Detection Of Different Concentrations Research Articles

Machine learning-driven 3D plasmonic cellulose sensor for in situ rapid SERS detection of bisphenol compounds in water sample

Rapid component separation and accurate identification of bisphenols compounds (BPs) in real water sample remain an attractive challenge due to the trace amounts and structural similarities of BPs, and complexity of real samples. Here, we designed and synthesized chemically modified cellulose p-toluenesulfonate (CTSA) to encapsulate octadecylamine-modified gold nanoparticles (Au-ODA), obtaining 3D plasmonic cellulose (Au@CTSA). Simultaneously, by virtue of the high surface area in the 3D network of CTSA and the solvent volatile deposition, BPs in water were in situ extracted and concentrated in Au@CTSA microspheres. Since the 3D network of Au@CTSA supports the formation of “hotspots”, the number of “hotspots” available is greatly improved, enabling excellent SERS detection of BPs. Based on the collected SERS spectra, machine learning was utilized to analyze the overall profile of BPs, which eliminated the subjective judgment of the concentration by the Au@CTSA sensor using a single characteristic peak. In this way, the accuracy of identification of BPs was significantly improved. The machine learning-driven Au@CTSA sensor realized the detection of traces bisphenol A (BPA), bisphenol S (BPS), and bisphenol F (BPF) in water sample, pushing quantitative detection of different concentrations of BPs and contributing facile indicators for water quality monitoring.

Double Fano sensing mechanism of waveguide coupled surface plasma

Based on the optical properties of waveguide-coupled surface plasmon resonance, a sensor of surface plasmon coupled waveguide resonance with double discrete states generated by the upper and lower waveguide structures combined with prisms and Au films, respectively, is proposed. In this paper, the sensing structure is studied numerically and analytically, and the transmission characteristics of surface equipartition excitations are analyzed and elaborated in-depth in combination with the reflection angle spectrum, as well as the generation and evolution mechanism of dual Fano resonance at different incidence angles at fixed wavelengths. The structural model of Fano resonance sensing based on angle modulation is established, and the sensing characteristics are analyzed to produce electromagnetic field enhancement at low-angle Fano. The mathematical model between structural parameters and spectral performance is established using back propagation (BP) neural network, and the particle swarm optimization (PSO) algorithm is used to find the input structural parameters corresponding to the optimal performance, The results show that the quality factor of resonance (FOM) and sensitivity is significantly improved; When it is used in the field of biosensing, the response curves of Fano with different angles of high and low to concentration are quite different, thus realizing high precision detection of different concentrations of solutions and reflecting excellent sensing performance.

The synthesis of fluorescent carbon quantum dots for tartrazine detection in food: a novel one-step microwave heating approach

Nowadays, carbon quantum dots (CDs) as semiconductor synthesized nanoparticles have become an attractive subject for lots of applications due to their remarkable features. In the current study, the highly fluorescent (FL) CDs with great characteristics were synthesized through a novel one-step microwave irradiation by citric acid monohydrate and urea as carbon precursors. The as-prepared CDs were quasi-spherical shape with an average diameter of 4.5 nm and emitted bright blue FL under ultraviolet light irradiation (UV). Furthermore, the synthesized CDs possessed different properties such as diverse functional groups, good sensitivity and selectivity, high water-solubility, low toxicity, and significant stability in various environmental conditions. The results indicated that the as-prepared CDs can be applied as a fluorescent probe for detection of different concentrations of tartrazine from 5 to 100 µM in food samples. In addition, the findings revealed that the good linear relationship was obtained between the FL intensity of CDs and different concentrations of tartrazine over the range of 5 to 100 µM with the detection limit of 2.58 µM.

Immunosensing for Early Detection of Rheumatoid Arthritis Biomarkers: Anti-Cyclic Citrullinated Peptide Antibodies Based on Tilted-Fiber Bragg Grating Biosensor

