Injectable chitosan cryogel microspheres with biocompatible properties on mammalian macrophages in vitro

Macrophages play a vital role in rejection of the implant materials by producing pro-inflammatory TNF and IL6 cytokines. They are also important for the normal function of the immune system to fight against infections. Therefore, characterizing the immunotoxicity on this cell type will be informative for the medical use of the biocompatible materials. Chitosan-based materials have been widely considered as biocompatible and safe. They have been suggested for the bone implants. Studies suggest that depending on the setup and chitosan functionalization, the immune system may react differentially to the chitosan-based materials. In this study, we characterized the immunocompatibility of injectable chitosan cryogel microspheres on mammalian macrophages by measuring their effect on cell viability and these cells’ ability to produce pro-inflammatory cytokines in the absence and presence of LPS, as a stimulant. Different sizes of microspheres were used to examine the effect of the size on their plausible effects. Our results suggest that independent of their size, chitosan cryogel microspheres were immunocompatible. They did not influence the cell viability and pro-inflammatory cytokine production by LPS-induced macrophages. Moreover, these materials lacked immunostimulatory activity as well, which means they would not activate the macrophages in the absence of any stimulant after their direct interaction with these cells. These properties are advantageous for their possible utilization in the medical fields as minimally invasive materials due to their injectable properties.