Preparation Of Hollow Mesoporous Silica Nanospheres Coated With Polymer And Their Performance On Drug Controlled Release

Hollow mesoporous silica nanoparticles(HMS) due to the small density and high surface area, chemical stability and tailored mesoporous structure, have been widely applied in catalysis, optics and electronics, energy storage, controlled release, and environmental protection. In particular, because of their excellent biocompatibility, modifiable Si-OH on surface, innate ability of sustained drug and high drug loading capacity, HMS have become the focus in the field of biomedical materials. The organic / inorganic composite particles along with the easy process ability of organic materials and rigidity, magnetic and optical properties and other special properties of inorganic materials, have been the concern of materials scientists. HMS polymer-modified nanoparticles with some special stimuli-responsive properties are able to solve the problem of targeted drug delivery and the control of drug release in practical applications.On the basis of the laboratory previous study, an environment-friendly method with mild conditions and simple steps for the synthesis of hollow mesoporous silica structures has been developed. We explored the best conditions for preparing hollow silica nanospheres by self-template strategy. By synergy of electrostatic attractions and hydrogen bonding interactions, silica spheres absorbed the cationic polyelectrolyte poly(N,N-dimethylaminoethyl methacrylate)(PDMAEMA) to form a robust protective layer on the surface, and subsequently treated in a weak alkaline aqueous solution, effectively transformed into hollow nanoparticles with pronounced hollow nature and well-defined mesoporous shell structure. As a protective layer, PDMAEMA not only effectively stabilized the outmost silica layer against etching, but also actively captured the negative silicate oligomers for shell-growth.Further, trimethoxysilyl-propyl-trithiocarbonyl-benzyl ester(BTPT), which is one of the silicone-based RAFT agents, was grafted onto the surface of silica spheres. Using the reversible addition-fragmentation chain transfer polymerization, nanospheres modified with the pH- and temperature-sensitive polyelectrolyte PDMAEMA were prepared. Then silica spheres grafted with PDMAEMA were transformed to the hollow mesoporous structure at ambient temperature by the above surface-protected etching strategy, and the hollow mesoporous silica nanospheres modified with the PDMAEMA(HMS@PDMAEMA) were obtained. The resultant hybrid nanoparticles with pH- and temperature-sensitive polymer shell and HMS core were characterized by a variety of techniques such as 1HNMR, FTIR, GPC and TEM. The pH-sensitive behavior was tested by nano-size and zeta potential analyzer.Finally, we used simulation drug Orange ?? and model drug sulfasalazine and doxorubicin to investigate the drug loading capacity and controlled release ability of the carrier by UV spectrophotometry, and calculate its loading rate and the release rate. The effect of the degree of polymerization of the surface grafting PDMAEMA on the controlled release ability was investigated. The results showed that the HMS@PDMAEMA possess high drug loading efficient and good capacity of controlled-release when PDMAEMA was in proper degree of polymerization. We envision that the HMS@PDMAEMA nanosystem should have the performance with acidity control of drug release.