Date of Award
Doctor of Philosophy (PhD)
Micro and Nanoscale Systems
A polymer nanostructured Fabry-Perot interferometer (FPI) based biosensor has been developed, fabricated, and tested. Different from a conventional FPI, this nanostructured FPI has a layer of Au-coated nanopores inside its cavity. The Au-coated nanostructure layer offers significant enhancement of optical transducing signals due to the localized surface Plasmon resonance (L-SPR) effect. Compared to a traditional FPI for label-free biosensing applications, the polymer nanostructured FPI based biosensor offers increased sensing surface area, extended penetration depth of the excitation light, and amplification of optical transducing signals. Using a nanostructured FPI, measurements taken had great improvements in free spectral range (FSR), finesse, and contrast of optical transducing signals over a traditional FPI without any device performance optimization.
Several chemicals have been evaluated using the prototype device. Fourier Transform has been performed on the measured optical signals to facilitate the analysis of the transducing signals. Control experiments incubating immunoglobulin G (IgG) on a gold surface confirmed the small affinity of IgG to the Au-coated sensing surface. Then, using fluorescent images, shifts of interference fringes for IgG and BSA interaction were indirectly confirmed.
Using this technical platform, the immobilization of capture proteins (Protein A) on the nanostructure layer and their binding with IgG was monitored in real time, resulting in the direct observation of the shift in interference fringes of the optical transducing signals. The results showed that the detection of limit (DOL) for this kind of biosensor should be lower than 10 pg/mL, which is approximately 55 fIVI of IgG, for IgG-Protein A binding. Control experiments were performed to confirm that the biodetection is only specific to Protein A and IgG recognition.
After the proof-of-concept demonstration for IgG-Protein A binding, the ultrasensitive label-free detection of a cancer biomarker free prostate specific antigen (fPSA) using this kind of nanostructured FPI was carried out. Experiments found that the DOL of the fabricated nanostructured FPI microchip for f-PSA is about 5 pg/mL and the upper detection range for f-PSA can be dynamically changed by varying the amount of mAb immobilized on the sensing surface. Control experiments have also demonstrated that the immunoassay protocol used shows excellent specificity and selectivity, suggesting great potential to detect cancer biomarkers at trace levels in biofluids.
Given its nature of low cost, simple operation, and batch fabrication capability, the nanostructured FPI microchip based platform could provide an ideal technical tool for point-of-care diagnostic applications and anti-cancer drug screening and discovery.
Zhang, Tianhua, "" (2012). Dissertation. 341.