Download files
Abstract
This thesis reports novel strategies for immobilizing gold nanoparticles (AuNPs) onto the surface of polymer substrates in the fabrication of poly(methyl methacrylate) (PMMA) based localized surface plasmon resonance (LSPR) biosensor chips and optical fibers. Thiol and amine functionalities were incorporated onto the surface of PMMA chips and optical fibers through direct surface chemical modifications, thus allowing for the subsequent covalent bonding or electrostatic adsorption of colloidal AuNPs. The modification conditions were optimized to achieve a monolayer distribution of nanoparticles and well defined LSPR absorption peaks. It was discovered that the sensitivity of the LSPR biosensor was substantially affected by the chemistries employed for the AuNP immobilization. AuNPs immobilized on both thiolated PMMA chips and fibers showed higher sensitivities compared to aminated PMMA substrates when tested against 1-thio-β-D-glucose and subsequent concanavalin A (Con A) bindings.
The performance of the PMMA based LSPR biosensor chips was enhanced through the surface grafting of glycopolymers carrying glucose moieties for the detection of Con A. Poly(pentafluorostyrene) (PPFS), with pre-determined polymer chain lengths, were synthesized via a reversible addition–fragmentation chain transfer (RAFT) polymerization technique. The synthesized PPFS were subsequently converted into glycopolymers via para-fluoro-thiol “click” reactions and grafted onto the surface of the sensor chips. The “glycocluster effect” induced by pendent carbohydrate moieties enabled a stronger binding affinity for Con A, which resulted in the dramatic expansion of the sensor’s response ranges. It was discovered that the longer polymer brushes did not always bring additional enhancements for the sensor chips, although they could lead to higher detection limits. In addition to the superior performance, the capabilities of the reported sensor chips can easily be manipulated to detect a diverse range of analytes by “clicking” various sensing elements onto the polymer brushes.