Insights into Anti-Inflammatory Activity and Internalization Pathway of Onion Peel-Derived Gold Nano Bioconjugates in RAW 264.7 Macrophages

Green synthesis of nanoparticles plays an important role in their efficient therapeutic effects in various biomedical applications. Here, we prepared gold nano bioconjugates (GNBCs) from the ethyl acetate fraction of onion peels and investigated their anti-inflammatory activity in lipopolysaccharide-stimulated RAW 264.7 macrophages. The GNBCs were characterized by UV-visible spectroscopy, dynamic light scattering, and transmission electron microscopy. Comparative studies have been conducted among GNBCs, fractionate alone [onion peel drug (OPD)], and the standard drug dexamethasone in various anti-inflammatory assays. It was observed that GNBCs showed comparatively good therapeutic efficacy than the fractionate alone. At the lowest 10 mu g/mL concentration, the GNBC and OPD exhibited 70.86 and 91.98% of reactive oxygen species production, 10.88 and 20.97 ng/mu L of nitrite production, 337 and 378 pg/mL of TNF-alpha production, 27.1 and 30.64 pg/mL of IL-6 production, respectively, by maintaining a satisfactory cell viability. Moreover, to understand the mechanistic pathway of GNBCs in their entry into the macrophages, their localization, and duration, uptake studies have been performed where a caveolar-mediated endocytosis pathway is found to be prominent. Hence, this study will lead to the development of cheap, green synthesis of nano bioconjugates and their role in inflammation.

Automated summary

Green synthesis of nanoparticles is important for their therapeutic effects in biomedical applications. In this study, gold nano bioconjugates (GNBCs) were prepared from onion peels and their anti-inflammatory activity was investigated. The results showed that GNBCs had better therapeutic efficacy than the fractionate alone, reducing reactive oxygen species production, nitrite production, TNF-alpha production, and IL-6 production while maintaining satisfactory cell viability. Additionally, a caveolar-mediated endocytosis pathway was found to be prominent in the entry of GNBCs into macrophages.