Nanocomposites of gold nanoparticles and graphene oxide towards an stable label-free electrochemical immunosensor for detection of cardiac marker troponin-I

• Nanocomposites based on GO and AuNPs were prepared and anchored on the electrode surfaces covalently to form a stable sensing interface.
• The anti-cTnI detection antibody was immobilized on GO tailored with ferrocene molecules, functioning as the signal reporter for the detection of cTnI.
• The detectable concentration of cTnI is 0.05 ng mL-1 in buffer with the assay time of less than 5 min.
• The herein simple and novel approach for fabrication of AuNP and graphene based platform is promising for future fabrication of point-of-care devices.

A stable label-free amperometric immunosensor is presented based on gold nanoparticles and graphene oxide nanocomposites for detection of cardiac troponin-I in the early diagnosis of myocardial infarction. For designing of the sensing platform, firstly the nanocomposites based on GO and AuNPs were prepared and anchored on electrode surfaces. The formed nanocomposites provided a platform with big surface area for loading anti-cTnI capture antibody, and worked as a bridge for fast electron transfer subsequently increased the sensitivity. Moreover, the linkages between AuNP, GO, and electrodes were based on covalent bonding by aryldiazonium salt coupling chemistry, which favors the stability of the sensing interface. Finally, the anti-cTnI detection antibody was immobilized on GO tailored with ferrocene molecules, functioning as the signal reporter for the detection of cTnI. The modification process was monitored using electrochemistry, SEM, XPS. The herein immunosensor demonstrates a good selectivity and high sensitivity against human-cTnI, and is capable of detecting cTnI at concentrations as low as 0.05 ng mL−1, which is 100 times lower than that possible by conventional methods. It is potential to design the portable sensing platform based on AuNPs and GO nanocomposites for future point-of-care diagnostics.

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