Visible light-accelerated formation of lipoprotein microgels within all-aqueous emulsions mediated by Au³

All-aqueous emulsions (AAEs) provide an oil-free template for fabricating biomicrogels. We show that visible light irradiation promotes the Au³⁺-induced oxidation of tyrosine residues in high-density lipoprotein (HDL), accelerating HDL microgel formation within AAEs. Au³⁺ is concomitantly reduced to Au nanoparticles (AuNPs). Irradiance at 50 mW cm^-2 yielded spherical microgels within ∼3 min, compared to ∼30 min without light (≈10×faster), and higher irradiance produced smaller particles. Fluorescence spectroscopy after AuNPs dissolution with potassium cyanide confirmed rapid di-tyrosine formation (λ_ex ≈330 nm, λ_em ≈391 nm), with faster kinetics under illumination than in the dark. Wavelength tests indicated that broad visible light was more effective than single-band illumination, consistent with overlap of protein and Au³⁺/AuNP absorption. Importantly, illumination reduced the Au³⁺ requirement for gelation. Microgels formed at Au³⁺-to-HDL ratios as low as 100-300:1 under light, whereas ≈500:1 was needed in the dark. Confocal and electron microscopy verified spherical morphology. These results demonstrate a mild, fully aqueous, and light-assisted route for producing HDL microgels through AAE templating. The work establishes a strategy for HDL microgel formation, while potential applications in microfluidics, 3D bioprinting, and controlled delivery require further investigation.