Nanoscale surface curvature modulates nanoparticle-protein interactions.

Rational optimization of nanoparticle (NP) surfaces is essential for successful conjugation of proteins to NPs for numerous applications. Using surface-roughened NPs (SRNPs) and quasi-spherical NPs (QSNPs) as two model nanostructures, we examined the effects of local surface curvature on protein conformation and interfacial behaviors by circular dichroism (CD) spectroscopy, fluorescence emission spectroscopy (FES), and isothermal titration calorimetry (ITC). The surface of SRNPs consisted of a mixture of undercoordinated and close-packed surface atoms at the highly curved and locally flat surface regions, respectively, whereas QSNPs were primarily enclosed by {100} and {111} facets covered with close-packed surface atoms. Our findings demonstrated that: 1) SRNPs possess higher tendency to denature BSA and accommodate a higher number of BSA molecules on the surface and 2) the aggregation of AuNP-BSA complexes, likely induced by either denatured BSA or reduced electrostatic repulsion between complexes, is dependent on both the BSA concentration and the NP surface curvature. This study also indicated that NP local surface curvature could potentially be used as a design strategy to preserve the biological function of proteins.

Nanoscale Surface Curvature Effects on Ligand-Nanoparticle Interactions: A Plasmon-Enhanced Spectroscopic Study of Thiolated Ligand Adsorption, Desorption, and Exchange on Gold Nanoparticles.

The interfacial adsorption, desorption, and exchange behaviors of thiolated ligands on nanotextured Au nanoparticle surfaces exhibit phenomenal site-to-site variations essentially dictated by the local surface curvatures, resulting in heterogeneous thermodynamic and kinetic profiles remarkably more sophisticated than those associated with the self-assembly of organothiol ligand monolayers on atomically flat Au surfaces. Here we use plasmon-enhanced Raman scattering as a spectroscopic tool combining time-resolving and molecular fingerprinting capabilities to quantitatively correlate the ligand dynamics with detailed molecular structures in real time under a diverse set of ligand adsorption, desorption, and exchange conditions at both equilibrium and nonequilibrium states, which enables us to delineate the effects of nanoscale surface curvature on the binding affinity, cooperativity, structural ordering, and the adsorption/desorption/exchange kinetics of organothiol ligands on colloidal Au nanoparticles. This work provides mechanistic insights on the key thermodynamic, kinetic, and geometric factors underpinning the surface curvature-dependent interfacial ligand behaviors, which serve as a central knowledge framework guiding the site-selective incorporation of desired surface functionalities into individual metallic nanoparticles for specific applications.