Highly sensitive paper-based electrochemical sensor for reagent free detection of bisphenol A

Snowflake Cu2S@ZIF-67: A novel heterostructure substrate for enhanced adsorption and sensitive detection in BPA

Developing semiconductor substrates with superior stability and sensitivity is challenging in surface-enhanced Raman scattering (SERS) research. Here, a snowflake Cu2S@ZIF-67 heterostructure was fabricated using a straightforward method, exhibiting a notable enhancement factor of 9.0 × 109 and a limit of detection (LOD) of 10-14 M for methylene blue (MB). In addition, the Cu2S@ZIF-67 heterostructure substrate demonstrates outstanding homogeneity (relative standard deviation (RSD) = 9.2%) and stability (120 days). Employing Cu2S generates highly sensitive hotspots via an electromagnetic (EM) mechanism, and the growth of ZIF-67 on its surface augments the adsorption capacity and charge transfer capability (chemical mechanism, CM), thereby enhancing the SERS detection sensitivity. Furthermore, the Cu2S@ZIF-67 heterostructure, which was used as a SERS substrate, facilitated the detection of bisphenol A (BPA) with an LOD of 10-11 M. The Cu2S@ZIF-67 heterostructure substrate has excellent selectivity and anti-interference, which is very suitable for BPA detection in complex environment applications. The accuracy of the Cu2S@ZIF-67 heterostructure as a SERS substrate for detecting BPA in real water samples (water bottles, tap water, and pure milk) was confirmed by comparison with high-performance liquid chromatography (HPLC). These results demonstrate that through the rational design of heterostructures can achieve the quantitative and accurate detection of hazardous substances in food and the environment can be achieved.

Covalent organic framework reinforced hollow fiber bar for extraction and detection of bisphenols from beverages

Bisphenols (BPs) can migrate from packaging materials into foods, resulting in potentially harmful residues. For example, accumulation of BPs is associated with endocrine disorders. Owing to matrix effects, development of an effective and eco-friendly sample pretreatment would be helpful for BPs detection in beverages packed in plastic containers. In this work, an extraction bar, composed of hollow fiber (HF) functionalized with covalent organic frameworks (COF@Tp-NDA) and 1-ocanol, was prepared for extraction of five BPs simultaneously. The synergistic effect of COF@Tp-NDA and 1-octanol improved the extraction efficiency of BPs from milk-based beverage, juice, and tea beverage. Under optimal conditions, limits of detection ranged from 0.10 to 2.00 ng mL-1 (R2 ≥ 0.9974) and recoveries ranged from 70.1 % to 106.8 %. This method has the potential to enrich BPs, supporting their accurate determination in complex beverages.

Paper-Based Electrochemical (Bio)Sensors for the Detection of Target Analytes in Liquid, Aerosol, and Solid Samples

The last decade has been incredibly fruitful in proving the multifunctionality of paper for delivering innovative electrochemical (bio)sensors. The paper material exhibits unprecedented versatility to deal with complex liquid matrices and facilitate analytical detection in aerosol and solid phases. Such remarkable capabilities are feasible by exploiting the intrinsic features of paper, including porosity, capillary forces, and its easy modification, which allow for the fine designing of a paper device. In this review, we shed light on the most relevant paper-based electrochemical (bio)sensors published in the literature so far to identify the smart functional roles that paper can play to bridge the gap between academic research and real-world applications in the biomedical, environmental, agrifood, and security fields. Our analysis aims to highlight how paper's multifarious properties can be artfully harnessed for breaking the boundaries of the most classical applications of electrochemical (bio)sensors.

Microfluidic sensors for the detection of emerging contaminants in water: A review

In recent years, numerous emerging contaminants have been identified in surface water, groundwater, and drinking water. Developing novel sensing methods for detecting diverse emerging pollutants in water is urgently needed, as even at low concentrations, these pollutants can pose a serious threat to human health and environmental safety. Traditional testing methods are based on laboratory equipment, which is highly sensitive but complex to operate, costly, and not suitable for on-site monitoring. Microfluidic sensors offer several benefits, including rapid evaluation, minimal sample usage, accurate liquid manipulation, compact size, automation, and in-situ detection capabilities. They provide promising and efficient analytical tools for high-performance sensing platforms in monitoring emerging contaminants in water. In this paper, recent research advances in microfluidic sensors for the detection of emerging contaminants in water are reviewed. Initially, a concise overview is provided about the various substrate materials, corresponding microfabrication techniques, different driving forces, and commonly used detection techniques for microfluidic devices. Subsequently, a comprehensive analysis is conducted on microfluidic detection methods for endocrine-disrupting chemicals, pharmaceuticals and personal care products, microplastics, and perfluorinated compounds. Finally, the prospects and future challenges of microfluidic sensors in this field are discussed.

One-step growth of Cu-doped carbon dots in amino-modified carbon nanotube-modified electrodes for sensitive electrochemical detection of BPA

Copper-doped carbon dots and aminated carbon nanotubes (Cu-CDs/NH2-CNTs) nanocomposites were synthesized by a one-step growth method, and the composites were characterized for their performance. An electrochemical sensor for sensitive detection of bisphenol A (BPA) was developed for using Cu-CDs/NH2-CNTs nanocomposites modified with glassy carbon electrodes (GCE). The sensor exhibited an excellent electrochemical response to BPA in 0.2 M PBS (pH 7.0) under optimally selected conditions. The linear range of the sensor for BPA detection was 0.5-160 μM, and the detection limit (S/N = 3) was 0.13 μM. Moreover, the sensor has good interference immunity, stability and reproducibility. In addition, the feasibility of the practical application of the sensor was demonstrated by the detection of BPA in bottled drinking water and Liu Yang River water.

