Enhanced multimodal biosensing using plasmonic paper-based nanoplatforms

The study of biosensing devices proving portability, high efficiency and sensitivity, ease of use and low-cost increases in research interest continuously. Such promising point-of-care tools are plasmonic paper-based... [ view full abstract ]

The study of biosensing devices proving portability, high efficiency and sensitivity, ease of use and low-cost increases in research interest continuously. Such promising point-of-care tools are plasmonic paper-based nanoplatforms due to their advantages such as facile fabrication, high specific surface area, flexibility, or excellent wicking ability due to capillary forces. The robustness of this nanosensor design enables the use of multiple techniques proving a decreased analysis time, improved molecule differentiation and ultra-low concentration detection.

In this work, we present a new plasmonic paper-based nanoplatform with enhanced multimodal Localized Surface Plasmon Resonance (LSPR) – Surface Enhanced Raman Spectroscopy (SERS) – Metal Enhanced Fluorescence (MEF) biodetection capabilities in terms of sensitivity, efficiency and reproducibility. Therefore, we took advantage of the unique optical properties of gold nanobipyramids (AuBPs) by synthesizing colloidal solutions with different aspect ratios. After the deposition onto cellulose fibers, confirmed by HRTEM, SEM and dark-field microscopic images, the bulk sensitivity of the platform was determined by changing the refractive index of the medium with water-glycerol mixtures of various concentrations. The previously chemically formed p-aminothiophenol@biotin linker is attached to the immobilized AuBPs ensuring thus: (i) the active binding spot for the target streptavidin molecule; (ii) the indirect SERS detection through the well-known p-ATP Raman reporter and (iii) the optimal distance between the gold surface and the proximal streptavidin-linked Alexa680 molecule for MEF to occur as a result of the target molecule capture. The multimodal streptavidin detection capabilities of the plasmonic paper-based nanoplatforms have been successfully demonstrated using three complementary analysis techniques. Subsequent to the biotin-streptavidin binding event, the change of the refractive index induces a LSPR red-shift, the presence of the p-ATP molecule fingerprint in the SERS spectrum provides indirectly information about the antigen-antibody interaction, while the evaluation of the emission behavior of Alexa680 proves the recognition interaction via MEF detection.

Acknowledgments Funding by the CNCS-UEFISCDI Romania, under the project number PN-III-P1-1.1-TE-2016-2095, and by the Babes-Bolyai University research funds – doctoral grants are gratefully acknowledged.