation showed good stability for more than 48 hours and the duration of the release of the acetochlor was longer than 25 days. Compared to the oil-in-water emulsion formulation, the mixed formulation can improve the holding efficiency and reduce or eliminate the use of organic solvent thus the environmental pollution. It can also reduce the loss of pesticide during the preparation thus the cost compared to the aqueous microcapsule-suspension formulation. Finally, this method can be operated easily with low cost.2. With ropivacaine hydrochloride as the core and PCL as the wall material, the microcapsules were prepared using the improved solvent evaporation of W/O/W emulsion. The optimum preparation condition was identified using the single factor and orthogonal experiments combined statistical analysis, which was:double emulsion stirring rate of 3000 rpm, the internal aqueous phase volume of 3 mL, PVA concentration of the external phase of 1 wt%, CP/OP mass ratio of 7.5, the oil phase PCL concentration of 3.5wt%. Under this condition, the packet of drugs could reach as high as 64.273 ± 1.563%, and the morphology of microspheres prepared were round particles with smooth surface and uniform size distribution. The DSC test showed that the ROP-HC1 was dispersed in PCL microspheres in the molecular or amorphous state. Meanwhile, the sustained period of ROP-PCL-MS in PBS buffer solution was longer than 17d, and the release kinetics agreed with Korsemeyer-peppas empirical model, the release mechanism is diffusion-erosion mechanisms.3.The combination of single factor experiments and response surface method was used to study the interactions between various factors, the effects of factors on the response value, and to establish the regression models so that to determine the optimum preparing condition. It could be found out that interactions between the ROP-HC1 concentration and NaCl concentration in the internal water phase were substantial, ROP-HC1 concentration in the internal water phase contributed most to the response value which the NaCl concentration in the inner water phase contributed least to the response value. The multiple-variable regression model was established to determine the optimum condition, which was concentration of ropivacaine hydrochloride the internal aqueous phase of 8mg/mL, NaCl concentration of 4mg/ mL, external aqueous phase ethanol concentration of 11.5%. The packet of drugs under this condition was 76.32%. |
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