Rheumatoid arthritis (RA) is regarded as a chronic, immune-mediated disease that leads to the damage of various types of immune cells and signal networks, followed by inappropriate tissue repair and organ damage. RA is primarily manifested in the joints, but also manifests in the lungs and the vascular system. This study developed a method for the in vitro detection of RA through cyclic citrullinated peptide (CCP) antibodies and antigens. The diameter of a tilted-fiber Bragg grating (TFBG) biosensor was etched to 50 μm and then bonded with CCP antigens and antibodies. The small variations in the external refractive index and the optical fiber cladding were measured. The results indicated that the self-assembled layer of the TFBG biosensor was capable of detecting pre- and post-immune CCP antigen and CCP peptide concentrations within four minutes. A minimum CCP concentration of 1 ng/mL was detected with this method. This method is characterized by the sensor's specificity, ability to detect CCP reactions, user-friendliness, and lack of requirement for professional analytical skills, as the detections are carried out by simply loading and releasing the test samples onto the platform. This study provides a novel approach to medical immunosensing analysis and detection. Although the results for the detection of different concentrations of CCP antigen are not yet clear, it was possible to prove the concept that the biosensor is feasible even if the measurement is not easy and accurate at this stage. Further study and improvement are required.

Ultra‐Flexible Giant Magnetoresistance Biosensors for Lab‐on‐a‐Needle Biosensing

AbstractFlexible biosensors exhibit great potential for the detection of various biomarkers with the ability to adapt to different surface textures. Here, a lab‐on‐a‐needle biosensing platform based on ultra‐flexible giant magnetoresistance (GMR) biosensors is developed. The fabricated flexible GMR sensors exhibit a MR ratio of 5.2% and a sensitivity of 0.13%/Oe in the linear region, which are comparable to their rigid counterparts. It is found that the magnetic properties of the flexible GMR sensors remain unchanged after 500 cycles of compressive and tensile stress, indicating strong robustness even when applied to a surface that is constantly in motion. The developed platform is then employed for the detection of different concentrations of canine osteosarcoma (OSCA‐8) cells with a limit of detection (LOD) of 200 cells in 20 µL sample (104 cells per mL), which demonstrate the ability to perform real‐time, sensitive, and quantitative cell detection.

In-situ SERS detection of aromatic amine pollutants in fire-fighting wastewater using low-cost flexible substrates

Surface-enhanced Raman scattering (SERS) technology has been widely used in the field of environmental pollutant detection due to its fast and intuitive characteristics and low water interference. Herein, a low-cost and flexible SERS substrate was fabricated by transferring gold nanoparticles (NPs) onto polydimethylsiloxane (AuNPs@PDMS) membranes, which enabled highly sensitive detection of aromatic amine pollutants in wastewater after fire suppression. Finite time domain-difference calculations confirmed that the uniformly distributed NP gap significantly enhanced the localized electromagnetic field. The AuNPs@PDMS substrate performed satisfactorily in testing for rhodamine 6G (R6G) with a detection limit (LOD) of 5.5 × 10−10 M. This substrate also demonstrated high reproducibility for detection of different concentrations of R6G and the relative standard deviation (RSD) was <7 %. These excellent SERS properties made AuNPs@PDMS a promising substrate in the detection of aniline and benzidine. Quantitative analysis of aniline and benzidine was achieved with LODs of 4.5 × 10−9 and 7.8 × 10−9 M, respectively. In addition, this substrate could be applied in rapid analysis of mixtures in wastewater after fire suppression using SERS without any complex pretreatments, displaying a great potential for rapid, high-sensitivity, and on-site detection of contaminants in fire-fighting sites.

(Invited) Optical Characterization of Bulk GaN Substrates and Homoepitaxial Films

Low ON-resistance and high breakdown voltage, made possible by improved critical electric field and mobility, has promoted GaN from a potential to the most promising semiconductor material for use in the next-generation of medium- and high voltage-power converters. The commercial availability of large area substrates, produced by HVPE (Hydride Vapor Phase Epitaxial, a quasi-bulk deposition technique) and ammonothermal bulk growth method, provides wafers with reduce concentrations of extended defect, allows the deposition of electronic grade epitaxial films and the realization of high performance electronic devices. Despite that, many steps of substrate preparation, such as miss-cut orientation and surface finishing, must be improved and standardized to yield reproducible epitaxial film growth. To verify the importance of substrate characteristics on the intrinsic properties of homoepitaxial MOCVD films, we initially evaluated substrate provided by various commercial supplies. The substrate effects on epi morphology, uniformity, and impurity incorporation were substantiated by growing simultaneously on wafers from different vendors. The goal of this work is to detect and identify defects in GaN substrates with a series of quick, non-destructive, inexpensive techniques with capabilities of mapping whole wafers.All evaluated substrates had nominally similar as-received specifications (resistivity, thickness, off-cut angle, bow, surface finish). The substrates were evaluated with a variety of techniques including Raman spectroscopy, photoluminescence, white light interferometry, and Nomarski imaging, enabling the detection of different concentrations of grain boundaries, impurities, point defects, v-shaped pits, polishing defects, crystal stress damage, and non-uniform insulating and conductive regions. The substrates can be grouped in two different categories: those with uniform characteristics, including carrier concentration, and those without. Comparing these results to those from homoepitaxial growth on the same wafers, the effects are both subtle and overt. Macroscopic surface morphology, which has shown a direct correlation to leakage current, copies and exaggerates that of the underlying substrate. Photoluminescence of the homoepitaxial surface along with Raman spectroscopy show that non-uniformities in the substrate carrier concentration can continue into the epitaxy.If time permits, results from vertical Schottky diodes, fabricated to quickly evaluate device performance, will presented. While most of the films showed the ability to withstand high electric fields, more uniform electrical properties were observed for those grown on substrates having more uniform properties. These results show that improving bulk substrates is the path to high voltage vertical devices, and that such substrates have a significant influence on device performance. Acknowledgments: Work at NRL is supported by the Office of Naval Research

