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Developing a non-toxic, cost-effective, and user-friendly indicator for detecting milk freshness and spoilage, with potential applications in smart packaging, presents a significant challenge. In this study, we extracted natural anthocyanins (ACNs) from Jaman (Syzgium cumini) and incorporated it in to filter paper. The presence of ACNs in the extract was confirmed through UPLC-MS/MS analysis. To enhance stability and prevent leaching, the ACNs-loaded filter paper was coated with 1 % chitosan (CH). The sensor strips were thoroughly characterized using FTIR, contact angle measurements, XRD, and FE-SEM. These strips displayed a distinct and quantifiable color change from red to colorless to yellow across different pH levels. Additionally, in real-time milk spoilage detection, the sensor transitioned from light purple to colorless. The strips demonstrated reproducibility and stability, even under high temperatures and extreme pH conditions. These findings suggest that the ACNs-loaded sensor strips hold promise for use as smart packaging materials., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The accurate monitoring of sulfide ion concentrations is vital for ensuring food safety, but current detection methods are often cumbersome and confined to laboratories. This study introduces an innovative paper-based colorimetric sensor that leverages the peroxidase-like activity of cobalt tetrasulfonate phthalocyanine (CoTsPc) for rapid, sensitive, and selective sulfide ion quantification. The underlying mechanism relies on the interaction between cobalt and sulfide ions, modulating the catalytic efficiency of CoTsPc and triggering a visible color change when 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide are present. By controlling solvent evaporation, the reaction kinetics are standardized, enabling reproducible and accurate colorimetric measurements. Experimental results show that adding sulfide ions to the TMB-H₂O₂ reaction system causes a gradual decrease in color intensity on the paper substrate. This change verifies effectiveness of the sensor, highlighting its potential for reliable sulfide ion detection in food safety applications, while providing a simple and portable alternative to conventional methods., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Hydrogen sulfide (H 2 S) is noxious gas and significantly threatens human health. Herein, a Bi-based metal-organic frameworks (Bi-MOFs) based paper analysis device (PAD) has been developed for rapid and effective dual-mode detection of H 2 S. The dominant H 2 S sensing mechanism is explored. The H 2 S can react with Bi-MOF to form bismuth sulfide (Bi 2 S 3 ) MOF (Bi 2 S 3 -MOF), changing the color of PAD from white to black. The distinguish color change makes it very convenience for visible detection. Meanwhile, the generated Bi 2 S 3 -MOF exhibits excellent photothermal property, endowing it possible for photothermal imaging detection. In this regard, the PAD boasts a wide linear detection range of 0-40 μM for H 2 S with an impressively low limit of detection (LOD) (0.23 μM). The constructed sensing system is demonstrated with outstanding selectivity and storage stability. Satisfied recovery is reached for H 2 S detection in diverse real samples. Interestingly, the PAD can be used as intelligent label for assessing meat freshness by monitor H 2 S release from meat under different storage temperatures. With integration capabilities of smartphones, the portable and user-friendly PAD offers a simple and rapid solution for on-the-go detection of H 2 S in food and environment. The investigation provides an instructive way for environment monitoring and food safety guarding., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The integration of barcode technology with smartphones on paper-based analytical devices (PADs) presents a promising approach to bridging manual detection with digital interpretation and data storage. However, previous studies of 1D barcode approaches have been limited to providing only a "yes/no" response for analyte detection. Herein, a method of using barcode readout for semiquantitative signal detection on PADs has been achieved through the integration of barcode technology with a distance-based measurement concept on PADs. To demonstrate the feasibility of this concept, a PAD fabrication strategy incorporating barcodes was explored, using the enzymatic reaction between horseradish peroxidase (HRP), 3,3'-diaminobenzidine (DAB), and H 2 O 2 as a model system. The enzyme-catalyzed polymerization of DAB to polyDAB in the presence of hydrogen peroxide results in the appearance of color observable by the naked eye inside a paperfluidic channel, with the color-changed length depending on the H 2 O 2 concentration. At the same time, the barcode pattern displayed as a result of this distance-based color evolution overlaid with a paper-based barcode layer can be read using a smartphone application. Parameters affecting the signal readout performance were studied. The developed device can be used to detect H 2 O 2 concentrations in the range of 0.25 to 10 mM within 90 min with 79.6% of barcode signals correctly readable. Additionally, results from different smartphone models showed a consistent reading performance (78.4-79.6%). Finally, the quantification of glucose levels in artificial urine samples was demonstrated. This developed PAD signaling strategy offers end-users more simplicity and can be used as a standalone device or in conjunction with other digital devices.

