Showing papers in "Sensing and bio-sensing research in 2020"

The role of sensors, big data and machine learning in modern animal farming

Abstract: Ever since man began domesticating animals several thousand years ago, we have always relied on our intuition, collective knowledge, and sensory signals to make effective animal production decisions. So far, this has helped us make significant gains in animal husbandry and farming. Together the growing demand for food and the advancement in sensing technology have the potential to make animal farming more centralized, large scale and efficient. It has the potential to change animal farming as we know it. At a broader level, this paper explores the challenges and opportunities that sensor technologies present in terms of helping animal farmers produce more meat and animal products. More specifically, this paper explores the role of sensors, big data, artificial intelligence and machine learning in helping animal farmers to lower production costs, increase efficiencies, enhance animal welfare and grow more animals per hectare. It also explores the challenges and limitations of technology. The paper reviews various animal farming technology applications to understand its value in helping farmers improve animal health, increase profits and lower environmental footprint.

Biosensing in dermal interstitial fluid using microneedle based electrochemical devices

Abstract: This article explores recent advances in the development of electrochemical biosensors on microneedle platforms towards on-device sensing of biomarkers present in dermal interstitial fluid. The integration of a biosensor with a microneedle platform opens the possibility for minimally invasive bio-chemical detection or continuous monitoring within the dermal interstitial fluid. An introduction to interstitial fluid is provided placing emphasis on sampling methods that have been employed to extract and/or sample tissue fluid for analysis. We look briefly at microneedle technologies used to extract dermal interstitial fluid for subsequent analysis. Successive content will focus on microneedle technologies which have been integrated with electrochemical biosensors for the quantification of various metabolites, electrolytes and other miscellaneous entities known to be present in the dermal interstitial fluid. The review concludes with some of the key challenges and opportunities faced by this next-generation wearable sensing technology.

Twin core photonic crystal fiber refractive index sensor for early detection of blood cancer

Abstract: This paper presents a twin-core photonic crystal fiber (TC-PCF) for early detection of blood cancer based on refractive index (RI) of the normal and cancerous blood cell. The samples of the normal and cancerous cells are considered at 30–70% and 80% in liquid form, respectively, and proposed to be infiltrated into the center air hole which is comparatively larger than the others. By considering the refractive index (RI), the change in the coupling length and transmitted spectrum of the proposed TC-PCF for the normal and cancerous cells is observed by using the finite element method (FEM). According to the transmitted spectrum shift, the proposed sensor can exhibit a large sensitivity of 8571.43 nm/RIU. Owing to simple detection mechanism, the proposed TC-PCF sensor can be used for blood cancer detection effectively and cheaply.

Photonic crystal fiber based terahertz sensor for cholesterol detection in human blood and liquid foodstuffs

Abstract: Low density lipoprotein (LDL) cholesterol is the leading cause of heart diseases, peripheral artery diseases, and stroke. An accurate, flexible, and efficient detection process is very urgent for identifying the cholesterol. In this context, an octagonal shaped hollow core with eight head star cladding structured photonic crystal fiber (PCF) has been proposed in this paper for cholesterol sensing in liquid analytes (human blood, cocking oil, liquid foods, etc.). The sensing performances of proposed PCF are evaluated through the COMSOL multiphysics software where the finite element method (FEM) has been used as a solver. The numerical investigation of the presented PCF structure exhibits highly sensitive characteristics for cholesterol detection in liquid samples and the proportion is 98.75% at 2.2 THz frequency. It also reveals negligible confinement loss of 3.14 × 10−20 cm−1 and low effective material loss of 0.0008 cm−1 at the same operating point. Furthermore, the commercial development feasibility of designed PCF in the existing manufacturing environment and other crucial optical properties such as effective area, dispersion, numerical aperture are also discussed in detail.

Development of a photonic crystal fiber for THz wave guidance and environmental pollutants detection

Abstract: In recent years, photonic crystal fiber (PCF) in the THz regime has gained popularity very swiftly for wave guidance and sensing applications. The optical properties of PCF can be controlled by the fine tuning of the geometrical parameters. In this context, PCF geometry has been developed for THz wave propagation as well as for environmental pollutants sensing applications. The proposed PCF structure contains a circular manner sectored cladding and square shaped core which is inserted by four square lattices. The finite element method based COMSOL multiphysics v.5.3a software has been used to design and characterize the optical properties rigorously for both applications. Numerical outcomes of developed PCF have significantly improved in both cases because of strategic geometry selection and parameters optimization. The simulated results render high sensitivity of 90 ± 1% for all the tested analytes at optimum condition, besides, ultra-low effective material loss (EML) of 0.009 cm−1 and flattened dispersion of ±0.05 ps/THz/cm are obtained at wave guiding environment. Moreover, implementation possibilities in the existing fabrication environment, physical attributes and comparative performance analysis are also stated in this article.

