A Functionalized-Gold Nanoparticles Based Optical Nanosensor for Biomolecule Detection

Over the past decade, gold nanoparticles (AuNPs) have stimulated great interest in various types of sensors because they possess many attractive properties such as optical, electronic and chemical features [1]. In order to gain more intrinsic properties and much more selectivity, the surface of AuNPs is functionalized by selective groups/macromolecules. In this regard, cyclodextrins (CD) are known as capable module units to host various molecules. Taking advantage of AuNPs and β-CD, we herein report an optical nanosensor for sensing of amino acid enantiomers. To this aim, we synthesized β-cyclodextrin functionalized gold nanoparticles (βCD@AuNPs) by reduction of HAuCl4 in the presence of β-CD. Within this respect, the prepared solutions of β-CD and HAuCl4 were mixed at room temperature to give a clear solution. Then the resultant was heated at 100 °C and stirred for 4 h leading to the formation of Au nanoparticles. The color turned to red wine proving the formation of AuNPs [2]. To prove the settlement of β-CDs on AuNPs, the structural characterization of β-CD@AuNPs was performed by FTIR and UV-Vis spectroscopy, and compared to bare β-CD and AuNPs. The sensor performance was evaluated by following the colour change in the presence of the tested bioactive molecules (herein, proline, phenylalanine, leucine, thereonine, valine, glutamine, tartaric acid, serine, mandelic acid, methionine, alanine, cystine, tryptophan, tyrosine, histidine, arginine, lysine were tested as model analytes) in solution. The results show that β-CD@AuNPs exhibits different affinity and this nanosensor can pave the way for selective detection of the other biomolecules.