Ultrahigh-sensitivity label-free optical fiber biosensor based on a tapered singlemode- no core-singlemode coupler for Staphylococcus aureus detection

Abstract

An ultra-high sensitivity label-free optical fiber biosensor for inactivated Staphylococcus aureus (S. aureus) detection is proposed and investigated in this study, with additional advantages of robust and stability compared to traditional tapered fiber structure. The proposed fiber biosensor is based on a tapered singlemode-no coresinglemode fiber coupler (SNSFC) structure, where the no core fiber was tapered to small diameter (taper-waist diameter of about 10 µm ) and functionalized with the pig immunoglobulin G (IgG) antibody for detection of S. aureus. The measured maximum wavelength shift of the sensor for an S. aureus concentration of 7×10 1 CFU/ml (colony forming unit per milliliter) is 2.04 nm, which is equivalent to a limit of detection (LOD) of 3.1 CFU/ml (a highest LOD reported so far for optical fiber biosensors), considering the maximum wavelength variation of the sensor in phosphate buffered saline (PBS) is ±0.03 nm over 40 minutes, where 3 times of maximum wavelength variation (3×0.03=0.09 nm) is defined as measurement limit. The response time of the developed fiber sensor is less than 30 minutes. The ultra-sensitive biosensor has potential to be widely applied to various areas such as disease, medical diagnostics and food safety inspection.

Singlemode-Multimode-Singlemode Fiber Structures for Sensing Applications—A Review

“…Fig. 10 A schematic diagram of tapered (a) SMF [226], (b) SNCS [245], (c) SMS fiber coupler [246] and (d) tapered SNCS for S. aureus measurement [245]. Reprinted with permission from [245].…”

“…Most recently tapered SNCS [245] and SMS fiber couplers [246] have been proposed with additional advantages such as mechanical stability and a ability to measure multiple parameters. For example, two parallel aligned SNCS fiber structures were tapered to small diameters to form a coupler structure, which achieved ultra-high sensitivity label-free quantification of inactivated Staphylococcus aureus (S. aureus) with an LoD of 3.1 CFU/mL [245] and a tapered SMS fiber coupler has been applied to detect hCG with a minimum concentration of 0.05 mIU/mL [246].…”

Biosensing Applications Using Nanostructure-Based Localized Surface Plasmon Resonance Sensors

“…The use of optical fibers as LSPR substrates has several advantages, including resistance to electromagnetic interference, chemical passivity, cost reduction, ease of use, and small footprint [ 76 , 77 ]. Easy reuse of the optical fiber-based LSPR sensor is also one advantage [ 75 , 78 , 79 , 80 , 81 ]. The general approach to reuse is to wash with phosphate buffered saline buffer or sodium dodecyl sulfate solution, and cut and polish the end of the used facet of the optical fiber.…”

“…Optical fiber-based LSPR sensors have been developed to detect different chemical and biomolecules such as enzymes, cortisol, cancer markers, and bacterial cells [ 78 , 79 , 90 , 91 , 92 , 93 ]. For example, cholesterol was detected by attaching cholesterol oxidase (ChOx) to AuNP-coated fiber via an adhesive layer of (3-mercaptopropyl) trimethoxysilane.…”

“…Recently, LSPR sensors coupled with different mode optical fibers were developed and applied to detect whole bacterial cells [ 78 , 91 ]. One example of these sensors exhibits two physical contact fiber structures: single mode fiber (SMF) and multi-core fiber (MCF).…”