Analysis of a gold coated plasmonic sensor based on a duplex core photonic crystal fiber

Abstract: An exploration of a gold-coated dual-core with hexagonally arranged circular air holes SPR-PCF sensor is presented in this paper. Chemically inactive and stable material gold is provided as plasmonic material in this design. Placement of the gold layer outside of the PCF structure simplifies the detection process of this sensor and also assures fabrication feasibility. The performance of this sensor is investigated in terms of wavelength sensitivity, amplitude sensitivity, resolution, sensor length and linearity response by using the Finite Element Method (FEM) based COMSOL Multiphysics software. Maximum wavelength sensitivity is found to be 10,700 nm/RIU for analyte sensing range between 1.39 to 1.40 by using wavelength interrogation method as well as maximum amplitude sensitivity reaches about 1770 RIU-1 for analyte RI 1.39 by using amplitude interrogation method. Besides, the sensor's resolution is found to be 9.34×10-6. The outcome of alternating structural parameters such as gold layer thickness, pitch, air hole diameter, different shapes of air hole in the core is also discussed as well. The reported sensor might be a fruitful aspirant in the field of biological sample detection, organic chemical sensing and biomolecule recognition.

Cerium oxide-monoclonal antibody bioconjugate for electrochemical immunosensing of HER2 as a breast cancer biomarker

Abstract: Metal oxide-based sensors have the advantage of rapid response and of high sensitivity to detect specific active biological species and are relatively inexpensive. This report of the present study concerns the development of a cerium oxide – monoclonal antibody bioconjugate for its application as a sensitive immunosensor to detect a breast cancer biomarker. A cerium oxide-anti HER2 bioconjugate was constructed by adding anti HER2 onto cerium oxide that had been previously reacted with APTMS and PEG-NHS-Maleimide. The FTIR spectra of the reaction product showed that the cerium oxide-anti HER2 bioconjugate was successfully synthesized. The resulted bioconjugate was then immobilized on a screen-printed carbon‑gold nanoparticles electrode surface by using the amine coupling bonding systems. The interaction of the synthesized cerium oxide-anti-HER2 bioconjugate with HER2 was found to inhibit an electron transfer and a decrease in the voltammetric Fe(CN)63-/4- peak current, which was proportional to the concentration of HER2. The optimal response of the current signal was generated at an anti-HER2 concentration of 5.0 μg/mL. The two linear ranges of HER2 concentration were found: that were 0.001 to 0.5 ng/mL and 0.5 to 20.0 ng/mL. By using the first calibration curve, the limit of detection was 34.9 pg/mL. The developed label-free immunosensor was used to determine HER2 in a human serum sample with satisfactory results, as shown by a consistent result with the addition of standard. Thus, the resulted immunosensor in this study is promising and has a potential application in clinical bio-analysis.

Real-time measurement of tumour hypoxia using an implantable microfabricated oxygen sensor

Abstract: Hypoxia commonly occurs within tumours and is a major cause of radiotherapy resistance. Clinical outcomes could be improved by locating and selectively increasing the dose delivered to hypoxic regions. Here we describe a miniature implantable sensor for real-time monitoring of tissue oxygenation that could enable this novel treatment approach to be implemented. The sensor uses a solid-state electrochemical cell that was microfabricated at wafer level on a silicon substrate, and includes an integrated reference electrode and electrolyte membrane. It gave a linear response to oxygen concentration, and was unaffected by sterilisation and irradiation, but showed susceptibility to biofouling. Oxygen selectivity was also evaluated against various clinically relevant electroactive compounds. We investigated its robustness and functionality under realistic clinical conditions using a sheep model of lung cancer. The sensor remained functional following CT-guided tumour implantation, and was sufficiently sensitive to track acute changes in oxygenation within tumour tissue.

