Detection of adulteration in pure honey utilizing Ag-graphene oxide coated fiber optic SPR probes

Rapid absolute quantification of glucose and fructose isomers in honey using a boronic acid-based reactive matrix by MALDI-TOF/TOF tandem mass spectrometry

The slight structural differences between carbohydrate isomers pose considerable difficulties for their identification and quantification. Herein, a rapid method for the absolute quantification of glucose and fructose isomers using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry (MALDI-TOF/TOF MS/MS). A novel reagent, 4-trimethylamino-6-(4-methoxy-1-naphthyl)-1,3,5-triazine-2-(3-aminophenylboronic acid) (TMNTA), was synthesized and employed as a reactive matrix. This matrix significantly enhances the ionization efficiency of monosaccharides while avoiding matrix interferences. Glucose-13C6 was utilized as an internal standard for the quantitative analysis of both monosaccharides, exhibiting a strong linear correlation (R2 ≥ 0.990). By integrating the concentration relationships of glucose and fructose derived from two diagnostic ions produced from the TMNTA-derivatized monosaccharides, this approach facilitates the absolute quantification of glucose and fructose. The method was successfully applied to the absolute quantification of these monosaccharides in honey. The proposed approach offers a simple, rapid, and high-throughput analysis of glucose and fructose isomers in complex samples.

Multimodal Interference-Based Fiber Optic Sensors for Glucose and Moisture Content Detection in Honey

Fiber optic sensors (FOSs) have transformed industrial applications with their high sensitivity and precision, especially in real-time monitoring. This study presents a fiber optic sensor based on multimodal interference (MMI) applied to detect honey adulteration. The sensor is built using a non-core multimode fiber (NC-MMF) segment spliced between two standard single-mode fibers (SMFs). We focus on reporting the detection of two main adulterants in honey that modify its refractive index (RI): the presence of glucose and moisture content. Detailed testing was performed with two commercially approved honey brands, named A and B. The sensor successfully detected glucose concentrations from 1% to 5% and moisture content from 0% to 20% for both brands. For glucose detection, we obtained sensitivity values −0.55457 nm/% for brand A and −2.61257 nm/% for brand B. In terms of moisture content in honey, we observed a sensitivity around −0.3154 nm/% and −0.3394 nm/% for brands A and B, respectively. Additionally, temperature tests were performed, showing that the sensor works optimally up to 30 °C. The results were validated using a conventional refractometer, showing a close agreement with the data obtained and confirming the reliability and accuracy of the proposed sensor. Compared to other refractometers, the MMI sensor offers advantages such as real-time monitoring, ease of assembly, cost-effectiveness, and minimal maintenance. Furthermore, the sensor represents an alternative tool to guarantee the quality and authenticity of honey, overcoming the limitations of conventional measurement techniques.

Recent Progress on Microfluidics Integrated with Fiber-Optic Sensors for On-Site Detection

This review introduces a micro-integrated device of microfluidics and fiber-optic sensors for on-site detection, which can detect certain or several specific components or their amounts in different samples within a relatively short time. Fiber-optics with micron core diameters can be easily coated and functionalized, thus allowing sensors to be integrated with microfluidics to separate, enrich, and measure samples in a micro-device. Compared to traditional laboratory equipment, this integrated device exhibits natural advantages in size, speed, cost, portability, and operability, making it more suitable for on-site detection. In this review, the various optical detection methods used in this integrated device are introduced, including Raman, ultraviolet-visible, fluorescence, and surface plasmon resonance detections. It also provides a detailed overview of the on-site detection applications of this integrated device for biological analysis, food safety, and environmental monitoring. Lastly, this review addresses the prospects for the future development of microfluidics integrated with fiber-optic sensors.

