Polypeptide complex coacervate core micelles as model nanoreactors for mild synthesis of gold nanoparticles.

Complex coacervate core micelles (C3Ms) assembled from cationic poly(D,L-lysine) (PRK, R is racemic) and poly(L-glutamate)-b-poly(ethylene glycol) (PLE-b-PEG) are investigated as preassembled, biomimetic nanoreactors for the mild synthesis of gold nanoparticles (AuNPs). Systematic comparison across coacervate architectures (AB + C, A + BC, AB + BC, and bulk A + C) demonstrates that the presence of a polymer-rich coacervate phase results in AuNP formation, with the PEG corona playing a dual role as both a microphase-separation driver and a steric stabilizer. Small-angle X-ray scattering (SAXS) experiments indicate that only architectures producing a well-defined dense coacervate core support AuNP formation, and that nanoreactor morphology is preserved during the early nucleation and growth periods. Time-resolved UV-visible light absorption spectroscopy, dynamic light scattering, and SAXS collectively allude to a kinetic framework consistent with the classical LaMer mechanism. These results establish polypeptide C3Ms as simple nanoreactors for mild metal/metal oxide nanoparticle synthesis.