Design of a liquid sensing photonic crystal fiber with high sensitivity, bireferingence & low confinement loss

Abstract: This paper represents a Photonic Crystal Fiber (PCF) based sensor structure with concurrently high sensitivity, high birefringence and low confinement loss for liquid sensing applications. We explored the efficiency of the constructed PCFs for Water to be sensed as a liquid sample. The numerical analysis of the proposed structure is performed using the full Finite Element Method (FEM). To minimize the fabrication complexity, circular air holes have been chosen instead of elliptical holes in the core region. The substantial analysis is described at a broad spectrum of wavelengths (1.3 μm–2 μm) and the effect of different design parameters of proposed structures has been studied very sincerely. According to FEM numerical results, the designed PCF sensor offers considerable performance in terms of sensitivity is 49.13% as well as birefringence is 0.008. The suggested framework can be used extremely in the area of bio-sensing studies and commercial applications.

Aptamer-NanoZyme mediated sensing platform for the rapid detection of Escherichia coli in fruit juice

Abstract: Pathogenic strains of Escherichia coli (EC) have emerged as a threat to public health due to its ability to contaminate food and water. Early detection of EC contamination in food products is of fundamental importance to avoid any severe medical situations associated with its infection. We herein report a rapid and facile; aptamer and NanoZyme-based assay for EC detection in fruit juice. The developed assay is highly rapid, sensitive, and affordable. The test can be completed within 5 min without any requirement of a sophisticated instrument and cost roughly $ 2. Moreover, the detection is visible to naked eyes. We have also adapted the aptamer on to an electrochemical sensing platform to evaluate its diagnostic utility. The aptamer performed impressively with both NanoZyme-based colorimetric and electrochemical assay and displayed a low-end detection limit of ~10 CFU. The approach presented in the current study is a generic strategy and in principle, may be used for the detection of various analytes, including other bacterial pathogens.

Highly sensitive electrochemical detection of E. coli O157:H7 using conductive carbon dot/ZnO nanorod/PANI composite electrode

Abstract: A selective electrochemical sensor based on carbon dot (CD)/ZnO nanoroad/PANI nanoassembly has been developed towards the detection of cadmium (II) present in the environmental samples. In this work, a conductive nanocomposite electrode, CDs/ZnO/PANI, was successfully fabricated by polymerizing aniline (PANI) in the presence of carbon dot and Zinc oxide nanorod and followed by coating onto printed carbon sheet. These CDs were nearly spherical with good size distribution and excellent monodispersity, and the average size of CD were around 3–5 nm as evidence from Transmission electron microscope (TEM). ZnO nanorod having average length of 20 nm has been synthesized and characterized by TEM. The nanocomposite CDs/ZnO/PANI was characterized by Fourier transforms infrared spectroscopy, UV–Vis spectroscopy, Scanning Electron Microscopy (SEM) and electrochemical analyzer. SEM investigation confirms that the CD and ZnO are uniformly dispersed in PANI matrix. In addition, the outstanding electrical conductivity of CD/ZnO/PANI was found to increase the sensitivity for the detection of E.Coli. The developed electrochemical biosensor also showed good selectivity and was successfully detected E. coli O157:H7 with a detection limit of 1.3×10−18M, in water samples.

Paper-based (bio)sensor for label-free detection of 3-nitrotyrosine in human urine samples using molecular imprinted polymer

Abstract: Over the last years, paper technology has been widely spread as a more affordable, sustainable and reliable support material to be incorporated in the design of point-of-care (POC) diagnostic devices. However, the single work employing a paper-based device for 3-nitrotyrosine (3-NT), a relevant biomarker for oxidative stress (OS) that is a major origin for many diseases, is incapable of reading successfully complex samples because every species that oxidizes before ~0.75 V will also contribute to the final response. Thus, the introduction of a selective element was made into this set-up by including a molecularly-imprinted polymer (MIP) tailored in-situ. Herein, a novel MIP for 3-NT was assembled directly on a paper platform, made conductive with carbon ink and suitable for an electrochemical transduction. The biomimetic material was produced by electropolymerization of phenol after optimizing several experimental parameters, such a scan-rate, number of cycles, range of potential applied, monomer and template concentrations. Under optimal conditions, the label-free sensor was able to respond to 3-NT from 500 nM to 1 mM, yielding a limit of detection of 22.3 nM. Finally, the applicability of the (bio)sensor was tested by performing calibration assays in human urine samples and a good performance was obtained in terms of sensitivity, selectivity and reproducibility. Overall, the attributes of the herein described sensing approach can be compared to a very limited number of other electrochemical devices, that are still using a conventional three electrode system, making this paper-sustained device the first electrochemical (bio)sensor with potential to become a portable and low-cost diagnostic tool for 3-NT. In general, the incorporation of molecular imprinting technology coupled to electrochemical transduction enabled the fabrication of suitable smart sensors for wide screening approaches.

