Green synthesis and characterization of Lawsonia inermis-mediated Au-Ag bimetallic nanoparticles: in-vitro antioxidant activity and preliminary in-vivo evaluation in an ICV-STZ mouse model

Abstract

Alzheimer’s disease (AD) is associated with progressive cognitive decline, oxidative stress, neuroinflammation, and amyloid-related pathology. This study investigated the green synthesis and physicochemical characterization of gold-silver bimetallic nanoparticles (Au-AgNPs) using an aqueous leaf fraction of Lawsonia inermis, assessed their in-vitro antioxidant activity, and integrated preliminary in-vivo findings from an intracerebroventricular streptozotocin (ICV-STZ) mouse model. Synthesis conditions were optimized by varying extract volume, precursor concentration, pH, and temperature. The optimized preparation used 100 µL extract, 1 mM metal precursor, pH 7, and 30 °C and displayed a surface-plasmon-resonance band near 537 nm. FT-IR indicated changes in plant-associated functional groups, XRD and SAED supported a crystalline face-centred cubic structure, EDX detected both Au and Ag, and HR-TEM showed particles approximately 10-32 nm in size. Au-AgNPs showed concentration-dependent in-vitro activity, reaching 88.78% DPPH, 90.03% hydrogen-peroxide, and 88.08% nitric-oxide scavenging at 100 µg/mL. In the supplied ICV-STZ dataset, Au-AgNP treatment was associated with cholinesterase activity, hippocampal cytokine concentrations, and cholesterol values closer to healthy-control values. Some animal-protocol details and biomarker results were incomplete in the source material and require verification. These data support further investigation but do not establish cognitive efficacy, definitive nose-to-brain targeting, or efficacy of an in-situ gel formulation. Complete safety, pharmacokinetic, brain-distribution, behavioural, and reproducibility studies are needed.