UC Riverside

The goal of this dissertation focuses on addressing the challenges in advancing biomedical application of SPR techniques, particularly towards drug discovery, cell-drug interactions, and biomarker detection. We first developed and characterized potential peptide inhibitors against the SARS-CoV-2 virus using SPR spectroscopy with a competition assay format. Two peptides were developed with an increasing sequence length based on α-helix of ACE2 PD [22-44] and [30-42] peptides, which were prepared using solid-phase peptide synthesis (SPPS). SPR assays show that these peptides are strong inhibitors to block SARS-CoV-2 spike protein binding to the ACE2 receptor. Results of molecular docking study by PatchDock suggest that both peptides act to block most of the RBD residues that are known to bind to the original ACE2 PD. The work could provide useful information for developing novel anti-SARS-CoV-2 agents without the adverse side effects of small molecules or recombinant proteins. In an effort to augment understanding of cell-based assay with SPR, drug-cell interactions were investigated and monitored in real-time using SPR in combination with optical microscopy. Our results indicate that different concentrations of propranolol (POA), a beta-blocker, exhibit different modes of interaction with HeLa cells, reflected by both SPR peak angular position (PAP) and peak minimum intensity (PMI). Theoretical SPR curves from models based on confluency were compared to the experimental results, suggesting at a high drug concentration, the experimental SPR response agrees well with microscopic characterization based on confluency. At low concentrations, cell confluency is insufficient to explain the entire SPR response to the apoptotic events, pointing to a complex cytotoxic mechanism. To enhance the biomarker detection sensitivity, we investigated two types of interfaces: an affinity interface based on modified antibody layer and a covalent interface based on thiolated selfassembly monolayer. IgE was chosen as a target model protein biomarker. Results indicate that IgE immobilized by an affinity interface shows a higher binding capacity than those through the covalent interface. In addition, SPR signal amplification using AgNP conjugates was compared on the two interfaces. Furthermore, MD simulation was performed to investigate structural changes and their impact of the amyloid-beta fragments, an Alzheimer’s disease biomarker, on the lipid bilayer. Analysis of the simulation results reveals that both Amyloid-beta fragments Aβ (15-27) and Aβ (28-40), along with the POPC lipid bilayer, undergo conformational change in respect to the original structure.