Four-dimensional voltammetry: An efficient strategy for simultaneous determination of ascorbic acid and uric acid in the presence of dopamine as uncalibrated interference

Abstract: In this work, we have developed a novel electroanalytical methodology based on generation of third-order differential pulse voltammetric (DPV) data for simultaneous determination of ascorbic acid (AA) and uric acid (UA) in the presence of dopamine (DPA) as uncalibrated interference. To generate third-order DPV data, two instrumental parameters including pulse height and pulse time were changed. Each sample had a three-way data array containing six matrices recorded at six different pulse times and each matrix had six vectors recorded at six different pulse heights. By joining three-way data arrays, we could generate a four-way data array. After data pre-processing, a calibration model was built by augmented parallel factor analysis (APARAFAC) and multivariate curve resolution-alternating least squares (MCR-ALS) and their performance for simultaneous determination of AA and UA in the absence and presence of DPA as uncalibrated interference was examined by predicting concentrations of validation and test set, respectively. Our records confirmed successfulness of MCR-ALS in predicting concentrations of AA and UA in both validation and test sets and then, it was applied to the analysis of real samples. Fortunately, the results of MCR-ALS in analyzing real samples were acceptable which also confirmed development of a novel method.

Review: Applications of surface-enhanced fluorescence (SEF) spectroscopy in bio-detection and biosensing.

Abstract: Surface-enhanced fluorescence (SEF) is rapidly becoming one of the main spectroscopic techniques for the detection of a variety of biomolecules and biomarkers. The main reasons for this trend are the high sensitivity and selectivity, robustness, and speed of this analytical method. Each year, the number of applications that utilize this phenomenon increases and with each such work, the complexity and novelty of the used substrates, procedures, and analytes rises. To obtain a clearer view of this phenomenon and research area, we decided to combine 76 valuable research articles from a variety of different research groups into this mini-review. We present and describe these works concisely and clearly, with a particular interest in the quantitative parameters of the experiment. These sources are classified according to the nature of the analyte, on the contrary to most reviews, which sort them by substrate nature. This point of view gives us insight into the development of this research area and the consequent increase in the complexity of the analyte nature. Moreover, this type of sorting can show possible future routes for the expansion of this research area. Along with the analytes, we can also pay attention to the substrates used for each situation and how the development of substrates affects the direction of research and subsequently, the choice of an analyte. About 108 sources and several interesting trends in the SEF research area over the past 25 years are discussed in this mini-review.

Single and simultaneous voltammetric sensing of lead(II), cadmium(II) and zinc(II) using a bimetallic Hg-Bi supported on poly(1,2-diaminoanthraquinone)/glassy carbon modified electrode

Abstract: In this work, bimetallic film of mercury and bismuth (Hg-Bi) was incorporated with poly(1,2-diaminoanthraquinone)/glassy carbon electrode (PDAAQ/GC) using applied potential method. The obtained Hg-Bi/PDAAQ/GC electrode was characterized by square wave voltammetry (SWV), scanning electron microscope (SEM) and energy dispersive X-ray (EDX) techniques. The proposed electrode had been used as a highly sensitive sensor for both single and simultaneous determination of lead (Pb2+), cadmium (Cd2+) and zinc (Zn2+) ions in acetate buffer solution by anodic stripping voltammetry (ASV). The adopted ASV method was achieved by optimizing different parameters such as metal deposition method (either in-situ or ex-situ), metals pre-concentration potential, pre-concentration time and different pH of values for acetate buffer solution. The prepared sensor provided a good reproducible response, high sensitivity with a linear range of 0.0–50.0 μg/L for Cd2+ and Zn2+ with a low detection limit of 0.107 and 0.037 μg/L, respectively. The linear range of Pb2+ was 10.0–120.0 ng/L with a detection limit of 3.18 ng/L. Also, the sensor was used for the analysis of the analytes in water samples with satisfactory results in comparison with inductively coupled plasma – mass spectroscopy (ICP-MS).

