Simple Detection System Research Articles

Employing Convolutional Neural Networks And Explainable Artificial intelligence for the Detection of Seizures from Electroencephalogram Signal

A seizure is a rapid, uncontrolled burst of electrical activity in the brain. Epilepsy is a neurological disorder caused by repeated seizures. Effective management requires early detection. This research aims to create a convolutional neural network (CNN) and explainable artificial intelligence (XAI) integrated system for epileptic seizure detection, using techniques such as Shapley additive explanation (SHAP) for better interpretability. The relevant data is acquired from a variety of electroencephalogram (EEG) dataset to facilitate the development of the model. To identify the EEG data, the proposed system combines deep learning models with feature extraction technique. Model visualization and XAI approaches like feature importance analysis from SHAP values offer clear insights into the model's decision-making process. Evaluation criteria like specificity and accuracy are used to assess the models' performance. This framework's objective is to create simple seizure detection systems that assist early epilepsy patient identification and individualized treatment plans. This research aims in opening the door to improved patient care and treatment by developing the field of epilepsy seizure detection.

Simple and Ultrasensitive Nanozyme-Linked Immunosorbent Assay for SARS-CoV-2 Detection on a Syringe-Driven Filtration Device.

This work proposed a simple and ultrasensitive nanozyme-based immunoassay on a filtration device for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid protein (NP). Gold core porous platinum shell nanoparticles (Au@Pt NPs) were synthesized with high catalytic activity to oxidize 3,3',5,5'-tetramethylbenzidine, leading to an oblivious color change. The filtration device was designed based on the size difference of magnetic beads, filter membrane pore, and Au@Pt NPs. A simple, rapid, and consistent washing procedure can be performed with the help of a plastic syringe. This detection method could realize the quantitative detection of SARS-CoV-2 NP within 80 min for point-of-care needs. The limit of detection for the SARS-CoV-2 antigen was 0.01 ng/mL in buffer. The coefficients of variation of the assay were 1.78% for 10 ng/mL SARS-CoV-2 antigen, 2.03% for 1 ng/mL SARS-CoV-2 antigen, and 2.34% for the negative sample, respectively. The specificity of the detection platform was verified by the detection of various respiratory viruses. This simple and effective detection system was expected to promote substantial progress in the development and application of virus immunodetection technology.

Gold nanoparticles decorated magnetic nanozyme for colorimetric detection of mercury (II) ions via enhanced peroxidase-like activity

Mercury is one of the heavy metal ions that are released to the environment through various means including anthropogenic pollution. A very low dose of mercury in environmental systems such as water can lead to debilitating effects on the health of humans and animals, if consumed untreated. To reduce this effect, it is critical to develop a simple, non-expensive, and non-sophisticated detection and monitoring system of mercury. Here, we report a simple colorimetric method based on the peroxidase-like activity of AuNPs/ZnO/Fe3O4. Different characterization techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and surface-enhanced Raman spectroscopy (SERS) were used to investigate the successful formation of these composites. The formation of AuNPs was assisted by ZnO. The low Km value (0.7368 mM) obtained from the kinetic study of the catalytic oxidation of 3, 3′, 5, 5′ − Tetramethylbenzidine (TMB) showed strong affinity of TMB to AgNPs/ZnO/Fe3O4. The peroxidase-like activity of AgNPs/ZnO/Fe3O4, was further enhanced in the presence of mercury (II). The absorption intensities of the resulting oxidized TMB (oxTMB) increased linearly in a concentration range of 0.05 – 20 µM. The method also exhibited high selectivity to mercury (II) ions. The limit of detection (LOD) in this linear range was found to be 28.1 nM. The feasibility of the method in determination of mercury (II) ions from real samples was confirmed from high recovery rates in tap water samples. The method shows a great potential for determination of mercury (II) ions in environmental samples.

