A specific Tween-80-Rhodamine S-MWNTs phosphorescent reagent for the detection of trace calcitonin

The present study proposed a simple sensitive and specific immunoassay for the quantification of calcitonin (CT) in human serum with water-soluble multi-walled carbon nanotubes (MWNTs). The COOH group of MWNTs could react with the NH group of rhodamine S (Rhod.S) molecules to form Rhod.S-MWNTs, which could emit room temperature phosphorescence (RTP) on acetate cellulose membrane (ACM) and react with Tween-80 to form micellar compound. Tween-80-Rhod.S-MWNTs (TRM), as a phosphorescent labelling reagent, could dramatically enhance the RTP signal of the system. The developed TRM phosphorescent reagent was used to label anti-calcitonin antibody (AbCT) to form the TRM-AbCT labelling product, which could take high specific immunoreaction with CT, and the ΔIp (= Ip2 − Ip1, Ip2 and Ip1 were the phosphorescence intensity of the test solution and the blank sample, respectively) of the system was linear to the content of CT. Hence, a new solid substrate room temperature phosphorescence immunoassay (SSRTPIA) was established for the determination of CT in human serum. This sensitive (limit of quantification (LOQ) was 8.0 × 10−14 g mL−1), accurate, selective and precise method has been applied to determine CT in human serum and predict primary osteoporosis and fractures, with the results in good agreement with those obtained by chemiluminescence immunoassay (CLIA). Simultaneously, the structure of MWNTs was characterized with scanning electron microscopy (SEM) and infrared spectroscopy (IR), and the reaction mechanisms of both labelling AbCT with TRM and SSRTPIA for the determination of trace CT were discussed.

A new Tween-80-Rhodamine S-water-soluble multi-walled carbon nanotubes (Tween-80-Rhod.S-MWNTs-EDC-NHS, TRMEN) phosphorescent labelling reagent was developed. High sensitive solid substrate room temperature phosphorescence immunoassay (SSRTPIA) for the determination of calcitonin (CT) in human serum and the prediction of human diseases based on the TRMEN could be used to label anti-calcitonin antibody (AbCT) to form the TRMEN-AbCT labelling product, which could take high specific immunoreaction with CT causing that the ΔIp of the system was linear to the content of CT. Moreover, the reaction mechanisms of both labelling AbCT by TRMEN and SSRTPIA for the determination of trace CT were discussed. This research not only provides a new hormones analysis method, but also expands the application field of MWNTs and promotes the development of SSRTP and IA.Figure optionsDownload as PowerPoint slideHighlights
► A Tween-80-Rhodamine S-multi-walled carbon nanotubes labelling reagent was developed.
► The phosphorescence immunoassay was established for the determination of calcitonin.
► This method has been applied to determine CT and the prediction of diseases.
► The structure of MWNTs was characterized with SEM and IR.
► The mechanisms for both determining trace CT and labelling AbCT were discussed.