In this paper, a tapered optical fiber-based sensor is developed for the detection of uric acid (UA) in human serum. The fiber probes were fabricated using single-mode fiber (SMF) with taper diameter of 40 lm. The diameter of taper section has culminated on the basis of excretion of evanescent waves and their handling capacity. To enhance the sensitivity, taper section (sensing region) was immobilized with synthesized gold nanoparticles (AuNPs). The AuNPs were used to initiate the excitation of surface plasmons (SP) at the fiber surface and ultimately leads to the localized surface plasmon resonance (LSPR) phenomenon. The comparative studies were also done to analyze the effect of size of AuNPs by immobilizing the sensor probes with ∼10 nm and ∼30 nm size of AuNPs. The UV-Vis spectrophotometry, high resolution-transmission electron microscopy (HR-TEM) and scanning electron microscopy (SEM) were used for the characterization of AuNPs solution and developed sensor probes. The sensing ability of sensors was authenticated by recording the transmitted intensity of LSPR spectrum for a wide range of UA from 10 lM to 800 lM. The detected range of UA completely covers its concentration available in human serum that is from 150 µM to 420 µM. Thereafter, the wavelength shift in LSPR spectrums was evaluated to determine the sensitivity and detection limit of sensors. The selectivity of the sensor probe was enhanced by functionalizing it with uricase enzyme (0.672 U/ml). The specificity of uricase functionalized sensor probes were also analyzed in the presence of other biomolecules found in human-serum.

In this work, a hetero-core optical fiber sensor structure is developed for the diagnosis of L-Cysteine content in human urine. The hetero-core structure is created by sequentially cascading the single mode-multimode-single mode fibers using thermal fusion splicing. The multimode section of fiber probe is etched out and coated with synthesized gold nanoparticles (AuNPs), polyvinyl alcohol stabilized silver nanoparticles (PVA-AgNPs) and graphene oxide (GO). The AuNPs and PVA-AgNPs are used to initiate the localized surface plasmon resonance (LSPR) phenomenon on the application of exponentially decaying evanescent waves. The layer of GO is used to provide the larger surface area and binding sites for the L-Cysteine (L-Cys) molecules. Based on the combination of NPs, two different configurations of sensor probes are developed. In first one, a layer of AuNPs is deposited over fiber surface and further followed by the coating of GO, and named Probe I. In the second one, a layer of PVA-AgNPs is sandwiched between the fiber surface and GO layer and termed as Probe II. The characterization of synthesized NPs and GO solutions, and developed sensor probes are done by using UV-Vis spectrophotometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). To authenticate the biocompatibility of developed sensor probes, the artificial aqueous samples of L-Cys ranges from 0 μM to 1 mM are tested. To determine the stability of L-Cys, a pH level based study is also carried out to ensure the good stability of analyte in aqueous samples. From the results, it was ascertained that the response of Probe II is better in terms of attained limit of detection and sensitivity that is 126.6 μM and 0.0009 nm/μM, respectively.

In this work, a photosensitive (PS) optical fiber-based Mach-Zehnder interferometer (MZI) structure is developed to diagnose the presence of collagen-IV in human bodies. The MZI is fabricated by sequentially splicing the single mode-multimode-photosensitive-multimode single mode (SMPMS) fiber segments. The sensing region in MZI structure is created by partially removing the cladding of photosensitive fiber by using 40% hydrofluoric (HF) acid and depositing the layers of highly reflective metal nanoparticles (NPs) over it. The used NPs are polyvinyl alcohol stabilized silver nanoparticles (PVA-AgNPs), gold nanoparticles (AuNPs), and zinc oxide nanoparticles (ZnO-NPs). The size of AuNPs, PVA-AgNPs, and ZnO-NPs are 10 ± 0.2 nm, ~ 4-5 nm, and <; 50 nm, respectively. In order to avoid the interference of other biomolecules in the detection of collagen-IV, the sensing region is functionalized with a collagenase enzyme. The sensing ability of the probe is ascertained by sensing a wide concentration of collagen solution ranging from 0 ng/ml to 1 μg/ml. It is observed that sensing performance of probe is much better on immobilizing it with PVA-AgNPs and ZnO-NPs.

Nowadays, Food additives and preservatives have become a hot topic especially formalin, which is a chemical substance used to preserve food. Chronic cancer is caused by swallowing the formalin-contaminated food on a regular basis. As a result, detection of the formalin in food ingredients is a critical need, and this requirement is becoming increasingly important in new terrains. Therefore, a new approach, planar waveguide-based surface plasmon resonance (SPR) sensor is presented in this paper employing silver-chloride materials-black phosphorus structure to detect the formalin. In this study, the optimization of metal thickness and optimal performance of chloride material are analyzed by observing the transmittance power and resonance shift for conventional and chloride-based sensors, respectively. Moreover, the performance parameters, such as sensitivity of 344°/RIU, quality-factor of 166.99RIU^-1, detection-accuracy of 3.34 and figure-of-merit of 164.74, are observed for the proposed sensor. Furthermore, the performance comparative study is conducted and found that the proposed sensor highlighted the enhanced the SPR sensor and highlighted the performance of FOM. Finally, the electromagnetic filed distributions of the proposed WG-based SPR sensor are shown using the Opti-FDTD software.

Human health is affected by a vast spectrum of ailments, collectively called diseases, which obstruct the proper functioning of the body and may stem from diverse origins, including genetic alterations, environmental factors, or pathogenic infections. These diseases are often categorized into groups, such as infectious diseases, triggered by bacteria, viruses, fungi, or parasites, and non-infectious diseases, encompassing genetic disorders, autoimmune conditions, and persistent illnesses like cardiovascular disease and diabetes. Infectious diseases may disseminate through direct or indirect contact, air, food, water, or vectors, whereas non-infectious diseases are frequently associated with lifestyle practices, genetic predisposition, or environmental influences. Progress in modern medicine, including vaccines, antibiotics, and diagnostic technologies, has markedly reduced the impact of numerous diseases; however, challenges continue due to the emergence of new infections, antibiotic resistance, and the escalating prevalence of non-communicable diseases. Confronting human diseases necessitates a holistic strategy that integrates public health measures, healthcare interventions, and biomedical research to enhance prevention, diagnosis, and treatment methods, consequently improving global health outcomes. Infectious and non-infectious diseases (autoimmune disorders, cancer, and cardiovascular diseases) caused by bacteria, viruses, and fungi can be identified quickly and accurately with Surface Plasmon Resonance (SPR) sensors. The ease and capacity of SPR technology to track biomolecular interactions enhances its adaptability which allows early diagnosis and individualized treatment plans for a variety of medical disorders.