Encapsulation of Chlorhexidine in Spherical and Rod-like Mesoporous Silica Nanoparticles

Objective: Chlorhexidine (CHX) is an active ingredient in mouthrinse, due to its effective antibacterial property. Currently, nanotechology has increasingly used in biomedical area. The mesoporous silica nanoparticles (MSNs) with large surface area may serve as a potential drug delivering vehicle for oral care. The present study aimed to synthesize the MSNs with two representative morphologies (spherical and rod-like) and compare their CHX loading efficiency and release profiles. Method: A surfactant-templating mechanism was introduced and the morphology of MSNs was controlled by adjusting the concentration of cetyltrimethylammonium bromide (CTAB). The diameter of MSNs was determined by transmission electron microscopy (TEM). After a reflux in acidic ethanol, extra CTAB was removed from MSNs by calcination. CTAB residue was analyzed using Infrared (IR) spectrometry. The loading concentrations of CHX were 1 and 2 mg/mL, which were determined by thermogravimetric analysis. The CHX release from MSNs with highest loading efficiency was studied by UV/visible absorption spectroscopy. Result: The diameter of spherical MSNs was 220 nm, while the width and length of rod-like MSNs were approximate 60 and 480 nm, respectively. IR and TEM results showed that 4-hour programmed calcination could remove CTAB completely without serious particle aggregation. CHX loading efficiency in rod-like MSNs was significantly higher than that in spherical particles at 1 mg/mL. Moreover, CHX release from the spherical MSNs was faster than the rod-like MSNs at 24 h. Conclusion: The present study shows for the first time that MSNs can be programmed heated to remove CTAB completely without causing serious particle aggregation. Rod-like MSNs may have a higher loading efficiency of CHX than the spherical MSNs with a prolonged release effect.