Present study demonstrates the fiber-optic localized surface plasmon resonance (LSPR) based sensitive biosensor for detection of Shigella bacterial species. The proposed sensor is comprised of multi-core fiber (MCF) having seven cores arranged in a hexagonal shape and spliced with single-mode fiber (SMF) for efficient detection. An increase in evanescent waves (EWs) and coupling of modes between MCF cores was achieved by etching process in a controlled manner. The etching process also increases the refractive index sensitivity (RIS) of the proposed sensor. Further, coating with nanomaterials like gold nanoparticles (AuNPs) and molybdenum disulfide (MoS ₂ ) helps in the excitation of localized plasmons. Here, Shigella specific oligonucleotide probes are used as a recognition element. The results demonstrate that the proposed sensor can successfully and efficiently detect the Shigella bacterial species with high sensitivity. Shigella in the range of 10 - 100 CFU/mL (colony-forming unit/mL) can cause serious intestinal infection and therefore, its detection in this range is critical. The proposed sensor demonstrates a linearity range from 1 to 10 ⁹ CFU/mL with a detection time of 5 min and a limit of detection (LoD) of 1.56 CFU/mL. The proposed sensing methodology can be a potential alternative to the commercially existing ones in the near future.

This article presents a concise summary of current advancements in novel nanomaterial-based optical fiber biosensors. The beneficial optical and biological properties of nanomaterials, such as nanoparticle size-dependent signal amplification, plasmon resonance, and charge-transfer capabilities, are widely used in biosensing applications. Due to the biocompatibility and bioreceptor combination, the nanomaterials enhance the sensitivity, limit of detection, specificity, and response time of sensing probes, as well as the signal-to-noise ratio of fiber optic biosensing platforms. This has established a practical method for improving the performance of fiber optic biosensors. With the aforementioned outstanding nanomaterial properties, the development of fiber optic biosensors has been efficiently promoted. This paper reviews the application of numerous novel nanomaterials in the field of optical fiber biosensing and provides a brief explanation of the fiber sensing mechanism.

Aflatoxins are a kind of fungal toxin that causes great damage to humans and animals due to its wide distribution, secretive nature, and high toxicity. For the purpose of achieving qualitative and quantitative detection of aflatoxin B1 (AFB1), a novel tri-taper-in-taper fiber-optic structure based on core mismatch of four-core fiber with a multimode fiber-based WaveFlex biosensor is developed and tested. The sensor probe's surface is coated with gold nanoparticles (AuNPs). Multi-walled carbon nanotubes and zinc oxide nanoparticles are sequentially immobilized on the sensing probe surface to enhance the sensor's sensing capabilities. Then, the AFB1 antibody is utilized to functionalize the sensor to possess specific selectivity. After the modification of nanomaterials and the corresponding bioreceptors, the final sensor structure is formed. By stimulating the localized surface plasmon resonance phenomenon of AuNPs, different concentrations of AFB1 can be detected. The sensor demonstrates high sensitivity (38.29 nm/μM) as well as low LOD (7.12 nM) within the range of 0–100 nM for detection. The sensor is also found to be stable and reproducible in repeated measurements, indicating its potential for practical application. Additionally, it exhibits satisfactory specific recognition of AFB1. These results show that AFB1 can be detected in food and agricultural products using LSPR-based optical fiber sensors, which could have significant ramifications for public health and food safety.

In this work, a localized plasmon-based sensor is developed for para-cresol (p-cresol) - a water pollutant detection. A nonadiabatic $40~\mu \text{m}$ of tapered optical fiber (TOF) has been experimentally fabricated and computationally analyzed using beam propagation method. For optimization of sensor’s performance, two probes are proposed, where probe 1 is immobilized with gold nanoparticles (AuNPs) and probe 2 is immobilized with the AuNPs along with zinc oxide nanoparticles (ZnO-NPs). The synthesized metal nanomaterials were characterized by ultraviolet-visible spectrophotometer (UV–vis spectrophotometer) and transmission electron microscope (HR-TEM). The nanomaterials coating on the surface of the sensing probe were characterized by a scanning electron microscope (SEM). Thereafter, to increase the specificity of the sensor, the probes are functionalized with tyrosinase enzyme. Different solutions of p-cresol in the concentration range of $0~\mu \text{M}$ – $1000~\mu \text{M}$ are prepared in an artificial urine solution for sensing purposes. Different analytes such as uric acid, $\beta $ -cyclodextrin, L-alanine, and glycine are prepared for selectivity measurement. The linearity range, sensitivity, and limit of detection (LOD) of probe 1 are $0~\mu \text{M}$ – $700~\mu \text{M}$ , 7.2 nm/mM (accuracy 0.977), and $59.90~\mu \text{M}$ , respectively; and for probe 2 are $0~\mu \text{M}$ – $1000~\mu \text{M}$ , 5.6 nm/mM (accuracy 0.981), and $57.43~\mu \text{M}$ , respectively. Thus, the overall performance of probe 2 is quite better due to the inclusion of ZnO-NPs that increase the biocompatibility of sensor probe. The proposed sensor structure has potential applications in the food industry and clinical medicine.

This article discusses optically active nanomaterials and their optical biosensing applications. In addition to enhancing their sensitivity, these nanomaterials also increase their biocompatibility. For this reason, nanomaterials, particularly those based on their chemical compositions, such as carbon-based nanomaterials, inorganic-based nanomaterials, organic-based nanomaterials, and composite-based nanomaterials for biosensing applications are investigated thoroughly. These nanomaterials are used extensively in the field of fiber optic biosensing to improve response time, detection limit, and nature of specificity. Consequently, this article describes contemporary and application-based research that will be of great use to researchers in the nanomaterial-based optical sensing field. The difficulties encountered during the synthesis, characterization, and application of nanomaterials are also enumerated, and their future prospects are outlined for the reader’s benefit.