Manganese ferrite nanoparticles functionalized with gallic acid for inhibition of insulin amyloids formation and mitigation of oxidative stress

Protein misfolding and aggregation into amyloid fibrils are central features of several chronic diseases, including type 2 diabetes and neurodegenerative disorders. Oxidative stress further exacerbates amyloid-related cytotoxicity, highlighting the need for multifunctional therapeutic strategies. In this study, manganese ferrite nanoparticles (MnFe₂O₄ NPs) were synthesized and functionalized with gallic acid (GA), a natural antioxidant, to create nanocomposites (NCs) with both anti-amyloidogenic and antioxidant properties. Two functionalization strategies were investigated: (i) direct covalent conjugation of GA onto oleylamine-coated MnFe₂O₄ NPs using EDC/NHS chemistry (MFO@GA), and (ii) physical adsorption of GA onto polymer-coated MnFe₂O₄ NPs using polyethylene glycol (PEG) or polyethylenimine (PEI) as matrices (MF@PEG-GA and MFO@PEI-GA, respectively). The resulting NCs were thoroughly characterized by FTIR, UV-Vis, TGA, and magnetic measurements, confirming successful GA incorporation. Antioxidant activity, evaluated via DPPH and H₂O₂ assays, revealed that GA incorporation significantly enhanced radical scavenging capacity. MFO@PEI-GA exhibited the lowest DPPH IC₅₀ values (24.8 μg/mL at 30 min), while MFO@GA showed the strongest H₂O₂ scavenging effect (IC₅₀ = 68.55 μg/mL). Anti-amyloidogenic activity against insulin fibrillation was assessed via Thioflavin T (ThT) assay. MFO@GA achieved the highest inhibition of fibril formation (74.3% inhibition; final aggregation 25.7%), along with the most effective fibril disassembly (21.82% remaining fluorescence, t₁/₂ = 0.89 h). Polymer coatings modulated GA release profiles, with PEI matrices enabling sustained release over 48 hours. These findings underscore the synergistic antioxidant and anti-amyloid properties of GA-functionalized MnFe₂O₄ NPs and suggest their potential for mitigating amyloidosis and oxidative stress. • MnFe₂O₄ nanoparticles were functionalized with gallic acid via two distinct methods. • Polymer matrices (PEI, PEG) modulated gallic acid release and enhanced bioactivity. • MFO@GA showed superior insulin amyloid inhibition and radical scavenging ability. • Release kinetics followed Fickian or anomalous diffusion depending on formulation. • These nanocomposites hold promise for oxidative stress and amyloidosis treatment.