A dual-mode assay kit using a portable potentiostat connected to a smartphone via Bluetooth communication and a potential-power angle-based paper device susceptible for low-cost point-of-care testing of iodide and dopamine

BACKGROUND

Considering that the brain controls most of the body's activities, it is very important to measure the factors affecting its function, such as dopamine and iodide. Due to the growing population in the world, it is necessary to provide fast, cheap and accurate methods with the capability of on-site analysis and without the need for invasive sampling and operator skill. As a result, there is a strong desire to replace laboratory instruments with small sensors for point-of-care testing. Paper-based analytical devices (PADs) are one of the popular zero-cost approaches to achieve this goal.

RESULTS

We developed a simple and disposable diagnostic paper system based on electroanalytical and potential-power angle-based methods. First, we prepared an angle-based analytical system capable of performing semi-quantitative iodide analysis simply by reading the colored angle traveled. This system design is based on a channel containing complex reagents and two pencil-drawn electrodes to apply a constant voltage accelerating the anions migration. Meanwhile, a three-electrode system based on conductive pencil graphite is developed to measure dopamine concentration based on linear sweep voltammetry. For the quantitative analysis, the voltammetric data was wirelessly transmitted to a mobile device via Bluetooth communication. In this context, a power supply providing the required voltage for the migration of iodide ions, a portable potentiostat system, and a mobile application for measuring dopamine were developed. The calibration curves for I- and dopamine range from 3.5 × 10-4-47.0 × 10-4 and 10.0 × 10-6-1000.0 × 10-6 mol L-1 with LODs of 2.3 × 10-4 and 5.0 × 10-6 mol L-1, respectively.

SIGNIFICANCE AND NOVELTY

A new portable dual-mode voltage-assisted integrated PAD platform was designed for iodide and dopamine analysis. The characteristics of this device allow non-experts to carry out in-field analysis using sub-100 μL saliva sample with a time-to-result of <10 min along with reducing the overall cost and operational complexity.

Bisphenol A contamination in Hilsa shad and assessment of potential health hazard: A pioneering investigation in the national river Ganga, India

The anadromous Hilsa, often known as the "Queen of Fishes" (Tenualosa ilisha), is the most valuable fishery in the Ganga-Hooghly delta estuary. Although BPA exposure has been shown to be harmful to aquatic organisms, no research has looked at the effects of BPA on the commercially valuable Hilsa shad of river Ganga. To close this information vacuum, we examined BPA levels in Hilsa fish from the Ganga estuary. Liver, muscle, kidney, and gonads were all positive for BPA among the Hilsa fish of all ages. Liver BPA levels were highest in adult males (272.16 ± 0.38 ng/g-dw), and lowest in juveniles (5.46 ± 0.06 ng/g-dw). BPA concentrations in the Hilsa shad muscle were highest in reproductively mature females (196.23 ± 0.41 ng/g-dw). The study also discovered a correlation between fish development and BPA exposure, with higher levels of BPA being identified in adult Hilsa species. This is the first study to look at the impact of BPA pollution on aquatic ecosystems and fisheries, and it showed that Hilsa shad is contaminated with BPA and poses health hazards to human beings. The results, which demonstrate BPA contamination, are useful for protecting Hilsa in the river Ganga.

An all-in-one portable colorimetric detection platform for sensitive detection of bisphenol A based on target-mediated CeO2@ZIF-8/Apt biocomposites

BPA aptamers functionalized cerium oxide nanoparticles encapsulated in zeolitic imidazolate framework-8 (CeO2@ZIF-8/Apt) were developed to fabricate an all-in-one portable platform for on-site quantitative detection of BPA. By combining biocomposites with a 3,3',5,5'-tetramethylbenzidine (TMB)-based sodium alginate (SA) hydrogel and smartphone-based RGB analysis, highly sensitive and convenient monitoring of BPA was achieved. CeO2@ZIF-8 composites were constructed using a novel surfactant-modified concentration-controlled synthesis strategy. After being functionalized with BPA aptamers, CeO2@ZIF-8/Apt biocomposites were used as target-response colorimetric probes for target recognition and signal transduction. The oxidase-like activity of CeO2@ZIF-8 was effectively sealed by BPA aptamers and controllably released in a concentration-dependent manner through aptamer-BPA reactions. Utilizing SA hydrogels containing TMB in the caps, a one-step sample addition and one-pot detection can be conveniently achieved and reliably quantified by smartphone-based RGB analysis in an instrument-free way. The detection range of this portable detection platform is 50 pg/mL to 500 ng/mL with limit of detection calculated as 34.88 pg/mL, comparable to that of conventional detection in the solution system (4.57 pg/mL). The recoveries in tap water, apple juice, and milk ranged from 91.02 % and 106.75 %. This work contributes new insights into the design of all-in-one detection platforms for contaminants monitoring in resource-constrained regions.

