Development and characterization of silver nanoparticles obtained by green synthesis from leaves of Aguaribay (Schinus areira).

BORDÓN, ANAHI; FERREYRA MAILLARD ANIKE PV; CUTRO, ANDREA C.; HOLLMANN, AXEL

Congreso; XLIX Reunión Anual de la Sociedad Argentina de Biofísica; 2021

Sociedad Argentina de Biofisica

The increased emergence of antibiotic-resistant bacteria is a serious health problem worldwide. This situation has motivated the research of new antimicrobial agents. In this sense, nanoparticles have received increasing attention for their antimicrobial activity. The objective of this work was to obtain silver nanoparticles (AgNPs), from AgNO3, by green synthesis using an aqueous extract of leaves of Schinus areira as a reducer and stabilizer agent, and characterization of its antimicrobial action against gram-positive and gramnegative bacteria. The AgNPs obtained were evaluated by UV-vis spectroscopy, Zeta Potential and DLS, confirming the presence of AgNps with a maximum absorbance at 420nm and the absorption intensity of the resulting spectra increased as a function of the amount of extract used (2 %, 4% and 8%). The AgNPs obtained with the low concentration of extract show the highest size and polydispersity (66,3±35,8 nm) while there were no significant differences between the other two remaining conditions with an average size around 40 nm. Later, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (CBM) of the AgNPs obtained using 4% and 8% of leaves extract were determined in E. coli and S. aureus. Both nanoformulations showed high antibacterial activity with MIC values of around 2 pM and CBM of 4 to 8 pM. To a better knowledge of the antibacterial action, death curves were carried out. In agreement with the CBM data, both syntheses at 2 x MIC managed to reduce 90% of the bacterial population after 1 hour of incubation. Finally, to characterize the mechanism of action,determination of the oxygen reactive species (ROS) and membrane damage were evaluated by spectrofluorometry. Both AgNPs tested were able to increase ROS levels in E.coli and S. aureus, as well as induce some damage in the bacterial membrane, but with some differences among each synthesis. Overall, it can be concluded that these biosynthesized produce AgNPs that have colloidal stability and antibacterial activity toward gram-positive and gram-negative bacteria. Regarding the mechanism of action,our findings suggest that the intracellular ROS induction by AgNPs could induce oxidative stress followed by damage to bacterial membrane leading to cell death.