Sensors & diagnostics最新文献

This article presents a simple and cost-effective headspace paper-based analytical device (hPAD) for the quantification of ammonia in human biological samples. The aim of this approach is to enhance the detection selectivity for ammonia in complex samples. The detection principle leverages basic chemistry, wherein ammonia reacts with copper sulfate (CuSO₄) to form the complex ion tetraamminecopper(II) sulfate ([Cu(NH₃)₄]SO₄), resulting in a colour change from pale blue to dark blue on a paper substrate. The quantitative analysis of ammonia is straightforward through placement of the sensor on the inside lid of the sample vial, and the resulting colour change is measured using a smartphone and image processing software. Upon optimization, the developed assay demonstrated a linear range between 2.5 and 40.0 μM (R² = 0.9955) with a detection limit (LOD) of 0.90 μM. The sensor also exhibited high precision, with the highest relative standard deviation (RSD) recorded at 6.17%. Moreover, the method showed remarkable selectivity, as the sensor showed no response to common interfering molecules in a complex biological matrix. The technique is fast, requiring only 4 min for the reaction, and does not necessitate any heating procedures. Furthermore, the developed method provides excellent accuracy for detecting ammonia levels in both human serum and urine samples, with recovery rates ranging from 93.4% to 107.6%. Therefore, the hPAD offers a simple and affordable solution by sensing in the headspace that overcomes the limitations of direct measurement in the sample, which may be affected by the colour, pH, other existing ions and molecules in the sample solution. Overall, this approach is suitable for various applications in both medical and environmental analysis.

The design and fabrication of sensor probes to check food freshness and assess food quality is an essential area of research. Every year, millions of people are affected by food poisoning and fall victim to foodborne-related health problems. Cadaverine (1,5-pentanediamine) is a biogenic amine and an important biomarker to determine food freshness. Measuring cadaverine concentration allows us to assess the quality and freshness of food. Recently, fluorescence-based sensing methods have been used extensively as a viable probe to measure cadaverine concentrations. In this review article, we have summarized reactivity-based small-molecule fluorescence chemosensors reported to date for sensing and quantification of cadaverine. We provide a detailed discussion of the design, synthesis, and fluorescence-sensing properties of several small-molecule sensors employed for cadaverine detection. Lastly, the limitations of existing fluorescence sensors and our view on future perspectives for developing practically useful fluorescence sensor systems for real-time monitoring of the concentrations of cadaverine biomarkers have been stated. Given its importance, this review article will attract and greatly benefit scientists working in related research areas.

There have been notable advancements in the technology associated with using waste resources to create novel and beneficial products. This study demonstrates that the kernel part of Azadirachta indica (Neem) seeds can be sustainably used for this purpose. Carbon dots (CDs) of approximately ca. 4–8 nm in size were synthesized from the kernel Azadirachta indica seeds through calcination, followed by surface modification using diethylamine, sodium methoxide, and alcohol. This produced waste seed-derived luminous surface-quaternized CDs (Ai-CDs). These CDs were used as a fluorescent nanoprobe to detect inorganic contaminants at concentrations ranging from low (5 μM) to high (120 μM), due to their strong photostability and excitation-dependent emission in aqueous solutions. Ai-CDs were used to measure the levels of Cd⁺² and As³⁺ in solution through quenching of luminescence intensity (“turn-off”), while cupric ions (Cu⁺²) selectively increased fluorescence (“turn-on”) for sensing. The current method of synthesising CDs offers quick reaction times, along with great selectivity and sensitivity. The CDs preferentially absorbed Cd²⁺ and As³⁺, causing a sharp dimming in fluorescence intensity by 27% and 30%, respectively. In contrast, for Cu⁺² and Cu⁺ the fluorescence intensity was enhanced. Consequently, this unique characteristic was utilized to exclude and identify Al³⁺, Cd²⁺, Mn²⁺, Ni²⁺, Co²⁺, Cu²⁺, and Cu⁺ ions, with detection limits ranging from 5 μM to 120 μM. Furthermore, we demonstrated the heavy metal ion sensing activity of CDs from their salt solutions, highlighting their potential as environmentally friendly metal ion detection agents. A cell viability assay was carried out, revealing that the CDs are non-toxic.

