Direct synthesis of silver nanoparticles modified spherical mesoporous silica as efficient antibacterial materials

Abstract

The development of new antimicrobial agents that can overcome antibiotic-resistance and possess improved antibacterial activity is of important global need. A one-step process is demonstrated to prepare silver nanoparticle decorated MCM–41 type mesoporous silica nanoparticles (AgMSN, average diameter ~ 200–500 nm) using a novel cationic surfactant that does not lead to precipitation of AgBr. The resulting nanostructure was characterized using powder X-ray diffraction, nitrogen physisorption and chemisorption analyses, electron microscopy techniques, and UV–vis spectroscopy. Together, these data demonstrated the silver nanoparticles were uniformly dispersed on the MSN. Gram-negative E. coli K12 and Gram-positive B. subtilis were used to study the antibacterial properties of these nanocomposites by both the plate count method and optical density measurements. In the antibacterial tests for E. coli K12 and B. subtilis , the AgMSN exhibited low minimum inhibitory concentrations of 85 μg mL −1 AgMSN (Ag content 6.1 μg mL −1 ) and 90 μg mL −1 (Ag content is 6.4 μg mL −1 ), respectively, revealing the high antibacterial activity. Additionally, >95% growth reduction in continuous re-culturing tests (6 cycles, 25 days) at minimum bactericidal concentration demonstrate excellent long-term antibacterial activity of AgMSN. The nanocomposites showed excellent antibacterial activity against both. These results demonstrate that AgMSN composites possess great potential as an antibacterial material. Silver nanoparticle decorated MCM–41 type mesoporous silica nanoparticles (AgMSN) have been synthesized by a one-step process which exhibits excellent long-term antibacterial activity against E. coli K12 and B. subtilis . • Silver nanoparticle decorated MCM–41 type mesoporous silica nanoparticles. • A one-step process of synthesis without using any reducing agent. • Excellent antibacterial activity against both Gram-positive and Gram-negative bacteria. • Re-culturing test to prove long-term antibacterial property. • Study of antibacterial mechanism.