Synthesis and Characterization of Biogenic Selenium Nanoparticles with Antimicrobial Properties Made By Staphylococcus Aureus, Methicillin-Resistant Staphylococcus Aureus (MRSA), Escherichia coli, and Pseudomonas Aeruginosa

Antimicrobial resistance is a global concern that affects more than two million people each year, and that will kill more people than all the known diseases by the year 2050. Thus, new approaches to treat bacteria are required. The use of metallic nanoparticles shows as one of the most promising approaches, since bacteria may not develop a resistance to these nanostructures as they do for antibiotics. While metallic nanoparticle synthesis processes have been well studied, they are often accompanied by significant drawbacks such as cost, extreme processing conditions, and toxic waste production. In this work, we explored the environmentally safe synthesis of selenium nanoparticles, which have shown promise in killing bacteria. Using Escherichia coli, Pseudomonas aeruginosa, Methicillin-resistance Staphylococcus aureus (MRSA) and Staphylococcus aureus, 90-150 nm average diameter selenium nanoparticles were synthesized using an environmentally-safe approach. Nanoparticles were characterized using transmission electron microscopy (TEM) energy dispersive X-ray spectroscopy (EDX) to determine the chemical composition, and ICP-MS to validate chemistry. Nanoparticles were also characterized and tested for their ability to inhibit bacterial growth. A decay in bacterial growth after 24 hours experiment was achieved against both Staphylococcus aureus and Escherichia coli at biogenic selenium nanoparticle concentrations from 25 to 250 µg/mL and showed no significant cytotoxicity effect against human dermal fibroblasts (HDF) cells for 24 hours. Bacteria were able to synthesize selenium nanoparticles through the use of different functional structures within the organisms, mainly enzymes such as selenite reductases. Therefore, biogenic selenium nanoparticles made by bacteria represent a viable approach to reduce bacteria growth overcoming the drawbacks of synthetic methods that employ toxic chemicals.