Immobilization-free and label-free electrochemical DNA biosensing based on target-stimulated release of redox reporter and its catalytic redox recycling

Herein, we demonstrate a simple, homogenous and label-free electrochemical biosensing system for sensitive nucleic acid detection based on target-responsive porous materials and nuclease-triggered target recycling amplification. The Fe(CN)63− reporter was firstly sealed into the pores of Fe3O4 nanoparticles by probe DNA. Target DNA recognition triggered the controllable release of Fe(CN)63− for the redox reaction with the electron mediator of methylene blue enriched in the dodecanethiol assembled electrode and thereby generating electrochemical signal. The exonuclease III (Exo III)-assisted target recycling and the catalytic redox recycling between Fe(CN)63− and methylene blue contributed for the enhanced signal response toward target recognition. The low detection limit toward target was obtained as 478 fM and 1.6 pM, respectively, by square wave voltammetry and cyclic voltammetry methods. It also possessed a well-discrimination ability toward mismatched strands and high tolerance to complex sample matrix. The coupling of bio-gated porous nanoparticles, nuclease-assisted target amplification and catalytic redox recycling afforded the sensing system with well-controllable signal responses, sensitive and selective DNA detection, and good stability, reusability and reproducibility. It thus opens a new avenue toward the development of simple but sensitive electrochemical biosensing platform.

Ultrasensitive ECL immunosensor for trenbolone detection based on double-assisted signal amplification strategy of Nb2O5-decorated TiO2 nanorods and Co3O4-Co3(PO4)2 nanosheets

Trenbolone (TB) is used for treating malnutrition in livestock and increasing their muscle mass. However, its excessive intake can lead to metabolic and reproductive disorders in animals. In addition, it causes adverse effects in humans even at very low concentrations. Herein, an innovative electrochemiluminescence (ECL) immunosensor based on a double-assisted signal amplification strategy has been proposed for the sensitive detection of TB. Nb2O5-decorated TiO2 nanorods, with a large surface area, good biocompatibility, and excellent catalytic properties, were used as the substrates for the effective loading of TB antibodies. In addition, Co3O4-Co3(PO4)2 nanosheets, used as labels, improved the ECL signals and were used to incorporate TB antigens for designing competitive ECL immunosensors. Various experimental factors, such as the pH of the phosphate buffer solution, concentration of the co-reactant, and time of incubation, were examined. The proposed ECL immunosensor exhibited high sensitivity, good repeatability, and high stability for TB concentration and was successfully implemented for the analysis of real water samples. Under optimal conditions, the proposed immunosensor responded linearly to relevant concentrations of TB from 1.0 × 10−3 to 1.0 × 103 ng/mL, with a detection limit of 0.39 × 10−3 ng/mL (S/N = 3). Notably, this study fabricated a simple and ultrasensitive TB detection system with novelty of practical application in environmental monitoring.

Rapid quantitative detection system for measles virus-neutralizing antibodies using HiBiT-tagged virus-like particles.

Immunological testing to detect neutralizing antibodies (NAbs) is important in measles (MV) infection control. Currently, the plaque reduction neutralization testis the only credible method for measuring actual virus NAbs; however, its feasibility is hampered by drawbacks, such as long turnaround times, low throughput, and the need for laboratory biosafety equipment. To solve these problems, we developed a simple and rapid MV-NAb detection system using lentivirus-based virus-like particlesincorporated with the NanoLuc fragment peptide HiBiT comprising the MV fusion protein and hemagglutinin on their exterior surface. Overall, this simple, safe, and rapid method could be used to detect MV NAbs.

Development of an inexpensive and simple test system for the differential detection of avian influenza viruses and avian paramyxoviruses in environmental monitoring

Development of an inexpensive and simple test system for the differential detection of avian influenza viruses and avian paramyxoviruses in environmental monitoring

Guided mode resonance based phase sensing with spectral interferometry

In photonic biosensor designs, the phase-detection methods offer better sensing capabilities and lower detection limits in contrast to other conventional interrogation schemes. However, this class of detection scheme is explored very limitedly for realizing compact biosensing detection schemes. Predominantly, complex experimental setups involving bulk optical components are required for the phase interrogation scheme, which constrains the practical applicability of phase detection apart from the laboratory environment. Here, we present a common-path spectral interferometric technique utilizing a birefringent crystal and spectrometer to evaluate the phase of the guided mode resonance (GMR) signal operating in transmission mode. The common path method offers better stability and constitutes a simple and compact detection modality that can be incorporated into the practical world. A Window Fourier Transform method is implemented to extract the phase of the GMR signal. From the proposed technique, a sensitivity of 103.4 rad/RIU and a limit of detection of 9.8 × 10−5 RIU could be obtained experimentally. This method provides an improved limit of detection as compared to the conventional wavelength interrogation techniques, which also use a spectrometer as the detection system. Hence, this proposed simple and compact detection system enables the realization of highly sensitive portable biosensors.

