Biodistribution and hepatotoxicity of co-administered PEGylated gold and silver nanoparticles in rats following intravenous injection

The physicochemical properties of nanoparticles (NPs) critically influence their interactions with biological systems. Conventional approaches to study these relationships require separate animal groups for each NPs formulation, linking toxicity and pharmacokinetics (PK) to a single attribute (e.g., size or shape). Alternatively, co-administering NPs with distinct properties into a single organism enables simultaneous tracking and multiplexed quantification, reducing animal use and inter-group variability. Gold (AuNPs) and silver nanoparticles (AgNPs) are ideal platforms for this purpose due to their compatibility with advanced imaging techniques. By co-injecting paired NPs, biological variability is minimized and administration conditions are standardized. Here, we evaluated this co-administration approach by assessing the biodistribution and toxicity of polyethylene glycol (PEG)-modified AuNPs and AgNPs following intravenous administration in rats. PEG-AuNPs and PEG-AgNPs were synthesized and characterized for hydrodynamic size, surface charge, optical properties, morphology, and colloidal stability. Rats were given vehicle control, PEG-AuNPs alone, PEG-AgNPs alone, or co-administered via intravenous injection. Blood and several organs were obtained post 24 h. Biodistribution analysis was done using ICP-MS, metabolomic profiling via LC-MS/MS and FIA-MS/MS, followed by RT-qPCR analysis of liver injury biomarkers, cytochrome P450 enzymes, and phase II enzymes. PEG-AuNPs and PEG-AgNPs had spherical shape with core diameters of 13 and 20 nm, respectively, and a zeta potential near-neutral. At 24 h post-injection, both NPs accumulated mainly in the blood, liver, and spleen. Based on comprehensive toxicity evaluation, the treatment groups did not significantly differ from controls in liver injury markers (ALT/AST), cytochrome P450 enzymes, phase II metabolism-related gene expression, or inflammation-associated metabolomic profiles. Importantly, co-administration of PEG-AuNPs and PEG-AgNPs did not alter their biodistribution patterns or increase toxicity. In rats, co-administered PEG-AuNPs and PEG-AgNPs showed predicted biodistribution patterns without causing hepatotoxicity or metabolic disturbance. Multiplexed nanoparticle testing approaches could reduce animal use in nanotoxicology studies and accelerate material characterization and nano-formulation development due to the lack of synergistic toxicity or altered PK. As long as stability and surface chemistry are maintained, PEGylated metal nanoparticles offer attractive platforms for combinatorial nanomedicine development.