Core-Shell Nanoparticles: Preparation And The Encapsulation And Release Of Drugs

With no any surfactant and in the presence of casein (CA), polymethyl methacrylate (PMMA)/CA and polybutylacrylate (PBA)/CA nano-sized core/shell latex particles based on MMA/CA and BA/CA with about 150 nm in diameter were prepared through emulsion polymerization using tert-butyl hydroperoxide (TBHP) as initiator. The designed core-shell structure was confirmed by transmission electron microscopy (TEM) observation. The TEM images of the nanoparticles clearly showed well-defined core-shell morphology, where hydrophobic PMMA and PBA cores were coated with CA shells, respectively. Latex particle size and size distribution were determined by light scattering particle size analysizer. The PMMA and PBA grafting efficiency was detected by soxhlet extraction with chloroform. The effects of reaction temperature, initiator dosage, ratio of core-shell materials, and total materials content on the monomer conversion, grafting efficiency of PMMA or PBA, latex particle size and distribution were studied.For the preparation of PMMA/CA nanoparticles, monomer conversion and particle size at different reaction time were determined. The results showed that a sharp decrease in particle size was observed within the first 20 min of the polymerization, and the particle size remained quite constant afterwards. Monomer conversion reached about 70% within 30 min of the initiation, followed by a very slow increase to about 73% up to 3 h of polymerization. Optimization of the polymerization process demonstrated that, to achieve high MMA conversion, high PMMA grafting on CA and relatively narrow size distribution for the core-shell particles, polymerization temperature should be kept between 70 oC and 80 oC, TBHP level at 0.18% to 0.36% of CA mass, MMA/CA ratios at 4 by mass and total content of MMA and CA not higher than 10% by weight in the system. The latex particles are coated with hydrophilic CA,it contained amino, hydroxyl and carboxyl which could form strong hydrogen bonds with water, viscosity increased rapidly as the CA in the system increased. Then when the total content of MMA and CA reached 30%, the coagulation appeared.For the preparation of PBA/CA nanoparticles, the experiment results revealed that PBA-CA core-shell particles were well formed under following optimized experimental conditions: BA/CA mass ratio of 4, TBHP at 0.22% of CA mass, total content of BA and CA at 10%, and at polymerization temperature of 75 oC. And high BA conversion and PBA grafting were obtained at aforementioned conditions. Deviation from this optimization would lead to lower BA conversion and PBA grafting with a broader particle size distribution.The obtained latexes were purified through dialyzing. The unreacted monomer was detected through gas chromatography. Paclitaxel-loaded core-shell particles latexes were prepared by ultrasonic or shaking. The encapsulation of paclitaxelon core-shell nanoparticles was primarily studied.