Smart and Functional Interfaces for Sensitive SPR Biosensing Towards Biomedical Applications

The aim of this thesis is to develop Surface Plasmon Resonance (SPR) methods that improve biosensing performance, in particular the sensitivity and selectivity of the analysis and their adaptation for biomedical applications to samples with complex background. This is of significant importance in translating the biosensor technologies to deliver the same results as the conventional methods but in a more accessible, efficient, and economical manner. The first study exploited SPR as a DNA biosensor for the detection of Malaria Plasmodium falciparum parasite with the hybridization chain reaction (HCR), which resulted in the formation of self-assembled target DNA nanostructures for signal enhancement. The sensitivity was further improved by using gold nanoparticles (AuNPs) for additional signal amplification. Tests with human blood plasma indicated the results were comparable to analyses in buffer, despite noticeable non-specific binding from the plasma. The concern of non-specific binding was systematically investigated in the second study where an antifouling surface consists of supported lipid bilayer membranes (SLBs) and protein A was developed for detection of trace amount of proteins in undiluted human serum. Specifically, cholera toxin (CT) spiked into the serum was used as the target, and advanced interface was further extended to immunosensing of immunoglobulin G (IgG). In the third study, SPR biosensor was employed in combination of bright field microscopy to characterize cellular apoptosis. HeLa cells undergoing apoptosis induced by hydrogen peroxide (H2O2) were monitored by SPR and the signals were compared to microscopic analysis of the morphological changes. SPR study revealed a decreased signal as cell confluency decreases, with the rates increasing as H2O2 concentration increases. An abnormality was found at high concentrations when both apoptosis and necrosis were induced. A mathematical model was proposed to explain SPR response where a non- uniform adsorbed layer was partially responsible. The significance of this thesis is that a number of high performing biosensing approaches have been developed and demonstrated. In addition to the advantages of SPR (e.g. label-free, real-time biomolecules binding, and portability), these methods have paved the way towards realizing effective sensing in biomedical research, especially in the early detection of infectious diseases and in the treatment of cancers