Review of plasmonic fiber optic biochemical sensors: improving the limit of detection

Anal Bioanal Chem (2015) 407:3883–3897 DOI 10.1007/s00216-014-8411-6 REVIEW Review of plasmonic fiber optic biochemical sensors: improving the limit of detection Christophe Caucheteur & Tuan Guo & Jacques Albert Received: 6 October 2014 / Revised: 2 December 2014 / Accepted: 12 December 2014 / Published online: 24 January 2015 # Springer-Verlag Berlin Heidelberg 2015 Abstract This paper presents a brief overview of the technologies used to implement surface plasmon resonance (SPR) effects into fiber-optic sensors for chemical and biochemical applications and a survey of results reported over the last ten years. The performance indicators that are relevant for such systems, such as refractometric sensitivity, operating wavelength, and figure of merit (FOM), are discussed and listed in table form. A list of experimental results with reported limits of detection (LOD) for proteins, toxins, viruses, DNA, bacteria, glucose, and various chemicals is also provided for the same time period. Configurations discussed include fiberoptic analogues of the Kretschmann–Raether prism SPR platforms, made from geometry-modified multimode and singlemode optical fibers (unclad, side-polished, tapered, and Ushaped), long period fiber gratings (LPFG), tilted fiber Bragg gratings (TFBG), and specialty fibers (plastic or polymer, microstructured, and photonic crystal fibers). Configurations involving the excitation of surface plasmon polaritons (SPP) on continuous thin metal layers as well as those involving localized SPR (LSPR) phenomena in nanoparticle metal coatings of gold, silver, and other metals at visible and near-infrared wavelengths are described and compared quantitatively. Published in the topical collection Direct Optical Detection with guest editors Guenter Gauglitz and Jiri Homola. C. Caucheteur Electromagnetism and Telecommunication Department, University of Mons, Boulevard Dolez 31, 7000 Mons, Belgium T. Guo Institute of Photonics Technology, Jinan University, 601 Huangpu Road West, Guangzhou 510632, China J. Albert (*) Department of Electronics, Carleton University, 1125 Colonel By Drive, Ottawa K1S 5B6, Canada e-mail: Keywords Plasmonics . Polaritons . Photonics . Optical fiber . Grating . Bragg . Chemical sensing . Biochemical sensing . Immunosensing . Gold . Nanoparticles Introduction The purpose of this paper is to review advances in opticalfiber-based, label-free direct detection devices using surface plasmon resonance (SPR) effects. Throughout the paper, but apart from context-specific instances, the SPR acronym will be used both for devices involving surface plasmon polaritons (SPP) along metal surfaces and for localized SPR (or LSPR) which refers to three-dimensional plasmon resonances in metal particles. Furthermore, SPR is meant here in its broadest possible sense, i.e., for the measurement of the properties of light waves interacting with nanoscale metal particles or films [1–3]. Using such resonances in sensing has been the object of much research, dating back over 20 years, as reviewed elsewhere [4–8]. More specialized reviews dealing with fiberbased SPR sensors also appeared up to five years ago [9, 10]. Based on these pioneering investigations, research in the last few years has led to notable advances. These advances go beyond laboratory proof-of-principle experiments and report impressive limits of detection (LOD) in real-life applications, using both conventional configurations and new device geometries. It was therefore felt that a critical survey of recent developments would be useful at this time so that research groups and user communities could get a good understanding about the performance of current technologies and methods as well as about the potential of the newer ones. The rapid and accurate detection of analytes in small concentration (proteins, ADN, pathological markers, toxins etc.) is crucial in numerous fields such as medical diagnosis, environmental monitoring, or quality control in the food industry. 3884 layers, excitation of LSPRs in nanoparticles), and to the interrogation technique (mainly spectral absorption and gratingassisted mode coupling, as well as multimode vs single-mode fibers). A general survey of the literature is presented in table form where the main characteristics and performance indicators of representative reported results are given. Those performance indicators include the bulk refractometric sensitivity, which indicates how the device responds to changes in its environment and is usually the first metric used to predict the performance of (bio)chemical sensors. However, refractometry is definitely not the main purpose of SPR sensors and the last section presents another group of publications that report on the performance of fiber SPR devices in actual applications, as measured by their experimentally determined analyte LODs. The most striking finding is that widely different approaches, from the “standard” cladding-removed, goldcoated multimode fiber with spectral interrogation, to very sophisticated, nano-patterned customized fiber design, with grating-assisted devices in between, are all able to achieve impressive LODs. This is likely because the most important factors in lowering the LOD and increasing the specificity in label-free detection lie in the noise properties of sources and detectors [13], as well as in the quality of the surface functionalization, where great advances have been made over the last few years [14, 15]. SPR generation on optical fibers Surface plasmon polaritons (SPP) Optical prism Li gh to ut The most common approach to excite surface plasmon waves on thin metal films is the Kretschmann–Raether configuration sketched in Fig. 1 [2]. In this approach, light is injected through a prism towards a plane face coated by a thin layer of noble metal. The incidence angle at the glass–metal n ti gh Li In the context of these applications, detection systems can be divided into two general categories: laboratory-based and field-based systems, where “field” is taken to mean detecting in samples where they happen to be located in contrast to having to bring samples back to a laboratory. A further distinction can be made between direct detection and labeled method, whereby the latter requires some sort of tag added to the analyte in order to enable its detection. Direct detection methods are generally preferred over labeled approaches from the point of view of cost and ease of use (and for field use in particular), but direct detection is also generally less sensitive because labeling enables the use of additional selection and amplification methods that raise the signal level of very small concentrations over the background response of samples. The use of optical-fiber devices as sensors presents many well-known desirable features (size, cost, light path control) for both labeled and label-free methods but those advantages are best expressed in label-free solutions as they contribute t (...truncated)