In addition to IL-1β, IL-12 p70, and TGF-β, increased TNF-α levels were observed for NP5000 (Figure ). TNF-α plays a significant role in the pathophysiology of OA along with IL-1β as both cytokines have synergistic pro-inflammatory effects. We observed varying levels of IL-1β and TNF-α depending on the conditions, with IL-1β levels increasing in the ADA condition alongside decreased TNF-α levels, while TNF-α levels increased in the COL condition along with reduced IL-1β levels. In comparison to NP0, such results indicate that the physicochemical properties of the surface dictate the immune system response, potentially due to the hydrodynamic radius owing to PEG shielding.