L -Proline bio-inspired synthesis of AuPt nanocalliandras as sensing platform for label-free electrochemical immunoassay of carbohydrate antigen 19-9

Abstract In this study, an ultra-sensitive and selective label-free immunosensor based on monodispersed AuPt nanocalliandras (AuPt NCs) was constructed for the determination of carbohydrate antigen 19-9 (CA 19-9). AuPt NCs were synthesized by a one-step eco-friendly wet-chemical method, using L -proline as the green growth-director and stable agent. The architectures were mainly characterized by transmission electron microscopy (TEM), high-angle annular dark-field scanning TEM (HAADF-STEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results revealed that AuPt NCs provided desired microenvironment to immobilize CA 19-9, amplify the currents of CA 19-9 by using K 3 [Fe(CN) 6 ] as the probe, and improve the electrical conductivity of the immunosensor. The immunoassay showed wide linear range from 0.05 to 50 U mL −1 and low detection limit of 0.03 U mL −1 , which was explored to detect CA 19-9 in human serum samples. The as-developed approach can be extended for ultrasensitive detection of biomolecules in clinical analysis.