Developing localized surface plasmon resonance biosensor chips and fiber optics via direct surface modification of PMMA optical waveguides

•AuNPs were directly attached onto PMMA surfaces without an intermediate layer.•Two methods were employed and compared for monolayer formation and LSPR effect.•The surface chemistry of PMMA for AuNPs attachment has impacts on the sensitivity.•LSPR fiber and chip sensors showed positive responses for Con A analyte testing.

This paper presents novel strategies of immobilizing gold nanoparticles (AuNPs) onto the surface of polymer substrates in the fabrication of PMMA based localized surface plasmon resonance (LSPR) biosensor chips and optical fibers. Thiol and amine functionalities were incorporated onto the surface of poly(methyl methacrylate) (PMMA) chips and optical fibers through direct surface chemical modifications, thus allowing for subsequent covalent bonding or electrostatic adsorption of colloidal AuNPs. The modification conditions were optimized to achieve a monolayer distribution of particles 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 lower Con A detection limit using this thiol immobilization method was shown to be 0.49 nM and 1.41 nM for PMMA chips and PMMA fibers, respectively. The successful proof-of-concept fabrication of LSPR PMMA fiber optic biosensors is the first step in generating facile polymeric optical fiber biosensors as a potential replacement for traditional glass optical fibers.

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