A new application of scanning electrochemical microscopy for the label-free interrogation of antibody–antigen interactions: Part 2

Within this paper we describe the use of scanning electrochemical microscopy (SECM) to fabricate a dotted array of biotinylated polyethyleneimine which was then used to immobilise first neutravidin and then a biotinylated antibody towards a relevant antigen of interest (PSA, NTx, ciprofloxacin). These antigens were selected both for their clinical relevance but also since they display a broad range of molecular weights, to determine whether the size of the antigen used effects the sensitivity of this approach. The SECM was then used to image the binding of both complementary and non-complementary antigens in a label-free assay. Imaging of the arrays before and following exposure to various concentrations of antigen in buffer showed clear evidence for specific binding of the complementary antigens to the antibody functionalised dots. Non-specific binding was also quantified by control experiments with other antigens. This demonstrated non-specific binding across the whole of the substrate, thereby confirming that specific binding does occur between the antibody and antigen of interest at the surface of the dots. The binding of ciprofloxacin was investigated both in simple buffer solution and in a more complex media, bovine milk.

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► Employed scanning electrochemical microscopy for label-free detection of antigen binding.
► Demonstrated selective and quantitative binding of three different antigens.
► Detected antigens with a wide range of molecular weights.
► Demonstrated detection of ciprofloxacin in bovine milk.