Immobilisation of engineered molecules on electrodes and optical surfaces

Monolayers of genetically modified proteins with an hexahistidine tag, (His)6, were obtained by using a Ni–NTA chelator synthesized on gold-sputtered surfaces (via sulphide bonds), or on gold and graphite (via sililating agents) working electrodes of screen-printed devices. nds of proteins were produced and purified for this study:(a) mbinant antibody, derived from the ‘single-chain Fv’ (scFv) format, and osystem II (PSII) core complex isolated from the mutant strain CP43-H of the thermophilic cyanobacterium Synechococcus elongatus. v previously isolated from a synthetic ‘phage display’ library was further engineered with an alkaline phosphatase activity genetically added between the carboxy-terminal of the scFvs and the (His)6 to allow direct measurement of immobilisation. ble specific binding of (His)6 proteins to gold and graphite surfaces and fast and sensitive electrochemical or optical detection of analytes were obtained. Additionally, “on chip” protein preconcentration was conveniently achieved for biosensing purposes, starting from crude unpurified extracts and avoiding protein purification steps.