Aminosilane-Coated Magnetic Nanoparticles for Antimicrobial Peptide Immobilization

To obtain aminosilane coated magnetic nanoparticles, co-precipitation of iron salts and then polycondensation of (3-aminopropyl)trimethoxysilane (APTMS) was carried out^{52 (link), 53} . In the next step, reaction with glutaraldehyde was performed to obtain a platform for CSA-13 immobilization via imine bonding^{22 (link)}. In turn, functionalization of aminosilane modified magnetic nanoparticles by cathelicidin LL-37 was achieved by an amidation reaction between the peptide carboxyl group and the primary propyloamine group presented on the MNPs surface^{54 (link)}. MNPs functionalized with LL-37 and CSA-13 were characterized by FT-IR spectroscopy using a Thermo Scientific Nicolet 6700 FT-IR spectrophotometer. The thermal properties including differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were determined using a TA instruments USA (DSC Discovery; TGA Q500 Thermogravimetric Analyzer). Transmission electron microscopy TEM/EDX (Tecnai G2 X-TWIN) system was used to evaluate functionalized MNP size and morphology. The zeta potential was determined using the Zetasizer Nano ZS (Malvern Instruments, UK).