Simultaneous detection of AFB1 and aflD gene by "Y" shaped aptamer fluorescent biosensor based on double quantum dots.

The developed method for simultaneous detection of aflatoxin B1 (AFB1) and aflD genes can effectively monitor from the source and reduce the safety problems and economic losses caused by the production of aflatoxin, which can be of great significance for food safety regulations. In this paper, we constructed a sensitive and convenient fluorescent biosensor to detect AFB1 and aflD genes simultaneously based on fluorescence resonance energy transfer (FRET) between quantum dots (QDs) and a black hole quenching agent. A stable "Y" shaped aptasensor was employed as the detection platform and a double quantum dot labeled DNA fragment was utilized to be the sensing element in this work. When the targets of AFB1 and aflD genes were presented in the solution, the aptamer in the "Y" shaped probe is specifically recognized by the target. At this time, both Si-carbon quantum dots (Si-CDs) and CdTe QDs are far away from the BHQ1 and BHQ3 to recover the fluorescence. The linear range of the prepared fluorescence simultaneous detection method was as wide as 0.5-500ng·mL-1 with detection lines of 0.64ng·mL-1 for AFB1 and 0.5-500nM with detection lines of 0.75nM for aflD genes (3σ/k). This fabricated fluorescent biosensor was further validated in real rice flour and corn flour samples, which also achieved good results. The recoveries were calculated by comparing the known and found amounts of AFB1 which ranged from 88.4 to approximately 115.32% in the rice flour samples and 90.7 ~ 102.58% in the corn flour samples. The recoveries of aflD genes ranged from 84.32 to approximately 109.3% in the rice flour samples and 89.48 ~ 100.99% in the corn flour samples. Therefore, the proposed biosensor can significantly improve food safety and quality control through a simple, fast, and sensitive agricultural product monitoring and detection system.

Modification of substrate specificity of l-arginine oxidase for detection of l-citrulline

Enzymatic detection of citrulline, a potential biomarker for various diseases, is beneficial. However, determining citrulline levels requires expensive instrumental analyses and complicated colorimetric assays. Although l-amino acid oxidase/dehydrogenase is widely used to detect l-amino acids, an l-citrulline-specific oxidase/dehydrogenase has not been reported. Therefore, in this study, we aimed to develop an l-citrulline-specific enzyme by introducing a mutation into l-arginine oxidase (ArgOX) derived from Pseudomonas sp. TPU 7192 to provide a simple enzymatic l-citrulline detection system. The ratio of the oxidase activity against l-arginine to that against l-citrulline (Cit/Arg) was 1.2%, indicating that ArgOX could recognize l-citrulline as a substrate. In the dehydrogenase assay, the specific dehydrogenase activity towards l-arginine was considerably lower than the specific oxidase activity. However, the specific dehydrogenase activity towards l-citrulline was only slightly lower than the oxidase activity, resulting in improved substrate specificity with a Cit/Arg ratio of 49.5%. To enhance the substrate specificity of ArgOX, we performed site-directed mutagenesis using structure-based engineering. The 3D model structure indicated that E486 interacted with the l-arginine side chain. By introducing the E486 mutation, the specific dehydrogenase activity of ArgOX/E486Q for l-citrulline was 3.25 ± 0.50 U/mg, which was 3.8-fold higher than that of ArgOX. The Cit/Arg ratio of ArgOX/E486Q was 150%, which was higher than that of ArgOX. Using ArgOX/E486Q, linear relationships were observed within the range of 10–500 μM l-citrulline, demonstrating its suitability for detecting citrulline in human blood. Consequently, ArgOX/E486Q can be adapted as an enzymatic sensor in the dehydrogenase system.Graphical

A simple coumarin-based system for the effective detection of superoxide in bacteria

Superoxide anion is a highly reactive ROS however the sensing of this species is relatively unexplored. The current methods to sense superoxide requires the construction of complex probes which are often hard to synthesize. With this research we report a simple one step high yielding (90%) method to prepare a probe for the detection of O2.- in bacteria using a coumarin core and trifluoromethanesulfonate locking group.