Advances in optical and electrochemical sensing of bisphenol a (BPA) utilizing microfluidic Technology: A mini perspective

Continuous exposure to toxic pollutants highlights the need for sensitive detection technologies that can be rapidly applied in the current world for quick screening of real samples. Bisphenol A (BPA) is one of the most common environmental contaminants, and it has the potential to harm both the environment and human health, notably causing reproductive disorders, cancer, heart disease, infertility, mental disorders, etc. Thus, significant attention has been paid to the detection of BPA and microplastics to promote food safety, environmental health, and human health on a sustainable earth. Among the current technologies, microfluidic based systems have garnered a lot of interest as future diagnostic tools for healthcare applications. Microfluidic devices can be deployed for quick screening and real-time monitoring, with inherent advantages like portability, miniaturisation, highly sensing tool and ease of integration with various detection systems. Optical and electrochemical sensors are two major analytical tools found in almost all microfluidic-based devices for ultrasensitive BPA and microplastics determination. In this review, we have evaluated and discussed microfluidic-based detection methods for BPA and microplastics.

An Overview to Molecularly Imprinted Electrochemical Sensors for the Detection of Bisphenol A

Bisphenol A (BPA) is an industrial chemical used extensively in plastics and resins. However, its endocrine-disrupting properties pose risks to human health and the environment. Thus, accurate and rapid detection of BPA is crucial for exposure monitoring and risk mitigation. Molecularly imprinted electrochemical sensors (MIES) have emerged as a promising tool for BPA detection due to their high selectivity, sensitivity, affordability, and portability. This review provides a comprehensive overview of recent advances in MIES for BPA detection. We discuss the operating principles, fabrication strategies, materials, and methods used in MIES. Key findings show that MIES demonstrate detection limits comparable or superior to conventional methods like HPLC and GC-MS. Selectivity studies reveal excellent discrimination between BPA and structural analogs. Recent innovations in nanomaterials, novel monomers, and fabrication techniques have enhanced sensitivity, selectivity, and stability. However, limitations exist in reproducibility, selectivity, and stability. While challenges remain, MIES provide a low-cost portable detection method suitable for on-site BPA monitoring in diverse sectors. Further optimization of sensor fabrication and characterization will enable the immense potential of MIES for field-based BPA detection.

Advancement in Paper-Based Electrochemical Biosensing and Emerging Diagnostic Methods

The utilization of electrochemical detection techniques in paper-based analytical devices (PADs) has revolutionized point-of-care (POC) testing, enabling the precise and discerning measurement of a diverse array of (bio)chemical analytes. The application of electrochemical sensing and paper as a suitable substrate for point-of-care testing platforms has led to the emergence of electrochemical paper-based analytical devices (ePADs). The inherent advantages of these modified paper-based analytical devices have gained significant recognition in the POC field. In response, electrochemical biosensors assembled from paper-based materials have shown great promise for enhancing sensitivity and improving their range of use. In addition, paper-based platforms have numerous advantageous characteristics, including the self-sufficient conveyance of liquids, reduced resistance, minimal fabrication cost, and environmental friendliness. This study seeks to provide a concise summary of the present state and uses of ePADs with insightful commentary on their practicality in the field. Future developments in ePADs biosensors include developing novel paper-based systems, improving system performance with a novel biocatalyst, and combining the biosensor system with other cutting-edge tools such as machine learning and 3D printing.

MOF-derived CeO2/Co3O4-Fe2O3@CC nanocomposites as highly sensitive electrochemical sensor for bisphenol a detection

A novel CeO₂/Co₃O₄-Fe₂O₃@CC electrode derived from CeCo-MOFs was developed for detecting the endocrine disruptor bisphenol A (BPA). Firstly, bimetallic CeCo-MOFs were prepared by hydrothermal method, and obtained material was calcined to form metal oxides after doping Fe element. The results suggested that hydrophilic carbon cloth (CC) modified with CeO₂/Co₃O₄-Fe₂O₃ had good conductivity and high electrocatalytic activity. By the analyses of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the introduction of Fe increased the current response and conductivity of the sensor, greatly increasing the effective active area of the electrode. Significantly, electrochemical test proves that the prepared CeO₂/Co₃O₄-Fe₂O₃@CC had excellent electrochemical response to BPA with a low detection limit of 8.7 nM, an excellent sensitivity of 20.489 μA/μM·cm², a linear range of 0.5-30 μM, and strong selectivity. In addition, the CeO₂/Co₃O₄-Fe₂O₃@CC sensor had a high recovery rate for the detection of BPA in real tap water, lake water, soil eluent, seawater, and PET bottle samples, which showed its potential in practical applications. To sum up, the CeO₂/Co₃O₄-Fe₂O₃@CC sensor prepared in this work had excellent sensing performance, good stability and selectivity for BPA, which can be well used for the detection of BPA.

Integration of nanomaterial sensing layers on printable organic field effect transistors for highly sensitive and stable biochemical signal conversion

Organic field effect transistor (OFET) devices are one of the most popular candidates for the development of biochemical sensors due to their merits of being flexible and highly customizable for low-cost large-area manufacturing. This review describes the key points in constructing an extended-gate type OFET (EGOFET) biochemical sensor with high sensitivity and stability. The structure and working mechanism of OFET biochemical sensors are described firstly, emphasizing the importance of critical material and device engineering to higher biochemical sensing capabilities. Next, printable materials used to construct sensing electrodes (SEs) with high sensitivity and stability are presented with a focus on novel nanomaterials. Then, methods of obtaining printable OFET devices with steep subthreshold swing (SS) for high transconductance efficiency are introduced. Finally, approaches for the integration of OFETs and SEs to form portable biochemical sensor chips are introduced, followed by several demonstrations of sensory systems. This review will provide guidelines for optimizing the design and manufacturing of OFET biochemical sensors and accelerating the movement of OFET biochemical sensors from the laboratory to the marketplace.

