Low-cost Detection Research Articles

In situ deposition of bismuth on pre-anodized screen-printed electrode for sensitive determination of Cd2+ in water and rice with a portable device

Electrochemical detection is favorable for the rapid and sensitive determination of heavy metal cadmium. However, the detection sensitivity needs to be further improved, and a portable, low-cost device is needed for on-site detection. Herein, an in-situ bismuth modified pre-anodized screen-printed carbon electrode (SPCE) was developed for Cd2+ determination by square wave anodic stripping voltammetry (SWASV). The in-situ bismuth modification enhances the enrichment of Cd2+, and together with pre-anodization improve the electron transfer rate of electrode, thus enhancing the detection sensitivity. The electrode modification method combines pre-anodization and in-situ bismuth deposition, which is very easy and effective. Furthermore, a self-made PSoC Stat potentiostat coupled with a stirring device was fabricated for portable and low-cost electrochemical detection. After comprehensive optimization, the developed method can reach a testing time of 3 min, a detection limit of 3.55 μg/L, a linear range of 5–100 μg/L, and a recovery rate of 91.7–107.1% in water and rice samples for Cd2+ determination. Therefore, our method holds great promise for the rapid, sensitive and on-site determination of Cd2+ in food samples.

Fluorescent sensor/tracker for biocompatible and real-time monitoring of ultra-trace arsenic toxicants in living cells

Real-time monitoring and tracking of extreme toxins that penetrate into living cells by using biocompatible, low-cost visual detection via fluorescent monitors are vitally essential to reduce health hazards. Herein, we report a simple engineering design of biocompatible and fluorescent sensors/trackers for real-time monitoring and ultra-trace tracking (up to ppb) of extremely toxic substances (such as arsenic species) in living cells. The biocompatible As(V) sensor (BAS) design is fabricated via successful dressing/decoration process of 2-hydroxy 5-methyl isophthalaldehyde fluorescent receptor into hierarchical organic-inorganic carriers that have micro-hollow geodes, swirled caves and nest-shaped cages, and uniform cubic structures. The BAS monitors show evidence for the selective trapping/detecting/tracking of As(V) species in biological cells (i.e., HeLa cells) despite the coexistence of highly competitive and interfered species. Our simple batch-contact sensing assays shows real-space evidence of the continuous monitoring of As(V) species in HeLa cells with ultra-sensitive detection (i.e., with a low detection limit of 0.149 ppb) and rapid recognition (i.e., in the order of seconds). Significantly, the BAS monitors did not affect the cell population and achieved low cytotoxicity and high cell viability during the monitoring/tracking process inside HeLa cells. The high biocompatibility of BAS remarkably allows precise quantification and real-time monitoring/tracking of toxicant targets in living cells.

Portable and ultrasensitive detection of traces of water in alcoholic solvents by a polypyrrole-modified screen-printed electrode

In industrial production, the water content in alcoholic solvents is crucial for determining the quality and yield of the final products, and excessive water can potentially lead to accidents. However, in-situ, rapid, and accurate detection of trace amounts of water in alcoholic solvents has been a persistent challenge. Herein, we report a screen-printed electrode (SPE) modified with electroactive polypyrrole (PPy@SPE), which enables rapid and ultrasensitive quantification of water content in four alcoholic solvents. The amine groups on PPy provide hydrogen bonding sites, which, in conjunction with the rough surface of the SPE, enhance the adsorption of alcohol molecules and decrease the electrochemical response of the PPy@SPE due to the hindrance of charge transfer. Under optimal conditions, the PPy@SPE can detect water levels as low as 0.02 %, 0.01 %, 0.01 %, and 0.01 %, in methanol, ethanol, n-propanol, and isopropanol, respectively, and can be reused for six cycles or more. Furthermore, the capability for in-situ detection of water in alcoholic solvents was demonstrated by integrating the PPy@SPE with a miniaturized potentiostat. With the advantages of being ultrasensitive, robust, low-cost, and facile detection, this sensor is potentially a valuable tool for on-site water content monitoring in chemical industries.