Aptamer-enhanced particle aggregation inhibition assay for simple homogeneous protein detection using DNA aptamer and thermo-responsive magnetic nanoparticles

A simple and sensitive homogeneous protein detection system is required for the early detection of biomarkers. Thermo-responsive magnetic particles (TM) have already been developed to achieve easy bound/free separation at the homogeneous protein detection system, but they are still limited owing to the requirement of secondary antibodies and negatively charged polymers, and it is challenging to control the TM aggregation behavior because of the size of the TM. Therefore, at new method to control TM aggregation behavior that is simple, easy, and highly sensitive is required. In this study, we developed a DNA aptamer-based TM assay as a simple protein detection system without additional secondary molecular recognition elements or negatively charged polymer. In the first attempt, a DNA aptamer was modified on the TM surface, and its aggregation behavior was monitored depending on the target molecule concentration. The TM aggregation rate during the heating process decreased depending on the amount of the DNA aptamer and increased depending on the target protein level. This suggests that the DNA aptamer prevented TM aggregation owing to its negative charge and achieved target protein detection owing to the cancellation of repulsion. Capturable aptamers were used in the TM assay to improve the sensitivity and limit of detection. The designed Capture DNA was modified on the TM surface, and the aptamer was captured in the presence of the target protein through a conformational change. Eventually, Capturable aptamer-based TM assay achieved a sub-nanomolar limit of detection and higher sensitivity than that of our initial investigation. Through this study and the ease of the DNA aptamer design, it was shown that the DNA aptamer-modified TM assay enabled the development of a simple and sensitive homogeneous protein detection system.

Detection of laser beams based on intensity interferometry

We describe an approach to detecting off-axis radiation of laser beams propagating in scattering media, especially in the atmosphere, in the presence of background (solar) radiation. The method relies on a generalization of the conventional intensity interferometry (II) theory to scenarios involving coexisting sources of relatively long (laser radiation) and much shorter (background) coherence times. In such circumstances, the high coherence of the laser light allows its discrimination against even much stronger, but low-coherence, background. We propose a simple detection system consisting of a small array of photodetectors (e.g. photodiodes) and estimate the ratio of the background-to-laser irradiances at which the laser radiation is expected to be detectable.

Green in situ immobilisation of gold nanoparticles on bacterial nanocellulose membranes using Tannic acid and its detection of Fe3.

Oxidative stress is one of the factors that promote melanogenesis. Trivalent iron ions play a key role in regulating the iron-catalysed oxidative stress response. A novel SERS flexible membrane sensor based on tannic acid with good sensitivity and uniformity was prepared by green in situ reduction of gold nanoparticles on bacterial cellulose membrane（BCM）with a simple and highly selective method to detect Fe3+. Under alkaline conditions, Fe3+ is adsorbed on the BCM-TA@Au NPs flexible membrane by tannic acid (TA) through chelation, thus enabling the detection of Fe3+. Furthermore, this simple detection system has a wide linear detection range and high sensitivity to effortlessly evaluate Fe3+ at concentrations up to 10-7 M. More importantly, the proposed SERS flexible substrate performed well in determining Fe3+ concentrations in B16 melanocytes, providing new insights into the factors affecting the melanin synthesis pathway and providing a potential biomarker for melanoma treatment.

