Development of a mini-array immunosensor platform

Prior work by the Millner laboratory, principally arising from EC Framework 6 Project ELISHA, led to the development of a new electrochemical immunosensor platform. ELISHA immunosensors comprise immobilised antibodies on the surface of a transducer and can be interrogated by AC impedance or electrical pulse decay after binding the analyte to be interrogated. The sensors are truly reagentless and measurement is simply 'incubate and read' with quantification of the analyte being carried out against a calibration curve. Background signal is typically much less than 10-15% of specific signal and can be accounted by two main approaches; tuning of the sensor surface chemistry for the analyte and matrix in which it occurs, and subtraction of a 'control' electrode signal that bears a non-specific antibody. To date we have demonstrated the ELISHA principle for >30 analytes, ranging from heavy metal ions, through small molecules like pesticides and antibiotics, macromolecules such as various protein markers of disease, and up to viruses and bacteria. ELISHA immunosensors function in 'real' fluids such as milk, serum and blood, urine and saliva with no prior processing. We are now at a stage where ELISHA commercialisation is being actively pursued and the challenge is to understand how best to fabricate immunosensor chips to acceptable batch reproducibility. In addition we wish to develop multi-analyte 'mini-array'chips where a panel of up to 10-12 analytes can be measured simultaneously within a sample. Discussion with both medical and veterinary companies and with the biotech industry servicing life science R & D indicates this to be a major requirement. Against this background Abcam Ltd, globally one of the major suppliers of antibodies for R & D; wish to collaborate with us in developing such a multi-analyte platform which for them will represent a future product portfolio. For the academic partner, the alliance would give access to Abcam's very large product portfolio and expertise in producing and handling all types of antibodies. The project strategy will be to examine ELISHA biosensor fabrication and interrogation at four key points. These are electrode (transducer) design, optimisation of transducer composition and nanostructure, optimisation of surface chemistry for antibody coupling from the several approaches available to us, and choice of best interrogation strategy. To accomplish these aims we will work with panels of antibodies, where the analytes are also readily available. Electrodes will be fabricated by both screen printing and inkjet procedures and several multi-electrode layouts will be compared. Then a range of conducting polymeric surfaces will be compared, bearing appropriate pendant chemical groups (amine, hydroxyl, and thiol) to permit gentle chemical coupling of antibodies to the transducer surface. Direct coupling and affinity mediated coupling (avidin/biotin, complementary oliognucleotide pairs), and non-specific versus oriented antibody immobilisation, will be compared. Finally, low frequency AC impedance interrogation protocols will be compared with fast pulsed electrochemical approaches we have developed; if the fast pulsed methodology gives reproducible measurements this would represent a step improvement in biosensor interrogation. During the project we will focus on antibody/analyte sets for which is an analytical requirement is known by Abcam to exist within the R& D community (e.g. cytokines, second messengers, protein and peptide neurotransmitters). We also have expertise in place to drive onward development of any successful findings emerging from this project. ELISHA Systems Ltd, a spin-out from project ELISHA and Uniscan Instruments Ltd, a partner in the ELISHA project, already have IP in place and a prototype ELISHA chip reader respectively which could be further developed to produce a simple handheld chip reader for the generic multi-analyte immunosensors we hope to develop.