Development of biodegradable hybrid polymer film for detection of formaldehyde in seafood products

Abstract: Despite the enormous accomplishments of current sensing methods, portable and sensitive sensing materials remains a challenging issue. Herein, a novel of a biodegradable hybrid polymer film was developed for quantitative analysis of formaldehyde seafood, including Lutjanus erythropterus, Euthynnus affinis, Caranx indicus, and Penaeus monodon at Sabah, Malaysia. In this research, starch and chitosan were introduced as the substrate to entrap Nash colorimetric reagents for the fabrication of biodegradable films for detection of formaldehyde. Under optimal conditions, excellent linearity (R2 = 0.9918) of colorimetric response was obtained in formaldehyde concentration ranges of 100 to 0 ppm, with a limit of detection and quantification calculated to be 5 and 16.8 ppm, respectively. The developed film was successfully applied to the identification and quantification of formaldehyde in four different seafood samples with satisfactory recoveries, and RSD values obtained range between 98.80%–104.65% and 0.12%–1.21%, respectively. The present research demonstrated short response time (within 5 min) that provides reliable methods for application in biosensing, which exhibited the advantage of this well-performing platform for application in the food, environmental, and medical disciplines sensing.

Biogenic capped selenium nano rods as naked eye and selective hydrogen peroxide spectrometric sensor

Abstract: The Biogenic selenium(0) nano rods were synthesized and stabilized in citric acid and flavonoids from lemon juice by wet chemical route. As synthesized nanorods were characterized using physicochemical analysis techniques as UV–Vis, FITR, PXRD spectrometry, SEM and TEM surface morphology imaging techniques. These nano rods had exhibited trigonal Se packing lattice, 90 nm mean crystallite size and surface capping with flavonoid and citric acid functionality. The Se nanorods show selective sensing of peroxide by visible color change from reddish to faint pink and also through spectrometric sensing plots for concentrations from 60 ppm to 5 ppm with sensing limit up to 75 μM peroxide with interfering cellular cations as K, Na, Ca, Mg and Fe. These biogenic green sensor Se nano rods get converted to nano ovals after surface leaching with peroxide and show SPR based selective sensing mechanism in spectrometric plots. These developed nanorods finds suitable applications in biomedical cellular peroxide sensing with low limits through naked eye cost effective spectrometric sensing method.

Protein based biomarkers for non-invasive Covid-19 detection

Abstract: COVID-19 has become a substantial lethal disease worldwide, and early diagnosis is a significant concern for this virus. Currently, RT-PCR is being used worldwide for the detection of this virus with human to human transmission. Furthermore, the recent develop biosensor leading to others diagnosis approach but being invasive are painful and time taking. Another possibility can be protein-based biomarkers as an application of biosensors for detection and early diagnostics. Considering the other approach, that is, microfluidics-based biosensor, though being a non-invasive method, will be restricting virus transmission. This review commences with the recent develop biosensor for Covid-19 detection and listing down the available biomarkers with their secretion range comparison of normal to COVID-19 patients through clinical analysis in china and concludes with the future approach for the diagnosis.

Selective determination of ammonia, ethanol and acetone by reduced graphene oxide based gas sensors at room temperature

Abstract: This work reports a new technique for the selective determination of three organic vapors– ammonia, ethanol and acetone by employing two resistive sensors. These two resistive sensors are based on reduced graphene oxide (RGO) and RGO– rosebengal (RB) composites. The chemically synthesized RGO and RGO–RB based sensors were tested for four different concentrations of ammonia (400–2800 ppm) and two different concentrations (1000, 2000 ppm) of ethanol and acetone each, at room temperature. The RGO sensor was found to exhibit response of 10.3% to 25.3% to 400–2800 ppm of ammonia, 1.01% to 1.15% to 1000 and 2000 ppm of acetone respectively, and 1.05% to 1.56% to 1000 and 2000 ppm of ethanol respectively. The RGO–RB composite-based sensor exhibited an enhanced response ranging from ~17% to 36.6% for 400–2800 ppm of ammonia, 1.6% to 3.2% for 1000 and 2000 ppm of acetone and 1.1% to 1.7% for 1000 and 2000 ppm of ethanol at room temperature. An algorithm, based on the soft margin classifier was developed to accurately determine the concentrations of all the three organic vapors. The initial 100 s of the response values of both the sensors for all the targeted vapors were considered for this purpose. This resulted into classification of all the concentrations of the three organic vapors much before the full-scale response of the sensors. It is believed that this work will aid in development of portable devices comprising of array of sensors having the capability of determining the vapors and their concentrations accurately.

