title: Label-free impedimetric immunosensors for psoriasin--increased reproducibility and sensitivity using an automated dispensing system.
abstract: We describe within this paper the construction of a label-free immunosensor for the protein psoriasin (S100A7), which is associated with a number of clinical conditions such as skin diseases or cancer. Antibodies to psoriasin were immobilised onto screen-printed carbon electrodes that had been pre-modified with the conductive polymer polyaniline. We compared and contrasted a number of different methods of assembly to optimise the construction and properties of the immunosensor. Immunosensors were fabricated using both manual liquid handling (pipette) and an automated liquid dispensing platform, the BioDot AD3200(TM). Two immobilisation methods were also utilised; simple electrostatic binding of the antibody to polyaniline as well as a more complex procedure using a biotin-neutravidin bridge. The optimum results in terms of sensitivity and reproducibility were obtained utilising the automated system and the biotin-avidin assembly procedure. The resultant immunosensors could be interrogated using AC impedance without the need for any labelling and demonstrated quantification of psoriasin from 250 pg ml(-1) to 10 ng ml(-1)-a concentration range suitable for determining physiological levels of psoriasin.
authors: Cranfield Health, Cranfield University, Bedfordshire, UK.
authors: Timothy R J
authors: TR
authors: Holford
authors: Joanne L
authors: JL
authors: Holmes
authors: Stuart D
authors: SD
authors: Collyer
authors: Frank
authors: F
authors: Davis
authors: Séamus P J
authors: SP
authors: Higson
mesh_terms: D000327:Adsorption; D000814:Aniline Compounds / Q000737:chemistry; D055910:Antibodies, Immobilized / Q000737:chemistry; D001360:Avidin / Q000737:chemistry; D015374:Biosensing Techniques / Q000295:instrumentation*; D001710:Biotin / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D017097:Electric Impedance; D004566:Electrodes; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation*; D000075023:S100 Calcium Binding Protein A7; D009418:S100 Proteins / Q000032:analysis*; D012680:Sensitivity and Specificity; D055672:Static Electricity
chemical_list: D000814:Aniline Compounds; D055910:Antibodies, Immobilized; D000075023:S100 Calcium Binding Protein A7; D009418:S100 Proteins; C089242:S100A7 protein, human; C416807:polyaniline; D001360:Avidin; D001710:Biotin; D002244:Carbon