Developing low-cost self-service portable sensors to detect viruses is an important step in combating the spread of viral outbreaks. Here, we describe the development of an aptamer-free paper-based molecularly imprinted sensor for the instrument-free detection of influenza virus A (H5N1). In this sensor, Whatman paper loaded with Fe 3 O 4 nanoparticles (WP@Fe 3 O 4 ) was prepared as a substrate upon which silicon imprinting occurred in the presence of the template virus H5N1. After removal of the template virus, Fe 3 O 4 which exposed in the imprinted cavities was able to catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) by hydrogen peroxide to form blue TMB + ions. Therefore, the concentration of virus can be semi-quantified by the color change of the solution after the catalytic reaction in the absence of any instruments. The color reaction can be clearly observed within 20 min. In addition, the remaining TMB could be quantified fluorometrically, with a limit of detection of 1.16 fM and an imprinting factor of 4.7. As far as we know, this sensor detects the target with the highest sensitivity that has yet been achieved in aptamer-free molecular imprinting sensors. Importantly, the cost of materials used for each sensor was as low as 4 cents (0.23 Yuan) per sensor. This sensitive self-service sensor, which is relatively easy and inexpensive to produce, will provide an effective new avenue for the rapid detection of viruses.

Dipicolinic acid (DPA) is a key biomarker of bacterial spores. In this study, we present a novel distance-based paper analytical device (d-PAD) for the fluorescence sensing of DPA. The detection mechanism relies on the complexation of ofloxacin (OFL) with Cu 2+ ions, where Cu 2+ quenches the fluorescence of OFL via static quenching. Upon the introduction of DPA, it interacts with the OFL-Cu 2+ complex, resulting in an enhanced fluorescence signal from OFL. The assay demonstrated a limit of detection (LOD) of 0.08 μM over a range of 0.6-120 μM, as measured using a spectrofluorometer. The d-PAD was designed for efficient reagent transport through capillary action on paper substrates, allowing for rapid on-site DPA analysis without requiring advanced laboratory equipment. The length of the fluorescent bands on the d-PADs was proportional to the concentration of DPA, providing a simple and effective readout method. With a sensitivity of 0.6 μM, the device shows a strong response to varying DPA concentrations. This distance-based platform offers a straightforward and quantitative approach to result interpretation, making it a promising tool for detecting bacterial spores in real samples. The development and optimization of this paper-based microfluidic assay represent a significant step forward in portable diagnostic technologies.