Design and analysis of a chemical sensing octagonal photonic crystal fiber (O-PCF) based optical sensor with high relative sensitivity for terahertz (THz) regime

Abstract: This article represents a new structure of octagonal cladding with a rotated-hexa core in photonic crystal fiber (O-PCF) for chemical sensing application in the terahertz (THz) waveguide. The five layers octagonal shape in circular air holes of cladding region with two layers rotated-hexa shape in circular air holes of core area are proposed in this study. The mathematical analysis is achieved from the technique of perfectly matched layers (PML) boundary condition with a finite element method (FEM) at the terahertz (THz) wave propagation. After the simulation process, the designed O-PCF sensor performs the extreme relative sensitivity at 77.14%, 78.06% and 76.11% at 1 THz for three chemicals such as Ethanol (n = 1.354), Benzene (n = 1.366) and Water (n = 1.330). Alternatively, the low confinement losses are 2.26 × 10−03 dB/m, 3.02 × 10−06 dB/m and 2.72 × 10−02 dB/m for similar three chemicals at 1 THz. The effective area, effective mode index and total power fraction are also concisely explained here. Furthermore, we hope that the suggested excellent designed of octagonal photonic crystal fiber (O-PCF) can be utilized particularly for chemical sensing in material study, industrial areas, nano-optics, biomedical and others communication areas in THz technology.

Deep learning in a sensor array system based on the distribution of volatile compounds from meat cuts using GC–MS analysis

Abstract: Generally, people distinguish the type of meat by looking at the color, texture, and even aroma of meat. These three methods have less effective approaches to distinguish the types of meat from meat cuts. Some researchers analyze the differences in the aroma of meats by using laboratory equipment, which is gas chromatography–mass spectrometry (GC–MS). This tool is mostly accurate, but it requires some time to determine the meat types completely. Moreover, the analysis process using GC–MS is also complicated. Nowadays, the electronic nose (e-nose) is a promising technology because it has a faster process of identifying various food types with reasonable production costs. Hence, the development of an e-nose for distinguishing volatile compounds from some meat types is appealing. Not only to determine the type of meat, but this study can also differentiate the part of the body from the meat, which has never been done by previous researchers. GC–MS was used as ground truth for the e-nose system, which helped the results to meet the standards. To achieve the objective in differentiating two meat cuts from three types of meat, this study uses statistical parameters for extraction feature, PCA for reducing the dimension, and deep learning. Furthermore, to get more improvements from the previous researches, this study aims to optimize the parameters of deep learning. The result of the proposed method was compared to several machine learning algorithms that were used in previous studies, i.e., k-nearest neighbor (k−NN), support vector machine (SVM), Multi-Layer Perceptron (MLP), and basic deep learning. The experimental results showed that e-nose could detect meat cuts for 120 s, and the proposed method provides a significant improvement.

Alcohol sensing and classification using PCF-based sensor

Abstract: This paper focuses on designing a Photonic Crystal Fiber (PCF) based sensor model. The anticipated sensor is modelled and simulated using COMSOL Multiphysics to carry-out experiments on multiple optical parameters that evaluate the efficiency of this model. This model aims to detect alcohol and classify it. Three variants of alcohol, namely methanol, ethanol, and propanol, have been considered in this study. These analytes are then injected into the core-region separately. The model is then simulated between 1.0 THz and 2.5 THz frequency band to evaluate the optical properties. Simulation results demonstrate higher relative sensitivity of approximately 88%, 91%, and 92% at 2.0 THz for methanol, ethanol, and propanol, respectively. Besides, the confinement loss for this model approaches nearly zero immediately after 1.2 THz. Furthermore, a shallow effective material loss (EML) is found for this sensor model to sense these three types of alcohol. For instance, the EML value is only 0.0056 cm−1 in the case of methanol sensing. Finally, different optical parameters presented in this study demonstrate the effectiveness of the proposed model in sensing various alcohols.

Fabrication of electrospun sensor based on a synthesized component doped into PAN (polyacrylonitrile) nanofibers for electrochemical detection of zearalenone mycotoxin in foods simulant

Abstract: The aim of this research was to fabricate a nanofiber-modified pencil-graphite electrode using electro-spinning technique to application in the food simulant especially liquid foods, including dairy, juices and other liquid foods to detect the Zearalenone (ZEN) mycotoxin. This sensor was made at room temperature by Britton–Robinson (B- R) buffer with pH =6 to optimize the chemical and mechanical parameters. Cyclic voltammetry (CV), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were used for electrochemical and morphological characterization of the composite fibers. This sensor responded to ZEN over the concentration range of 5–30 and 60–100 nm with a linear behavior. According to the SEM images, bare graphite electrode, has a fairly unusable smooth surface. ZEN cathode peak is dependent on the pH changes related to the proton receptor groups on the structure of ZEN and the best signal for the square wave spectrum in the B-R buffer based on the maximum signal of the received stream was pH = 6 for ZEN. Based on the results 0.5 M of potassium nitrate as a supporter electrolyte was suitable to measure ZEN in the presence of the optimal electrode. Therefor electrospun sensor doped into PAN/nanofiber has a good characteristic in recognisation of ZEN in the liquid foods especially dairy product.

