Preparation Of Drugs/Silica Composites And Its Controlled Release Property

Since the appearance of controlled release technology, it had become a hot topic of scientific researches because of its specific properties. However, problems caused by the carriers, such as poor biocompatibility, pollution to environment, have limited the applications. In this work, silica was used as carrier in the study of the preparation of controlled release drugs. Three different drug/silica particles were synthesized by dry impregnation, emulsion encapsulation, and in-situ hydrolysis method, respectively. SEM, TEM, FTIR, TG, XRD, and N2adsorption-desorption analyses were applied for products characterizations, and some novel results were found. The main contents are as follows:1. Using ibuprofen (IBU) as model drug and porous hollow silica nanoparticles as carrier, IBU/SiO2nano composites were prepared by dry impregnation method. The as-prepared nano composites are spherical particles. Crystallized ibuprofen was distributed on the outer surface, in the pore channels, and in the inner hollow spaces by physical adsorption. The drug loading amount is influenced by preparation conditions such as drug dosage, concentration of drug solution, and the solvent used. Drug release could be divided into an initial burst and a following sustained release phases, and the release properties are related to preparation conditions.2. By adopting the interfacial hydrolysis of TEOS in a drug acid solution/cyclohexane W/O emulsion system, the model drugs of gentamicin sulfate and salbutamol sulfate were successfully encapsulated and drug encapsulated silica microcapsules (DESMs) with a diameter of3～15μm and a hollow structure were formed. The shell is porous silica with pore size concentered at3.4nm, and drug was embedded in the inner hollow spaces in a physical way. DESMs showed good controlled release properties. The release time can last more than60hours, and the drug release rate is fast at the beginning and then slows down. The drug release is affected by drug loading amount, shell thickness, and shell density, etc, which could be adjusted by changing drug concentration in the water phase, TEOS amount used, and drying temperature, respectively.3. Amorphous spherical CH-SiO2composites with a diameter of300-700nm were synthesized from the in-situ hydrolysis of sodium silicate in acid solution of ciprofloxacin hydrochloride. The drug loading amount is about28.8wt%, and the drug is combined with silica in a physical way. The CH-SiO2composites have an excellent controlled release proerties.45%of total drug amount in the composites were delivered in6days. The release rate is steady and no burst occurs. The well fit of Higuchi model proved that the drug release is a diffusion controlled process. The CH-SiO2composites are possibly formed by condensation of silica sol particles from sodium silicate hydrolysis after CH molecules adsorbed.