Fiber optic biosensor for the detection of C-reactive protein and the study of protein binding kinetics.

Application of a fiber optic biosensor (FOB) to the real-time investigation of the interaction kinetics between FITC-conjugated monoclonal sheep anti-human C-reactive protein (CRP) antibody and CRP isoforms on the surface of optical fiber is described. Recently, both the native pentameric CRP (pCRP), an acute phase protein belonging to pentraxin family, and an isoform of pCRP, modified CRP (mCRP), have been suggested to have proinflammation effects on vascular cells in acute myocardial infarction (AMI). In current studies, we generate mCRP from pCRP, and use several methods including fluorescence spectral properties, circular dichroism, analytical ultracentrifuge, and Western blotting to demonstrate their differences in physical and chemical properties as well as the purity of pCRP and mCRP. In addition, we design and implement an FOB to study the real-time qualitative and quantitative biomolecular recognition of CRP isoforms. Specifically, the association and dissociation rate constants of the reaction between FITC-conjugated monoclonal sheep anti-human CRP antibody and the pCRP and mCRP are determined. The feasibility of our current approach to measure the association and dissociation rate constants of the reaction between tested CRP isoforms was successfully demonstrated.

Tip-enhanced Raman spectroscopy of graphite irradiated by focused ion beam.

Tip-enhanced Raman spectroscopy with a spatial resolution of 25 nm is conducted on a sample of graphite that has been exposed to a 50 keV focused Ga ion beam with a diameter of 20 nm. The G mode located at 1579 cm(-1) does not exhibit a measurable tip enhancement, while the D mode at 1364 cm(-1) is significantly enhanced. A method is proposed to calculate the enhancement factor of anisotropic materials due to the electromagnetic field using the measured signal enhancement induced by the tip.