Poly(N-heterocyclic carbene)-Protected Water-Soluble Gold Nanoparticles with Tunable Functions for Biosensing Applications

Gold nanoparticles (Au NPs) are often susceptible to environmental changes, especially a complexly biological environment, significantly hindering the potential application of biosensors for practical detection. However, the controllable construction of ultrastable water-soluble Au NPs for biosensing applications remains a major challenge today. Here, ultrastable water-soluble Au NPs protected by tris-N-heterocyclic carbene (NHC) ligands (2·Au NPs) have been controllably designed and synthesized. The tris-NHC shell on the Au NP surface increases the chemical and electrochemical stability of the materials, making them stable in biological environments and even in excess biomercaptan. In addition, the ammonium salt substituent on the imidazolium nitrogen not only regulates the water solubility of Au NPs but also facilitates electrostatic interactions with biological substances. Ultimately, based on the controlled synthesis of ultrastable 2·Au NPs, it is convenient to build a probe for toxic substances of ochratoxin A detection with two signal readouts. A low limit of detection (0.66 pmol·L–1) and a wide linear response range (2.5 pmol·L–1 to 25 μmol·L–1) are achieved. Meanwhile, this proposed aptasensor exhibits excellent selectivity toward various potential interfering bioanalytes and sundry ions. This work demonstrates an efficient method to regulate the properties of Au NPs by functional NHC anchors and paves the way for practical biosensing application purposes.