Investigation of solution-phase and on-chip binding of C-reactive proteins and antibodies

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Noonan, Ethel
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University College Cork
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Gold nanoparticles can self-assemble into nanostructures in the presence of suitable linker molecules. The self-assembly of gold nanoparticles functionalized with C-reactive protein (CRP) antibodies in the presence of CRP antigen linker molecules was explored. A ratio of antigen linker molecules to nanoparticle (2:1) that resulted in rapid nanoparticle self- assembly was identified, evidenced as a distinct solution colour change from red to blue within 5 minutes. Higher linker molecule- nanoparticle ratios (12:1, 18:1, 72:1) resulted in slow formation of nanostructures and only a slight solution colour change (even after periods of several days), the rate being dependent on the number of available binding sites. The propensity of nanoparticles to rapidly assemble into nanostructures at certain linker molecule- nanoparticle ratios was corroborated employing citrate-stabilized nanoparticles and di- isothiocyanate terminated metal-organic rhenium linker molecules, whereby again rapid formation of nanostructures was dependent on specific molecule-nanoparticle ratios as distinct from other molecule-nanoparticle ratios. UV-visible spectroscopy and scanning electron microscopy characterization confirmed visual observations. Surface-based assays also show much promise in application to point-of-care detection. It was of interest to determine if surface-based assays void of complex chemical processes and elaborate equipment could compete with laboratory-based assays in terms of specificity, stability and sensitivity but also offer faster and inexpensive diagnosis. The binding of CRP antibody to silanised silicon-silicon oxide substrates implemented using the organosilane APTES and the subsequent binding of CRP antigen to this immobilised CRP antibody was explored. The binding event of CRP antigen to surface immobilised CRP antibody was electrically characterised in ambient conditions. The formation of the antibody-antigen complex resulted in a corresponding decrease of the sensor capacitance at a CRP antigen concentration of 20 µg/mL (2 hours). However, it was demonstrated that nanoparticle amplification can facilitate rapid visual surface-based detection of CRP antigen of between 5 and 20 µg/mL.
Nanotechnology , Nanomaterials , Self-assembly , Nanoassemblies , Detection , C-reactive protein , Surface chemistry , Point-of-care technology
Noonan, E. 2014. Investigation of solution-phase and on-chip binding of C-reactive proteins and antibodies. PhD Thesis, University College Cork.