Chrysanthemum-like Au@Polydopamine synthesized using one-pot method and its advantage in immunochromatographic assay

Flower-like gold nanoparticle (AuNF) is widely used as a probe. However, the performance of conventional AuNF is not satisfactory because of complex synthesis, insufficient uniformity, and ordinary optical performance. In this paper, a novel chrysanthemum-like Au@polydopamine (AuNC@PDA) prepared using one-pot method was compared with conventional AuNF@polydopamine (AuNF@PDA) prepared using three-step method. AuNC@PDA had more branch structures with more uniform petaloid shape and narrower particle size distribution compared with AuNF@PDA. The grayscale of AuNC@PDA both in aqueous solution and on nitrocellulose membrane was approximately threefold higher than that of AuNF@PDA. Because of PDA coating, the stability and coupling efficiency of AuNC@PDA were much higher than that of conventional nanoprobes − AuNF and AuNS (gold nanosphere). These results indicated that AuNC@PDA had superior morphological and optical performance. The AuNC@PDA was first utilized as a probe in immunochromatographic assay (ICA), and compared with conventional AuNF@PDA. The limits of detection (LOD) of ICA based on AuNC@PDA, AuNS, and AuNF@PDA were 1.59, 9.58, and 5.13 mIU/mL, respectively, when human chorionic gonadotropin was detected as the target. The LOD of ICA based on AuNC@PDA had 6.0-fold and 3.3-fold improvement compared with that based on AuNS and AuNF@PDA, respectively. Our results could be used as a basis for developing novel probes in practical ICA applications.