Biologically produced silver chloride nanoparticles from B. megaterium modulate interleukin secretion by human adipose stem cell spheroids.

Stem cell tissue constructs are likely to come into contact with silver-based nanoparticles-such as silver chloride nanoparticles (AgCl-NPs)-used as microbicidals at the implant site or in cosmetics. However, the effect of silver-based nanoparticles on 3D cell cultures with potential for tissue engineering has received little attention. Here, we examined the effect of sub-lethal doses (5, 10 and 25 µg/mL, for 1, 7 and 21 days) of AgCl-NPs produced by 'green' bacterial-based synthesis on spheroid 3D cultures of human adipose tissue stem cells (ASCs). Light microscopy analysis revealed that the shape and diameter of ASC spheroids remained largely unchanged after AgCl-NP treatment. Flow cytometry analysis with 7-AAD and 2',7'-dichlorofluorescein diacetate revealed no statistically significant differences in cell death but showed an increase of ROS levels for the untreated group and significant differences for the groups treated with 5 and 10 µg/mL at day 7 (p = 0.0395, p = 0.0266, respectively). Electron microscopy analysis showed limited cell damage in the periphery of AgCl-NP-treated spheroids. However, treatment with AgCl-NP had statistically significant effects on the secretion of IL-6, IL-8, IL-1β and IL-10 by spheroids, at specific treatment periods and concentrations, and particularly for IL-6, IL-8 and IL-1β. TGF-β1 and -β2 secretion also changed significantly throughout the treatment period. Our results indicate that, despite having little effect on cell viability and morphology, sub-lethal AgCL-NP doses modulate ROS production at day 7 for the groups treated with 5 and 10 µg/mL and also modulate the secretory profile of ASC spheroids. Thus, the use of skin implants or products containing Ag-NPs may promote long-term disturbances in subcutaneous adipose tissue homeostasis.