PANI/Ferrous Oxide Based Hybrid Material for Ammonia Sensing Applications

AbstractIn the present study, polyaniline (PANI) and ferrous oxide (α‐Fe2O3) are amalgamated for ammonia sensing purpose. The hybrid nanocomposite is prepared by a single step in situ chemical oxidative polymerization of aniline in presence of hydrothermally prepared α‐Fe2O3 nanoparticles. The structural and compositional analyses of the hybrid material are fully executed by FTIR, PXRD, and SEM techniques. A naive, exceedingly selective, quickly restorable, and ambient temperature functioning ammonia detecting device is established by using PANI/α‐Fe2O3. The investigation results indicate that the PANI/α‐Fe2O3 hybrid nanocomposite exhibits selective sensing ability towards ammonia vapors. The PANI/α‐Fe2O3 displays excellent response for 5 ppm and maximum response for 100 ppm of ammonia. The response time of the PANI/α‐Fe2O3 sensor is found to be quick with reasonably short recovery time. Due to excellent reusability, good environmental stability, and highly economical synthesis the PANI/α‐Fe2O3 delivers a capable, simple, and efficient sensor system for ammonia detection at ambient temperature.

Dual-signal fluorescence aptasensing system for adenosine triphosphate assisting by MoS2 nanosheets

Adenosine triphosphate (ATP) has an irreplaceable role in the maintenance of many physiological processes and biological functions, and can be employed as an indicator of many diseases. In this work, we constructed a simple and sensitive dual-signal fluorescence aptasensing system for ATP detection with berberine as the signal reporter, ATP-aptamer as the recognition unit and MoS2 nanosheets as the signal amplification. In the absence of ATP, berberine can bind to the single-stranded DNA (ssDNA) of ATP-aptamer and selectively assemble on the surface of MoS2 nanosheets, leading to the fluorescence quenching of bererbine based on the fluorescence resonance energy transfer, denoted by “OFF”. Accordingly, the fluorescence anisotropy signal is enhanced due to restriction on rotate of the fluorescent probe and denoted as “ON”. Conversely, in the presence of ATP, it specifically interacts with ATP-aptamer and switches the free-curled single-stranded of ATP-aptamer to the G-quadruplex structure of ATP-aptamer/ATP/berberine, causing the detachment from the surface of the MoS2 nanosheet. Accordingly, the fluorescence signal was reversed from “OFF” to “ON”, and the fluorescence anisotropy signal was turned “ON” to “OFF”. The developed aptasensing system achieved a desirable sensitivity of 40.0 nM with fluorescent mode, and of 20.8 nM with fluorescent anisotropic mode. The sensing system has demonstrated high quality detection performance in human serum sample, and obtained the satisfactory recovery results for fluorescent of 93.0–108.5%, fluorescent anisotropic of 96.4–106.7%.

Thermal Imaging Detection System: A Case Study for Indoor Environments.

Currently, there is an increasing need for reliable mechanisms for automatically detecting and localizing people-from performing a people-flow analysis in museums and controlling smart homes to guarding hazardous areas like railway platforms. A method for detecting people using FLIR Lepton 3.5 thermal cameras and Raspberry Pi 3B+ computers was developed. The method creates a control and capture library for the Lepton 3.5 and a new person-detection technique that uses the state-of-the-art YOLO (You Only Look Once) real-time object detector based on deep neural networks. A thermal unit with an automated configuration using Ansible encapsulated in a custom 3D-printed enclosure was used. The unit has applications in simple thermal detection based on the modeling of complex scenes with polygonal boundaries and multiple thermal camera monitoring. An easily deployable person-detection and -localization system based on thermal imaging that supports multiple cameras and can serve as an input for other systems that take actions by knowing the positions of people in monitored environments was created. The thermal detection system was tested on a people-flow analysis performed in the Czech National Museum in Prague. The contribution of the presented method is the development of a small and simple detection system that is easily mountable with wide indoor as well as outdoor applications. The novelty of the system is in the utilization of the YOLO model for thermal data.

