Search

Alpha-fetoprotein (AFP), a biomarker for liver cancer detection, has important clinical significance. Here, an S-tapered WaveFlex fiber biosensor is developed that is based on the structure of multimode fiber (MMF)–multicore fiber (MCF)–MMF and leaks more energy when excited by light. ZnO nanowires (ZnO-NWs)/WS2 nanosheets (WS2-NSs) and gold nanoparticles (AuNPs) are functionalized on the probe surface to further enhance the sensing performance. 1-D ZnO-NWs possess a larger specific surface area and can provide more sites for antibodies. The fold structure of WS2-NSs provides ample space for functionalization. The combination of the above two nanomaterials is conducive to the immobilization of AuNPs and AFP antibodies and improves the performance of the developed biosensor. AuNPs and AFP antibodies are used to generate localized surface plasmon resonance (LSPR) and enhance the specificity of the probe, respectively. The developed probe is employed to detect AFP solution in the range of 0–1000 ng/mL, and the sensitivity and limit of detection (LoD) are obtained as 1.32 nm/log(ng/mL) and 84 pg/mL, respectively. Moreover, the practical application capability of the probe is verified by the selectivity test, pH test, reproducibility, and reusability experiments. The results demonstrate the potential application of the developed S-tapered WaveFlex AFP sensor in the detection of liver cancer markers.

In this work, we develop a portable, sensitive waveflex biosensor that could be used for glycosylated hemoglobin A1c (HbA1c) detection. The probe consists of multimode fiber (MMF) and multicore fiber (MCF)-based W-shaped innovative sensing structures. Localized surface plasmon resonance (LSPR) is induced by modifying the optical fiber surface with gold nanoparticles. The functionalization of zinc oxide nanowires (ZnO-NWs), tungsten disulfide quantum dots (WS2-QDs), and HbA1c antibodies on the probe surface increases the specific surface area of the fiber probe and enhances the biological specificity of the sensor, respectively. Finally, the linear range, sensitivity, and limit of detection (LoD) of the sensor probe are tested, and the results are as follows: 30– $1500~\mu $ g/mL (2.7–577 mmol/mol), 0.005 nm/( $\mu $ g/mL), and $61.8~\mu $ g/mL, respectively. The repeatability, reusability, stability, selectivity, and pH test of the probe are also evaluated to showcase its sensing performance. In addition, to verify the usefulness of the sensor, HbA1c concentrations in serum samples were tested using the sensor and the D-10 Hemoglobin Testing System. The results of the sensor are consistent with those of the D-10 Hemoglobin Testing System. Therefore, the sensor can be used to detect HbA1c concentration in human serum samples.

Acrylamide (AA), a detrimental aliphatic amide, is generated during food thermal processing as a result of the Maillard reaction occurring between asparagine and reducing sugars. WaveFlex fiber is a fiber-optic flexible sensor designed to enhance the evanescent wave (EW) for effectively exciting the localized surface plasmon resonance (LSPR) phenomenon, and in this study, the authors use this type of sensor to detect varying levels of AA. By immobilizing gold nanoparticles (AuNPs) on the probe’s surface, the evanescent field has the capability to trigger the activation of AuNPs and induce the occurrence of LSPR phenomenon. In order to excite LSPR better and generate a stronger evanescent field, the WaveFlex biosensor is fabricated using a single-mode fiber (SMF). Cerium oxide nanorods (CeO2-NRs) and MXene are used to modulate the LSPR phenomenon by altering the dielectric environment of AuNPs. As a result, the sensing performance of the sensor is improved and the surface area of the fiber probe is increased, providing an additional attachment point for the AA antibody. The AA sensor’s specific selectivity is enhanced by functionalizing the surface of the sensing probe with AA antibody. The sensor has a linear range of 3– $13~\mu $ g/mL with a detection limit of $1.13~\mu $ g/mL. Finally, the recoveries of AA in biscuits and chips are 82.8% $\sim ~99.7$ % and 83.7% $\sim ~100.4$ %, respectively. Furthermore, the probe’s potential for detecting AA levels is demonstrated through rigorous testing of its reusability, reproducibility, stability, pH, and selectivity. The obtained results indicate a promising application scope for this WaveFlex biosensor.

Histamine, an organic nitrogen-containing compound, is produced by histidine under the action of a decarboxylase. Many tissues, especially the mast cells of the skin, lung, and intestinal mucosa, contain large amounts of histamine. Histamine poisoning occurs when histamine-metabolizing enzymes are damaged or submerged by dietary histamine. Based on the localized surface plasmon resonance (LSPR) phenomenon, the taper-in-semi-taper (TST) optical fiber-based WaveFlex biosensor (plasmonic wave-based optical fiber sensor) is proposed. The TST fiber-based WaveFlex biosensor is designed and manufactured to detect the concentration of histamine in different foods such as fish and corn to determine food spoilage. Specifically, the gold nanoparticles (AuNPs) are first attached to the probe surface to effectively excite the LSPR phenomenon. Second, zinc oxide-nanowires (ZnO-NWs)/tungsten disulfide nanosheet (WS2-thin layer) are fixed on the sensing area to enhance the biocompatibility and finally functionalized with diamine oxidase (DAO) enzyme to increase the specificity of the probe. This experiment also tested the stability, reusability, reproducibility, pH, and selectivity of the biosensor and found that the biosensor has high sensitivity, good stability, and strong selectivity in the linear range of 0– $900~\mu $ M, which can meet the requirements of histamine content detection and for rapid detection of food spoilage.

