A rapid and quantitative detection method for plasma soluble growth stimulating gene protein 2 based on time resolved fluorescence immunochromatography

Abstract

Background: plasma soluble growth stimulating gene protein 2 (sST2) is a new generation biomarker in heart failure (HF), which is an independent predictor of adverse outcomes of heart failure. Thus, the establishment of a rapid and sensitive method for detecting sST2 is urgently needed. Methods: lanthanide element Eu³⁺ coated fluorescent nanometer microspheres (Eu³⁺@FMN) can be used as markers to label monoclonal mouse anti-human sST2 antibody ST-01 (ST-01-Eu³⁺@FMN). When the immune sandwich complex formed between the monoclonal mouse anti-human sST2 antibody ST-02 and ST-01-Eu³⁺@FMN on the test band with the appearance of target object sST2, we can detect the fluorescence intensity of Eu³⁺ on the test band and the quality control band using a dry fluorescence analyzer. We calculated the T/C value (T/C = fluorescence intensity of the test band/fluorescence intensity of the quality control band), fitted to the calibration curve, and measured the concentration value of sST2 in the corresponding sample. Results: the best reaction time was 15 min after condition exploration, and the optimal sample volume was 80 μL. The detection sensitivity of the scheme was 2.14 ng mL⁻¹. The calibration curve of the assay was y = 0.0113x + 0.0033, and the linear range was 5–200 ng mL⁻¹. No cross reaction was found when the samples contained BNP, NT-proBNP, and galectin-3, indicating a good specificity. The precision was good with a relative deviation < 15%. The coefficient of variation of detection results of low-concentration samples and high-concentration samples was 4.20% and 3.30% respectively in the same batch of strip tests, so the intra-assay CV was set as <10%; when different batches of strips were used for testing, the coefficient of variation of detection results of low-concentration samples and high-concentration samples was 10.06% and 8.38% respectively, so the inter-assay CV was set as <15%. Stability test results showed that the relative deviation of test results at each time node was <15%, indicating good stability of the assay strips. The correlation coefficient between the ST-01-Eu³⁺@FMN based time-resolved fluorescence immunochromatography analysis and sST2 ELISA kit was 0.98. To confirm the usage of our proposed TRF-ICA for clinical samples, it was used to determine the concentration of sST2 in samples obtained from 34 patients with heart insufficiency, acute and chronic heart failure. As a result, we successfully detected a minimal concentration of 5.21 ng mL⁻¹ and a maximum concentration of 184.26 ng mL⁻¹ for sST2. Conclusion: this technique provides a rapid, simple and quantitative detection method for sST2 in clinics. It can help clinicians to predict the incidence of adverse events in patients with HF.