Advances and Prospects in Liquid Biopsy Techniques for Malignant Tumor Diagnosis and Surveillance.

Liquid biopsy technology provides invaluable support for the early diagnosis of tumors and surveillance of disease course by detecting tumor-related biomarkers in bodily fluids. Currently, liquid biopsy techniques are mainly divided into two categories: biomarker and label-free. Biomarker liquid biopsy techniques utilize specific antibodies or probes to identify and isolate target cells, exosomes, or molecules, and these techniques are widely used in clinical practice. However, they have certain limitations including dependence on tumor markers, alterations in cell biological properties, and high cost. In contrast, label-free liquid biopsy techniques directly utilize physical or chemical properties of cells, exosomes, or molecules for detection and isolation. These techniques have the advantage of not needing labeling, not impacting downstream analysis, and low detection cost. However, most are still in the research stage and not yet mature. This review first discusses recent advances in liquid biopsy techniques for early tumor diagnosis and disease surveillance. Several current techniques are described in detail. These techniques exploit differences in biomarkers, size, density, deformability, electrical properties, and chemical composition in tumor components to achieve highly sensitive tumor component identification and separation. Finally, the current research progress is summarized and the future research directions of the field are discussed.

An Ultra-Compact and Low-Cost LAMP-Based Virus Detection Device.

Timely and accurate detection of viruses is crucial for infection diagnosis and treatment. However, it remains a challenge to develop a portable device that meets the requirement of being portable, powerless, user-friendly, reusable, and low-cost. This work reports a compact ∅30 × 48 mm portable powerless isothermal amplification detection device (material cost ∼$1 USD) relying on LAMP (Loop-Mediated Isothermal Amplification). We have proposed chromatographic-strip-based microporous permeation technology which can precisely control the water flow rate to regulate the exothermic reaction. This powerless heating combined with phase-change materials can maintain a constant temperature between 50 and 70 °C for a duration of up to 49.8 min. Compared with the conventional methods, it avoids the use of an additional insulation layer for heat preservation, greatly reducing the size and cost. We have also deployed a color card and a corresponding algorithm to facilitate color recognition, data analysis, and storage using a mobile phone. The experimental results demonstrate that our device exhibits the same limit of detection (LOD) as the ProFlex PCR for SARS-CoV-2 pseudovirus samples, with that for both being 103 copies/μL, verifying its effectiveness and reliability. This work offers a timely, low-cost, and easy way for respiratory infectious disease detection, which could provide support in curbing virus transmission and protecting the health of humans and animals, especially in remote mountainous areas without access to electricity or trained professionals.

Microsyringe-assisted visual volume detection based on phase separation: the case of chymosin milk-clotting activity study.

The constantly diverse demand scenarios for rapid on-site analysis have put forward high requirements for developing low-cost and user-friendly visual detection methods. Therefore, developing a visual detection method with simple operation and intuitive results has important practical value in the field of analysis and detection, but it is also challenging. In this work, we propose a microsyringe-assisted visual volume detection method based on phase separation, and apply it to analyze the milk-clotting activity of chymosin. Chymosin can cause phase separation of milk with whey in the mobile phase and curd in the gel state. The network structures of casein in curd can trap water molecules, resulting in separation of whey from curd gradually. Therefore, the analysis of chymosin milk-clotting activity can be realized according to the volume of whey measured using a portable microsyringe. This method shows a good linear correlation when the concentration of chymosin ranges from 1.02 U L-1 to 1020 U L-1 and the limit of detection of this method for chymosin is calculated to be 0.03 U mL-1. This work successfully realizes the visual analysis of chymosin milk-clotting activity based on the enzyme-triggered phase separation. It also shows great promise to be applied in other phase separation-based detection systems with the advantages of high accuracy, great portability and user-friendliness.

