Synthesis of mesoporous silica-gel core-shell structural microparticles and their multiple drug delivery.

CONTEXT: Release of two drugs safely and independently should be necessary in medical or reaction engineering fields to overcome many complex problems such as multi-drug resistance in treatment of disease. OBJECTIVES: Core-shell structural microparticles that can load/release two drugs simultaneously are designed and prepared. MATERIALS: The microparticles are composed of mesoporous silica core and hyaluronate (HA)/poly (N-isopropylacrylamide) hybrid gel shell. METHODS: The synthesis processes are monitored by powder x-ray diffraction and Fourier transform infrared spectroscopy. The properties of microparticles are characterized by nuclear magnetic resonance, dynamic light scattering and transmission electron microscope methods. Two kinds of drugs are loaded into the mesoporous-core and gel-shell, respectively, and then released under various conditions. RESULTS: The microparticles show uniform spherical shapes with core-shell structures. When temperature is higher than the lower critical solution temperature, the microparticles shrink abruptly and assemble. The drug release rates have been found to depend on the concentration of the microparticle suspensions and pH of the release medium. DISCUSSION: The swellability of the microparticles are controlled by the HA size and gel crosslink density; and the main effect factors on drug releasing behavior are the drug properties and drug diffusion ability. CONCLUSION: The experimental results confirmed different drugs could be safely loaded into the core-shell structural microparticles and released independently, which might be potential carriers for drugs or catalysts. These microparticles would be expected to make sense for applying in medical or reaction engineering fields.

A lattice model for thermally-sensitive core-shell hydrogels.

A lattice molecular thermodynamic model for describing the swelling behavior of thermally-sensitive core-shell hydrogels was developed by integrating a close-packed lattice model for mixing free energy and a Flory Gaussian chain model for the elastic free energy. The thermodynamic model is characterized with two parameters: the temperature-dependent exchange energy parameter ε and the Topology-dependent size parameter V(*). The input values of both parameters can be obtained by experimental results of pure polymer hydrogels. With the help of proposed model, swelling behaviors of two kinds of hydrogel systems were analyzed: one is a doubly thermally-sensitive core-shell hydrogels (with two LCSTs) and the other comprises a thermally-sensitive hydrogel shell with a hard internal core. We show that the calculated results are in good agreement with the experimental data.