Papertronics: Marriage between Paper and Electronics Becoming a Real Scenario in Resource-Limited Settings

Integrating electronic applications with paper, placed next to or below printed images or graphics, can further expand the possible uses of paper substrates. Consuming paper as a substrate in the field of electronics can lead to significant innovations toward papertronics applications as paper comprises various advantages like being disposable, inexpensive, biodegradable, easy to handle, simple to use, and easily available. All of these advantages will definitely spur the advancement of the electronics field, but unfortunately, putting electronics on paper is not an easy task because, compared to plastics, the paper surface is not just rough but also porous. For example, in the case of lateral flow assay testing the sensor response is delayed if the pore size of the paper is enormous. This might be a disadvantage for most electrical devices printed directly on paper. Still, some methods make it compatible when fit with a rough, absorbent surface of the paper. Building electronic devices on a standard paper substrate have sparked much interest because of its lightweight, environmental friendliness, minimal cost, and simple fabrication. A slew of improvements have been achieved in recent years to make paper electronics perform better in various applications, including transistors, batteries, and displays. In addition, flexible electronics have gained much interest in human-machine interaction and wireless sensing. This review briefly examines the origins and fabrication of paper electronics and then moves on to applications and exciting possible paths for paper-based electronics.

Electrochemical (bio)sensors based on carbon quantum dots, ionic liquid and gold nanoparticles for bisphenol A

Electrochemical (bio)sensors were developed for bisphenol A (BPA) determination. Screen printed carbon electrode (SPCE) was modified with ionic liquid 1- butyl-3-methylimidazolium tetrafluoroborate (IL), carbon quantum dots (CQD) and gold nanoparticles (AuNP) for the fabrication of the BPA sensor. Electrode surface composition was optimized for the deposition time of AuNP, amount of CQD and percentage of IL using the central composite design (CCD) method. The results of the CCD study indicated that maximum amperometric response was recorded when 9.8 μg CQD, 3% IL and 284 s AuNP deposition time were used in modification. Tyrosinase (Ty) was further modified on the AuNP/CQD-IL/SPCE to fabricate the biosensor. Analytical performance characteristics of the BPA sensor were investigated by differential pulse anodic adsorptive stripping voltammetry and the AuNP/CQD-IL/SPCE sensor exhibited a linear response to BPA in the range of 2.0 × 10^-8 - 3.6 × 10^-6 M with a detection limit of 1.1 × 10^-8 M. Amperometric measurements showed that the linear dynamic range and detection limit of the Ty/AuNP/CQD-IL/SPCE were 2.0 × 10^-8 - 4.0 × 10^-6 M and 6.2 × 10^-9 M, respectively. Analytical performance characteristics such as sensitivity, reproducibility and selectivity were investigated for the presented (bio)sensors. The analytical applicability of the (bio)sensors to the analysis of BPA in mineral water samples was also tested.

Electrochemical behaviour of cellulose/reduced graphene oxide/carbon fiber paper electrodes towards the highly sensitive detection of amitrole

Amitrole is a non-selective triazole herbicide that is widespread used to control a variety of weeds in agriculture, but it may pollute the environment and do harm to organisms. Thus, it is of critical significance to enlist a low-cost, sensitive, stable and renewable method to detect amitrole. In this paper, electrochemical experiments were carried out using carbon fibers/reduced graphene oxide/cellulose paper electrodes, which demonstrated good electrocatalytic performance for amitrole detection. The electrochemical process of amitrole on the surface of the reduced paper electrode was a quasi-reversible reaction controlled by diffusion. Cyclic voltammetry and the amperometric i-t curve method were used for amitrole determination at a micro molar level and higher-concentration range with the following characteristics: linear range 5 × 10^-6 mol L^-1 to 3 × 10^-5 mol L^-1, detection limit 2.44 × 10^-7 mol L^-1. In addition, the relative standard deviation of repeatability is 3.74% and of stability is 4.68%. The reduced paper electrode with high sensitivity, low detection limit, good stability and repeatability provides novel ideas for on-site amitrole detection in food and agriculture.

Paper-Based Electrochemical Biosensors for Food Safety Analysis

Nowadays, foodborne pathogens and other food contaminants are among the major contributors to human illnesses and even deaths worldwide. There is a growing need for improvements in food safety globally. However, it is a challenge to detect and identify these harmful analytes in a rapid, sensitive, portable, and user-friendly manner. Recently, researchers have paid attention to the development of paper-based electrochemical biosensors due to their features and promising potential for food safety analysis. The use of paper in electrochemical biosensors offers several advantages such as device miniaturization, low sample consumption, inexpensive mass production, capillary force-driven fluid flow, and capability to store reagents within the pores of the paper substrate. Various paper-based electrochemical biosensors have been developed to enable the detection of foodborne pathogens and other contaminants that pose health hazards to humans. In this review, we discussed several aspects of the biosensors including different device designs (e.g., 2D and 3D devices), fabrication techniques, and electrode modification approaches that are often optimized to generate measurable signals for sensitive detection of analytes. The utilization of different nanomaterials for the modification of electrode surface to improve the detection of analytes via enzyme-, antigen/antibody-, DNA-, aptamer-, and cell-based bioassays is also described. Next, we discussed the current applications of the sensors to detect food contaminants such as foodborne pathogens, pesticides, veterinary drug residues, allergens, and heavy metals. Most of the electrochemical paper analytical devices (e-PADs) reviewed are small and portable, and therefore are suitable for field applications. Lastly, e-PADs are an excellent platform for food safety analysis owing to their user-friendliness, low cost, sensitivity, and a high potential for customization to meet certain analytical needs.

