Correlation between heparin release and polymerization degree of organically modified silica xerogels from 3-methacryloxypropylpolysilsesquioxane

Enoxaparin-immobilized poly(ε-caprolactone)- based nanogels for sustained drug delivery systems

Enoxaparin-immobilized gelatin/poly(ε-caprolactone) (PCL) or Eudragit® RS230D nanogels in the presence of tetraethyl orthosilicate (TEOS) as polycondensation reagent were designed and characterized for their sustained drug delivery ability. Enoxaparin (anti-Xa 1000 UI/mL) was used as a model drug at different concentrations (300, 500, and 1000 UI/mL). The resulting nanogels were prepared using sol-gel technique and analyzed using several analytical tools such as: thermal analysis (DSC and TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning and transmitting electron microscopes (SEM and TEM). In addition to particle size, zeta potential and in vitro release profiles were also investigated. A burst effect was observed, afterwards, the release rate became steady. The immobilization of enoxaparin into the gel network led to the formation of stable nanogels with ionic functional groups, which enable the efficient loading and sustainable release. The preliminary results showed that enoxaparin-immobilized PCL-based nanogels in this study can be utilized in the design of a sustained delivery system.

Sustained release of heparin on enlarged-pore and functionalized MCM-41

Mesoporous silica MCM-41 and SBA-15 were chosen to study the adsorption and release of bulky biomolecule heparin, in order to develop new heparin controlled delivery system and expand the application of mesoporous materials in life science. To explore how the structure of support such as pore size and surface state affects the accommodation and release of heparin, we used decane as swelling agent to enlarge pores of MCM-41, introduced amino groups for improving the biocompatibility of support, and controllably retained templates in the as-synthesized sample. The influence of modification on the structure of samples was investigated by XRD and N(2) adsorption-desorption, whereas their performance of adsorbing and releasing heparin was assessed with that of toluidine blue method. Both enlarged pore and organic modification significantly promoted the adsorption and prolonged the release of heparin in MCM-41, and the release was characterized with a three-stage release model. The mechanism of heparin release from mesoporous material was studied by fitting the release profiles to the theoretical equation. As expected, some mesoporous composites could release heparin in the long term with tuned dosage.

Structure-directing agents for the synthesis of TiO(2) -based drug-delivery systems

A series of titanium oxides was prepared by using a surfactant-template method (STM) and used as a carrier for the sustained release of ibuprofen, which was chosen as a model drug. This STM provides an efficient route to TiO(2) matrices with both high surface area (when compared with those that were obtained by using traditional synthetic approaches) and well-defined mesoporous textures. Some parameters of the synthetic procedure were varied: pH value, surfactant, and thermal treatment. The physicochemical nature of the surface carriers were investigated by means of N(2) -physisorption measurements and FTIR spectroscopy. The effect of the amount of drug on the release kinetics was also investigated. The drug delivery was evaluated in vitro in four different physiological solutions (that simulated the gastrointestinal tract) to analyze the behavior of the TiO(2) -based systems if they were to be formulated as oral DDSs. Our optimized approach is a good alternative to the classical methods that are used to prepare efficient TiO(2) -based drug-delivery systems.