Recent advancements in nanomaterial based optical detection of food additives: a review

Food additives have become a critical component in the food industry. They are employed as preservatives to decelerate the negative effects of environmental and microbial factors on food quality. Currently, food additives are used for a variety of purposes, including colorants, flavor enhancers, nutritional supplements, etc., owing to improvements in the food industry. Since the usage of food additives has increased dramatically, the efficient monitoring of their acceptable levels in food products is quite necessary to mitigate the problems associated with their inappropriate use. The traditional methods used for detecting food additives are generally based on standard spectroscopic and chromatographic techniques. However, these analytical techniques are limited by their high instrumentation cost and time-consuming procedures. The emerging field of nanotechnology has enabled the development of highly sensitive and specific sensors to analyze food additives in a rapid manner. The current article emphasizes the need to detect various food additives owing to their potential negative effects on humans, animals, and the environment. In this article, the role of nanomaterials in the optical sensing of food additives has been discussed owing to their high accuracy, ease-of-use, and excellent sensitivity. The applications of nanosensors for the detection of various food additives have been elaborated with examples. The current article will assist policymakers in developing new rules and regulations to mitigate the adverse effects of toxic food additives on humans and the environment. In addition, the prospects of nanosensors for the optical detection of food additives at a commercial scale have been discussed to combat their irrational use in the food industry.

Long-range surface plasmon resonance-based hollow fiber temperature sensor with ultrahigh sensitivity and tunable detection range

A dielectric/Ag-coated hollow fiber (HF) temperature sensor based on long-range surface plasmon resonance (LRSPR) is proposed and experimentally demonstrated. The structural parameters, including the dielectric material and layer thicknesses, are optimized through comprehensive theoretical analysis to achieve the best performance. By filling it with a high refractive index (RI) thermosensitive liquid, the GK570/Ag-coated HF temperature sensor with optimal structural parameters is fabricated. Due to the high sensitivity of the LRSPR sensor and the optimized design, the fabricated sensor achieves a temperature sensitivity of 3.6∼20.5 nm/°C, which is almost the highest among the optical fiber temperature sensors based on surface plasmon resonance reported experimentally. Moreover, the detection range of the proposed sensor can be easily tuned up to 170°C by varying the RI of the filled thermosensitive liquid, and the sensor performance remains stable. Considering that most temperature sensors using polydimethylsiloxane have a fixed detection range, this is an outstanding advantage that could expand the application field of the optical fiber temperature sensor.

Deposition of Graphene Oxide on an SPR Fiber Refractometer for Sensor Applications

Graphene-based materials have been increasingly incorporated to optical fiber plasmonic sensors due to the peculiar physical and chemical properties of these materials (hardness and flexibility, high electrical and thermal conductivity, and very good adsorption for many substances, etc.). In this paper, we theoretically and experimentally showed how the addition of graphene oxide (GO) to optical fiber refractometers permits the development of surface plasmon resonance (SPR) sensors with very good characteristics. We used doubly deposited uniform-waist tapered optical fibers (DLUWTs) as supporting structures because of their already proven good performance. The presence of GO as an effective third layer is useful to tune the wavelength of the resonances. In addition, the sensitivity was improved. We depict the procedures for the production of the devices and characterize the GO+DLUWTs produced in this way. We also showed how the experimental results are in agreement with the theoretical predictions and used these to estimate the thickness of deposited GO. Finally, we compared the performance of our sensors with other ones that have been recently reported, showing that our results are among the best reported. Using GO as the medium in contact with the analyte, in addition to the good overall performance of devices, permit consideration of this option as an interesting possibility for the future development of SPR-based fiber sensors.

Design Considerations of an ITO-Coated U-Shaped Fiber Optic LMR Biosensor for the Detection of Antibiotic Ciprofloxacin