A novel bimetallic MOFs combined with gold nanoflakes in electrochemical sensor for measuring bisphenol A

In this paper, a novel bimetallic Fe-Cu metal-organic framework combined with 1,3,5-benzenetricarboxylic acid (Fe-Cu-BTC) are synthesized using hydrothermal reaction. The bimetallic Fe-Cu-BTC with high BET (1504 cm³ g^-1) and high Langmuir surface area (1831 cm³ g^-1) is composited by gold nanoparticles to improve the conductivity and to develop their synergistic effect. A novel bisphenol A (BPA) sensor was prepared by dropcasting Fe-Cu-BTC on glassy carbon electrodes (GCE) followed by AuNPs electrodeposition. The Fe-Cu-BTC framework were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy studies (TEM), FT-IR, BET measurements and EDX spectra. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were carried out for surveying the electrochemical properties of the sensors and for the quantification of BPA. Two linear ranges of BPA concentrations 0.1-1.0 μM and 1.0-18 μM with 18 nM limit of detection were obtained. The developed sensor was used to measure the concentration of BPA in samples extracted from rain coat with the recovery ranging from 85.70 to 103.23%.

Alternative methods of monitoring emerging contaminants in water: a review

Anthropogenic activities have steadily increased the release of emerging contaminants (ECs) in aquatic bodies, and these ECs may have adverse effects on humans even at their trace (μg L^-1) levels. Their occurrence in wastewater systems is more common, and the current wastewater treatment facilities are inefficient in eliminating many of such persistent ECs. "Gold standard" techniques such as chromatography, mass spectrometry, and other high-resolution mass spectrometers are used for the quantification of ECs of various kinds, but they all have significant limitations. This paper reviews the alternative methods for EC detection, which include voltammetry, potentiometry, amperometry, electrochemical impedance spectroscopy (EIS) based electrochemical methods, colorimetry, surface-enhanced Raman spectroscopy (SERS), fluorescence probes, and fluorescence spectroscopy-based optical techniques. These alternative techniques have several advantages over conventional techniques, including low sample volume, excludes solid phase extraction procedure, high sensitivity, selectivity, portability, reproducibility, rapidity, low cost, and the ability to monitor ECs in real time. This review summarises each of the alternative methods for detecting ECs in water samples and their respective limits of detection (LODs). The sensitivity of each technique varied depending on the type of EC measured, type of electrochemical probe and electrode, substrates, type of nanoparticle (NP), the physicochemical parameters of water samples tested, and more. Nevertheless, this paper also focuses on some of the current challenges encountered by these alternative methods in monitoring ECs.

The Road to Unconventional Detections: Paper-Based Microfluidic Chips

Conventional detectors are mostly made up of complicated structures that are hard to use. A paper-based microfluidic chip, however, combines the advantages of being small, efficient, easy to process, and environmentally friendly. The paper-based microfluidic chips for biomedical applications focus on efficiency, accuracy, integration, and innovation. Therefore, continuous progress is observed in the transition from single-channel detection to multi-channel detection and in the shift from qualitative detection to quantitative detection. These developments improved the efficiency and accuracy of single-cell substance detection. Paper-based microfluidic chips can provide insight into a variety of fields, including biomedicine and other related fields. This review looks at how paper-based microfluidic chips are prepared, analyzed, and used to help with both biomedical development and functional integration, ideally at the same time.

Covalent organic framework modified carbon cloth for ratiometric electrochemical sensing of bisphenol A and S

A novel ratiometric electrochemical sensor was developed based on a carbon cloth electrodeposited with silver nanoparticles and drop-coated by covalent organic framework (COF-LZU1) for simultaneous determination of bisphenol A (BPA) and bisphenol S (BPS). Carbon cloth exhibited a significantly larger electrochemical active area than common glassy carbon electrodes (27.5 times). Silver nanoparticles not only provided a stable reference signal but also enhanced electroactivity for the oxidation of BPA and BPS. COF-LZU1 with good adsorption performance and large periodic π-arrays promoted the enrichment of BPA and BPS to further increase the current response. Compared with the traditional single-signal electrochemical sensor, the developed ratiometric sensor exhibited better reproducibility and a wider linear range for BPA and BPS from 0.5 to 100 μM with a limit of detection of 0.15 μM. Furthermore, the developed sensor showed excellent stability and superior anti-interference ability. The real sample analysis for BPA and BPS has been successfully carried out in mineral water, electrolyte drink, tea, juice, and beer with recoveries of 88.3-111.7%. The developed ratiometric sensor is expected to be a candidate for the preparation of other electrochemical sensors and the analysis of additional practical samples.

Advances in Chicken IgY-Based Immunoassays for the Detection of Chemical and Biological Hazards in Food Samples

As antibodies are the main biological binder for hazards in food samples, their performance directly determines the sensitivity, specificity, and reproducibility of the developed immunoassay. The overwhelmingly used mammalian-derived antibodies usually suffer from complicated preparation, high cost, frequent bleeding of animals, and sometimes low titer and affinity. Chicken yolk antibody (IgY) has recently attracted considerable attention in the bioanalytical field owing to its advantages in productivity, animal welfare, comparable affinity, and high specificity. However, a broad understanding of the application of IgY-based immunoassay for the detection of chemical and biological hazards in food samples remains limited. Here, we briefly summarized the diversity, structure, and production of IgY including polyclonal and monoclonal formats. Then, a comprehensive overview of the principles, designs, and applications of IgY-based immunoassays for these hazards was reviewed and discussed, including food-borne pathogens, food allergens, veterinary drugs, pesticides, toxins, endocrine disrupting chemicals, etc. Thus, the trend of IgY-based immunoassays is expected, and more IgY types, higher sensitivity, and diversification of recognition-to-signal manners are necessary in the future.