The reusability of biosensors is a crucial advancement in environmental monitoring and laboratory efficiency. In this study, we introduce the concept of a regenerable aptasensor based on digital photocorrosion (DIP) of a GaAs–AlGaAs biochip, designed with alternating nanolayers of GaAs (12 nm) and AlGaAs (10 nm). Each GaAs–AlGaAs bilayer acts as an independent sensing unit. By employing a specific thiolated aptamer, we achieve efficient detection of Bacillus thuringiensis spp. kurstaki spores. The interaction between the thiolated aptamers with the targeted spores leads to the formation of aptamer-spore hybrids, which bind to the GaAs surface. The GaAs–AlGaAs nanoheterostructure biochip supports multiple biosensing cycles. After consumption of the first GaAs–AlGaAs bilayer, a simple regeneration step with a high ionic strength buffer releases the bound spores and prepares subsequent nanolayers of the same biochip for reuse. The capability to regenerate and reuse individual nanolayers presents a novel and practical solution for reducing biosensor waste while improving operational efficiency. We further explore the conditions necessary for sustainable DIP operation in biochips containing multiple GaAs–AlGaAs nanolayer pairs, ensuring reliable performance over numerous biosensing cycles. Our findings establish a cost-effective and durable biosensing platform. This work marks a significant step toward quasi-autonomous biosensing technologies, paving the way for cost-effective and robust reusable biosensors suitable for remote and field applications.

Nitrate ions are widespread environmental pollutants in water and soil, posing critical risks to both human health and ecosystems. This study introduces a molecular cage as a novel ionophore for potentiometric nitrate-selective ion-selective electrodes (ISEs) designed for enhanced specificity and sensitivity. Among six synthetic candidates, the electrode incorporating a 1,3,5-tri(p-hydroxyphenyl)benzene-based chlorotriazine pillared cage molecule (CAGE-1) exhibited superior performance, characterized by a linear response in the nitrate concentration range of 1.0 × 10⁻⁵ to 1.0 × 10⁻¹ M, with a high coefficient of determination (R² = 0.9971) and a slope of −53.1 ± 1.4 mV dec⁻¹. The electrode also achieved a limit of detection of 7.5 × 10⁻⁶ M. These findings highlight the potential of molecular cages as ionophores for nitrate sensing in environmental applications.

MicroRNAs (miRNAs) regulate gene expression and are important biomarkers in molecular diagnostics, prognosis, and personalized medicine. The miRNAs that are found within exosomes, also known as exo-miRs, have been shown to demonstrate increased levels of both abundance and stability. Thus, exo-miRs show potential as a reliable biomarker for further investigation. Due to the programmable nanostructures, biocompatibility, and excellent molecular recognition ability, biosensing platforms based on DNA nanomaterial are considered promising for detecting exo-miRs in clinical analysis, including cancer, neurodegenerative disorders, and infectious diseases. Although considerable advancements have been achieved in exo-miR-based testing, there are ongoing challenges in accurately detecting and analyzing multiple targets concurrently at low concentrations in complex biological samples. The primary focus of our research is to thoroughly analyze the biogenesis of exo-miRs, carefully assess their levels of expression in various clinical diseases, and comprehensively investigate their correlations with a wide range of diseases, including cancer, infection, and neurodegenerative disorders. We also examined recent progress in DNA nanomaterial-based detection methods for exo-miRs. This study explores the challenges and intricacies faced during the creation and execution of exo-miR tests within a clinical setting to diagnose diseases. The successful development and implementation of DNA nanomaterials for exo-miR detection can significantly revolutionize the early detection, monitoring, and management of various medical conditions, leading to enhanced healthcare outcomes.