Low-cost fabrication and characterization process for development of a sensitive optical fiber structure.

The structure of silica single-mode fiber (SMF) must be modified in order to develop optical fiber-based biosensors. To reduce the diameter of the optical fiber, a low-cost chemical etching method is very popular. The proposed chemical etching method is a simple, rapid, and cost-effective technique for removing the silica cladding up to a desired diameter. In the laboratory, hydrofluoric acid (HF acid, 40% concentration) is used for etching. A variation on etching is also proposed and tested with 40% HF as well as with magnetic stirring at the different speeds. The etching experiments are also carried out at different temperatures. The etching results of silica fiber are presented through a step-by-step procedure using a rapid and resource-efficient method for the fabrication of optical fiber-based biosensors. The etched diameter characterization is done using a calibrated compound microscope. The sensing experiment with unetched and etched optical fiber is also performed for the detection of different concentrations of glucose biomolecules.

Electrochemical and Optical Evaluation of the Stability of Enzymatic Hydrogels (BPEI-GOx) Used in Glucose Biosensors

At present, research and development of a large number of new devices for the detection and quantification of biomedical analytes incorporated into miniaturized platforms of high interest such as organ-on-a-chip (OCC), lab-on-a-chip (LOC), and implantable devices. Together, these systems are characterized by taking continuous measurements for long periods (hours, days, weeks) of the products and/or by-products generated by these platforms[1, 2]. Based on the above, it is essential to detect the failure mechanisms of the systems developed to make improvements in the operational stability of these devices, which could generate biosensing instruments with a longer life span.In this work, the stability of hydrogels was evaluated for the detection of glucose, made up of the branched polyethyleneimine/glucose oxidase (BPEI/GOx) system using ethylene glycol diglycidyl ether (EGDGE) and glutaraldehyde (GA) as crosslinking agents. The stability of these systems was evaluated by light, fluorescence, and electrochemical microscopy (SECM).First, the hydrogels formed were deposited by drop-casting on glass surfaces, gold, and a combination of both (polycrystalline gold chips deposited on glass substrates). The surfaces were treated with different cleaning methodologies and the impact they had on the adhesion of the hydrogels was subsequently evaluated. For their part, the hydrogels were subjected to different conditions such as exposure to aqueous media and potential disturbances to measure their adhesion to the surfaces described. The results showed that, when cleaning the surfaces with the RCA process for 15 minutes, both the hydrogels with EGDGE and GA show better adhesion. Likewise, both hydrogels showed better adherence on gold surfaces compared to glass ones. This can be attributed to electrostatic interactions between the surface and the amino groups present in BPEI and GOx.Subsequently, the spatial arrangement of the BPEI and GOx of both systems was evaluated by fluorescence microscopy and SECM. For this, the GOx was labeled with the fluorophore fluorescein-5-isothiocyanate (FITC) and the BPEI with tetramethylrhodamine-5-Isothiocyanate (5-TRITC). The hydrogels were irradiated with blue, green, and UV light. In the fluorescence images of the controls, unlabeled hydrogels, it was observed that when cross-linked with GA, there was an intense emission of fluorescence at the three wavelengths evaluated. According to the literature, this fluorescence can be attributed to the mechanism proposed by Liu et al.