Preparation Of PAA/SiO₂ And Hollow Spheres And Mechanism In Ibuprofen Controlled Release

The influence of surface effect on drug adsorption and diffusion behavior was studied by grafting pH sensitive polymer onto the surface of dense silica sphere,eliminating the influence of pore effect.Afterwords,a series of pH-responsive hollow polymer spheres with different shell thickness were prepared,and their drug loading and release properties were studied.The specific contents mainly include the following aspects:1.Using modified dense silica sphere?DNSS?with a size of 130 nm as the template,the pH-responsive polyacrylic acid was coated onto its surface through one-step method to prepare core-shell hybrid microspheres P/SiO₂-MPS with different shell thickness.The surface effects of PAA shell grafted onto the surface of DNSS and their effects on the loading and release properties of ibuprofen?IBU?were investigated.Particularly,the fractal feature dimensions of P/SiO₂-MPS before IBU-loading and after releasing was characterized by small angle X-ray scattering?SAXS?technique.The results showed that all samples had surface fractal feature,which increased from 2.19 for SiO₂-MPS,to 2.41 for P/SiO₂-MPS,to 2.54 for IBU-loaded P/SiO₂-MPS,and to 2.65 for IBU-released P/SiO₂-MPS.The surface fractal dimension increased with the increase of grafted PAA amounts,which revealed the surface became rougher,proving the successful encapsulation of PAA.On the other hand,the surface effect of PAA on the surface of silicon sphere was reflected.Moreover,the IBU loading of P/SiO₂-MPS was fitted into the pseudo-second-order model,the phenomenon of low drug-loading capability reflected the surface effect of P/SiO₂-MPS,at the same time.Furthermore,the IBU-releasing behaviors were pH-dependent,showing that the cumulative amount at pH 3.0 was much higher than that at pH 7.4,particularly,the release rate was gradually rapid with the increasing thickness of PAA layers,to a certain extent.In addition,the fractal dimension of the samples after release in different conditions reflected the effect of the micro-environment of the release medium on the surface roughness of the PAA shell,further proving the remarkable surface effect of PAA shells.2.In order to achieve the purpose of improving the stimulation performance of the functional polymer while improving the drug loading rate,the hybrid microspheres P?AA-co-DVB?@SiO₂ with core-shell structure were synthesized firstly.The hollow polymer microspheres HPAA with hollow structure were obtained by solving the SiO₂ core,and the effects of monomer additive amounts on the hollow structure of HPAA and the shell thickness of hollow spheres were systematically investigated.The results showed that the hollow polymer microspheres HPAA with stable hollow structure could be successfully prepared,and the thickness of the polymer encapsulated on SiO₂ can be controlled by adjusting the additive amount of monomer AA to prepare HPAA with different shell thickness.In addition,the zeta potential results proved that the prepared HPAA had good pH sensitivity.3.In order to study the application of hollow polymer spheres HPAA in the drug controlled release system,we used IBU as drug model to study its drug loading capacity and release performance in phosphate buffer solutions at different pH values?pH=3.0 and pH=7.4?.The results demonstrated that the loading process of IBU could not affect the structure and morphology of hollow polymer spheres.Meanwhile,the drug loading rates of HPAA with varies shell thickness were 13.50,17.18,15.76and 13.81%,respectively.With the increase of HPAA shell thickness,its drug-loading ability showed a downward trend.As to the release performance,the equilibrium release rate of the IBU in the alkaline condition was much higher than that of the acidic condition and exhibited good pH sensitivity.In addition,the equilibrium release rate of the IBU decreased with the increase of shell thickness of the hollow polymer spheres,reflecting the distance control mechanism,and the drug release followed the Korsmeyer-Peppas model.4.The hybrid microspheres P/SiO₂-MPS and Hollow polymer spheres HPAA as well as drug loaded and released samples were characterized by means of SEM,TEM,FT-IR,TGA,EDS,elemental analysis,UV-vis,DLS,CNMR,SAXS,and so on.In particular,SAXS,as a nanoscale material structure analysical method,provides fractal features from a new perspective to describe the surface structure and roughness of all nanocomposite particles.