| Silver nanoparticles(AgNPs) have been widely used in the fields of photoelectricity, biology, chemistry and material due to their unique optical, electrical, thermal and magnetic properties. However, the properties of AgNPs are drastically affected by the preparation process. Therefore, it will be of great importance to investigate the preparation method of AgNPs. Theoretically, physical and chemical methods are generally conducted under more rigorous reaction condition, require the use of toxic chemicals, and will produce hazardous by-products, while microbiological method is time consuming and requires suitable microbial strain and costly media for microbial growth, which limit their practical application immensely. Comparatively speaking, plant extract method is a green method to prepare AgNPs, which can overcome the above-mentioned drawbacks. Moreover, the AgNPs prepared by this method are more stable and safer, which makes their application in many fields especially in biomedicine received considerable attention.In the first part of this work, Lycium barbarum L. aqueous extract was prepared by a simple ultrasonic extraction method and acted as reducing agent to synthesize AgNPs under visible light. The effects of Lycium barbarum L. aqueous extract concentration and the illumination time on the preparation of AgNPs were investigated. The results showed that under the optimized conditions(i.e., the Lycium barbarum L. aqueous extract concentration of 4 mg/mL, the illumination time of 5 h), the yield of AgNPs reached 100%. The characterization of XRD and TEM showed that the obtained nanoparticles were single crystalline and near spherical AgNPs with a particles size range of 10- 45 nm. The mechanism of the preparation of AgNPs by Lycium barbarum L. aqueous extract has been put forwarded: Ag+ interacts with Lycium barbarum L. aqueous extract through coordination and other intermolecular interactions to form their complex compound and then transforms to Ag0 by receiving an electron from Lycium barbarum L. aqueous extract in the complex compound under visible light irradiation, and AgNPs will be obtained later on with the Lycium barbarum L. aqueous extract acting as capping agent. As expected, a certain amount of Lycium barbarum L. aqueous extract was adsorbed on the AgNPs, which was confirmed by the result of both FTIR and EDS. The obtained AgNPs exhibited excellent antimicrobial activity for both Gram negative bacteria and Gram positive bacteria, in which the Lycium barbarum L. aqueous extract exerted important regulating effect. Moreover, MTT-test showed that the AgNPs synthesized by Lycium barbarum L. aqueous extract possessed good biosecurity for their negligible cytotoxicity, which were expected to be used in biomedical fields.In view of the good biosecurity of AgNPs synthesized by Lycium barbarum L. aqueous extract, in the second part of this work, the Goji-AgNPs/PVA hydrogel dressing was prepared by the freezing-thawing method with the AgNPs synthesized by Lycium barbarum L. aqueous extract acting as raw material. The characterization of TEM and FTIR accompanying with the theoretical calculation based on density functional theory(DFT) showed that AgNPs distributed in the Goji-AgNPs/PVA hydrogel dressing and could stably existed due to the interaction between Goji-AgNPs and PVA hydrogel. In addition, experimental results confirmed that the Goji-AgNPs/PVA hydrogel dressing owned several advantages: 1) the transparency was very good, which made it convenient to observe the status of wound healing; 2) the moisture content was greater than 90%, which could keep the wound in a moist environment; 3) the Goji-AgNPs/PVA hydrogel dressing exhibited excellent antimicrobial activity for both Gram negative bacteria and Gram positive bacteria; 4) trypan blue staining results indicated that the Goji-AgNPs/PVA hydrogel dressing was without obvious cytotoxicity. Therefore, this Goji-AgNPs/PVA hydrogel dressing possessed great application prospect in the field of wound healing. |
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