Preparation And Performance Of P(MMA-BA)、PLA/EC Hollow Microspheres By Spray-drying

Polymer hollow microspheres presents advantages of being lightweight, largespecific surface area, the internal space for being loaded etc and thus has been appliedwidely in drug-delivering, biochemistry, catalyzing and coating industry. Polymerhollow microspheres with large particle size have been put into commercial processalmost by emulsion/suspension polymerization-osmotic welling process. However, thecurrent process is usually associated with several disadvantages including complexproduction runs and fussy post-treatments. In this study, we fabricated poly（methylmethacrylate-butyl acrylate）（P（MMA-BA））hollow microspheres and polylacticacid-ethyl cellulose（PLA-EC） hollow microspheres by spray-drying method. Theapplications in effluent treatment and drug sustained-release system are discussedrespectively according to the characteristics of materials. The spray-drying methodwas proved to be a convenient and time-saving way by which polymer microspheresof ideal hollow construction were prepared. Owing to the dry powder could beobtained directly by one step, the spray-drying method turned out to be valuable incommercial application.（1） P（MMA-BA） hollow microspheres with shells of nanoparticles werefabricated by the combination of seed emulsion polymerization and spray dryingmethod. The formation mechanism of the microspheres was analyzed, as well as theinfluences of emulsion formulation and process conditions on morphological features,particle size and yield. The results revealed that hollow microspheres with regularshape and high yield were fabricated when the condition as follows： emulsionconcentration of2%, inlet temperature of125℃, outlet temperature of50℃, feed rateof250mL/h, prepolymer amount of2wt%, monomer ratio （MMA:BA） around7:3,crosslinking agent amount of10²0wt%. In addition, the phenol adsorptionproperties of hollow microspheres were discussed. The results showed that adsorptivecapacity in low microspheres concentrations was up to7.8568mg·g^-1. Especially，theadsorptive capacity improved with the increase of monomer ratio and specific surfacearea. Compared with solid microspheres fabricated by suspension polymerization,hollow microspheres had a better phenol-adsorption performance due to the smallerparticle size and larger specific surface area.（2） PLA-EA hollow microspheres with rock melon-like morphology were fabricated by spray-drying method. The formation mechanism of the microsphereswas analyzed, as well as the influences of formulation and process conditions onmorphological features, particle size and specific surface area. The EC content raised,microspheres were better formed. With the increase of solids content, particle size,void volume and specific surface area increased too, but if the content is too high,more floccus existed in the product. The inlet temperature was important too. Theappropriate conditions were given as follows: components ratio （PLA: EC）（2:1to1:2）, solids content （1wt%to3wt%）, inlet temperature（20℃to50℃）.（3） Roxithromycin （RXM）-loaded PLA-EC hollow microspheres were prepared,the yield, encapsulation efficiency and drug-release properties of microspheres werestudied too. The results showed that encapsulation efficiencies of all drug-loadedmicrospheres were up to higher than90%. The dosing rate was closely related to therelease mechanism of the microspheres: release rate and release speed weredramatically higher with a bigger dosing rate. In addition, sustained-release propertyof microspheres was adjustable by changing the components ratio: sustained-releaseperiod was extended with more PLA content in the microspheres. When the processconditions were given as follows: components ratio （PLA: EC） of1:1, solids contentof2wt%, dosing rate of1:2, the sustained-release period was about20h, and releaserate was about91.4%, which could meet the demand of medicating once per day. As acomparison with the hollow microspheres, multiporous microspheres were preparedby emulsion-spray drying method. Test results showed that multiporous microsphereshad a lower release speed and release rate because of the relatively small particle sizeand specific surface area.