Interactions at the Silica–Peptide Interface: Influence of the Extent of Functionalization on the Conformational Ensemble

Abstract

In this contribution, the effect of silica particle size (28 and 210 nm) and surface chemistry (i.e., hydroxyl, methyl, or amino groups) on peptide binding response is studied with a specific emphasis on the effect of the extent of functionalization on binding. Exhaustive characterization of the silica surfaces was crucial for knowledge of the chemistry and topography of the solid surface under study and, thus, to understand their impact on adsorption and the conformational ensemble of the peptides. The extent of surface functionalization was shown to be particle-size dependent, a higher level of 3-aminopropyl functionality being obtained for smaller particles, whereas a higher degree of methyl group functionality was found for the larger particles. We demonstrated that peptide interactions at the aqueous interface were not only influenced by the surface chemistry but also by the extent of functionalization where a "switch" of peptide adsorption behavior was observed, whereas the changes in the conformational ensemble revealed by circular dichroism were independent of the extent of functionalization. In addition to electrostatic interactions and hydrogen bonding driving interaction at the silica-peptide interface, the data obtained suggested that stronger interactions such as hydrophobic and/or covalent interactions may moderate the interaction. The insights gained from this peptide-mineral study give a more comprehensive view of mechanisms concerning mineral-peptide interactions which may allow for the design and synthesis of novel (nano)materials with properties tailored for specific applications.

Anchoring of a hydrophobic heptapeptide (AFILPTG) on silica facilitates peptide unfolding at the abiotic–biotic interface

“…Raman spectra are taken from liquid droplets deposited solutions on an unprotected gold mirror, PFSQ05-03-M03 (Thorlabs), without any cover. For structural analysis comparing CD response we utilised spectral responses as reported previously [28].…”

The role of human serum and solution chemistry in fibrinogen peptide–nanoparticle interactions

“…The ease of peptide synthesis and modication means that peptide-NP studies have served to establish an understanding of the biophysical principles behind biomolecular interactions with NPs. 5,[22][23][24] Moreover, peptide-coated NPs are valuable biomedical tools for drug delivery, uptake, imaging, and labeling. 4,5 In the present study, we focus on a gamma-brinogen (GF) peptide interacting with silica particles.…”

“…We focus on silica NPs because of their increasing popularity in biomedical applications including molecular imaging, drug delivery, and other biomedical assays. 24,[32][33][34][35] Silica NPs are wellstudied in reaction with blood proteins 36,37 and provide a broad platform with exible silanization chemistries for functionalization. 22,38 Peptides are oen applied to silica NPs to not only increase NP stability, but also enhance biomedical applications, such as increasing cell penetration.…”

“…39 In studies of silica NPspeptide interactions, NP size and functionalization mediate binding, as do the peptide biophysical properties. 22,24,[39][40][41] A comparison of positively, negatively, and neutrally charged peptides identies electrostatic, hydrophobic, and hydrogen bonding interactions at the aqueous silica interface. 39,41,42 These interactions are dominated by electrostatics as the silica NP size increases.…”

“…As previously noted, the low isoelectric point of silica NPs and surface siloxide groups enable interactions via positively charged amino acids and via hydrogen bonding. 22,24,39 Thus, changes in pH that disrupt or charge H-bonds are expected to alter binding, 22,39 while increases in sodium chloride may shield charged interactions and weaken peptide-silica NP complexes. 24,40 On the other hand, the glucose concentrations we chose to study are higher than physiological relevance to…”