Impact of multivalent charge presentation on peptide-nanoparticle aggregation

Abstract

Strategies to achieve controlled nanoparticle aggregation have gained much interest, due to the versatility of such systems and their applications in materials science and medicine. In this article we demonstrate that coiled-coil peptide-induced aggregation based on electrostatic interactions is highly sensitive to the length of the peptide as well as the number of presented charges. The quaternary structure of the peptide was found to play an important role in aggregation kinetics. Furthermore, we show that the presence of peptide fibers leads to well-defined nanoparticle assembly on the surface of these macrostructures.

Keywords: coiled-coil peptides; controlled aggregation; gold nanoparticles; multivalency; α-helical fibrils.

Figure 1

Helical wheel representation and sequences of the peptides used in this study.

Figure 2

CD spectra of 30 µM peptide VW05, R1A3, R2A2, R2A3, R2A4 and R2A5 at (A) pH 9 and (B) pH 11 in 10 mM Tris/HCl buffer. Dynamic light scattering of (C) VW05 and (D) R2A2 both at 15 µM at (red) pH 9 and (green) pH 11. All measurements were carried out in 10 mM Tris/HCl buffer.

Figure 3

(A) TEM of 100 µM R2A2 in 10 mM Tris/HCl buffer, pH 9. Sample was negative stained with 2% PTA; defocus −0.5 µm. (B) Cryo TEM of 100 µm R2A2 in 10 mM Tris/HCl buffer, pH 9; defocus −1.8 µm.

Figure 4

(A) Dynamic light scattering of 0.05 µM Au/MUA nanoparticles at pH 9. (B) Cryo TEM image of 0.05 µM Au/MUA nanoparticles at pH 9. (C) UV–vis spectra of 0.05 µM Au/MUA nanoparticles at pH 9 and in the presence of 30 µM VW05. (D) Time and concentration dependent shift in the absorption maximum of 0.05 µM Au/MUA nanoparticles in the presence of different amounts of R2A2. (E) Time-dependent shift in the absorption maximum at a fixed peptide concentration of 30 µM.

Figure 5

CD spectra of 15 µM peptide in the presence 0.05 µM Au/MUA nanoparticles at pH 9 after (A) 0 hours and (B) three hours.

Figure 6

Agarose gel of (A) VW05, (B) R1A3, and (C) R2A2 in the presence of 0.05 µM Au/MUA nanoparticles at pH 9 visualised by UV light (left) and visible light (right).

Figure 7

Cryo TEM images of 100 µM R2A2 and 0.05 µM Au/MUA nanoparticles at pH 9 at a defocus of (A) −1.2 µm, (B) −1.8 µm and (D) after pH switch from 11 to 9 at a defocus of −1.8 µm. (C) Cryo TEM images of 100 µM R2A2 and 0.4 µM Au/MUA nanoparticles at pH 9 at a defocus of −1.8 µM.