Hydrogen peroxide biosensor based on hemoglobin-modified gold nanoparticles–screen printed carbon electrode

Abstract: A biosensor based on hemoglobin immobilized on screen-printed carbon electrode (SPCE) pre-electrodeposited with gold nanoparticles (AuNPs) was developed to measure hydrogen peroxide (H2O2) concentration. Cyclic voltammetry method was utilized for AuNPs electrodeposition process and characterized the Hb behaviour in the modified electrode. The highest electro active surface area (0.07 cm2) of working electrode in SPCE was obtained when the potential was swept (in electrodeposition experiment) from 0 to +1 V for 15 cycles in phosphate buffer solution (PBS) (pH 7) containing 0.1 nM AuNPs. Direct electrochemical of hemoglobin in the modified electrode showed quasi-reversible redox behaviour at −0.2 V and −0.3 V on forward and revers scan respectively, in PBS (pH 7) at scan rate 0.05 Vs−1 vs. Ag/AgCl. The modified electrode was used to measure hydrogen peroxide concentration with a linear response over 3 μM to 240 μM and a detection limit of 0.6 μM at −0.35 V. The apparent Michaelis-Menten constant value of Hb in the modified SPCE to measure H2O2 was calculated to be 235 μM with sensitivity of 0.918 AM−1 cm−2. The surface morphology of the SPCE and its modification were investigated using Atomic Force Microscope (AFM). As a result, the new modified biosensor exhibited a high sensitivity, good reproducibility and stability.

Nanocellulose- based biosensor for colorimetric detection of glucose

Abstract: This work reports for the first time a colorimetric based biosensor using nanocellulose (NC) based supports drop-deposited onto a cellulose paper substrate for glucose detection in point-of-care. For this purpose, microcrystalline cellulose (MCC) samples were oxidized with 2,2,6,6-tetramethylpiperidine-N-oxyl radical (TEMPO), sodium hypochlorite, and potassium bromide, to produce NC that corresponded to carboxyl- NC. For the characterization, we used several methods: TEM, FTIR and conductometric titration. In all samples, the primary alcohol groups were selectively oxidized into carboxyl groups, provided the sodium hypochlorite is added dropwise and the reaction is performed at constant pH 10. Carboxyl- NC was further casted on a cellulose substrate and used as support for glucose oxidase (GOx), horseradish peroxidase (HRP) and 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) reactions, aiming to yield a coloured detection system for glucose. The sensing system was generated by integrating GOx on the carboxyl- NC /cellulose substrate. Upon reaction with glucose, the enzyme produced hydrogen peroxide, which was converted into a blue-coloured product by reaction with HRP and the chromogenic reagent ABTS. The test-strip was calibrated by incubating it in different concentrations of glucose. The colours obtained were further analysed by a suitable image analysis software. Linear response for glucose ranged 1.5 to 13.0 mM. Overall, this new test-strip used renewable material for glucose determination, which is an advantage when compared to other systems that require more complex technological approaches. Moreover, it was found that Carboxyl- NC improved the colour homogeneity of the test-strip and the intrinsic linear response of concentration range.

Sandwich SERS immunoassay of human immunoglobulin on silicon wafer compared to traditional SERS substrate, gold film

Abstract: Likely the first application of silicon wafer as a substrate for sandwich immunoassay with Surface Enhanced Raman Scattering (SERS) detection is reported hereafter. Human immunoglobulin (hIgG) was used as a model biomarker in the simultaneous comparative assay on gold film and on Si wafer, an alternative (less expensive and potentially more resistant to surface contamination and non-specific binding) substrate. The Limits of Detection calculated from the data obtained with two-laser wavelength (633 nm and 785 nm) were about 1 × 10−12 mol of antigen or less for both substrates, which is close to the minimal detectable concentration of 30 pM. An approximately logarithmic response was observed across at least a factor of 133 in the dynamic range 0.03–4 nM. However, if four parametric logistic curve is used for the calibration, LOD on silicon would become significantly lower than LOD on gold (3 pM vs 28 pM). A much smaller slope of calibration plot was compensated by a significantly smaller standard deviation in the signal of the blank for the assay on silicon, as compared to the assay on gold. This report may encourage researchers to try silicon or other non-noble metal materials as SERS substrates for the detection of biomarkers.