Covalent organic framework DQTP modified pencil graphite electrode for simultaneous determination of bisphenol A and bisphenol S

The sensitivity and selectivity of electrochemical analysis are challenging due to the materials used for electrode modification as well as electrical conductivity, catalytic activity and recognition ability of the working electrode. In this work, a portable 3D-printed electrochemical electrode clamp was designed and applied in combination with the developed covalent organic framework (COF DQTP)-modified pencil graphite electrode (DQTP/PGE). The β-ketoenamine-linked COF DQTP synthesized by 1,3,5-triformylphloroglucinol (TP) and 2,6-diaminoanthraquinone (DQ) through solvothermal method is a porous crystalline with excellent conductivity and large periodic π-arrays, coupled with commercial available pencil graphite electrode to fabricate a disposable sensor for simultaneous determination of environmental endocrine disruptors bisphenol A and bisphenol S. The DQTP/PGE sensor exhibited high electrical conductivity and catalytic activity, and a good linearity was obtained in a range of 0.5-30 μM for two bisphenols with a detection limit of 0.15 μM (S/N = 3). Moreover, the sensor showed a reproducible and stable response over one month with negligible interference, and an accepted recovery with real food packaging samples.

Development of highly sensitive and selective bisphenol A sensor based on a cobalt phthalocyanine-modified carbon paste electrode: application in dairy analysis

The development of an accurate, sensitive and selective sensor for the detection of bisphenol A (BPA) based on the incorporation of a new phthalocyanine derivative, cobalt phthalocyanine, C,C,C,C-tetracarboxylic acid-polyacrylamide (CoPc-PAA) into a carbon-paste matrix is presented using voltammetry and constant potential techniques. The influence of measuring parameters such as pH and scan rate on the analytical performance of the sensor was evaluated. Several kinetic parameters such as electron transfer number (n), charge transfer coefficient (α), electrode surface area (A) and diffusion coefficient (D) were also calculated. Under optimum conditions, particularly at pH 7.2, the BPA sensor resulted in a wide linear range from 25 × 10^-11 M to 2.5 × 10^-7 M and a limit of detection as low as 63.5 pM. Based on these findings, it can be concluded that our sensor can be substantially utilized for detecting BPA in spiked milk samples.

Origami Paper-Based Electrochemical (Bio)Sensors: State of the Art and Perspective

In the last 10 years, paper-based electrochemical biosensors have gathered attention from the scientific community for their unique advantages and sustainability vision. The use of papers in the design the electrochemical biosensors confers to these analytical tools several interesting features such as the management of the solution flow without external equipment, the fabrication of reagent-free devices exploiting the porosity of the paper to store the reagents, and the unprecedented capability to detect the target analyte in gas phase without any sampling system. Furthermore, cost-effective fabrication using printing technologies, including wax and screen-printing, combined with the use of this eco-friendly substrate and the possibility of reducing waste management after measuring by the incineration of the sensor, designate these type of sensors as eco-designed analytical tools. Additionally, the foldability feature of the paper has been recently exploited to design and fabricate 3D multifarious biosensors, which are able to detect different target analytes by using enzymes, antibodies, DNA, molecularly imprinted polymers, and cells as biocomponents. Interestingly, the 3D structure has recently boosted the self-powered paper-based biosensors, opening new frontiers in origami devices. This review aims to give an overview of the current state origami paper-based biosensors, pointing out how the foldability of the paper allows for the development of sensitive, selective, and easy-to-use smart and sustainable analytical devices.

Recent advances of environmental pollutants detection via paper-based sensing strategy

Paper has become one of the most promising substrates for building low-cost and powerful sensing platforms due to its self-pumping ability and compatibility with multiple patterning methods. Paper-based sensors have been greatly developed in the field of environmental monitoring. In this review, we introduced the research and application of paper-based sensors in environmental monitoring, focusing on the deposition and patterning methods of building paper-based sensors, and summarized the applications of detecting environmental pollutants, including metal ions, anions, explosives, neurotoxins, volatile organic compounds, and small molecules. In addition, the development prospects and challenges of promoting paper-based sensors are also discussed. The current review will provide references for the construction of portable paper-based sensors, and has implications for the field of on-site real-time detection of the environment.

Lab-on-Paper Devices for Diagnosis of Human Diseases Using Urine Samples-A Review

In recent years, microfluidic lab-on-paper devices have emerged as a rapid and low-cost alternative to traditional laboratory tests. Additionally, they were widely considered as a promising solution for point-of-care testing (POCT) at home or regions that lack medical infrastructure and resources. This review describes important advances in microfluidic lab-on-paper diagnostics for human health monitoring and disease diagnosis over the past five years. The review commenced by explaining the choice of paper, fabrication methods, and detection techniques to realize microfluidic lab-on-paper devices. Then, the sample pretreatment procedure used to improve the detection performance of lab-on-paper devices was introduced. Furthermore, an in-depth review of lab-on-paper devices for disease measurement based on an analysis of urine samples was presented. The review concludes with the potential challenges that the future development of commercial microfluidic lab-on-paper platforms for human disease detection would face.