Nucleobase-modulated copper nanomaterials with laccase-like activity for high-performance degradation and detection of phenolic pollutants

Laccases are the most commonly used agents for the treatment of phenolic pollutants. To address the instability and high cost of natural laccases, we investigated nucleobase-modulated copper nanomaterial with laccase-like activity. Various nucleobases, including adenine, guanine, cytosine, and thymine, were investigated as templates for Cu2+ reduction and copper nanomaterials formation due to their coordination capacity. By comparing structure and catalytic activity, the cytosine-mediated copper nanomaterial (C–Cu) had the best laccase-like activity and other nucleobase-templated copper nanomaterials exhibited low catalytic activity under the same conditions. The mechanism of nucleobase regulation of the catalytic activity of copper nanomaterials was further analyzed using X-ray photoelectron spectroscopy and density functional theory. The possible catalytic mechanisms of C–Cu, including substrate adsorption, substrate oxidation, oxygen binding, and oxygen reduction, were proposed. Remarkably, nucleobase-modulated copper nanozymes showed high stability and catalytic oxidation performance at various pH values, temperatures, long-term storage, and high salinity. In combination with electrochemical techniques, a portable electrochemical sensor for measuring phenolic pollutants was developed. This novel sensor exhibited a good linear response to catechol (10–1000 μM) with a limit of detection of 1.8 μM and excellent selectivity and anti-interference ability. This study provides not only a new strategy for the regulation of the laccase-like activity of copper nanomaterials but also a novel tool for the effective removal and low-cost detection of phenolic pollutants.

Low-Cost Early Detection Device for Breast Cancer based on Skin Surface Temperature

One of the deadly diseases that attacks many women is breast cancer. It was recorded that breast cancer cases in 2020 were 2.3 million, with deaths accounting for 29% of these cases. The BSE technique is an easy way of early identification of breast cancer that can be done independently. However, this technique often goes wrong when practiced, making it ineffective. An early breast cancer detection system is proposed to make it easier for women to carry out early identification independently. Detection is carried out based on the measured temperature of the breast surface. The temperature difference at each point is a reference for the potential for breast cancer. This system was built in a bra and tested with a mannequin as a simulator subject. The MLX90614 temperature sensor, as the primary sensor, succeeded in measuring the surface temperature of the dummy with 99% accuracy. Final testing of the proposed system can also differentiate the temperature differences in each zone.

A novel approach for rapid and quantitative immunodetection of Brucella abortus, leveraging carbon nanotubes to enhance electrochemical responses

This work presented a high-performance inmunosensor for detecting B. Abortus onto a transducer nanomaterial. Low-cost and rapid detection is achieved using single-walled carbon nanotubes (SWCNT), protein A solution (pAs), and antibodies from B. Abortus (AB-B) as detection and selection components. The inmunosensor was characterized by microscopy (TEM, CLSM, SEM) and spectroscopy (FTIR, Raman) techniques, while a suitable build was achieved. The electrochemical responses show excellent selectivity for B. Abortus and stability under current with a highly responsive and sensitive response that can be used decentralized from the laboratory.

Graphitic carbon @ silver nanoparticle @ porous silicon Bragg mirror composite SERS substrate for gallic acid detection

Graphite carbon (G) @ silver (Ag) @ porous silicon Bragg mirror (PSB) composite SERS substrate was successfully synthesized using electrochemical etching (ec) and hydrothermal carbonization (HTC) techniques with silver nitrate as the source of silver and glucose as the source of carbon. The PSB was used as a functional scaffold for the synthesis of graphite-carbon and silver composite nanoparticles (G@AgNPs) on its surface, thereby combining SERS activity and antioxidant properties. To our knowledge, this is the first time that G@AgNPs has been synthesized on the PSB using glucose as a carbon source. The synthesized G@Ag@PSB was utilized as a SERS platform for the detection of gallic acid (GA). Test results demonstrated that the substrate exhibited a remarkable SERS enhancement capability for GA, with the enhancement factor (EF) reaching 2 × 105. The reproducibility of the SERS spectral signal was excellent, with a relative standard deviation (RSD) of 7.5 %. The sensitivity test results showed that the linear range of GA detection based on G@Ag@PSB composite SERS substrate was 2 × 10-3-2 × 10-12M. The relationship between GA concentration and SERS signal intensity exhibited a strong linear correlation, with a linear correlation coefficient (R2) of 0.97634. Moreover, even with an extended storage period, only a marginal decline in the signal intensity of GA on the substrate was observed. The results of this study demonstrate that the prepared G@Ag@PSB composite SERS substrate had good potential application performance as a low-cost SERS detection platform suitable for commercial use. In addition, this advance facilitates the further exploration of more nanomaterials with ultra-high sensitivity in SERS technology.