High sensitivity property of dual-core photonic crystal fiber temperature sensor based on surface plasmon resonance

Abstract: In this paper, we design and simulate a dual core photonic crystal fiber (DC-PCF) temperature sensor in terms of wavelength sensitivity. The dual core design of the PCF makes it possible to deposit the gold (plasmonic material) layer and analyte (high temperature coefficient liquid) outside the PCF thus makes the fabrication easier. The sensor performance is demonstrated with the help of Matlab environment as well as the finite element method (FEM). Different loss spectra with the variation of temperature has been analyzed. The computational result shows that a wide range of temperature from 0 °C to 60 °C can be detected to investigate the sensor performance. The designed sensor exhibits flat wavelength sensitivity of 2.25 nm/°C with a sensor resolution of 4.44 × 10−2 for y-polarized light. In order to achieve high sensitivity, the structural parameters such as air hole diameter, pitch, gold thickness and core diameter are optimized. In view of wide detection range of temperature and flat sensitivity, this DC-PCF temperature sensor can be a promising candidate for various applications such as for the real time detection of the temperature of manufacturing industry, medical environment, electric vehicle, transformer oil etc.

Design and numerical analysis of a PCF-based bio-sensor for breast cancer cell detection in the THz regime

Abstract: Breast cancer is a serious issue in today's medical science and for this reason, an accurate, as well as efficient detection technique of the breast cancer cell is urgent. Photonic crystal fiber (PCF) makes this process easier and unique since it has tremendous optical sensing capabilities. We represent a PCF sensor model for detecting the breast cancer cell where all the designed configurations are accomplished using finite element method and its different performances are examined in MATLAB. This PCF sensor is capable of operating at the 1.5–3.0 THz region. Simulation results namely higher relative sensitivity (92.2%), lower confinement loss of only 6.52 × 10−14 cm−1, lower effective material loss of only 0.0117 cm−1, lower effective area of approximately 9.4 × 104 μm2, a higher numerical aperture of 0.194, and birefringence demonstrate the efficiency of the proposed model. Besides, the simplicity in design also ensures the fabrication possibilities of this proposed sensor

Hexagonal photonic crystal Fiber (H-PCF) based optical sensor with high relative sensitivity and low confinement loss for terahertz (THz) regime

Abstract: This paper presents an analysis on a hexagonal cladding with a rotated-hexa core in photonic crystal fiber (H-PCF) based optical sensor formation with simultaneously minimal confinement loss and higher sensitivity for chemical sensing functions. The numerical assessment of the designed structure is achieved with the procedure of finite element method (FEM) and perfectly matched layers (PML) boundary condition in the comsol multiphysics software tool. As per FEM numerical analysis, the proposed PCF sensor presents the extreme relative sensitivity at 81.46%, 82.26% and 79.22% for three chemicals at 1 terahertz (THz) such as Ethanol (n = 1.354), Benzene (n = 1.366) and Water (n = 1.330), respectively. Moreover, at 1 terahertz (THz) the low confinement losses are 5.85 × 10−08, 6.07 × 10−08 and 5.84 × 10−08 dB/m for similar three chemicals. The effective area, the effective mode index and the total power fraction are also elaborately explained. Furthermore, we hope that our proposed structure can be operated intensely in the field of biomedical, bio-sensing experiments and industrial applications in terahertz (THz) waveguide technology.

All printed organic humidity sensor based on egg albumin

Abstract: In this paper, bio-compatible layer based on egg albumin (EA) is used for humidity sensing. The EA composed of different types of globular proteins. The chemical composition of these hydrophilic proteins makes the EA membrane sensitive towards humidity. The relative humidity (RH) variation of EA humidity sensor was recorded in the range between 0% and 100% RH. The impedance response of EA humidity sensor varied from 3.965 MΩ to 65.84 kΩ at 1 kHz and from 407.81 kΩ to 3.99 kΩ at 10 kHz. The capacitance response varied from 4.5 nF to 1.36 μF at 1 kHz and from 9.05 nF to 705.71 nF at 10 kHz respectively. The EA humidity sensor shows a high capacitance sensitivity ~ 30,122.22% at 1 kHz, and ~ 7697.9%. at 10 kHz. The sensor presents fast transient response and for real time application inhale and exhale test was performed, which shows high sensitivity in a range from 35% to 100% RH. The proposed EA humidity sensor will open new possibilities towards biocompatible electronic devices.