Evaluation of antimicrobial and antibiofilm activity of green synthesized metal nanoparticles

Recent advances in nanotechnology are drawing attention today due to the increased surface area of nano-sized structures and the many different properties they possess. Nanoparticle related studies provide extraordinary contributions to the study areas that contribute to transforming the scientific world. Nanoparticles continue to develop the technology in a way that leads to very important changes with its unique properties while it finds application in consumer and industrial products. However, increased production of nanoparticles and their use or unwanted release in the environment reveals the need for policies and processes that provide consumer and environmental safety. Once we combine the safe preparation of nanoparticles with potentially safe methods, it is possible to remove any harmful effect that may occur. Biosynthesis of nanoparticles using different biological methods is effective for numerous applications in different disciplines. Despite the use of different approaches (physical and chemical) for the synthesis of nanoparticles, green synthesis has become the most preferred method due to its high efficiency, cost effectiveness and environmental benefits. Within the scope of thesis study; the synthesis of silver (AgNP), copper oxide (CuONP) and iron oxide (FeONP) nanoparticles using plant extracts and their characterization, and the evaluation of the biological activities of nanoparticles synthesized in this way have been identified as the main targets. It is also one of the basic objectives of the study to determine the role of the size and shape of metallic nanoparticles and the plant extract source, which is used in nanoparticle synthesis, in various biological activities, especially antimicrobial and antibiotic effect of nanoparticles. In accordance with this purpose; AgNP, CuONP and FeONP were obtained by green synthesis at room temperature using different concentrations of aqueous extracts of Thymbra spicata L. var. spicata (Zahter). Using the Cynara scolymus (Artichoke) and Mentha piperita (Mint) leaf extracts in AgNP synthesis, the biological activities of nanoparticles synthesized through leaf extracts of three plants with economic importance were studied comparatively. Nanoparticles were characterized using different spectroscopic and microscopic analysis methods. As a result; TEM analysis of AgNPs synthesized using plant extracts revealed that the size and shape of AgNPs could be controlled by plant extract concentration. The average AgNP diameter decreased from 70.2 nm to 25.1 nm with increasing T. spicata leaf extract concentration according to TEM results. Moreover, according to size analysis of TEM study, CuONP and FeONP have been found to have average particle diameters around 25 and 100 nm, respectively. At the same time, when the size analysis of nanoparticles was examined by different techniques, it was revealed that the nanoparticle size was listed as DLS> AFM> TEM> XRD. AgNPs synthesized using leaf extracts of three different plants exhibited significant antibacterial activity against two different gram-negative and gram-positive bacteria. It was determined that the CsAgNP obtained from C. scolymus leaf extract showed the maximum antibacterial activity with a maximum inhibition zone of 18.53 mm in diameter and 12.5 μg/mL MIC value against S. aureus. Antibiofilm acitivity for S. aureus was evaluated to determine the antibiofilm activity of the synthesized nanoparticles. In addition, it shows that the antibacterial and cytotoxic activity of AgNPs synthesized using the T. spicata leaf extract is shape-dependent. In the thesis study, samples containing nanoparticles of different shapes were observed to show strong antibacterial and cytotoxic activity, compared to samples with nanoparticles in spherical form. The results demonstrate that the biological activities of AgNPs are influenced by the nanoparticle's shapes and the plant extract source used in the synthesis. In addition, antimicrobial, antibiofilm, antioxidant and cytotoxic activities of CuONP and FeONP synthesized using T. spicata leaf extract were evaluated. According to obtained results, it was observed that FeONPs showed the least antibacterial activity while AgNPs showed the highest antibacterial activity.