In order to enhance the detection capabilities of large-area detectors operating at room temperature, particularly in terms of response time and sensitivity parameters, we have developed an innovative terahertz detector featuring bowtie arrays based on projection microstereolithography ( $\text{P}\mu $ SL). This device integrates the localized surface plasma (LSP) effect of nonmicrocavities with the exceptional properties of Weyl semimetal materials within its subwavelength structure. To further investigate the detection performance and improve the response time, we have employed a laser field to enhance the surface carrier mobility of the device, thereby enhancing its detection capabilities. At room temperature, the terahertz sensitivity for 0.1 THz has been enhanced from 0.30 to 0.54 MV/W, representing an 80% improvement, while the noise equivalent power (NEP) has been reduced from 92 to 50 pW/Hz1/2, marking 45.6% improvement. The response time of the device under external field stimulation is 50 ms. Given the ease and high reproducibility of the ultrahigh-resolution 3-D printing for fabricating microstructures and the straightforward crystallization of WTe2 magnetron-sputtered thin films, our proposed high-performance terahertz wave photodetector scheme holds promise for effective terahertz wave detection, with potential applications in the realms of 6G communication and terahertz radar.

Alkaline phosphatase (ALP) is a phosphomonoesterase used to hydrolyze biologically active molecules containing phosphate ester groups. Many tissues, such as bone, liver, and kidney, contain ALP; 2,4-dichlorophenoxyacetic acid (2,4-D) inhibits the reaction of ALP with phenyl phosphate. Based on the localized surface plasmon resonance (LSPR) phenomenon, a WaveFlex biosensor is designed and manufactured using multiwalled carbon nanotubes (MWCNTs)/cerium dioxide nanorods (CeO2-NRs)-immobilized multitapered fiber for detecting pesticide residues. Specifically, first, gold nanoparticles (AuNPs) are attached to the surface of the sensing region of the probe, which effectively stimulates the LSPR phenomenon. Second, MWCNTs and CeO2-NRs are fixed to the surface of the sensing region of the probe, and finally, ALP is uniformly used at a concentration of 300 IU/L. In this experiment, the authors tested the stability, repeatability, pH effect, and selectivity of the biosensor and found that it exhibits high sensitivity, good stability, and strong usability in the linear range of 0–8 mg/L, meeting the requirements for pesticide residue detection in agricultural food crops.

In this study, we present an optical fiber biosensor (i.e., a WaveFlex biosensor) developed for the precise quantification of xanthine, a crucial metabolite presents in the human body, and certain food items. Elevated xanthine levels are often indicative of various health conditions, making accurate concentration detection essential for disease diagnosis, assessing physiological states, and pre-emptively evaluating food quality. Our WaveFlex biosensor is fabricated using a single-mode fiber with a unique taper-in-taper with four tapered (TIT4T) fiber structure, achieved through a series of meticulous tapering processes. After nanoparticle coating and enzyme functionalization, this fiber-based biosensor becomes adept at detecting xanthine concentrations. The tapered structure facilitates the interaction of the optical field transmitted through the fiber with the external environment. The presence of immobilized gold nanoparticles (AuNPs) and MXene quantum dots (MXene-QDs) on the fiber’s surface collectively triggers localized surface plasmon resonance (LSPR) phenomena, enhancing detection sensitivity. By functionalizing the optical fiber with the xanthine oxidase (XO) enzyme, we enable highly specific xanthine detection. Our sensor demonstrates impressive capabilities, with a sensitivity of 1.93 nm/mM, a wide linear detection range spanning from 0 to $800\,\,\mu \text{M}$ , and a low limit of detection at $146.11\,\,\mu \text{M}$ . Furthermore, we conducted rigorous tests to assess the sensor’s reusability, stability, pH test, and reproducibility, further highlighting its exceptional performance.

Tyramine, a vasoactive amine with sympathomimetic properties, is commonly found in various foods. Elevated levels of tyramine in the blood can lead to adverse reactions, such as migraines and high blood pressure, underscoring the importance of detecting its content in food. This study introduces a WaveFlex biosensor utilizing the optical fiber-based localized surface plasmon resonance (LSPR) sensing principle to detect tyramine levels efficiently and accurately in different samples. The probe surface was covered with gold nanoparticles (AuNPs) to stimulate the LSPR effect, and then, molybdenum disulfide nanosheets (MoS2-NSs) and tungsten disulfide quantum dots (WS2-QDs) were sequentially aligned on the probe surface. It enhanced the LSPR effect and, at the same time, provided more contact sites for tyrosinase enzyme functionalization and significantly improved the sensor’s sensitivity in detecting tyramine. Experimental findings reveal a detection limit of $2.80~\mu $ M and a sensitivity of 0.01122 nm/ $\mu $ M for the biosensor. The probe’s reproducibility, reusability, stability, and selectivity, as well as its performance with real samples and varying pH levels, were evaluated. The results highlight the promising application potential and wide-ranging development opportunities for this WaveFlex biosensor in detecting tyramine levels across diverse samples.