Author:

Abstract:

The Surface Plasmon Resonance (SPR) technology is an effective tool in food and medical diagnostics. An innovative SPR sensing platform was previously described by our group with a gold coated multimode optical fiber (FO) used as biosensor in various proof-of-concept studies. Thus far, successful applications in screening of DNA single-point mutations or detection of pathogens and allergens in food revealed great potential of this platform. However, the FO-SPR probe remained with some limitations, mostly related to the stability of gold layer, and with the capacity for improving the sensitivity towards low detection limits. In this context, two strategies for enhancing the FO-SPR performance are presented. First, in order to improve the adherence of the thin gold layer, an intermediate silane coupling agent (MPTMS) was chemically deposited onto the FO silica core. The results pointed out a highly improved attachment of gold when MPTMS was used, enhancing further the stability of the FO-SPR probe and thus the robustness of the platform. The reproducibility of the fabrication protocol was evaluated through statistical analysis of various sensor features essential for defining its sensitivity. Second, targeting sensitivity improvements, a colloidal lithography approach, carefully adapted to the FO probe geometry, was employed. Nanostructuring the FO surface was achieved by means of settling nanoparticles onto the FO silica core, followed by gold deposition and their eventual lift-off through ultrasonication in dichloromethane. The size distribution of particles was found to play an essential role in realizing their structured dispersion on the fiber surface and consequently anticipated triangularly shaped gold nanostructures.