| During microencapsulation process, the core material was embedded in another functional material so as to protect the core material from the severe environment. Interestingly, in most studies reported so far in the literature, only one drug was entrapped within microcapsules at a time. Only little knowledge is yet available on the microbial cells and the co-encapsulation of two drugs, especially if the drugs exhibit significantly different solubility behaviors.In order to solve the above problems, the following work has been done:(1)The effect of the process parameters such as temperature, the volume ratio of primary emulsion and the outer water, PVA concentration, PCL amount, the second emulsification intensity and the emulsification time on the stability of the double emulsion. The results showed that the stability of the double emulsion increased first and then decreased as the ratio of primary emulsion volume to the outer water, the second emulsification intensity and the emulsification time increased. The stability increased as PCL amount and temperature decreased.(2)Yeast microcapsules were produced by double emulsion solvent diffusion method. And the influence of PVA concentration, Span 80 dosage, emulsification time, PCL amount and emulsifying speed of first and double step on the size of the emulsion droplets, the size of the microcapsules and the encapsulation efficiency. With the increase of PVA concentration, the size of the emulsion droplets and microcapsules increased first and then decreased. With the increase of the emulsification speed of the first step, the size of the emulsion droplets and the yeast microcapsules did not change significantly. With the emulsification speed of the second step, the emulsification time and the use of Span 80 increased the size of the emulsion droplets and the microcapsules reduced. With the amount of PCL decreased the size of the emulsion droplets and the microcapsules reduced. With the increase of PVA concentration, Span 80 dosage, emulsification time, PCL amount and emulsifying speed of first and double step the encapsulation efficiency increased first and then decreased.(3) The formation of co-delivery microcapsules containing the hydrophilic drug Rhodamine B and the hydrophobic drug Nifedipine with the water-in-oil-in-water (W/O/W) double emulsion diffusion technique. Using EtAc and DCM as the oil phase in combination can significantly improve the quality of multiple emulsions and microcapsules. Microcapsules prepared by moderate HLB value emulsifier PVA dispersed best. The size of emulsion droplets and micro capsules decreased with PVA concentration, the second stirring speed increased. The size of emulsion droplets and microcapsules decreased with the PCL amount reduced. The size of emulsion droplets and microcapsules increased first and then decreased with the inner aqueous pahse increased. The encapsulation efficiency of hydrophilic model drug Rhodamine B decreased as PVA concentration, the second emulsification speed, the inner aqueous phase increased and the amount of wall material reduced. The encapsulation efficiency of hydrophobic model drug Nifedipine increased as wall material increased and the amount of the inner aqueous phase reduced and less affected by the concentration of PVA and emulsification speed of the second step. Under the same process parameters, the microcapsules Rhodamine B release rate is higher than Nifedipine. With the increase of the secondary emulsification speed, the amount of PCL, the release rate of Rhodamine B and Nifedipine both increased. With the increase of the amount of W1, the release rate of Rhodamine B increased, and the release rate of Nifedipine decreased first and then increased. While Rhodamine B burst release phenomenon is more serious, and Nifedipine release rate relatively constant, basically no burst release occur. By comparison, the size of the mirocapsules has obvious influence on the release performance. |
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