A fluorescent aptasensor based on berberine for ultrasensitive detection of bisphenol A in tap water

The residues of bisphenol A (BPA) in food packaging and water systems have a potential impact on human health; therefore, its analysis and detection have drawn scientists' attention. In this work, based on the change in fluorescence intensity resulting from the conformational switch of a berberine/BPA-aptamer system in the presence and absence of BPA, an ultra-sensitive fluorescence aptasensing system is proposed, in which BPA-aptamer is employed as the identification unit and berberine as the fluorescent probe. Various factors affecting the detection of BPA, including the concentration of the fluorescent probe, BPA-aptamer, BPA, pH, system stability time and other experimental conditions, were investigated in detail. Under the optimal experimental conditions, the fluorescence intensity of the sensing system of berberine/BPA-aptamer exhibited a good linear correlation with the BPA concentration in the range of 0-1300 μM with a LOD of 32 nM. The proposed fluorescent sensing system also exhibited excellent recoveries of 92.4-102.3% in tap water samples and showed good application prospects for the analysis and detection of BPA.

An ultra-sensitive electrochemical sensor of Ni/Fe-LDH toward nitrobenzene with the assistance of surface functionalization engineering

Hypersensitive detection of organic pollutions with high toxicity in drinking water always keeps its challenge in electroanalysis due to their low concentration and electrochemical redox inert. In this work, a novel nanomaterial modified electrode for the sensitive detection of nitrobenzene (NB) is presented, based on environmental friendly and cost-effective Ni/Fe layered double hydroxides functionalized with sodium dodecyl sulfate (Ni/Fe(SDS)-LDH). Such 2D layered composites were prepared and used to improve the sensitivity for NB detection, due to its good catalytic activity for NB reduction. Besides, the proposed electrode shows a remarkably promoted sensitivity to NB compared to Ni/Fe-LDHs modified one. It is because that the surface modifier SDS can provide more adsorption sites to significantly improve the adsorption of NB, which has been confirmed by the adsorption experiment and the characterization of Fourier transform infrared spectroscopy (FTIR). As a result, an impressive sensing behaviour is achieved at the proposed Ni/Fe(SDS)-LDHs modified electrode with a sensitivity of 15.79 μA μM^-1 cm^-2. This work provides a promising way to build more advanced nanomaterials to electrochemical detection of organic pollution based on energetically synergizing of adsorption by surface functionalization engineering.

Multilayered iron oxide/reduced graphene oxide nanocomposite electrode for voltammetric sensing of bisphenol-A in lake water and thermal paper samples

A multilayered iron oxide/reduced graphene oxide (ION-RGO) nanocomposite electrode is reported for the voltammetric sensing of bisphenol-A (BPA). Structural characterizations reveal the nanocomposite features RGO sheets decorated with nanometric spherical ION in a mixture of maghemite and magnetite phases. ITO substrate modified with the ION-RGO multilayered film exhibits strong electrocatalytic effect toward BPA oxidation, which is made possible by Fe(III) catalysts generated at the ION's surface after scanning the electrode potential from below 0 V (vs Ag/AgCl) and followed by the RGO phase conducting the transferred electrons. Under optimized differential pulse voltammetry conditions, the proposed sensor shows three linear working ranges 0.09-1.17 (r² = 0.999), 1.17-3.81 (r² = 0.995) and 3.81-8.20 (r² = 0.998), with the highest sensitivity equaling 7.76 μA cm^-2/μmol L^-1 and the lowest limit of detection of 15 nmol L^-1. A single electrode can be used for at least twenty consecutive runs loosing less than 15% of sensitivity, whereas electrodes fabricated in different bacthes exhibit almost identical perfomances. Determination of BPA in a thermal paper sample shows no difference (at 95% confidence level) between the proposed sensor and HPLC/UV. The sensor is neither influenced by the matrix composition nor by other emerging contaminants.

Research progress on the applications of paper chips

Due to the modern pursuit of the quality of life, science and technology have rapidly developed, resulting in higher requirements for various detection methods based on analytical technology. Herein, the development, fabrication, detection and application of paper-based microfluidic chips (μPAD) are summarized. We aim to provide a comprehensive understanding of paper chips, and then discuss challenges and future prospects in this field.

Molecularly imprinted curcumin nanoparticles decorated paper for electrochemical and fluorescence dual-mode sensing of bisphenol A

A molecularly imprinted paper-based analytical device (MIP-μPAD) was developed for the sensing of bisphenol A (BPA). The platform was screen-printed onto a filter paper support, where the electrodes and the fluorescence μPADs were designed. Owing to its dual electrochemical and fluorescence responses, molecularly imprinted curcumin nanoparticles were used to sense BPA. The μPAD design was characterized by transmission electron microscopy, scanning electron microscopy, fluorescence spectroscopy, and electrochemical techniques. The sensor design comprised a wide linear range from 1 to 200 μg L^-1 with limits of detection of 0.47 ± 0.2 and 0.62 ± 0.3 μg L^-1 (LOD, S/N = 3) for electrochemical and fluorescence sensing, respectively. Furthermore, the system showed good analytical performance such as selectivity, stability, and reproducibility. The feasibility of the MIP-μPAD was demonstrated for the sensing of BPA in seawater, foods, and polycarbonate plastic packaged water with recovery values of 97.2 and 101.8%.