A method was developed for quantifying single-stranded DNA (ssDNA) through enzymatic digestion and using commercially available glucose test strips. The process involves the initial digestion of ssDNA using a combination of exonuclease 1 and alkaline phosphatase enzymes, leading to the liberation of phosphates from the ssDNA backbone as free orthophosphate. Subsequently, the orthophosphates react with maltose and maltose phosphorylase, producing equivalent amounts of glucose to orthophosphate. The resulting glucose, which can be related to the ssDNA concentration, can be measured amperometrically with an off-the-shelf glucose test strip connected to a mini potentiostat. This method offers versatility, allowing the determination of ssDNA, regardless of nucleotide-count or sequence, with increased sensitivity as the number of nucleotides (NT) in the DNA increases. The method exhibits a limit of detection of 780 nM for 22-NT, 527 nM for 53-NT, 422 nM for 75-NT, and 329 nM for 87-NT ssDNA, and a linear range of 0–2 μM. To selectively quantify a specific ssDNA target, a magnetic microparticle-based isolation step was incorporated, demonstrating high selectivity for quantifying a particular ssDNA target from a mixture. The method holds potential for label-free quantification of ssDNA that can have an impact in myriad fields.

The development of paper-based systems has revolutionized point-of-care (POC) applications by enabling rapid, robust, accurate and sensitive biochemical analysis, infectious disease diagnosis, and fertility monitoring, in particular, in male fertility monitoring, offering portable, cost-effective solutions compared to traditional methods. This innovation addresses high costs and limited accessibility of male fertility testing in resource-poor settings. Male infertility, a significant issue globally, often faces stigma, hindering men from seeking care. This study introduces a novel approach to male fertility testing using colorimetric analysis of paper-based assays, enhanced by synthetic imagery and the YOLOv8 (You Only Look Once) object detection algorithm. Synthetic imagery was employed to train and fine-tune YOLOv8, enhancing its capability to accurately detect color changes in paper-based tests. This colorimetric detection leverages smartphone imaging, making it both accessible and scalable. Initial experiments demonstrate that YOLOv8’s precision and efficiency, when combined with synthetic data, significantly enhance the system's ability to recognize and analyze colorimetric signals, positioning it as a promising tool for male fertility POC diagnostics. In our study, we evaluated 39 semen samples for pH and sperm count using standard clinical tests, comparing these results with a novel paper-based semen analysis kit. This kit utilizes reaction zones that exhibit color changes when exposed to semen samples, with images captured using a smartphone under varied lighting conditions. Despite a limited number of images, our synthetically trained YOLOv8 model achieved an accuracy of 0.86, highlighting its potential to improve the reliability of colorimetric analysis for both home and clinical use.

Paper-based sensors have been widely used thanks to their potential for creating simple, low-cost, and sustainable analytical devices, making them particularly suitable for environmental monitoring. The aim of this work is to develop a ready-to-use colorimetric paper sensor, based on the Griess reaction, for nitrite on-site monitoring. We here address the requirement for a sustainable, sensitive, and low-cost nitrite sensor that combines, for the first time i) the use of paper as a support, ii) the immobilization of Griess reagents, iii) the origami strategy for triggering chemical reactions without the need for handling chemicals, and iv) a smartphone as a detector for quantitative measurements. While previous sensors for nitrite detection rely on a complex assay workflow and require separate instrumentation, our paper sensor simply needs a smartphone or, for qualitative results, the naked eye for instrument-free detection. The paper sensor showed satisfactory analytical performance for analysis of drinking water with recoveries from 87 to 110% and limits of detection and quantification for NO₂⁻ of 0.27 mg L⁻¹ and 1.11 mg L⁻¹, respectively. The sustainability of the sensor was also evaluated supporting its potential use for rapid monitoring of nitrites across a range of applications, including water quality assessment in agricultural runoff, wastewater treatment, and surface water monitoring.

Nitric oxide (NO) is a ubiquitous and important biological mediator. However, its detection and chemical analysis are challenging due to its short lifetime in biological conditions. Paper-based NO sensors combining the ease of fabrication and affordability of paper with the quantitative capabilities of electrochemical methods are presented for the detection and quantification of NO in cultured cells. Nafion-coated and eugenol-functionalized paper devices were built and characterized using a NO donor. The electrochemical interferences from nitrite, a common interferent for NO sensing, were successfully screened out. Finally, preliminary data were obtained from 100 000 endothelial cells cultured directly, in an extracellular matrix, on the paper device. In response to vascular endothelial growth factor exposure, NO secretion was detected and quantified.