Characterising the biosensing interface.

The development of diagnostic devices relies heavily on the immobilization of biomolecules on supportive substrates, that is the generation of interfaces that can thereafter produce a quantifiable signal upon exposure to a specific target. The ability of a biosensor to selectively recruit analytes is highly dependent on the quality of this receptive biolayer and its functionality. Key performance metrics are selectivity and sensitivity and both are highly dependent on the interfacial structural and physical properties, though often these are not well resolved; in many cases analyses are performed, for example with little knowledge of receptor surface coverage, orientation and/or distribution. In this review, we provide a, necessarily concise, but comprehensive summary of accessible and relevant characterization techniques, noting operational principles, limitations, and the value they can bring in optimising downstream sensor performance.