The Strategies Of Label-free Electrochemiluminescent Immunoassay For Biomarkers Based On Novel Nanomaterials

Iron is a necessary element in the cells of mammals. It plays important roles in most life process, such as oxigen transport, electron transfer, reduction or oxidation, cell differentiation and growth. Transferrin (TRF) is a major iron-binding monomeric glycoprotein with a typical concentration range of2-4mg mL"1in plasma. Hepatitis, anemia, and pregnancy often lead to increased levels of transferrin, while nephritic syndrome, rheumatism, cirrhosis, malignant tumor, and leukemia result in concentration decrease of this protein. Therefore, real-time monitoring the levels of transferrin in plasma has important significance in the diagnosis and researchs of these diseases.Electrochemiluminescence (ECL) is a kind of luminescence produced during electrochemical reactions in solutions. ECL analysis not only retains many advantages of chemiluminescent analysis, but also posses lots of other merits including strong controllability, good reproducibility, high selectivity and capability for in-situ detection. In recent years, dozens of breakthrough were achieved in the fileds of ECL analysis and new ECL materials. The appearance of ECL immunoassay significantly facilitates the development of ECL in bioanalytical applications, particularly in the field of biomarker analysis. Unfortunately, traditional labeling techniques are still defectively because the labeling process is always labor-intensive and time-consuming. Moreover, the conjugation chemistry involved in the labeling process increases the risk of damaging the activities of the biomolecules such as antibody and enzyme. Sometimes poor sensitivity is also obtained from the low conjugation efficiency of irrational conjugation chemistry. Therefore, a label-free ECL immunoassay is a promising method for the detection of biomarkers. In this paper, a simple and sensitive label-free ECL detection method for TRF has been developed by using ECL nanomaterial, and the main contents are described as following:A label-free electrochemiluminescence immunosensor using luminol-reduced gold nanoparticles (Lu-Re-GNPs)-modified screen-printed carbon electrode (SPCE) as the sensing platform was proposed for the sensitive detection of TRF, an anemia biomarker in human serum. To achieve the purpose of low cost and disposable use, a SPCE was used as the substrate of the immunosensor. The Lu-Re-GNPs-modified sensing platform exhibited stable and strong ECL emission, which could be employed for the recognition of target antigen with the aid of the unconjugated antibody immobilized on the electrode. With a simple label-free mode, the SPCE-based ECL assay with the advantages of low cost and facile manipulation was established successfully. In the presence of TRF, a decrease in the ECL intensity could be observed because of the immuno-binding event. This decrease in ECL intensity permitted sensitive detection of TRF in a linear range of0.10-18ng mL-1, with a detection limit of0.033ng mL-1. The assay results of TRF in serum samples were in a good agreement with those of ELISA. The reproducibility, the stability and the specificity of the proposed strategy were acceptable. The approach could also be further extended to facile immunoassay of other biomarker proteins.