Colloidal stability of silica nanoparticles during bioconjugation reactions with a silylated amyloidogenic peptide

Silica nanoparticles functionalized with bioactive biomolecules have been studied extensively in last year, because of their potential application as selective response of biosensors, drug delivery systems and “smart” material. Molecular self-assembly of oligopeptides into well-ordered nanostructures provide us models to exploring development of new materials, and the involvement of peptide aggregates in several degenerative diseases.1 Recently, we have shown a systematic fibrillation behavior of an alternating [RF]n=1-5 peptide (R = L-arginine, F = L-phenylalanine), which exhibit physicochemical properties of a beta-amyloid protein.2 In order to create new properties and to stimulate particular desired functionalities, we proposed the synthesis of a silylated octapeptide [(CH3CH2O)3Si-G(RF)4] (where G = L-glycine), by using solid-phase peptide synthesis, and its conjugation with 3-(triethoxysilyl)propyl isocyanate. At the same time, SiO2NPs were prepared by using Stöber-based solvent varying method, which allows obtaining nanoparticles with a narrow size distribution and diameter of ~90 nm (as shown in the SEM micrograph below), followed by surface functionalization for colloidal stabilization, by incorporating different amounts of [(CH3CH2O)3Si-G(RF)4] and sulfobetaine siloxane (SBS) in aqueous solution. In the proportion of (1:9, m/m), the functionalization was successfully achieved, obtaining a zeta potential value of −51 mV and a hydrodynamic diameter of 110 nm for SiO2-NPs, and −44 mV and a hydrodynamic diameter of 119 nm for peptide-dressed silica nanoparticles in aqueous solution. In addition, XPS analysis (Figure 1B) showed a peak with a binding energy of 400 eV, which was assigned to the N(1s) in the silylated peptide. Future studies for cellular targeting are underway.