Fe₃O₄-Chitosan/MXene-Assisted MMF-MCF-MMF-Based WaveFlex Biosensor With Improved Features for Doxorubicin Detection

The integration of hybrid nanomaterials and hybrid fiber structures within fiber optic biosensors has emerged as a potent strategy to augment sensing capabilities. In this study, we developed a fiber optic-based WaveFlex biosensor that features a tapered multimode fiber (MMF) to multicore fiber (MCF) to MMF configuration, coated with a composite of gold nanoparticles (AuNPs), magnetite (Fe3O4), chitosan, and MXene. This biosensor was specifically designed for the detection of the doxorubicin (DOX) drug. The synergistic combination of Fe3O4 and chitosan with MXene leverages the beneficial properties of each constituent, thereby creating an enhanced platform with an increased number of binding sites for ligand immobilization. This, in turn, significantly boosts the sensor’s performance. Furthermore, the composite-core modal structure facilitates the excitation of higher-order modes, a mechanism that is known to amplify the sensitivity of fiber optic sensors. The periodic WaveFlex fiber architecture, when illuminated, generates an abundance of evanescent waves (EWs), thereby enhancing the interaction between the sensor and the analyte. Through a series of transmittance experiments, we determined that the sensitivity and limit of detection (LoD) of the DOX WaveFlex biosensor, within the concentration range of 0–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10~\mu $ </tex-math></inline-formula>M, were 0.885 nm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>M and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.37~\mu $ </tex-math></inline-formula>M, respectively. Our findings suggest that the localized surface plasmon resonance (LSPR) effect is significantly enhanced through the incorporation of 2-D materials and an innovative fiber optic configuration. This advancement presents a novel avenue for enhancing the sensitivity of WaveFlex biosensors, offering potential applications in the field of biosensing.