Engineering a well-ordered, functional protein-gold nanoparticle assembly

• Published in: Journal of inorganic biochemistry 2014-01, Vol.130, p.59-68
• Main Authors: Cheung-Lau, Jasmina C., Liu, Dage, Pulsipher, Katherine W., Liu, Weiren, Dmochowski, Ivan J.
• Format: Article
• Language: English
• Subjects: Biomineralization; Catalysis; Circular Dichroism; Ferritin assembly; Ferritins - chemistry; Ferritins - metabolism; Gold - chemistry; Metal Nanoparticles - chemistry; Nanoparticle–protein interaction; Protein Conformation; Protein self-assembly; Proteins - chemistry; Proteins - metabolism; Protein–nanoparticle association constant; Surface Plasmon Resonance; Time Factors
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/j.jinorgbio.2013.10.003

The study of interactions between proteins and nanoparticles is important to advancing applications of nanoparticles in biology, medicine, and materials science. Here, we report the encapsulation of a 5-nm diameter gold nanoparticle (AuNP) by thermophilic ferritin (tF), achieved in nearly quantitative yield under mild conditions that preserved the secondary structure, ferroxidase activity, and thermal stability of the native, 4-helix bundle protein subunits. Chromatography-based assays determined that stable protein assembly around AuNPs occurred on long time scales (~48h) and was reversible. Apparent association constants were determined at 25°C for equilibrated tF-BSPP-capped AuNP samples (KA=(2.1±0.4)×1078M−11) and compared favorably to salt-assembled tF samples (KA=(2.2±0.5)×1068M−11) at the same protein concentration (0.3mg/mL). Finally, addition of gold ions and mild reducing agent to the tF–AuNP assembly produced 8-nm diameter AuNPs with surface plasmon resonance band unchanged at 520nm, indicative of templating by the protein shell. Thermophilic ferritin 4-helix bundle dimer assembles into 24mer in presence of high salt, but appropriately sized gold nanoparticle can also induce room-temperature assembly, with nanoparticle encapsulated inside protein shell. [Display omitted] •Synthesis: Ferritin-5-nm gold nanoparticle assembly occurred at room temperature within 48 h.•Characterization: Protein-AuNP maintained secondary structure and passaged sizing chromatography.•Functional Assays: Protein preserved ferroxidase activity and templated gold nanoparticle growth.•Overview: This approach creates stable protein assemblies at metallic colloidal interfaces.