12 Month Public Progress Report

21/Apr/2005


The ELISHA project has successfully demonstrated a labeless format immunosensor, with a calibration curve for PSA.


Background

The ELISHA project is designed to improve knowledge in molecular interfaces and enable manufacture of new affinity sensors, by understanding the rules for controlled manufacture at the nanoscale. Interrogating antibodies on electroconductive surfaces will help us to produce nanostructured immunosensor formats that in practice work as simply the most successful commercial biosensors and which can be manufactured at high quality and low cost. These are the main aims of ELISHA, which stands for: Electronic Immuno-Interfaces and Surface Nanobiotechnology: A Heterodoxical Approach. To provide significant breakthroughs in science often requires a change of orthodox thinking, hence the addition of heterodoxy in the title of the project to indicate a departure from existing knowledge and traditional electrochemical thinking.

Practically the project is focussing on 3 areas

When an antibody recognises and transiently binds to its antigen there is a small electrode current produced in the supporting electroconductive matrix which can be measured and which is concentration dependant with respect to the antigen detected. The project is investigating the nature and origin of the signal transduction mechanism observed in these nanostructured affinity-reagent based biosensors.

Using the knowledge obtained, immunosensor model prototypes will be designed and optimised to give simple, novel, low-cost and reliable affinity sensors for a number of important clinical, environmental and related model analytes. These include cancer markers as a representative protein target (PSA) and fluoroquinoline antibiotics as a representative hapten target (small molecule types).

The manufacture of electrochemical, label free immunosensors will also be complimented by the development of dedicated electronics to provide specific interrogation protocols to deal with any non-specific binding events and to amplify the affinity event occurring.


Project Progress: First 12 Months.

Affinity reagent production has been very successful to date with 1 monoclonal and 3 polyclonal antibodies being made available to the project for early evaluations in immunosensor development. The production of the first polyclonal antibodies for fluoroquinoline antibiotics are well underway and the recombinant monoclonal antibody production is also in progress.

Specifically designed gold on silicon transducers have been produced. These form the basis of the sensor research program and are giving detailed information for the bulk production of low cost immunosensors for the future.

Sensor production is a core workpackage of the project, consisting of three closely interlinked workpackages and much work has been done in this area in the production of new electropolymerisable monomers that form the matrices for the immunosensors, the development of novel immobilisation strategies and the actual production of 3 different affinity sensors based on the antibodies supplied.

In addition to this, three new types of immobilisation systems have been explored using the specialised monomers developed that have been electropolymerised to give reactive conducting polymers, able to form co-valent or biotin-avidin interactive matrices to give nano-structured immunosensor surfaces. A photo-activated immobilisation matrix has also been synthesised. These have been interrogated using impedance spectroscopy as the standard electrochemical research method to give clear calibration curves for a model protein - BSA (bovine serum albumin) and PSA (prostatic specific antigen) which is the biomarker used for diagnosis of prostate cancer and is one of the specific targets of the project.


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