A novel electrochemical ammonia sensor based on Pt NPs@MIL101(Cr)-NH2 for chemical leaks detection at room temperature

Achieving the real-time, low-cost, portable and accurate NH3 detection is of great importance in industry owing to the toxicity of NH3. In this paper, Pt NPs@MIL-101-NH2 composites modified screen-printed electrodes (SPEs) were prepared by solvothermal method and ionic liquids [BMIM][BF4] were used as electrolytes. Finally, the prepared Pt NPs@MIL-101-NH2/SPEs were combined with a miniature electrochemical workstation to construct a novel electrochemical NH3 sensor. The experimental results showed that Pt NPs@MIL-101-NH2 has excellent adsorption capacity for NH3, and the sensor has good linearity in the range of 0.7–600 ppm with low limit of detection (0.58 ppm) and fast response time for 10 ppm NH3 (8.0 s). Furthermore, this sensor also possesses excellent stability, reproducibility, anti-interference and accuracy. The synthesized Pt NPs@MIL-101-NH2 nanocomposite was proved to be an excellent candidate for constructing high-performance NH3 sensor for industry.

Selective and ultrasensitive detection of the herbicide glyphosate by means of plasmon catalysis on Ag nanoparticles

This work aims at the detection of the important herbicide glyphosate based on the previous modification of glyphosate in two stages and final detection by surface-enhanced Raman spectroscopy (SERS). In a first step, the affinity of glyphosate for metal plasmonic surfaces was increased by inclusion of a sulphur containing group (dithiocarbamate). In a second step, the cyclization of the latter intermediate rendered a thiazole derivative of the herbicide. The latter compound exhibits higher Raman cross section which leads to stronger SERS enhancement factors. The second step was possible thanks to the plasmon catalysis driven by metal nanoparticles, specifically silver adatoms created at the surface, and irradiated at a proper wavelength. This methodology was optimized by selecting the most appropriate experimental conditions for the chemical reactions. Density Functional Theory treatment of all the involved molecules was done in order to obtain the theoretical spectra and to identify the structural marker bands. A key goal of this work was to develop an effective system of glyphosate detection based on portable PickMolTM technology developed and patented by the SAFTRA Photonics Ltd. company to ensure an easy, quick, low cost, in-situ, and univocal detection of glyphosate in the environment.

Rapid, Low-Cost, and Portable Detection of Morphine and Codeine on Poppy Seeds via a Lateral Flow Immunoassay

Rapid, Low-Cost, and Portable Detection of Morphine and Codeine on Poppy Seeds via a Lateral Flow Immunoassay

Preparation of Mxene-AuNPs/TGA nanocomposites explored as an electrochemical aptasensor for Digoxin analysis

Despite the existence of numerous methods for measuring digoxin, advancements in science have led to improvements in methods, making it possible to measure very low levels of this drug. However, considering the high cost of previous methods, new methods are being developed, allowing for the measurement of very low amounts of this drug. An aptasensor was prepared by attaching digoxin aptamer to a Mxene and gold nanoparticles-modified screen-printed carbon electrode via thioglycolic acid molecules (SPCE/Mxene-AuNPs/TGA/Apt). The physicochemical features of the nanocomposite synthesized were characterized Microscopic and voltammetry techniques. The presence of Mxene, AuNPs, and TGA species all together contributed to the expansion of the active surface area, facilitating electron transfer phenomena, and improving the electrical conductivity, stability, and longevity of the prepared aptasensor. The detection limit of 0.03 pM was calculated based on a criterion of S/N = 3.Furthermore, the biosensor exhibited excellent stability and a prolonged shelf life, with a low detection cost of under 100 USD per sample. Given these benefits, the authors are confident that the electrochemical biosensor developed using Mxene-AuNPs/TGA for enhanced signal amplification offers a promising strategy for detecting digoxin in environmental samples.

