Site-specific adsorption of gold nanoparticles coated with thermo-responsive peptides

A thermo-responsive elastin, elastin-like peptide (ELP)–gold nanoparticle (AuNP) hybrid (ELP–AuNP), was successfully prepared via the in situ reduction of HAuCl 4 in the presence of lipoic acid-terminated ELP: (VPGVG) 4 (V:valine, P:proline, G:glycine) synthesized using a solid-phase peptide synthesis method. The conformation and aggregation properties of the ELP–AuNP in an aqueous buffer solution were examined using circular dichroism (CD) and ultraviolet-visible (UV-Vis) spectroscopies and transmission electron microscopy (TEM) observation. The phase transition of the ELP layer at the periphery of the AuNP because of the conformational change from random coil to β-turn structures was found to proceed gradually with increasing temperature and to simultaneously cause an aggregation of the ELP–AuNP because of the component’s hydrophobic interactions and a color change of the solutions from red to violet. The ELP–AuNPs were aligned selectively onto patterned, hydrophobic polystyrene stripes on a glass plate when the plate was immersed and incubated in the solution containing the ELP–AuNP above its phase transition temperature, as verified using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The elastin-like peptide (ELP)–gold nanoparticle (AuNP) hybrid can be aligned selectively on the micro-patterned polystyrene ridges by directed assembly based on a thermo-triggered hydrophilic and hydrophobic phase transition of the ELP shell.