| Demands for antibacterial materials and products have been increased when the drug resistance of microorganism is wide-spreaded. Silver nanoparticles (Ag NPs) as an inorganic antimicrobial agent, widely used in biomedical fields, possess high antimicrobial activity, good durability, broad antibacterial spectrum, low drug resistance and security. However, Ag NPs easily aggregate because of the high surface activity, which finally leads to a functional loss of nanoparticles. The dispersity and stability of Ag NPs can be greatly improved by the coverage of polymers, which is bound to expand the application of Ag NPs in biomedical fields. In this study, a series of Ag NPs/polymer compounds were synthesized by using silver nitrate as precursor, chitosan (CTS) and starch (ST) as protective agents. Moreover, the liquid phase reaction method and microwave radiation were used to obtain the AgNPs/polymer compounds.1. Nano-Ag/ST core-shell particles and nano-Ag/ST sols were prepared through a simple chemical reaction method by using ST as protective agent and NaBH4as reductant. The formation of Ag/ST sols was influenced by ST dosage, concentration of reductants, temperature, reaction time and the pH value. The results showed that the Ag/ST particles with small size, narrow size distribution and high stability were obtained under the condition of ST dosage of0.5g, molar ratio of NaBH4/AgNO3in2:1and the pH value of7.0. The complex particles had core-shell structures in size of5-20nm, with2nm of ST shell.2. Nano-Ag/ST sols were prepared through liquid phase reaction method by using ST as protectant and glucose as reductant. The morphology of nano-Ag/ST was affected by the pH value and the glucose concentration. The results showed that the optimum reaction conditions were the concentration of AgNO3solution in0.05-0.10mol/L, the molar ratio of glucose to AgNO3in3:1, the reaction time of10minutes and the temperature of70℃. The prepared particles were in uniform core-shell structure with the mean size of25nm.3. Ag/ST sols are synthesized by liquid phase reduction method by using sodium citra (Citra) as reductant. The optimal synthesis parameters are the molar ratio of Citra to AgNO3in3:1, the reaction temperature of70℃for120min. The most prepared Ag/ST particles presented a spherical core-shell structure in mean size of30nm and few ones were ellipsoidal.4. Nano-Ag/CTS complex sols were synthesized by microwave heating using sodium citrate as reductant and CTS as protectant. The results showed that spherical Ag NPs in mean size of30nm were prepared under conditions of molar ratio of CST to Ag in3:1, the pH value of6.0and microwave heating time of25min under medium and low power.5. The antibacterial performances of Ag/ST and Ag/CTS were tested by inhibition zone method and minimal inhibitory concentration (MIC) method, and E.coli and S. Aureus were selected as experimental strains, respectviely. The inhibition zone test showed that both of the two compounds had a great antibacterial activity. Moreover, the smaller and the more uniform the particles were, the stronger the antimicrobial activity was. The MIC of Ag/ST and Ag/CTS sols prepared by chemical reduction method and microwave method were125ppm and300ppm, respectively, and the bactericidal rates of the two compounds were greater than99.9%, indicating excellent antibacterial activities of Ag/ST particles. Additionally, Ag/CTS compounds presented higher antibacterial performance than that of Ag NPs or CTS used alone. The antibacterial mechanisms of Ag NPs and CTS were studied. The great antibacterial activities of Ag/CTS sols were due to the synergistic action of Ag NPs and CTS.In summary, as natural inorganic antimicrobial materials, nano-Ag/ST and-Ag/CTS sols have advantages of great antibacterial activities, biodegradability and nontoxicity, which are favor of their application to textile and biomedical fields. |
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