| Developing new techniques to detect biomolecular interactions (BMIs) taking place at a liquid/solid interface is of great interest for drug discovery, clinical diagnostics, and environmental analysis. This presentation covers the development of a new technique that uses a microwave coplanar transmission line (CTL) to detect the BMIs occurring at the solid/liquid interface. This new technique is label free, non-destructive, and the probe configuration is easy to integrate with microfluidics and nanostructures. Specific BMIs at the transmission line interface cause a subtle change in the dielectric constant. In this project, it is demonstrated that this subtle change in permittivity could be detected by measuring the dispersion property of the transmission line at the frequency range from a few Hertz to around 25GHz.; The CTL probe was used to investigate different BMIs in real-time, such as the biotin and anti-biotin (anti-biotin mouse gamma-immunoglobulin), and protein A and antibody (rabbit gamma-immunoglobulin) interaction. The results showed that the probe was sensitive to the dielectric property changes within a few molecular layers. The sensitivity of the probe reached x00 pg/mm 2. Two BMI assays with different parts of gamma-immunoglobulin involved were tested using the CTL probe. The probe was able to differentiate these two BMIs, which is usually not possible for other label-free techniques such as SPR (Surface Plasmon Resonance). CTL probe coupled with other detection techniques, fluorescence and atomic force microscopy, could gather more complete information about a BMI, including the protein orientation, protein package density, and protein-water interactions.; The nanoporous thin film was applied to the CTL probe surface to improve the loading of ligand molecules. The probe showed selectivity to the target molecules (avidin, and anti-biotin mouse IgG) based on their physical sizes. |
