SERS Platform Based on Hollow-Core Microstructured Optical Fiber: Technology of UV-Mediated Gold Nanoparticle Growth.

Anastasiia A Merdalimova,Alexander S Smirnov,Alexey M Yashchenok,Dmitry A Gorin,Polina A Demina,Boris N Khlebtsov,Julia S Skibina,Sergey S Kosolobov,Timur I Ermatov,Polina G Rudakovskaya

doi:10.3390/bios12010019

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for biosensing. However, SERS analysis has several concerns: the signal is limited by a number of molecules and the area of the plasmonic substrate in the laser hotspot, and quantitative analysis in a low-volume droplet is confusing due to the change of concentration during quick drying. The usage of hollow-core microstructured optical fibers (HC-MOFs) is thought to be an effective way to improve SERS sensitivity and limit of detection through the effective irradiation of a small sample volume filling the fiber capillaries. In this paper, we used layer-by-layer assembly as a simple method for the functionalization of fiber capillaries by gold nanoparticles (seeds) with a mean diameter of 8 nm followed by UV-induced chloroauric acid reduction. We also demonstrated a simple and quick technique used for the analysis of the SERS platform formation at every stage through the detection of spectral shifts in the optical transmission of HC-MOFs. The enhancement of the Raman signal of a model analyte Rhodamine 6G was obtained using such type of SERS platform. Thus, a combination of nanostructured gold coating as a SERS-active surface and a hollow-core fiber as a microfluidic channel and a waveguide is perspective for point-of-care medical diagnosis based on liquid biopsy and exhaled air analysis.

Highlights

Surface-enhanced Raman spectroscopy (SERS) is a powerful tool for biological analysis, as it is based on Raman spectroscopy, which overcomes such issues of predominantly used fluorescent probes as limited multiplexing capability, poor photostability, and autofluorescence background [1]
We introduced a method for SERS substrate deposition process control in hollow-core microstructured optical fibers (HC-microstructured optical fiber (MOF)), based on the change in its transmission spectra
We propose that the SERS substrate area reached by laser irradiation in HC-MOF is greater than on planar substrate, the efficiency of scattering signal collection by an objective is lower in this case

Summary

Introduction

Surface-enhanced Raman spectroscopy (SERS) is a powerful tool for biological analysis, as it is based on Raman spectroscopy, which overcomes such issues of predominantly used fluorescent probes as limited multiplexing capability, poor photostability, and autofluorescence background [1]. Surface enhancement is based on a local surface plasmon resonance on metallic nanostructures, that provides amplification of any radiation, including Raman scattering, in the vicinity of the structure [3]. Raman and SERS sensing have the following features: Raman signal intensity for a given liquid sample and measurement conditions depends on the irradiated number of molecules; the surface enhancement factor provided by a given SERS substrate depends on the area of the plasmonic surface irradiated. These challenges can be improved by using optical fibers as Raman/SERS platforms [8,9,10]. HC-MOFs allow the work in a low sample volume [12], for example, a fiber with a hollow core diameter of 240 μm and length of a few centimeters is filled with just a few microliters for analyte probing

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