Signal processing implementation of low-cost target speed detection of CW radar using FPGA

The low-cost Continuous Wave (CW) radar architecture for object speed detection is presented in this research. An FPGA (Field-Programmable Gate Array) processor is utilized to implement the CW radar dependably and optimally. The suggested approach uses a bank of filters made expressly to extract velocity information from radar signals to compute the target velocity. Depending on the needs of the particular application, the acquired data has either undergone additional processing or been presented in an approachable manner. The implemented design is checked in real-time with a chip scope, functionally simulated, and then inspected with lab instruments to compare all simulated and implemented outcomes. Numerous applications, such as industrial automation, surveillance, and automotive systems, where accurate velocity detection is crucial and low-cost design is required, could benefit from this concept.

Polydopamine modified colloidal gold nanotag-based lateral flow immunoassay platform for highly sensitive detection of pathogenic bacteria and fast evaluation of antibacterial agents

Bacterial infection is a great threat to human health. Lateral flow immunoassays (LFIAs) with the merits of low cost, quick screening, and on-site detection are competitive technologies for bacteria detection, but their detection limits depend on the optical performance of the adopted nanotags. Herein, we presented a LFIA platform for bacteria detection using polydopamine (PDA) functionalized Au nanoparticles (denoted as Au@PDA) as the nanotag. The introduction of PDA could provide enhanced light absorption of Au, as well as numerous functional groups for conjugation. Small recognition molecules i.e. vancomycin (Van) and p-mercaptophenylboronic acid (PMBA) were covalently anchored to Au@PDA, and selected as the specific probes towards Gram-positive (G+) and Gram-negative (G—) bacteria, respectively. Taken Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) as the representative targets of G+ and G— bacteria, two LFA strips were successfully constructed based on the immuno-sandwich principle. They could quantitatively detect S. aureus and E. coli both down to 102 cfu/mL, a very competitive detection limit in comparison with other colorimetric or luminescent probes-based LFIAs. Furthermore, the proposed two strips were applied for the quantitative, accurate, and rapid detection of S. aureus and E. coli in food and human urine samples with good analytical results obtained. In addition, they were integrated as a screening platform for quick evaluation of diverse antibacterial agents within 3 h, which is remarkably shortened compared with that of the two traditional methods i.e. bacterial culture and plate-counting.

Preparation of W-N-C single atom catalyst and Cu3(HHTP)2 metal-organic framework dual-decorated graphene nanoplatelet flexible electrode arrays for the rapid detection of carbendazim in vegetables

It is highly desirable to develop a low-cost and rapid detection method for trace levels of carbendazim fungicide residues, which would be beneficial for improving human health and mitigating environmental issues. Herein, isolated single tungsten atoms were implanted onto well-organized metal–organic framework (MOF)-derived N-doped carbons to form W-N-C single-site heterojunctions with ultrahigh electrocatalytic activity. The coupling of W-N-C with Cu3(HHTP)2, an electronically conductive MOF with a large surface area and porous structure, exhibited enhanced electrocatalytic performance for the oxidation of carbendazim (CBZ) when they were used for decorating graphene nanoplatelet flexible electrode arrays fabricated via template-assisted scalable filtration. A wide linear range (3.0 nM–50 μM) with an ultra-low detection limit of 0.97 nM and fast response was achieved for CBZ analysis. Moreover, the sensing platform has been utilised to monitor CBZ levels in vegetable samples with satisfactory recovery rates of 97.2–102% and a low relative standard deviation of 1.9%.

