Green Synthesis of Selenium Nanoparticles in the Presence of Mycobacterium Bovis Cell Lysate: a Novel Fabrication Approach and its Immune-Modulatory Effects

Mycobacterium bovis (M. bovis) is a slow-growing bacteria that can intracellularly reduce selenium ions to elemental selenium nanoparticles (SeNPs). We used bacterial lysates along with vitamin C to help the synthesis of SeNPs coated with M. bovis Bacille Calmette-Guérin (BCG) crude hydrophobic materials. However, the large-scale fabrication, separation, extraction, and purification of intercellular SeNPs which are prepared by using M. bovis, have many complexities. So, we developed a simple method for preparation of above BCG-coated nanoparticles and tested its potential immune-modulatory effects. In the current investigation, we cultivated the M. bovis in conventional media and prepared total cell lysates from this bacterium by just applying freeze and thaw and ultra-sonication. The resulting cell lysates were added to the solution containing selenium ions before adding the ascorbic acid as a reducing agent. At the end of the process, the fabricated selenium nanoparticles were separated by centrifugation and characterized by different instrumentation methods. In the next step, to evaluate the immune-modulatory effects of the hepatitis B surface antigen (HBsAg) vaccine alone, and in combination with plain SeNPs or SeNPs-BCG lysate, the serum level of interferon-gamma (IFN-γ) was determined in different groups by enzyme-linked immunosorbent assay (ELISA). This study showed adjuvant effects of prepared nanoparticles (in both 10 µg/300 µL and 100 µg/300 µL doses) in increasing the level of interferon-gamma (IFN-γ) in comparison with vaccine alone. Moreover, in both doses of SeNPs-BCG lysate, the level of interferon-gamma (IFN-γ) was remarkably higher than the same doses of plain SeNPs. As a result, synthesized SeNPs in the presence of whole-cell lysates of M. bovis indicated a greater ability to induce the interferon-gamma (IFN-γ) compared with other groups. Additionally, its easy fabrication procedure can be considered its superiority.