| Objective: Mesoporous silica nanoparticle(MSN) was applied in biomedical field due to its excellent properties in biocompatibility and controlled particle size. Moreover, loaded with calcium and phosphate ions, added with a outer-coated solid silica(s Si O2) shell as switch, this s Si O2-Ca/P@MSN system was introduced into the dentinal tubules to treat denting hypersensitivity(DH). In this facile system, not only MSNs act as occlusive materials, formation of Ca P precipitation come from the slow release of above mentioned ions further confirmed the full compaction in the tubules. This make sense for a long term treating efficiency.Materials And Methods: Using cetyltrimethyl ammonium bromide(CTAB) as surfactant, orthosilicate(TEOS) as silica source, MSNs were obtained from a diluted alkaline solution system after 2 hours of hydrothermal treatment at 58 o C. After a careful characterization of original MSNs, an additional design of switch for controlled release was proposed. A solid silica shell(s Si O2) was coated on the outer surface of MSNs to block loaded model drugs such as Ibuprofen or Ca and phosphate ions. Due to its controllable thickness, the outer shell’s degradation time in solution could be controlled, which sequentially leading to a controlled release of model drugs. In detail, we tested different volume of TEOS(0.25 m L, 1m L) in the coating procedure. As a result, the coating thickness was ascending from about 3 nm to 5 nm, which assuredly made difference in release profile of Ibuprofen(simulated body fluid, SBF, 37 o C). After that, this drug delivery system applied in loading calcium and phosphate ions. Further, a release profile of calcium ions also proved the validity of this system. Ultimately, this s Si O2-Ca/P @MSN system was plugged in the dentine tubules in vitro. The efficiency of this treatment was manifested by observation from both surface section and vertical section. Besides, evaluation named CCK-8 method for cytotoxicity test of this system was also implemented, and the result of that indicated an excellent performance in maintaining survival rate of cells.Over all,above mentioned samples were characterized by: Power X-ray diffraction(XRD) patterns were obtained on Rigaku D/Max-r A X-ray powder diffractometer(Japan) using Cu Kα(λ = 1.5418 ?) radia tion. Scanning electron microscopy(SEM) images were taken on the JSM-7001F(Japan) under a working voltage of 20 k V. Transmission electron microscopy(TEM) images were taken on the Hitachi HT- 7700(Japan) under a working voltage of 120 k V. The nitrogen adsorption-desorption isotherms were measured on an Tristar 3020 II(Micromeritics Co. Ltd.US) at 77 K. The concentration of IBU were monitored by UV-759 S spectrometer. The Ca2+ concentrations were monitored using a MP523 p H/ISE Meter(Shanghai San-Xin Instrumentation, Inc, China)Results: MSNs with uniform particles distribution between 80~110 nm and excellent dispersity were obtained. The XRD pattern verified typical features expected for MCM-41 materials, with peaks indexed at the(100),(110),(200) and(210) diffraction planes. After the s Si O2 coating procedure, a controlled outer shell between 3~5 nm was observed. As thickness of this accessional shell varied, the release profiles of Ibuprofen proved to be different. The release time could be extended to as long as about 200 hrs. When this model drug was change to calcium ions, the release profile was delayed to 7 hrs. Occlusive experiment using this s Si O 2-Ca/P@MSN system expressed an excellent performance in both surface occlusion and vertical penetration. Results of cytotoxicity test indicated its good biocompatibility.Conclusion: Overall we can say we have got a good method to the seal dentinal tubules, but more test should to be done to test it further ability. |
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