Electrochemiluminescent immunoassay for the determination of CA15-3 and CA72-4 using graphene oxide nanocomposite...

A novel immunoassay is introduced based on co-reactant enhancing strategy for the electrochemiluminescent (ECL) determination of CA15-3 and CA72-4 tumor markers in real samples. For the preparation of the signaling probe, CA15-3 and CA72-4 antibodies first were labeled using Ru(bpy)₃²⁺-N-hydroxysuccinimide ester (Ru(bpy)₃²⁺-NHS) and conjugated with L-cysteine capped cadmium selenide (CdSe) quantum dots. Finally, it was cross-linked with chitosan-grafted graphene oxide (GO@CS) nanocomposite. The capture probe was constructed by deposition of multi-walled carbon nanotubes (MWCNT) at the surface of dual-working gold screen-printed electrodes (MWCNT-dwSPE) and covalent attachment of capture CA15-3 and CA72-4 antibodies to MWCNT-dwSPE. ECL signals were recorded by applying cyclic potential ranging from 0.3 to 1.1 V (vs. pseudo-reference Ag/AgCl) at the scan rate of 100 mV.s^-1. This immunoassay was used for determination of CA15-3 and CA72-4 in real samples the detection limits of 9.2 μU.ml^-1 and 89 μU.ml^-1 within linear ranges of 10 μU.ml^-1-500 U.ml^-1 and 100 μU.ml^-1-150 U.ml^-1, respectively. This immunoassay also showed acceptable accuracy with recoveries in the range 96.5-108 % and high reproducibility with RSD of 3.1 and 4.9.