Fragment-based hapten design and screening of a highly sensitive and specific monoclonal antibody for ractopamine

Abstract

Ractopamine (RCT) is a beta-adrenergic agonist and its use is forbidden in many countries. With the aim of more sensitive and specific detection of RCT, a RCT structure fragment-based hapten was synthesized by introducing a carboxyl group to octopamine through a reductive amination reaction with ethyl levulinate. Six mice were immunized with a hapten–KLH conjugate, and the best monoclonal antibody (Mab) with an IC₅₀ value of 0.34 ng mL⁻¹ in PBST buffer and 0.41 ng mL⁻¹ in a 10-times diluted swine urine sample was obtained, which had no cross reactivity with clenbuterol and salbutamol. These results demonstrated that a fragment of RCT as a hapten can mimic the antigenicity and specificity of RCT very well, and the Mab has potential applications in the specific monitoring of the illegal use of RCT in real samples.