Peptide-Conjugated Ultrasmall Gold Nanoparticles (2 nm) for Selective Protein Targeting

Abstract

Ultrasmall gold nanoparticles with a metallic core diameter of 2 nm were surface-conjugated with peptides that selectively target epitopes on the surface of the WW domain of the model protein hPin1 (hPin1-WW). The binding to the gold surface was accomplished via the thiol group of a terminal cysteine. The particles were analyzed by NMR spectroscopy, highresolution transmission electron microscopy, and differential centrifugal sedimentation. The surface loading was determined by conjugating a FAMlabeled peptide, followed by UV−vis spectroscopy, and by quantitative 1 H NMR spectroscopy, showing about 150 peptide molecules conjugated to each nanoparticle. The interaction between the peptide-decorated nanoparticles with hPin1-WW was probed by 1 H− 15 N-HSQC NMR titration, fluorescence polarization spectroscopy (FP), and isothermal titration calorimetry (ITC). The particles showed a similar binding (K D = 10−20 μM) compared to the dissolved peptides (K D = 10−30 μM). Small-angle Xray scattering (SAXS) showed that the particles were well dispersed and did not agglomerate after the addition of hPin1-WW (no cross-linking by the protein). Each nanoparticle was able to bind about 20 hPin1-WW protein molecules. An unspecific interaction with hPin1 was excluded by the attachment of a nonbinding peptide to the nanoparticle surface. The uptake by cells was studied by confocal laser scanning microscopy. The peptide-functionalized nanoparticles penetrated the cell membrane and were located in the cytosol. In contrast, the dissolved peptide did not cross the cell membrane. Peptide-functionalized nanoparticles are promising agents to target proteins inside cells.

Metal–Ligand Interface and Internal Structure of Ultrasmall Silver Nanoparticles (2 nm)

“…62,73,74 This lattice compression of about 0.9% agrees with the literature. 75 The calculated crystallite size (CS = 0.9 ± 0.1 nm) was smaller than the particle size (2 nm by TEM), indicating a polycrystalline (twinned) structure of the nanoparticles in accordance with earlier results on ultrasmall gold nanoparticles, 76 general crystallographic considerations on small nanoparticles, 77 and our TEM analysis given in Figure 1.…”

“…Rietveld refinement showed that GSH-coated ultrasmall silver nanoparticles had a significantly compressed unit cell ( a = 4.05 ± 0.01 Å) compared to microcrystalline Ag ( a = 4.087 ± 0.001 Å; ICDD #4-0783). ,, This lattice compression of about 0.9% agrees with the literature . The calculated crystallite size (CS = 0.9 ± 0.1 nm) was smaller than the particle size (2 nm by TEM), indicating a polycrystalline (twinned) structure of the nanoparticles in accordance with earlier results on ultrasmall gold nanoparticles, general crystallographic considerations on small nanoparticles, and our TEM analysis given in Figure . The XRD results further demonstrate that the ultrasmall nanoparticles prepared here still have the fcc structure of the bulk silver metal (albeit twinned), unlike atom-sharp clusters. ,,,− However, the presence of single-crystalline particles cannot be ruled out, therefore it is possible that the sample contains both single-crystalline and twinned particles.…”

Pathways for Oral and Rectal Delivery of Gold Nanoparticles (1.7 nm) and Gold Nanoclusters into the Colon: Enteric-Coated Capsules and Suppositories

“…The spectrum of Au-GSH nanoparticles shows broadened, downfield-shifted signals. This NMR peak broadening is a well-known phenomenon that is caused by the presence of a metallic nanoparticle core [ 73 , 74 , 75 , 76 , 77 ]. It depends on the distance between magnetic nucleus and the metal particle.…”

Anionic Ultrasmall Gold Nanoparticles Bind to Coagulation Factors and Disturb Normal Hemostatic Balance

“…, biodistribution) can, in principle, be attained through a careful choice of design parameters, such as the particle size, density, and surface chemistry . In addition, usNPs are protein mimics, and usNP–protein interactions exhibit many similarities to a typical biomolecular complexation event. − This creates the opportunity to design usNPs having specific interaction modalities with biomolecules, be it through careful control over their sizes, surface chemistries, or both. − For example, we have prepared usNPs that selectively target the anion-binding exosites 1 and 2 on the surface of thrombina key enzyme of the coagulation cascadeto allosterically regulate its enzymatic activity. , …”