[3] which is based on the formation of Schiff bases from the reaction between aldehydes and amino acid residues. The above-described mechanism was used to confirm the crosslinking reaction between BPEI and enzyme with the crosslinking agent. On the other hand, in hydrogels with EGDGE, heterogeneous structures are seen, in which the distribution of each of the labeled components can be observed. Which facilitated the measurement of stability to time. The spatial arrangement of the enzyme and its stability to time was also evaluated by SECM using the generation of the substrate/collection at the tip (SG/TC) method. A 15 µm Pt UME was used, applying a potential of 0.45 V vs Ag│AgCl to follow the oxidation of H2O2 generated by the enzymatic reaction.As a final step, the concentration of EGDGE and GA was varied to observe the behavior of the hydrogels for the electrochemical detection of different concentrations of glucose in 0.1 M phosphate buffer pH 7.4, following the oxidation of H2O2. Calibration curves were made by chronoamperometry of solutions with concentrations of 0-50 mM of glucose. For EGDGE, the concentration of the solutions ranged from 7.5 to 20%. The results obtained showed that the variation in the concentration of the crosslinker does not affect the diffusion of glucose or H2O2 through the hydrogel and therefore the currents obtained are very similar. In the case of GA, the concentration of the solutions ranged from 4.5 to 0.45%. In this system, it was observed that the concentration of crosslinker significantly affects the diffusion of glucose and/or H2O2 through the hydrogel, reflecting on the currents obtained. In this way, it was determined that the GA concentration of 0.45% allows efficient diffusion through the hydrogel, allowing an increase in the current as of the glucose concentration increases.References Lopez GA, Estevez M-C, Soler M, Lechuga LM (2017) Recent advances in nanoplasmonic biosensors: applications and lab-on-a-chip integration. Nanophotonics 6:123–136. https://doi.org/doi:10.1515/nanoph-2016-0101Rebelo R, Barbosa AI, Correlo VM, Reis RL (2021) An Outlook on Implantable Biosensors for Personalized Medicine. Engineering. https://doi.org/https://doi.org/10.1016/j.eng.2021.08.010Liu SG, Li N, Ling Y, et al (2016) pH-Mediated Fluorescent Polymer Particles and Gel from Hyperbranched Polyethylenimine and the Mechanism of Intrinsic Fluorescence. Langmuir 32:1881–1889. https://doi.org/10.1021/acs.langmuir.6b00201

Design of a Highly Sensitive Self-Reference Tamm-Plasmon-Polariton Sensor Employing Ti3C2Tx MXene

This paper presents design and analysis of a self-reference refractive index sensor for precise detection of different concentrations of H5N1 virus in poultry. The sensor is based on the study of Tamm plasmon polariton (TPP) modes excited between Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Tx MXene and cavity layer integrated 1D photonic crystal (PhC). We demonstrate the self-reference characteristics of the sensor, which significantly decreases the error contributions by the environmental factors like the light intensity fluctuations and local temperature variations. The transfer matrix method (TMM) is employed to investigate the reflectance and absorbance of the sensor. The cornerstone of this work lies on the assay of the shift in the wavelength and intensity of the TPP mode vis-à-vis different concentrations of the H5N1 virus. Numerous structural parameters like selection of materials, thickness of the MXene layer, thickness of the cavity layer, and period of the PhC are judiciously optimized to envisage maximum sensing performance. The colormap plot of field distribution infers a strong electric field localization in the cavity layer, which indicates high absorption of TPP modes. Compared to the traditional TPP sensor designed with Ag thin film, the electric field intensity (EFI) and sensitivity of the proposed MXene-based TPP sensor have been boosted by 40% and 15.93% respectively. It is appraised that the proposed sensor delivers a maximum sensitivity of 60.9375 nm/HAU, quality factor of 5485.71, and detection limit of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${2.6}\times {{10}}^{-{6}}$ </tex-math></inline-formula> RIU. The proposed sensor can find suitable applications in the field of biomedical diagnostics, healthcare, food safety, and environmental monitoring.

Highly sensitive refractive index sensor based on plastic optical fiber balloon structure.