The extensive use of antibiotics has become a serious concern due to certain deficiencies in wastewater facilities, their resistance to removal, and their toxic effects on the natural environment. Therefore, substantial attention has been given to the detection of antibiotics because of their potential detriment to the ecosystem and human health. In the present study, a novel design of indium tin oxide (ITO) coated U-shaped fiber optic lossy mode resonance (LMR) biosensor is presented for the sensitive detection of the antibiotic ciprofloxacin (CIP). The performance of the designed U-shaped LMR sensor is characterized in terms of its sensitivity, full width at half maximum (FWHM), the figure of merit (FOM), and the limit of detection (LOD). For the proposed U-shaped LMR sensing probe, the various crucial factors such as the thickness (d) of the ITO layer, sensing region length (L), and bending radius (R) are optimized. The thickness of the ITO layer is optimized in such a way that two LMR curves are observed in the transmission spectrum and, thereafter, the performance parameters are evaluated for each LMR. It is observed that the designed U-shaped LMR sensor with optimized parameters shows an approximately seven-fold enhancement in sensitivity compared to the straight-core fiber optic LMR sensor. The numerical results revealed that the designed U-shaped fiber optic LMR biosensor can provide a maximum sensitivity of 17,209.9 nm/RIU with the highest FOM of 91.42 RIU^-1, and LOD of 6.3 × 10^-5 RIU for the detection of CIP hydrochloride in the concentration range of 0.001 to 0.029 mol∙dm^-3. Thus, it is believed that the designed LMR biosensor can practically explore its potential use in environmental monitoring and biomedical applications and hence, opens a new window of opportunity for the researchers working in the field of U-shaped fiber optic LMR biosensing.

Silver-Based Surface Plasmon Sensors: Fabrication and Applications

A series of novel phenomena such as optical nonlinear enhancement effect, transmission enhancement, orientation effect, high sensitivity to refractive index, negative refraction and dynamic regulation of low threshold can be generated by the control of surface plasmon (SP) with metal micro-nano structure and metal/material composite structure. The application of SP in nano-photonics, super-resolution imaging, energy, sensor detection, life science, and other fields shows an important prospect. Silver nanoparticles are one of the commonly used metal materials for SP because of their high sensitivity to refractive index change, convenient synthesis, and high controllable degree of shape and size. In this review, the basic concept, fabrication, and applications of silver-based surface plasmon sensors are summarized.

Antimonene-Coated Uniform-Waist Tapered Fiber Optic Surface Plasmon Resonance Biosensor for the Detection of Cancerous Cells: Design and Optimization

For early-stage cancer detection, a novel design of graphene-antimonene-coated uniform-waist tapered fiber optic surface plasmon resonance (SPR) biosensor is demonstrated. The proposed optical biosensor outperforms over a wide range of refractive index (RI) variations including biological solutions and is designed to detect various cancerous cells in the human body whose RIs are in the range of 1.36-1.4. Here, antimonene is used to enhance the performance of the designed SPR sensor for sensing cancer analytes because of its high binding energy toward adsorption of biomolecules and large active surface area. The design and analysis of the sensor are done with the help of a transfer matrix method-based simulation platform, and the effect of the taper ratio is also studied. The performance of the proposed SPR biosensor is evaluated with performance parameters such as sensitivity, full width at half maximum, detection accuracy (DA), figure of merit (FOM), and limit of detection (LOD). The numerical results show that the designed sensor is able to provide a sensitivity of 7.3465, 10.9250, 11.8914, and 15.2414 μm/RIU, respectively, for sensing skin, cervical, blood, and adrenal gland cancer with a maximum FOM of 131.1525 RIU^-1, DA of 14.2126 μm^-1, and LOD of 7.2 × 10^-5 RIU. Based on the derived results, the authors believe that the designed SPR sensor could practically find its potential applications in the field of medical science for the early-stage diagnosis of cancer and hence, opens a new window in the field of biosensing.

Surface plasmon resonance temperature sensor with tunable detection range based on a silver-coated multi-hole optical fiber

A novel surface plasmon resonance (SPR) temperature sensor based on a silver-coated multi-hole optical fiber (SMHOF) is presented. The central and surrounding air holes of the SMHOF are filled with two kinds of thermosensitive liquid with high and low refractive index (RI), respectively. Two separated resonance dips, which are related to the high and low RI filled liquid respectively, are observed at different wavelength in the transmission spectrum. Advantageously, the two dips move towards opposite direction with the temperature variation. The interval between the two SPR dips is measured under different environmental temperature and exhibits a good linearity. The proposed sensor with different detection range is fabricated by changing the RIs of the filled thermosensitive liquids. The temperature sensitivity of 7.72 nm/°C and -7.81 nm/°C is obtained in the range of 20-60 °C and -20-20 °C, respectively. Owing to the high temperature sensitivity and tunable detection range, the proposed sensor is expected to find potential applications in biomedicine, health care and environmental monitoring.