Fluorotelomer-based acrylate polymers and surfactants used to grease-proof food contact paper (FCP) are potential sources of dietary exposure to perfluoroalkyl substances (PFAS). Food contact substances (FCS) containing polyfluorinated long-chains (≥C8) were voluntarily removed by their manufacturers from the U.S. market in 2011 due to health concerns and largely replaced with FCSs containing short-chain (≤C7) PFAS. In 2020, FDA findings of potential biopersistence of 6:2 FTOH (CF 3 (CF 2 ) 5 CH 2 CH 2 OH) similarly prompted an additional voluntarily phase-out of FCSs containing 6:2 FTOH by their manufacturers that was completed by the end of 2023. To monitor the phase-out process, a screening method was developed to detect FCPs containing ester-linked polyfluorinated pendant chains. Direct Analysis in Real Time-Isotope Dilution-High Resolution Mass Spectrometry (DART-ID-HRMS) enabled rapid semi-quantitative detection of 6:2 FTOH in FCP saponification reaction headspace without requiring sample concentration or chromatography. 19 F-NMR analysis confirmed 6:2 FTOH pendant chain identity and detection dependence on saponification. The speed and specificity of this approach arise from ester saponification in the presence of stable isotopically labeled 6:2 FTOH; high FTOH differential volatility relative to nonfluorinated matrix, and the facile production of FTOH gas-phase anions ( e . g ., [M + O 2 ] ·- , [M-H + CO 2 ] - ) under ambient ionization conditions. The efficiency of this simple workflow makes it well-suited for monitoring the phase-out of FCS containing ester-linked polyfluorinated chains from the U.S. marketplace.

Drug overdoses have risen dramatically in recent years. We developed a simple nontargeted method using a disposable paper spray cartridge with an integrated solid phase extraction column. This method was used to screen for ~160 fentanyl analogs, synthetic cannabinoids, other synthetic drugs, and traditional drugs of abuse in over 300 authentic overdose samples collected at emergency departments in Indianapolis. A solid phase extraction step was implemented on the paper spray cartridge to enable subnanograms per milliliter synthetic drugs screening in plasma. Analysis was performed on a quadrupole orbitrap mass spectrometer using the sequential window acquisition of all theoretical fragment ion spectra approach in which tandem mass spectrometry was performed using 7 m/z isolation windows in the quadrupole. Calibration curves with isotopically labeled internal standards were constructed for 35 of the most frequently encountered synthetic and traditional illicit drugs by US toxicology labs. Additional qualitative-only drugs in a suspect screening list were also included. Limits of detection in plasma for synthetic cannabinoids ranged from 0.1 to 0.5 and 0.1 to 0.3 ng/mL for fentanyl and its analogs and between 1 and 5 ng/mL for most other drugs. Relative matrix effects were evaluated by determining the variation of the calibration slope in 10 different lots of biofluid and found to be between 3% and 20%. The method was validated on authentic overdose samples collected from two emergency departments in Indianapolis, Indiana, from suspected or known overdoses. Commonly detected synthetic drugs included fentanyl related substances, designer benzodiazepines such as flubromazolam, and the synthetic cannabinoid 5F-PB-22., (© 2024 The Authors. Drug Testing and Analysis published by John Wiley & Sons Ltd.)

Rapid-response in situ fluorogenic reactions in aqueous solution are important for designing sensitive and stable sensing platforms. Herein, a wavelength-changeable and rapid-response (within 5 s) fluorescence sensing platform for monitoring tyrosinase (TYR) activity is constructed. The developed assay is based on TYR catalyzing the hydroxylation of mono-phenol to o-diphenol and MnO 4 -triggered fluorogenic between dopamine (DA) and phenol derivatives in aqueous solution. The fluorescence wavelength can be changeable from 470 to 550 nm with strong fluorescence according to different phenol derivatives. Our proposed sensor not only exhibits a good recovery for TYR in high serum concentration (20 %), but also has been successfully applied to the screening of TYR inhibitors modeled on kojic acid. Furthermore, a paper-based wavelength-changeable fluorescence sensor was developed for on-site detection of TYR activity in potatoes with high recovery, which is consistent with our previously reported method. Consequently, the proposed sensing system has broad prospects in the practical application of TYR-associated food monitoring and clinical diagnosis.- -triggered fluorogenic between dopamine (DA) and phenol derivatives in aqueous solution. The fluorescence wavelength can be changeable from 470 to 550 nm with strong fluorescence according to different phenol derivatives. Our proposed sensor not only exhibits a good recovery for TYR in high serum concentration (20 %), but also has been successfully applied to the screening of TYR inhibitors modeled on kojic acid. Furthermore, a paper-based wavelength-changeable fluorescence sensor was developed for on-site detection of TYR activity in potatoes with high recovery, which is consistent with our previously reported method. Consequently, the proposed sensing system has broad prospects in the practical application of TYR-associated food monitoring and clinical diagnosis., Competing Interests: Declaration of competing interest There are no conflicts of interest., (Copyright © 2024. Published by Elsevier B.V.)

