Abstract: An electrochemical specific binding assay of a ligand (e.g., antigen, hapten or antibody) wherein at least one of the components is enzyme-labelled, and which includes the step of determining the extent to which the transfer of electrons between the enzyme substrate and an electrode, associated with the substrate reaction, is perturbed by complex formation or by displacement of any ligand complex relative to unbound enzyme-labelled component.The electron transfer is aided by electron-transfer mediators which can accept electrons from the enzyme and donate them to the electrode or vice versa (e.g. ferrocene) or by electron-transfer promoters which retain the enzyme in close proximity with the electrode without themselves taking up a formal charge.The electrochemical apparatus will typically comprise two or three electrodes, including one working electrode onto which components may advantageously be immobilized.

Abstract: A method of assaying a ligand in a sample which method includes the steps of contacting the sample with components comprising(a) a specific binding partner to the ligand and, if desired,(b) at least one reagent selected from ligand analogues and specific binding, partners,at least one of the said components (a) and (b) being labelled with an electron-donor or electron-acceptor,and determining whether (and, if desired, the extent to which) transfer of electrons between the said electron-donor or electron-acceptor label and a suitable charge-transfer partner resulting in charge-transfer complex formation is perturbed by ligand complex formation and/or by controlled external influences.

Abstract: In its broadest aspect, the present invention provides a method of effecting an electrochemical specific-binding assay of a ligand, either qualitatively or quantitatively, in an apparatus comprising at leasts one electrode, in which method a labelled component of the assay medium is, at least in part, magnetically held in the vicinity of the electrode. The electrochemical assay method may include a separation step, whereby bound label may be separated from free label in the assay medium. Preferably the electrochemical assay method will include the step of determining a perturbation in an electrochemical characteristic of components of the assay medium associated with a ligand complexing reaction.Such an assay method is applicable to, for example, antibodies and antigens and suitable labels include redox centers, enzyme labels in the presence of an electron-transfer mediator and electron-transfer mediator labels in the presence of an electron donor or acceptor.

Abstract: A ligand in a sample can be assayed using electrochemical apparatus containing a working electrode and components comprising:(a) the sample,(b) a specific binding partner to the ligand, or a specific binding partner to the ligand and selected from ligand analogues and specific binding partners, and(c) an electron-source or electron-acceptor; at least one of components (b) being labelled with an electron-transfer mediator capable of aiding the transfer of electrons between the electron-source or electron-acceptor and the working electrode by accepting electrons from the electron-source and donating them to the working electrode, or accepting the electrons from the electrode and donating them to the electron-acceptor.

Abstract: In its broadest aspect, the present invention provides a method of assaying a ligand in a sample which comprises contacting the sample with a predetermined quantity of a specific binding partner to the ligand, said specific binding partner being immobilized on the effective gate electrode of a field effect transistor, and determining whether (and, if desired, the extent to which) an appropriate transistor characteristic is changed as a result of complex formation between the ligand and the specific binding partner.