Synthesis and antibacterial activity of colloidal selenium nanoparticles in chitosan solution: a new antibacterial agent

High incidence of bacterial infections and antibiotic resistance as a growing problem has urged the need for novel antibacterial agents. The main purpose of this in vitro study was to evaluate the antibacterial activity of the chitosan-based selenium nanoparticles (Cts-Se-NPs) solution against gram-positive and gram-negative bacteria. The Cts-Se-NPs solution was synthesized using a simple chemical reduction method and characterized using ultraviolet-visible spectrophotometry, a particle size analyzer, and atomic force microscopy. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the Cts-Se-NPs solution were determined against gram-negative (i.e., Pseudomonas aeruginosa, Salmonella typhimurium, and Escherichia coli) and gram-positive (i.e., Streptococcus sanguinis, Staphylococcus aureus and Enterococcus faecalis) bacteria using a broth microdilution method. According to the results, S. sanguinis, S. aureus, and E. faecalis showed MIC values of 0.068, 0.137, and 0.274 mg ml(-1), respectively. Moreover, the results revealed that the concentration of 0.274 mg ml(-1) had a higher bactericidal effect than the other concentrations. As the concentration of Cts-Se-NPs increased to 0.274 mg ml(-1), S. sanguinis, S. aureus, and E. faecalis were completely killed after 1, 2, and 6 h, respectively. Further, S. aureus and S. sanguinis were totally killed after 24 and 6 h, respectively, at the concentration of 0.137 mg ml(-1). The Cts-Se-NPs solution did not elicit any significant antibacterial effect against P. aeruginosa, S. typhimurium, and E. coli. The Cts-Se-NPs solution can be further investigated for various antibacterial applications in the fields of medicine and dentistry, such as disinfection and sterilization of medical devices, as well as mouthwash in periodontal diseases and anti-caries agents.