A highly sensitive electrochemical sensor derived from peptide amphiphilic inspired self-assembled, ordered gold nanoparticles for determination of 22 β-lactams

Achieving ordered arrangement of gold nanoparticles (AuNPs) on an electrode can further improve the signal intensity of an electrochemical immunosensor. This ordered AuNPs self-assembly can be inspired by peptide amphiphile (PA). The rational design of hydrophobic chains in PA is a crucial step when the range of hydrophobic alkane chain from 14 to 18 carbons. As arginine (R) can combine specifically with Au surface plane (111), four PAs, i.e., C 15 H 23 CO-RR (C16R2), C 15 H 23 CO-RRR (C16R3), C 15 H 23 CO-RRRR (C16R4), and C 15 H 23 CO-RRRRR (C16R5), in this work are designed to investigate the extent of ordered AuNPs self-assembly. The results indicate that C16R4 presented a dominant electron donating ability and can inspire the self-assembly of AuNPs to form a mono-dispersed raspberry-like structure (C16R4-AuNPs) to obtain the largest ΔI (15.4 μA). In the detection system, C16R4-AuNPs firstly capture and immobilize anti-β-lactam receptor monoclonal antibodies (mAb) by electrostatic adsorption, and the anti-β-lactam receptor mAb possess antigen-antibody binding sites away from the active site of the receptors. Then, they capture β-lactam receptors through an antigen-antibody reaction to form a ternary complex (C16R4-AuNPs-mAb-β-lactam receptors). Based on this indirect-labeling process, the receptor active sites have been exposed completely, facilitating ligand recognition, which greatly further improves the sensitivity of the present method. Finally, a highly sensitive electrochemical immunosensor based on the ternary complex is developed to achieve the determination of 22 β-lactam antibiotics, which is more sensitive and applicable than other reported electrochemical sensors.