Paper-Based Screen-Printed Electrodes: A New Generation of Low-Cost Electroanalytical Platforms

Screen-printed technology has helped considerably to the development of portable electrochemical sensors since it provides miniaturized but robust and user-friendly electrodes. Moreover, this technology allows to obtain very versatile transducers, not only regarding their design, but also their ease of modification. Therefore, in the last decades, the use of screen-printed electrodes (SPEs) has exponentially increased, with ceramic as the main substrate. However, with the growing interest in the use of cheap and widely available materials as the basis of analytical devices, paper or other low-cost flat materials have become common substrates for SPEs. Thus, in this revision, a comprehensive overview on paper-based SPEs used for analytical proposes is provided. A great variety of designs is reported, together with several examples to illustrate the main applications.

Latest Advances in Determination of Bisphenols with Nanomaterials, Molecularly Imprinted Polymers and Aptamer Based Electrochemical Sensors

Contamination of environmental sources such as soils, sediments and rivers and human exposure caused by several endocrine disrupting compounds (EDCs) are considered as the most challenging issues of today's world. EDCs cover a wide variety of compounds ranging from phthalates to parabens and bisphenols (BPs) are the leading group among them. BPs are widely used during the production of different plastic materials such as food and beverage containers, toys, medical equipment and baby bottles that we use in every aspect of our lives. BPs may migrate from those products to different media under certain conditions and this situation causes chronic exposure for humans and other creatures in the environment. Especially bisphenol A (BPA) and its other analogues such as bisphenol F, bisphenol S and tetrabromobisphenol that have similar structures and are preferred as alternatives to BPA cause harmful adverse effects such as endocrine disruption, neurotoxicity, genotoxicity and cytotoxicity. There are legal restrictions and prohibitions by the European Union (EU) in order to prevent possible harmful effects. Therefore, it is important to develop highly sensitive, fast, easy to use and cheap sensors for the determination of BPs in biological, environmental and commercial samples. Electrochemical sensors, which are one of the most widely, used analytical techniques, provide these conditions. Additionally, it is possible to enhance the performance of electrochemical sensors with nanomaterials, molecularly imprinted polymers or aptamer based technologies. This review aims to give comprehensive information about BPs with summarizing most recent applications of electrochemical sensors for their determination in different samples.

Engineering strategies for enhancing the performance of electrochemical paper-based analytical devices

Applications of electrochemical detection methods in microfluidic paper-based analytical devices (μPADs) has revolutionized the area of point-of-care (POC) testing towards highly sensitive and selective quantification of various (bio)chemical analytes in a miniaturized, low-coat, rapid, and user-friendly manner. Shortly after the initiation, these relatively new modulations of μPADs, named as electrochemical paper-based analytical devices (ePADs), gained widespread popularity within the POC research community thanks to the inherent advantages of both electrochemical sensing and usage of paper as a suitable substrate for POC testing platforms. Even though general aspects of ePADs such as applications and fabrication techniques, have already been reviewed multiple times in the literature, herein, we intend to provide a critical engineering insight into the area of ePADs by focusing particularly on the practical strategies utilized to enhance their analytical performance (i.e. sensitivity), while maintaining the desired simplicity and efficiency intact. Basically, the discussed strategies are driven by considering the parameters potentially affecting the generated electrochemical signal in the ePADs. Some of these parameters include the type of filter paper, electrode fabrication methods, electrode materials, fluid flow patterns, etc. Besides, the limitations and challenges associated with the development of ePADs are discussed, and further insights and directions for future research in this field are proposed.

A paper-based colorimetric sensor array for discrimination and simultaneous determination of organophosphate and carbamate pesticides in tap water, apple juice, and rice

A colorimetric paper-based sensor is proposed for the rapid monitoring of six major organophosphate and carbamate pesticides. The assay was constructed by dropping gold and silver nanoparticles on the hydrophilic zones of a paper substrate. The nanoparticles were modified by L-arginine, quercetin, and polyglutamic acid. The mechanism of sensing is based on the interaction between the pesticide and the nanoparticles. The color of nanoparticles changed during the interactions. A digital camera recorded these changes. The assay provided a unique response for each studied pesticide. This method can determine six individual pesticides including carbaryl, paraoxon, parathion, malathion, diazinon, and chlorpyrifos. The limit of detection for these pesticides were 29.0, 22.0, 32.0, 17.0, 45.0, and 36.0 ng mL^-1, respectively. The assay was applied to simultaneously determine the six studied pesticides in a mixture using the partial least square method (PLS). The root mean square errors of prediction were 11, 8.7, 9.2, 10, 12, and 11 for carbaryl, paraoxon, parathion, malathion, diazinon, and chlorpyrifos, respectively. The paper-based device can differentiate two types of studied pesticide (organophosphate and carbamate) as well as two types of organophosphate structures (oxon and thion). Furthermore, this sensor showed high selectivity to the pesticides in the presence of other potential species (e.g., metal ions, anions, amino acids, sugar, and vitamins). This assay is capable of determining the pesticide compounds in tap water, apple juice, and rice samples.Graphical abstract.

Screen-Printed Electrodes: Promising Paper and Wearable Transducers for (Bio)Sensing

Screen-printing technology has revolutionized many fields, including that of electrochemical biosensing. Due to their current relevance, this review, unlike other papers, discusses the relevant aspects of electrochemical biosensors manufactured using this technology in connection to both paper substrates and wearable formats. The main trends, advances, and opportunities provided by these types of devices, with particular attention to the environmental and biomedical fields, are addressed along with illustrative fundamentals and applications of selected representative approaches from the recent literature. The main challenges and future directions to tackle in this research area are also pointed out.