Low-cost and scalable detection of sparse informal settlements using machine learning in Gcuwa, Eastern Cape, South Africa

ABSTRACT Informative and scalable cartography plays a pivotal role in curbing urban pollution, waste management, and mitigating environmental damage in the development of informal settlements. The contemporary capabilities of cloud computing facilitate streamlined access to comprehensive data repositories, computational infrastructure, and proficient tools that have rapidly advanced the execution of sprawl mapping procedures. This study tests the performance of four machine-learning algorithms, namely: Gradient Boost, K Nearest Neighbor [KNN], Random Forest [RF], and Support Vector Machine [SVM] with data extracted from cloud computing repositories for delineating informal settlements in Gcuwa, Eastern Cape, South Africa, using low-cost datasets. A systematic approach comprising iterative phases, encompassing data acquisition, the development of a training dataset, modeling, and evaluation was employed. The delineation process involved the extraction of both spectral and textural features from Sentinel-2 imagery. The Random Forest algorithm emerged as the top performer, exhibiting the highest levels of accuracy and F1 score, followed by the gradient boosting, support vector machine, and then the K-nearest neighbor algorithms. Consequently, this innovative use of machine learning algorithms with low-cost datasets and the scalable, resilient approach for detecting informal settlements offers a promising avenue for enhancing urban planning and addressing sustainable development challenges.

Comparison of qualitative and quantitative performance of two portable near-infrared spectrometers for intact Rehmanniae Radix and calibration transfer

As a Chinese herbal medicine with high medical value, Rehmanniae Radix (RR) has a wide variety of geographical origins leading to distinctly diverse quality, and moisture content during storage affects the critical active ingredient content. In this work, two portable near-infrared (NIR) spectrometers, DLP NIRscan Nano (DLP) and VIAVI MicroNIR 1700 (M1700) were used for in-situ spectral acquisition from intact RR. The partial least squares-discriminant analysis (PLS-DA) was employed for three geographical sources (Shandong, Shanxi, Henan). After multiple pre-processing and wavelength selection, the M1700-based PLS-DA model, accuracy (Acc), sensitivity (Sen), and specificity (Spe), achieved 100 % accuracy. In contrast, model predictions using the low-cost instrument (DLP) was not satisfactory. The partial least squares regression (PLSR) was applied to predict the moisture content of RR. The best correlation coefficients in the prediction set (R2p), Root Mean Square Error of Prediction (RMSEP), and residual prediction deviation (RPD) values (0.98, 0.98, 4.98) were obtained by DLP and were also employed for comparison with the M1700 model (0.99, 0.70, 7.00). Therefore, to further improve the model prediction effect of the low-cost DLP, we employed the improved principal component analysis (IPCA), direct standardization (DS), and piecewise direct standardization (PDS) calibration transfer techniques. Unequivocally, IPCA optimized the origin identification model (Acc, Sen, and Spe were all 1.00), the moisture content prediction model RPD was increased by 23 %, and its RMSEP was reduced by 18 %, leading to the improvement in prediction accuracy of the DLP model. This study provides a portable and low-cost detection method for the in-situ evaluation of the quality of RR quality and a feasible solution for the NIR techniques to be used in the rapid and accurate in-situ analysis of RR.

Miniature snapshot mid-infrared spectrometer based on metal-insulator-metal metasurface

Metasurfaces showcase the performance of light field manipulation at the subwavelength scale, generating tremendous applications in the field of optical imaging and sensing, especially in spectroscopic detection. Here, we demonstrate a spectral detector comprising metal-insulator-metal composite structures working in the mid-infrared band, which can effectively collect and restore target spectral characteristics in the mid-infrared band with a trained reconstruction algorithm. The proposed device consists of snapshot multichannel detection and spectral reconstruction, showing an average spectral reconstruction accuracy approaching 80% of the system. Moreover, we discuss the feasibility of applying this structural design to a miniature spectrometer over a wider infrared wavelength range by proposing a feasible design strategy. Our results provide a novel approach for low-cost and portable mid-infrared spectroscopic detection in ultracompact mid-infrared spectral imaging and sensing elements.