Amperometric indicator displacement assay for biomarker monitoring: Indirectly sensing strategy for electrochemically inactive sarcosine

Indicator displacement assay plays a fundamental role in the development of chemosensors. We explored here an ingenious yet effective strategy for amperometric assay of electrochemically inactive sarcosine based on an indicator displacement principle, in which 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS) was proposed as the receptor and the electroactive Ru(NH3)(6)(3+) cations used as an indicator. Due to the stronger binding affinity of the NQS toward sarcosine than toward Ru(NH3)(6)(3+), the developed amperometric indicator displacement assay (A-IDA) exhibits high selectivity and excellent sensitivity toward sarcosine determination as well as with a lower detection limit (30.00 nM, S/N = 3).