In order to improve the antimicrobial activity of bacterial cellulose (BC), the silver nanoparticles (Ag NPs) were in situ fabricated on the BC membranes, affording BC and Ag hybrid antimicrobial materials, BC + Ag, which possesses excellent antimicrobial performance. Typically, carboxyl groups were firstly introduced into BC by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation. Then, the carboxyl-functionalized BC was performed with ion-exchange reaction to change the sodium ions into Ag + by immersing in AgNO 3 aqueous solution, generating Ag + anchored BC. Finally, two types of distinct reductive reagents including NaBH 4 and sodium citrate were employed to transform Ag + into Ag NPs to fabricate BC + Ag. The diameters of Ag NPs were determined to be 3.8 nm for NaBH 4 -reduced BC + Ag, and 22.0 nm for sodium citrate-reduced one, respectively. The silver content of BC + Ag were determined to be 1.944 and 2.895 wt% for NaBH 4 -reduced sample and sodium citrate-reduced one, respectively. Two types of BC + Ag both showed a slow and persistent Ag + release profile, but the NaBH 4 -reduced one released much more Ag + than that of sodium citrate under the same measurement condition. In-depth antibacterial analysis via the disc diffusion and colony forming count method disclosed that BC + Ag exhibited strong bactericidal effects against both Escherichia coli and Staphylococcus aureus . And the antibacterial activity of NaBH 4 -reduced BC + Ag was higher than the sodium citrate-reduced one. Overall, this study would further improve the antibacterial efficiency of BC + Ag.
Silver nanoparticles (Ag NPs) have been widely used for the disinfection and prevention of pathogenic bacteria. However, the aggregation and instability of Ag NPs significantly limit their bactericidal activity. As an alternative method, stabilization of Ag NPs on an inorganic biomaterial is a promising strategy. In this study, an inorganic material with good biocompatibility and bioactivity, calcium silicate hydrate (CSH), was employed as the host substance. A facile and efficient method was proposed to produce Ag NPs deposited on a CSH (CSH/Ag) composite. Ag+ ions were first embedded into the surface of CSH through ion-exchange and subsequently reduced to Ag NPs by a reducing agent. Due to the high specific surface area and great ion-exchange capacity of CSH, a series of CSH/Ag composites with different silver contents were easily synthesized. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental mapping, X-ray diffraction (XRD), nitrogen sorption/desorption analysis, and inductively coupled plasma-atomic emission spectrometry (ICP-AES) were employed to characterize the synthesized CSH/Ag composites. Moreover, Ag+ ions release behaviours from the CSH/Ag composites were investigated and the release profiles showed dose-dependent and long-time sustained release properties. Furthermore, the synthesized CSH/Ag composite displayed good biocompatibility and high antibacterial activities against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Overall, the newly designed CSH/Ag composite is believed to be a promising bactericidal agent in biomedical applications.
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