A Novel Immunoprobe Strategy Integrating Tetrahedral DNA Nanostructure and Protein A for Sensitivity Enhancement: Application in Lead Ion Detection

Immunochromatographic assay (ICA) has been extensively utilized for on-site detection to ensure food safety. However, maintaining the bioactivity of immunoprobes while achieving efficient antibody labeling remains a significant challenge. In this study, a novel immunoprobe was developed by integrating tetrahedral DNA nanostructure (TDN) with protein A (PrA) and was subsequently applied in an ICA for the detection of lead ions. Notably, TDN served as a scaffold to enable a tailorable distribution of antibodies, while PrA acted as a bridging ligand to facilitate the oriented immobilization of antibodies. This strategy significantly enhanced the coupling efficiency of antibodies while maintaining their bioactivity. As expected, the proposed immunoprobe exhibited a higher affinity and a greater proportion of active antibodies compared to immunoprobes based solely on PrA or TDN. Moreover, the developed ICA achieved a visual limit of detection (vLOD) of 0.05 ng/mL and a scanning limit of quantitation (sLOQ) of 0.031 ng/mL for lead ions, respectively. By combining TDN and PrA, the AuNP-TDN-PrA-mAb immunoprobe enabled a controllable orientation and adjustable coverage density of antibodies. This unique property holds great potential for establishing a highly sensitive ICA, thereby meeting diverse detection requirements in practical applications.