Cooperative Dual-Stimuli-Triggered Aggregation of Poly-l-Histidine-Functionalized Au Nanoparticles

Nanoparticles that are responsive to multiple stimuli allow more precise control over the aggregation process and thus the structures and properties of the resulting aggregates. Au nanoparticles functionalized by poly-L-histidine (PLH), a simple polypeptide with a pK(a) value (approximately 6.2) around the physiological pH, are sensitive to pH and temperature simultaneously. The dual stimuli, pH and temperature, must act in a cooperative way to switch the hydrophobic beta-sheet structure of PLH and thus trigger the assembly/disassembly of the Au nanoparticles. The aggregation process and thus the conformation change of PLH can be well recognized by the color change of the Au nanoparticles by naked eyes.