Development of W-Type Four-Core Fiber-Based WaveFlex Sensor for Enhanced Detection of Shigella Sonnei Bacteria Using Engineered Nanomaterials

Shigella
, a highly infectious and pathogenic Gram-negative bacterium, is widely prevalent in everyday food items, prompting significant research due to its potential hazards. Addressing the need for
Shigella
detection, this study introduces a WaveFlex biosensor based on localized surface plasmon resonance (LSPR) using fiber optics. The sensor is tailored to detect a specific subspecies of
Shigella
, specifically
Shigella sonnei
(
S. sonnei
). It is fabricated using a combination of multimode fiber (MMF) and four-core fiber (FCF), creating a core-mismatched W-type fiber structure designed for efficient mode coupling. Furthermore, this sensor is enhanced with the utilization of nanomaterials, including cerium oxide nanorods (CeO
₂
-NRs), zinc oxide nanowires (ZnO-NWs), and copper selenide@gold nanocomposites (Cu
₃
Se
₂
@Au-NCs). CeO
₂
-NRs and ZnO-NWs contribute to improve biocompatibility and increase surface area for antibody functionalization, while Cu
₃
Se
₂
@Au-NCs promote the LSPR effect and enhance sensing performance. To enhance specificity, the optical fiber coated with these engineered nanomaterials is functionalized with
S. sonnei
antibody. The results of this work showcase the effective detection of
Shigella
bacteria by the proposed WaveFlex sensor, offering exceptional sensitivity (0.28 nm/(CFU/mL)), a low limit of detection (LoD) of 0.96 CFU/mL, and a swift detection time of 10 minutes. These findings underscore the sensor's potential for widespread applications in areas such as food safety, medical diagnostics, and environmental monitoring. This study significantly advances bacterial detection technology and contributes to the assurance of public health and food safety.