New Advances in Lateral Flow Immunoassay (LFI) Technology for Food Safety Detection

With the continuous development of China’s economy and society, people and the government have higher and higher requirements for food safety. Testing for food dopants and toxins can prevent the occurrence of various adverse health phenomena in the world’s population. By deploying new and powerful sensors that enable rapid sensing processes, the food industry can help detect trace adulteration and toxic substances. At present, as a common food safety detection method, lateral flow immunochromatography (LFI) is widely used in food safety testing, environmental testing and clinical medical treatment because of its advantages of simplicity, speed, specificity and low cost, and plays a pivotal role in ensuring food safety. This paper mainly focuses on the application of lateral flow immunochromatography and new technologies combined with test strips in food safety detection, such as aptamers, surface-enhanced Raman spectroscopy, quantum dots, electrochemical test strip detection technology, biosensor test strip detection, etc. In addition, sensing principles such as fluorescence resonance energy transfer can also more effective. Different methods have different characteristics. The following is a review of the application of these technologies in food safety detection.

Highly sensitive and selective surface plasmon resonance biosensor for the detection of SARS-CoV-2 spike S1 protein

The reality that the coronavirus disease 2019 (COVID-19) is still raging around the world and making a comeback with a strong presence has highlighted the need for rapid and sensitive quantitative detection methods of viral RNA, antibody and antigen for widespread tracking and screening applications. Surface plasmon resonance (SPR) detection technology has achieved rapid development and become a standard measurement method in the fields of biosensing, biomedicine, biochemistry and biopharmaceuticals due to its advantages of high sensitivity, fast response and no need for labelling. Here, we report a sandwiched structure-based SPR biosensor for detecting a specific viral antigen, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike S1 protein. The sensor combines a Ti₃C₂-MXene nanosheet modified sensing platform and polydopamine (PDA)-Ag nanoparticle (AgNP)/anti-SARS-CoV-2 spike S1 protein nanoconjugate signal enhancers, exhibiting a wide linear range of 0.0001 to 1000 ng mL^-1 with a low detection limit of 12 fg mL^-1 (S/N = 3). In the analysis of artificial saliva and human serum samples, the proposed SPR biosensor exhibits good reproducibility and high specificity, which indicates its potential for application in complex bodily fluids. The exploitation of the MXene-based SPR biochip for recognizing the SARS-CoV-2 antigen provides an accessible and rapid way for COVID-19 diagnosis, and promotes the application of 2D nanomaterial-based sensing chips in clinical diagnosis and disease screening. Significantly, the proposed method possesses general applicability that can be reprogrammed to detect any protein antigen if a corresponding specific nanobody is available.

Recent advances in Surface Plasmon Resonance (SPR) biosensors for food analysis: a review

Food safety is the prime area of concern that builds trust. With the prevailing advancements, it has become facile to ensure safety in almost all aspects. Technology has grown from tedious lab techniques to modern chromatographic techniques and immunoassays, progressed with more precise and rapid sensing through the advent of Biosensors. Biosensors provide an automated technology by presenting superfast, nondestructive and cost-effective detection in food analysis. SPR biosensor is an optical biosensor known for its versatility and has wider applications in food testing and analysis. It has an optical system for excitation and interrogation of surface plasmons, and a biomolecular recognition element to detect and seize the target analyte present in a sample. The optical signal detects the binding analyte, on the recognition element, which results in a change in refractive index at the surface and modifies the surface plasmons' propagation constant. SPR aids in label-free detection of various components such as adulterants, antibiotics, biomolecules, genetically modified foods, pesticides, insecticides, herbicides, microorganisms and microbial toxins in food and assures safety. The distinct advancements of SPR in food analysis have been found and discussed. The review also provides knowledge on the advantages and the key challenges encountered by SPR.

The facile fabrication and high-performance sensing of glucose of sea-urchin-like CoFeLDH/PBA/NF heterojunction

The sea-urchin-like CoFeLDH/PBA/NF heterojunction was successfully synthesized, exhibiting excellent glucose sensing performance with ultra-high sensitivity, outstanding reproducibility, stability and selectivity.