A simple agglutination system for rapid antigen detection from large sample volumes with enhanced sensitivity

Lateral flow assays (LFAs) provide a simple and quick option for diagnosis and are widely adopted for point-of-care or at-home tests. However, their sensitivity is often limited. Most LFAs only allow 50 μL samples while various sample types such as saliva could be collected in much larger volumes. Adapting LFAs to accommodate larger sample volumes can improve assay sensitivity by increasing the number of target analytes available for detection. Here, a simple agglutination system comprising biotinylated antibody (Ab) and streptavidin (SA) is presented. The Ab and SA agglutinate into large aggregates due to multiple biotins per Ab and multiple biotin binding sites per SA. Dynamic light scattering (DLS) measurements showed that the agglutinated aggregate could reach a diameter of over 0.5 μm and over 1.5 μm using poly-SA. Through both experiments and Monte Carlo modeling, we found that high valency and equivalent concentrations of the two aggregating components were critical for successful agglutination. The simple agglutination system enables antigen capture from large sample volumes with biotinylated Ab and a swift transition into aggregates that can be collected via filtration. Combining the agglutination system with conventional immunoassays, an agglutination assay is proposed that enables antigen detection from large sample volumes using an in-house 3D-printed device. As a proof-of-concept, we developed an agglutination assay targeting SARS-CoV-2 nucleocapsid antigen for COVID-19 diagnosis from saliva. The assay showed a 10-fold sensitivity enhancement when increasing sample volume from 50 μL to 2 mL, with a final limit of detection (LoD) of 10 pg mL−1 (∼250 fM). The assay was further validated in negative saliva spiked with gamma-irradiated SARS-CoV-2 and showed an LoD of 250 genome copies per μL. The proposed agglutination assay can be easily developed from existing LFAs to facilitate the processing of large sample volumes for improved sensitivity.

Superhydrophobic Rotation-Chip for Computer-Vision Identification of Drug-Resistant Bacteria.

The transport, distribution, and mixing of microfluidics often require additional instruments, such as pumps and valves, which are not feasible when operated in point-of-care (POC) settings. Here, we present a simple microfluidic pathogen detection system known as Rotation-Chip that transfers the reagents between wells by manually rotating two concentric layers without using external instruments. The Rotation-Chip is fabricated by a simple computer numerical control (CNC) machining process and is capable of carrying out 60 multiplexed reactions with a simple 30 or 60° rotation. Leveraging superhydrophobic coating, a high fluid transport efficiency of 92.78% is achieved without observable leaking. Integrated with an intracellular fluorescence assay, an on-chip detection limit of 1.8 × 106 CFU/mL is achieved for ampicillin-resistant Escherichia coli (E. coli), which is similar to our off-chip results. We also develop a computer vision method to automatically distinguish positive and negative samples on the chip, showing 100% accuracy. Our Rotation-Chip is simple, low-cost, high-throughput, and can display test results with a single chip image, making it ideal for various multiplexing POC applications in resource-limited settings.

Construction of Deoxynivalenol Enrichment and Detection System Based on Magnetosome Surface Display

Deoxynivalenol (DON) is a mycotoxin commonly found in cereals. It has strong toxicity with high stability, thus it is easy to remain in food and cause serious poisoning symptoms to consumers. To establish an efficient and simple DON detection system, a biological nano magnetic particle called bacterial magnetosomes (BMs) extracted from magnetotactic bacteria with ultrasonic crushing and magnetic adsorption was used in this study. A single-stranded DNA aptamer specifically binding to DON was coupled to the surface of MBs by two different crosslinking agents, glutaraldehyde and polyethyleneimine (PEI), respectively, to synthesize two kinds of BMs-aptamer complexes for enriching DON. Then, the adsorption rate of the complex to DON was determined by HPLC. In the results, the absolute DON adsorption capacity of 1 mg BMs-aptamer complex was 27.24 ng when glutaraldehyde was used as crosslinker and 27.64 ng when PEI was used as crosslinker. The optimization results of desorption conditions showed that under the optimal elution conditions (DNase I+methanol for 2 times), the elution rate of DON adsorbed by BMs-glutaraldehyde-aptamer reached 72.7%, while the elution rate of DON adsorbed by BMs-PEI-aptamer complex reached 64.1%. Overall, the current study enriched the applications of magnetosomes in mycotoxin detection, and also provides new idea for the efficient enrichment and recovery of DON.