Enhanced lateral flow immunoassay for point-of-care monitoring of sulfamethazine residues based on antibody labeled with Au/Ir@Cu/Zn-MOF signal amplification

Introduction Sulfamethazine (SM2) antibiotic residues in food pose a significant risk to human health, including pathogenic bacterial resistance, allergic reactions, and carcinogenicity. Current lateral flow immunoassay (LFIA) typically employing colloidal gold (AuNP) as a signal reporter exhibits unsatisfactory sensitivity. Recently, metal–organic frameworks (MOFs) nanomaterial as a supporting matrix for loading nanoparticles provides a powerful tool to improve the performance of LFIA. Objectives This study aims to develop an enhanced immunosensor based on antibody labeled Au/Ir@Cu/Zn-MOF signal amplification nano-composite for sensitive and point-of-care monitoring of SM2 antibiotic residues. Methods Firstly, the highly specific monoclonal antibody (mAb) against SM2 belonging to the IgG1 subclass was screened. Subsequently, the Au/Ir@Cu/Zn-MOF nanocomposite was synthesized by incorporating Au/Ir bimetallic nanoparticles into the previously prepared Cu/Zn-MOF composite. The anti-SM2 mAb was then conjugated to Au/Ir@Cu/Zn-MOF nanocomposite via a co-precipitation method to fabricate the mAb-Au/Ir@Cu/Zn-MOF probe. Finally, a lateral flow immunoassay was constructed for the detection of SM2 residues. Results The vLOD the Au/Ir@Cu/Zn-MOF-based LFIA for SM2 detection was approximately 2.5 ng/mL, which was at least 600 times greater than that of the AuNP-based LFIA (with the vLOD of 1563 ng/mL). Average recovery rates were 80.08–90.8% in milk sample, 88–89.3% in eel sample and 85.3–95.2% in pork sample, respectively. Conclusion The Au/Ir@Cu/Zn-MOF nanocomposite utilized as signal amplification probe demonstrated remarkable sensitivity for the detection of SM2. The developed Au/Ir@Cu/Zn-MOF-based LFIA exhibits significant potential for the rapid and sensitive detection of contaminants in environmental monitoring and food safety.