Determination of trace gastrin and diagnosis of human diseases using CdTe quantum dots labelled gastrin antibodies as phosphorescence sensors

Abstract

CdTe quantum dots (CdTe-QDs) can emit strong and stable room temperature phosphorescence (RTP) via the perturbation effect of a Pb²⁺ ion on the surface of a nitrocellulose membrane (NCM). CdTe-QDs-Ab_GAS, the product of CdTe-QDs labelled gastrin antibodies (Ab_GAS), can not only maintain good RTP characteristics, but can also be used as a RTP sensor and carry out highly specific immunoreactions with gastrin (GAS) to form GAS-Ab_GAS-CdTe-QDs causing the ΔI_p of the system to sharply enhance. Thus, a new solid substrate room temperature phosphorescence immunoassay (SSRTPIA) for the determination of GAS was established based on the linear relativity between the ΔI_p of the system and the content of GAS. The limit of quantification (LOQ) of this method was 0.43 fg spot⁻¹ with the corresponding concentration being 1.1 × 10⁻¹² g mL⁻¹ and sampling quantity being 0.40 per spot⁻¹. This highly specific, accurate, selective and sensitive RTP sensor has been applied to the determination of GAS in biological samples and the diagnosis of diseases, and the results agreed well with those obtained by radioimmunometric assay (RIA). Meanwhile, the mechanism of SSRTPIA for the determination of GAS using CdTe-QDs-Ab_GAS as the RTP sensor was discussed.