CP-SMARTSURFACES · Towards better point of care devices: Conducting polymers as smart surfaces in biosensors

Towards better point of care devices: Conducting polymers as smart surfaces in biosensors.

The overall goal of the proposed research was to develop a highly sensitive biosensing platform which also controls and reduces interfering non-specific protein binding (which will enhance sensitivity). Technical summary to date: • 4 articles published • 4 book chapters published • 8 conference presentations; 4 oral presentations and 4 poster presentations • Established improved techniques for functionalising nanostructures with antibodies • Achieved aim of reducing non-specific binding by alternative route Results to date: Conducting polymers (CPs) shrink when excess counter ions are washed out after vapour phase polymerisation. This shrinkage phenomenon allows incorporation of active molecules into the CP film. Using this shrinkage phenomenon, antibodies were incorporated into CP films. Enzyme-linked immunoassay (ELISA) studies confirmed antibody immobilisation in the films; which were characterised by UV, IR and Raman spectroscopy, in addition to full electrochemical characterisation. Scanning electron microscopy confirmed film nanostructure. The attachment of antibodies onto polyaniline (Pani) nanofibres was investigated. Pani nanofibres were functionalised with either amine or carboxylic acid hydrophilic side-groups which were further modified with antibodies. The resultant conjugates were characterised using infrared, UV-visible and Raman spectroscopy in addition to scanning and transmission electron microscopies. ELISA results indicate successful antibody binding to Pani nanofibres. Carboxyl functionalised Pani nanofibres were shown to decrease non-specific binding of proteins; a key objective of this project. We have also shown attachment of antibodies by varying the pH of the system. In this instance an anti-prostate specific antigen (PSA) antibody was immobilised on pani nanofibres and allowed detection of PSA at a level of 500ng/ml. Results from objectives 2 and 3 established that while modifying the surface chemistry of conducting polymers can help to control non-specific binding, it does so at the cost of biosensor sensitivity. Carbon nanotubes (CNTs) were therefore substituted as the electrode material for preliminary studies relating to in vitro sensing of glucose and lactate during cell differentiation. It was found that optimal results were obtained with a capacitive sensor made from CNTs, nanostructured carbon black, nanostructured manganese dioxide, the appropriate enzyme and a chitosan outer layer. Each component was separately optimised and results showed that this sensor operated well within the clinically relevant range. Appropriate surface chemistry in bioconjugation reactions of nanoparticles (NPs) is essential, both to maintain monodispersity and control non-specific binding. When using carboxyl functional dendrimer linkers for conjugation of antibodies to nanoparticles, the charge can be maintained by activation with sulfo-NHS/EDC chemistry. The use of dendrimers for conjugation of antibodies to nanoparticles resulted in a significantly higher surface coverage of active antibody, with an improved signal to noise ratio (of the dendrimer-activated nanoparticles compared to a dye-labelled antibody) by approximately four-fold, which is a main objective of this project. Expected potential impact and use: Low cost and easy to use tests need to be developed for use in a community setting as an alternative to expensive laboratory-based testing. The overall goal of the proposed research was to develop a highly sensitive biosensing platform which also controls and reduces interfering non-specific protein binding (which will enhance sensitivity). Robust protocols for nanoparticle modification were established, allowing the development of stable protein-functionalised nanoparticles, which can be used for a wide variety of biomedical applications.

Data: CORDIS, © European Union