Plasma-Corona Signatures of PEG-Mimetic Exscalar Ultra-Stable AuNPs beyond Conventional Stability: A Proteomics Perspective

Polyethylene glycol (PEG) has been the gold-standard ligand for imparting “stability” and “biocompatibility” to diverse nanocargos, imparting long-term systemic circulations. Growing concerns over accelerated blood clearance, anti-PEG immunogenicity, hypersensitivity, and nonbiodegradability compromised its status as the gold standard. Herein, we coanalyzed the interactions of our recently developed PEG-comparable ultrastable exscalar-AuNPs with PEG-AuNPs in two systems: complete Dulbecco’s Modified Eagle’s Medium (cDMEM) and human plasma. Using materials, physicochemical characterizations, proteomics, and mass spectrometry, we assessed the stability of these NPs alongside protein corona alterations. While both formulations remained stable in plasma, exscalar-AuNPs adsorbed only 67 proteins compared to 131 for PEG-AuNPs. Bioinformatics revealed distinct binding patterns; in cDMEM, exscalar-AuNPs bound specifically to α-trypsin, sulfhydryl oxidase, kininogen, and c-lectin. While in plasma, they predominantly bind immunoglobulins, complement C1q and C4-A, fibrinogen, plasminogen, platelet factor, with key biological functions in immunity, clotting, fibrinolysis, angiogenesis, cell adhesion, lipid transport, inflammation, and vasodilation. Notably, thrombospondin 1, apolipoprotein, and vitronectin were consistent. In contrast, PEG-Au in cDMEM interacted with hemoglobin, α2-heat shock glycoprotein, β-actin, apolipoprotein, vitronectin, and α-antiproteinase. In plasma, PEG-Au bonded to immunoglobulins, thrombospondin 1, amyloid-β, complement C1q and C3, fibrinogen, platelet factor, vitronectin, plasminogen, with the only common protein being vitronectin. Strikingly, exscalar-AuNPs preferred proteins with isoelectric points between 5 and 7, while PEG-AuNPs attracted proteins with pI > 9. These differences in protein binding are critical, as they influence nanoparticle fate, circulation time, biodistribution, cellular uptake, and immunogenicity. To our knowledge, this is the first proteomic demonstration of a biodegradable, oligopeptide-coated AuNP platform that mimics PEG in providing the Au stability and biocompatibility. Overall, the sustainable oligopeptide coating, reduced immune recognition, and refined biomolecular interactions position our exscalar-AuNPs as next-generation nanocargos for precision theragnostics.