Synthesis and characterization of amino acid functionalized gold nanoparticles and their interaction with lipid membrane

Abstract

Herein, we have synthesized different aromatic amino acid functionalized gold nanoparticles and studied their interaction with different lipid membranes. We used three aromatic amino acids, namely, Phenylalanine (Phe), Tryptophan (Trp), Tyrosine (Tyr) to synthesize the nanoparticles in an in situ method. The synthesized nanoparticles are of the size around 10-15 nm characterized by UV-Visible absorption spectra, Transmission Electron Microscopy (TEM) and Zeta potential Measurements. The modulation of the size of the nanoparticles can be done by varying the concentration of the amino acids. The nanoparticles are fairly stable in the pH range from 10 to 6.5, however, at lower pH, the aggregation takes place due to protonation of COO- group. We find that the synthesized nanoparticles were fluorescent in nature and we confirm this by steady-state and time-resolved fluorescence spectroscopy. We studied the interaction of the nanoparticles with lipid membrane of different charges. It is observed that the amino acid functionalized nanoparticles bring in dehydration in the lipid bilayer by the expulsion of the surface water. The maximum interaction takes place in case of negatively charged lipid membrane while positively charged lipid membranes exhibit the least interaction with the nanoparticles and for tryptophan functionalized nanoparticles, aggregation is observed. The extent of the interaction of nanoparticles with lipid membranes is governed by the bulkiness of the ligand. We find that the phenylalanine functionalized nanoparticles display maximum interaction to the lipid membrane.