A new detection method of mistletoe lectin I by surface plasmon resonance

Mistletoe lectin I (ML-I) is considered as the main effective substance in the extract of mistletoe and is currently widely applied in cancer therapy. The Plasmonic® surface plasmon resonance (SPR) device was used to establish an innovative, simple and rapid assay for detection of ML-I in buffer, serum and injection drugs. In the reported sandwich immunoassay, specific anti-ML-I A chain antibodies were used as capture and detection antibodies. Trials were undertaken to compare the influence of detection signals by using four different types of functionalised chips. It was found that alkylsilane-coated chip got the highest detection signal and showed the lowest unspecific binding of the detection antibody. Hence the assays were established on alkylsilane-coated chips in both buffer system and serum system. For the buffer system, it was measured as a detection range of 7.5-100 μg mL−1 and lower limit of detection of 1.0 μg mL−1. In the serum system, the linear standard calibration curve indicated that the detection limit of ML-I by SPR was 1.5 μg mL−1. The method also was verified to quantify the contents of mistletoe extract in commercially available injection drugs. In this novel approach, no laborious sample preparation is required. And it is less time-consuming compared to other biotechniques normally used at present. The system can be utilised not only for exploring properties of ML-I in biological research but also for the quality control of medicinal products of mistletoe in the pharmaceutical industry.