UC Riverside

Surface plasmon resonance (SPR) has been broadly used as a powerful biosensing technique for the study of biomolecular interactions. It has the capability of performing real-time and label-free quantitative measurement that is essential to analysis of proteins and many other biomolecules where fluorescent tagging has an adverse effect on accuracy and precision. To further extend the applicability of SPR biosensing, we have developed a new technique platform that allows for a parallel and multi-dimensional detection of molecules of interest on the same sensing interface. Specifically, mass spectrometric and Raman spectroscopic characterization has been enabled to acquire chemical and structural information along with quantitative SPR measurement. Calcinated silicate AuNP microarrays have been fabricated on a glass slide based on the concept of layer-by-layer deposition involving polyelectrolyte, which demonstrated soft ionization and thus highly effective MS analysis of peptides and small molecules in a high-throughput fashion. By deliberately controlling the self-assembly process of calcinated AuNPs into an ultrathin monolayer film, excellent optical performance was obtained, allowing for a cross-platform measurement by localized surface plasmon resonance (LSPR), mass spectrometry, and Raman spectroscopy. We have employed computer simulation based on finite-difference time-domain (FDTD) algorithm for the design of the new sensing substrates. FDTD simulation offers in-depth understanding of the plasmonic coupling conditions and EM field enhancement for the self-assembly of AuNPs, providing the foundation and guidance for advancing optical sensing with nanostructured materials. One Chapter of the thesis is dedicated to the construction of various nano-sized geometries for simulation of plasmonic materials. The work covers from construction of silver clusters with defined nanogap for enhancing fluorescent signal to the design of plasmonic gold nanorod arrays that enable coupling of multi-dimensional propagation of electric fields for novel SPR detection.

In addition, a new approach for SPR analysis of carbohydrate interactions has been developed with fluorochemistry and calcinated SPR gold film. Fluoroalkysilane was used to provide a monolayer modification of the hydrophobic interface for effective capturing of carbohydrate probes through non-covalent interaction. Molecular recognition with various lectins was investigated by real-time kinetic study. Polydimethylsiloxane (PDMS) channel chips were utilized that enabled parallel analysis for high-throughput detection of carbohydrate-protein interaction with SPR imaging technique. Matrix-free LDI-MS of the calcinated gold film and array is not compromised by the SAM coating, allowing for the development of new SPR-MS on-chip analysis. Finally, a novel label-free biosensing approach based on thin-film transmission interferometry (TTi) has been developed with nanoscale porous anodic alumina (PAA) film. The optical phenomenon of TTi has been successfully confirmed by simulation. Performance of TTi sensing in relation to the structural geometries of PAA nanofilm was studied, providing valuable insights into the optimization of TTi-substrate based on porosity, thickness, and pore diameter to achieve high biosensing sensitivity. This newly developed substrate also provides a convenient platform for biological studies of protein adsorption. As a surface-sensitive label-free detection, TTi shows a great potential to be incorporated into the ongoing on-chip SPR-MS biosensor development for achieving higher level of research possibilities.