A novel, to the best of our knowledge, design of plastic optical fiber (POF) balloon-based refractive index sensor for the detection of different concentrations of sodium chloride is proposed and experimentally investigated. The experimental characterization supports the finding that the transmission loss is sensitive to the external environment's targeted refractive index changes of the analyte. The proposed sensor achieves a maximum intensity-based sensitivity of 3105 RIU-1, resolution of 3.22 ×10-7, and the figure of merit (FOM) is 326 RIU-1 from 2 to 2.5 Mol/L of the analyte with the chosen refractive index changes at 680 nm for a diameter D = 0.1 cm of the POF balloon structure. Furthermore, a high linear performance of 0.9896 is achieved with good robustness against the fabrication imperfection. The ultra-sensitiveness to the refractive index with a simple demonstration of the POF balloon-based structure has potential applications in the chemical, biological, and food safety sensing fields.

Colorimetric assay for the detection of dopamine using bismuth ferrite oxide (Bi2Fe4O9) nanoparticles as an efficient peroxidase-mimic nanozyme

This work describes the preparation of ternary bismuth ferrite oxide nanoparticles (Bi2Fe4O9 NPs) with an enzyme mimetic activity for dopamine (DA) qualitative and quantitative detection. Bi2Fe4O9 NPs were prepared using a facile, low cost, and one-pot hydrothermal treatment. The chemical composition, morphology, and optical properties of Bi2Fe4O9 nanozyme were characterized using different techniques such as Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction pattern (XRD), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), dynamic light scattering (DLS), field-emission scanning electron microscopy (FESEM) imaging, FESEM-energy dispersive X-ray spectroscopy (EDS), UV–vis absorption, and fluorescence emission spectroscopy. Bi2Fe4O9 NPs were utilized to catalyze the oxidation of a typical chromogenic peroxidase substrate, 3,3′,5,5′-tetramethylbenzidine (TMB), to form the blue-colored oxidized product (oxTMB), in the presence of hydrogen peroxide (H2O2). All reactions occurred in acetate buffer solution (pH 3.5) to generate hydroxyl radicals (•OH) and the kinetics were followed by UV–vis absorbance at 654 nm. The steady-state kinetic parameters were obtained from the Michaelis-Menten equation and exhibited a good catalytic efficiency of Bi2Fe4O9 NPs as enzyme mimetics. Michaelis–Menten constant (Km) values were estimated as 0.07 and 0.73 mM for TMB and H2O2, respectively. The presented method is efficient, rapid, cost-effective, and sensitive for the colorimetric detection of dopamine with a linear range (LR) from 0.15 to 50 μM and a detection limit (LOD) of 51 nM. The proposed colorimetric sensor was successfully applied for the detection of different concentrations of dopamine in spiked fetal bovine serum (FBS) and horse serum (HS) samples. It is anticipated that Bi2Fe4O9 nanozyme holds great potential in biomedical analysis and diagnostic applications of dopamine-related diseases.

Wet-Etched Microchamber Array Digital PCR Chip for SARS-CoV-2 Virus and Ultra-Early Stage Lung Cancer Quantitative Detection.

We report a novel design of chamber-based digital polymerase chain reaction (cdPCR) chip structure. Using a wet etching process and silicon-glass bonding, the chamber size can be adjusted independently of the process and more feasibly in a normal lab. In addition, the structure of the chip is optimized through hydrodynamic computer simulations to eliminate dead space when the sample is injected into the chip. The samples will be distributed to each separated microchambers for an isolated reaction based on Poisson distribution. Due to the difference in expansion coefficients, isolation of the sample in the microchambers by the oil phase on top ensures homogeneity and independence of the sample in the microchambers. The prepared microarray cdPCR chip enables high-throughput and high-sensitivity quantitative measurement of the SARS-CoV-2 virus gene and the mutant lung cancer gene. We applied the chip for the detection of different concentrations of the mix containing the open reading frame 1ab (ORF1ab) gene, the most specific and conservative gene region of the SARS-CoV-2 virus. In addition to this, we also successfully detected the fluorescence of the epidermal growth factor receptor (EGFR) mutant gene in independent microchambers. At a throughput of 46 200 microchambers, solution mixtures containing both genes were successfully tested quantitatively, with a detection limit of 10 copies/μL. Importantly, the chips are individually inexpensive and easy to industrialize. In addition, the microarray can provide a unified solution for other viral sequences, cancer marker assay development, and point-of-care testing (POCT).

Design and Performance Analysis of Reconfigurable 1D Photonic Crystal Biosensor Employing Ge₂Sb₂Te₅ (GST) for Detection of Women Reproductive Hormones.

