title: Preparation and characterization of uniform-sized chitosan/silver microspheres with antibacterial activities.
abstract: The chitosan/silver microspheres (CAgMs), which possess effective inhibitory on microorganisms, were prepared by an inverse-emulsification cross-linking method using CS/Ag sol as dispersed phase, whiteruss as continuous phase, and glutaraldehyde as crosslinking agent. The size and shape of CAgMs, greatly affecting their antibacterial activities, were controlled by varying the concentrations of cross-linking agent, emulsifier and CS/Ag colloid. The preparation conditions for obtaining uniform-sized microspheres were optimized. The morphology of CAgMs was characterized by scanning electron microscopy (SEM) and laser particle size analysis. The spherical CAgMs with smooth surface in the mean size of ca. 5 μm exhibited a narrow particle size distribution. Energy Dispersive X-ray spectroscopy (EDX) revealed the elemental composition of the microspheres. Transmission electron micrographs (TEM) and Fourier transform infrared spectroscopy (FTIR) of the microspheres confirmed the formation of silver nanoparticles (AgNPs). The X-ray diffraction (XRD) patterns and UV-Visible diffuse reflectance spectroscopy (UV-vis DRS) of the sample showed that AgNPs with the diameter no more than 20 nm were face-centered cubic crystallites. X-ray photoelectron spectroscopy (XPS) proved that AgO bond existed in the microspheres. Thermogravimetric analysis (TGA) showed that the starting decomposition temperature of CAgMs (ca. 260°C) was much higher than that of CS (ca. 160°C), suggesting that the as-prepared CAgMs possessed better thermal stability than original CS did. Antimicrobial assays were performed using typical Gram bacteria and fungi. The inhibitory effect indicated that the as-prepared microspheres exerted a stronger antibacterial activity as the concentration of the AgNPs is increasing, and the microspheres in smaller size had much better antibacterial activity than those in the larger size. The antimicrobial mechanism of CAgMs was discussed.
authors.affiliation: School of Sciences, Hebei University of Science and Technology, Hebei, Shijiazhuang 050018, China.
authors.forename: Jing
authors.initials: J
authors.lastname: An
authors.affiliation: School of Sciences, Hebei University of Science and Technology, Hebei, Shijiazhuang 050018, China.
authors.forename: Zhenxing
authors.initials: Z
authors.lastname: Ji
authors.affiliation: School of Sciences, Hebei University of Science and Technology, Hebei, Shijiazhuang 050018, China. Electronic address: dswang06@126.com.
authors.forename: Desong
authors.initials: D
authors.lastname: Wang
authors.affiliation: School of Sciences, Hebei University of Science and Technology, Hebei, Shijiazhuang 050018, China.
authors.forename: Qingzhi
authors.initials: Q
authors.lastname: Luo
authors.affiliation: School of Sciences, Hebei University of Science and Technology, Hebei, Shijiazhuang 050018, China.
authors.forename: Xueyan
authors.initials: X
authors.lastname: Li
mesh_terms: D000900:Anti-Bacterial Agents / Q000138:chemical synthesis* / Q000494:pharmacology*; D048271:Chitosan / Q000138:chemical synthesis*; D004926:Escherichia coli / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D009089:Mucor / Q000187:drug effects; D053761:Nanocomposites / Q000737:chemistry / Q000648:ultrastructure; D010316:Particle Size; D056951:Photoelectron Spectroscopy; D012233:Rhizopus / Q000187:drug effects; D012834:Silver / Q000494:pharmacology*; D013052:Spectrometry, X-Ray Emission; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013211:Staphylococcus aureus / Q000187:drug effects; D013818:Thermogravimetry; D014961:X-Ray Diffraction
chemical_list: D000900:Anti-Bacterial Agents; D012834:Silver; D048271:Chitosan
keywords: Antibacterial activity; Chitosan microspheres; Colloidal sol; Emulsification cross-linking technology; Silver nanoparticles