Synthesis and characterization of nanoparticles for potential applications in wound healing

Abstract

In this work, Silver Nanoparticles (AgNPs) were synthesized in water using either polymer assisted chemical reduction synthesis method or green synthesis. The obtained AgNPs were characterized by Dynamic Light Scattering (DLS) and UV-visible spectroscopy (UV-vis), and further tested for antibacterial activity to evaluate their potential use in wound healing. At first polyvinylpyrrolidone (PVP 10 KD) and Low-Molecular Weight Chitosan were used as coating agents during the reduction of silver nitrate with a strong reducing agent sodium borohydride (NaBH4). Our DLS results demonstrated that AgNPs-polymer are in the range of 2-50 nm. Unfortunately, the AgNPs obtained with NaBH4 reduction were not very stable and aggregated with time (48 hours to one week). Therefore, in a second trial, the green synthesis was based on using turmeric powder to produce AETP (Aqueous Extract Turmeric Powder) which acted as both coating and reducing agents over silver nitrate. Different parameters were evaluated; the effect of temperature, concentration of Silver nitrate and reaction time. In all experiments, a color change from light yellow for AETP/Ag solution to dark brown was observed indicating the successful reduction of AgNO3 by AETP and formation of AgNPs-AETP. The temperature seemed to affect most the synthesis: in fact, the reaction was faster at high temperature and the NPs sizes were found to decrease as the temperature increases (50 to 100 ºC). It should be noted that an extensive heating at boiling temperature might aggregate the Ag NPs that were found to adsorb and stain the wall of the flask after 2 hours. Moreover, as the concentration of silver nitrate increases the resulting Ag NPs increased, this was translated in the red shift of the Surface Plasmon resonance band of Ag NPs accompanied by the size increase detected in DLS. The Ag NPs-AETP obtained after 1 hour at 80-85 ºC were tested on Escherichia coli (E. coli) and Staphylococcus aureus (S.aureus) bacteria to evaluate their antibacterial activity and compared to AgNPs-PVP obtained from the chemical reduction with NaBH4. The results showed positive effects with NPs produced from Turmeric powder, in terms of killing the E. coli and S. aureus bacteria. On the other side, NPs produced by PVP lead to aggregations that could not pierce the bacteria cell walls with direct leaching of Ag+ ions due to the PVP macro sizes. Another green synthesis was accomplished using coffee and zinc nitrate to produce ZnO NPs-CPE (Zinc oxide Nanoparticles-Coffee Powder Extract). We used FTIR method to identify the presence 12 of ZnO after calcination. An average size of 87 nm was observed after analysis by DLS and UVspectroscopy. The last syntheses in this study were based on using PVA, PVP and PEG polymers with zinc nitrate and PEG with copper nitrate to produce ZnO NPs-Polymer (PVA, PVP, PEG) and CuO NPs-PEG by a sonochemical method aided with base (NaOH). Our results showed particles sizes ranging from 85 to 1086 nm for ZnO NPs and an average of 80 nm for CuO NPs. Zinc and copper NPs though showed negative results on E. coli and S. aureus bacteria.