The present research demonstrates a novel 1D photonic crystal (PhC) based reconfigurable biosensor pertaining to label-free detection of different concentrations of progesterone and estradiol, which play a vital role in developing reproductive hormones in women. The proposed sensor is designed by an alternative arrangement of Na3 AlF6 and CeO2, with a central defect layer. A thin layer of novel phase change chalcogenide material (Ge2 Sb2 Te5) is deposited along the two sides of the defect layer to improve the sensing performance. Numerical simulation of transmission spectrum for TE mode is carried out by using the transfer matrix method (TMM). The mainstay of this research is centered on the assay of shift in the defect mode position and intensity with respect to different concentrations of analyte, by changing the phase of the GST material from amorphous to crystalline. Interestingly, we observed a high tunability in defect mode wavelength, when the phase is changed from amorphous to crystalline, which leads to accomplishment of a high sensitivity of 1.75 nm/nmol/L for progesterone and 20.5 nm/nmol/L for estradiol. Aside from sensitivity, other significant parameters like figure of merit and detection limit are computed, which give a deep insight into the sensing performance. These encouraging sensing performances pave the path for efficient detection of different concentrations of progesterone and estradiol to monitor various gynecological problems in women.

Rapid electrochemical immunodetection of SARS-CoV-2 using a pseudo-typed vesicular stomatitis virus model

The COVID-19 pandemic has highlighted the need for reliable and accurate diagnostic tools that provide quantitative results at the point of care. Real-time RT-PCR requires large laboratories, a skilled workforce, complex and costly equipment, and labor-intensive sample processing. Despite tremendous efforts, scaling up RT-PCR tests is seemingly unattainable. To date, hundreds of millions of COVID-19 tests have been performed globally, but the demand for timely, accurate testing continues to outstrip supply. Antigen-based rapid diagnostic testing is emerging as an alternative to RT-PCR. However, the performance of these tests, namely their sensitivity, is still inadequate. To overcome the limitations of currently employed diagnostic tests, new tools that are both sensitive and scalable are urgently needed. We have developed a miniaturized electrochemical biosensor based on the integration of specific monoclonal antibodies with a biochip and a measurement platform, and applied it in the detection of Spike S1 protein, the binding protein of SARS-CoV-2. Using electrochemical impedance spectroscopy, quantitative detection of sub-nanomolar concentrations of Spike S1 was demonstrated, exhibiting a broad detection range. To demonstrate the applicability of the biosensor, we have further developed a SARS-CoV-2 pseudovirus based on Spike protein-pseudo-typed VSV platform. Specific detection of different concentrations of pseudovirus particles was feasible in <30 min. This new tool may largely contribute to the fight against COVID-19 by enabling intensive testing to be performed and alleviating most of the hurdles that plague current diagnostics.

Detection of methamphetamine using aptamer-based biosensor chip and cyclic voltammetry technique

In this study, polycarbonate coated with Au nanoparticles and anti-methamphetamine aptamer is used for the detection of methamphetamine. Immobilization of aptamer on Au nanoparticle modified polycarbonate surface, and monitoring of methamphetamine were evaluated with AFM, ATR-FTIR, and DRS techniques. FT-IR reflection spectrum shows a pick at 3300–3500 ​nm range (related to amine groups of aptamer bases). After immobilization of aptamer on Au nanoparticle modified polycarbonate, 8% decrease in reflection was observed. To evaluate of detection power of the designed nanobiosensor, its sensitivity for the detection of different concentrations of methamphetamine was measured with cyclic voltammetry. The detection limits of the designed nanobiosensor in two methods of FT-IR and cyclic voltammetry were 2 and 5 ​μM, respectively. Notably, the designed nanobiosensor in two different methods didn't show any response to glucose.

Preparation of Nanographene and Its Effect on the Correlation Between N-Terminal Pro Brain-Type Natriuretic Peptide, Peripheral Blood Copeptin Level and Cardiac Function Grading of Patients with Heart Failure

