Sensitive and simultaneous detection of ractopamine and salbutamol using multiplex lateral flow immunoassay based on polyethyleneimine-mediated SiO2@QDs nanocomposites: Comparison and application

Abstract

The abuse of illegal additives poses a severe threat to human health. As such, it is of great significance to develop a simple, rapid and high-throughput analysis method for ensuring food safety from source to terminal. Herein, we proposed a multiplex fluorescent lateral flow immunoassay (LFIA) using the nanoassembly of silicon dioxide (SiO2) and quantum dots (QDs) as the advanced signal probe that can simultaneously detect ractopamine (RAC) and salbutamol (SAL) in swine urine and pork samples, and compared with other four conventional labels. The core–shell SiO2@QDs nanocomposites with strong luminescence, high stability, and abundant surface carboxyl groups were conjugated with antibodies to form high-performance SiO2@QDs immunoprobes, which improve the sensitivity and reliability of the LFIA. The developed SiO2@QDs-based LFIA achieved simultaneous detection of RAC and SAL in one strip within 13 min, with the limit of detection at 0.007 ng/mL and 0.032 ng/mL, respectively. The sensitivity of SiO2@QDs was superior to gold nanoparticles (AuNPs) and fluorescent microspheres (FMs), and exhibited comparative sensitivity with time-resolved microspheres (TRFMs), while overcoming the shortcomings of QDs that tend to aggregate. The recoveries in spiked swine urine and pork samples ranged from 73.7 to 111.0% with relative standard deviations between 4.7% and 15.5%. Good correlations were observed between the SiO2@QDs-based LFIA and commercial enzyme-linked immunosorbent assay for RAC (R2 = 0.936) and SAL (R2 = 0.979) detection. Briefly, the proposed method could be a promising screening on-site tool for convenient, rapid and sensitive detection of multiple illegal additives residues from the source to the terminal in food safety.