At present, biosensors based on nanomaterials are increasingly adopted in clinical detection of heart failure (HF) patients. This work aimed to analyze the correlation between N-terminal pro brain-type natriuretic peptide (NT-proBNP) and copeptin (CPT) levels in order to study the grading of heart function in patients with HF under the fluorescence platform built on nanographene. The and detection principle of of nanographene solution was prepared, and After its physical and chemical properties were tested, the nanographene solution was then used to detect the expression levels of NT-proBNP and CPT in patients with heart failure. Seventy-two patients with heart failure who came to hospital were selected as the observation group, and another 50 healthy people with physical examination were selected as the control group. The results showed that the constructed nanographene solution mixed with NT-proBNP didn’t exhibit fluorescence quenching. Therefore, it was feasible to detect NT-proBNP with nanographene solution. The test results obtained after the detection of different concentrations of nanographene showed that 20 μg/mL nanographene had the best fluorescence quenching effect. The ROC curve of the constructed nanographene had improved specificity in judging heart failure and had better diagnostic performance. The levels of pro-brain natriuretic peptide and copeptin in patients with heart failure were obviously higher than those in the observation group, and there was considerable difference between the two (P &lt; 0.05). After correlation analysis, it was found that the levels of terminal pro-brain natriuretic peptide and copeptin in patients with heart failure were positively correlated with the grade of heart function in patients with heart failure. In summary, the nanographene solution used in this study can accurately detect the expression level of NT-proBNP in patients with heart failure, and the accuracy and efficiency of diagnosis were improved in patients with heart failure. Moreover, the higher the grade of cardiac function in HF patients, the higher NT-proBNP and CPT levels, and there was positive correlation between cardiac function grade and NT-proBNP and CPT levels.

High-sensitivity cardiac troponins: detection and central analytical characteristics

Recently, there have been some important changes in the laboratory diagnosis of patients with acute coronary syndrome, due to the introduction into routine practice of new high- and ultra-sensitive techniques for detection of myocardial damage biomarkers — cardiac troponins. Each method for cardiac troponins’ detection, among the existing wide variety of troponin immunoassays, has different analytical characteristics and allows the detection of different concentrations of troponins in the same patient. With an increasing number of companies developing high-sensitivity troponin immunoassays receiving regulatory approval, there is an urgent need for independent analytical and clinical evaluation of each method. This article discusses high- and ultrasensitive techniques for detection of cardiac troponins. The modern data on biochemical and metabolic characteristics of troponins, obtained using high- and ultra-sensitive techniques, are described: sex, age, circadian features and potential for detecting troponins in other biological fluids. Considerable attention is paid to the analytical characteristics of troponin immunoassays: limit of blank, limit of detection and limit of quantitation, coefficient of variation, as well as the 99th percentile and factors influencing it.

Design and analysis of porous core photonic crystal fiber based ethylene glycol sensor operated at infrared wavelengths

A novel porous core photonic crystal fiber (PCF) sensor is reported for label-free detection of different concentrations of ethylene glycol present in aqueous solution, over a wavelength range from 1 to 2 μm. Both core and cladding are designed with elliptical air holes, which are arranged in a hexagonal structure with TOPAS as the background material. Various geometrical parameters are judiciously optimized to achieve an efficient sensor. Finite element analysis is employed for numerical simulation of the proposed structure, investigating various sensing parameters including effective refractive index, effective material loss, confinement loss, nonlinearity coefficient, shifts in peak reflected wavelengths, sensitivity, f-parameter, spot size and beam divergence angle. Simulation outcomes reveal a significant shift in the sensing parameters in response to changes in concentration of ethylene glycol, confirming the effectiveness of the sensor. Optimum wavelength sensitivity of 13,144.86 nm/RIU and resolution of $$7.46 \times 10^{ - 7}$$ RIU are attained, which provide a significant theoretical foundation for the design of novel photonic sensors. Benchmarking of the proposed PCF sensor is done against related research results to prove its superiority in terms of resolution and sensitivity.

Aptamer-Modified Ultrastable Gold Nanoparticles for Dopamine Detection

Metallic nanoparticles, in particular silver and gold nanoparticles, have been used in various fields for centuries. In the last few decades, their plasmon resonance has made them particularly attractive to biochemists because of their unparalleled optical properties, making them ideal probes for molecular detection. In this article, a new approach to dopamine detection based on ultrastable gold nanoparticles is presented. A dopamine-binding aptamer was used to modify ultrastable gold nanoparticles for the sensitive and selective detection of different concentrations of dopamine without inducing gold nanoparticles aggregation. Indeed, when dopamine binds to the aptamer present at the surface of the gold nanoparticle, the latter exhibits a plasmon shift relative to the dopamine concentration, allowing measurement of its dosage. Besides that, the target molecules can be filtered out to permit nanoparticles reuse. The detection assay showed good linearity between the dopamine concentration and gold nanoparticles' plasmon shift while common interfering molecules, such as ascorbic acid and tyramine, induced no or little plasmon shift.