A highly sensitive and selective electrochemical sensing platform with self-assembled porous 3-D trimetallic (Pd, Fe, and Co) hybrid anchored on a cost-effective and high-conducting carbon paper (CP) synthesized via a facile and cost-effective hydrothermal impregnation and thermal reduction technique was developed for determining indole-3-lactic acid (ILA) levels in buffer and serum samples. Before the analytical phase, the composite (PdFeCo 1-x ONPs@CP electrode) was thoroughly characterized, and different methods were used to investigate the electrochemical properties. The combination of tri-metallics with CP-fibers improved sensing capacities in the linear range of 0.05-30 μM, with sensitivity and limits of detection of and 0.165 ± 0.013 μA/μM and 7.8 ± 0. 2 nM, respectively, towards ILA determination. Furthermore, the developed sensing platform was utilized for the analyses of ILA in sigma, human normal, and alcohol use disorder patients' serum samples. Liquid chromatography in tandem with mass spectrometry was equally used to quantify ILA levels in the serum samples and the results of both methods were compared., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Biodegradable cellulosic mulch has been demonstrated as the promising alternative to traditional plastic mulch film in agriculture, whereas the highly hydrophilic property and poor wet strength severely restricted their practical application. Herein, a new waterproof dialdehyde cellulose (OR)-polyamide epichlorohydrin (P)-alkyl ketene dimer (A) (OR-P-A) was carefully designed as the green mulch film. The hydrogen bonds and Schiff base reaction between -CHO on dialdehyde cellulose fibers and -NH 2 on PAE reinforced the interfacial interaction of cellulosic fibers. Furthermore, the formed β-keto ester bonds of -OH on cellulose with AKD improved the water resistance of paper fiber. Compared with the pristine cellulose film, the dry and wet tensile strength of OR-P-A 2 were increased to 17 MPa and 3 MPa, respectively. Moreover, the water contact angle was increased from 25° for pristine cellulose film to 124° for OR-P-A 2 . In addition, the germination rate of cabbage seeds covered by OR-P-A 2 was similar to that of commercial polyethylene film in practical application. This strategy proposed a novel method to improve the hydrophobicity of cellulose film, which boosting the development of biodegradable mulch film and "green" agriculture., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This work demonstrates a novel, non-fluorescence approach to the length identification of polymerase chain reaction (PCR) and recombinase polymerase amplification (RPA) products, utilizing capillary flow velocities on paper microfluidic chips. It required only a blank paper chip, aminated microspheres, and a smartphone, with a rapid assay time and under ambient lighting. A smartphone evaluated the initial capillary flow velocities on the paper chips for the PCR and RPA products from various bacterial samples, where the pre-loaded aminated microspheres differentiated their flow velocities. Flow velocities were analyzed at different time frames and compared with the instantaneous flow velocities and interfacial tension (γ LV ) data. Subsequent error analysis justified the use of the initial time frames. A robust linear relationship could be established between the initial flow velocities against the square root of the product lengths, with R 2 values of 0.981 for PCR and 0.993 for RPA. The assay seemed not to have a significant dependency on the cycle numbers and initial target concentrations. This novel method can be potentially used with various paper microfluidic methods of nucleic acid amplification tests towards rapid and handheld assays., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The development of portable, cost-effective, and straightforward DNA biosensors holds immense importance in various fields, including healthcare, environmental monitoring, and food safety. This study contributes to the objective by introducing an innovative approach for synthesizing carbon dots (Cdots) with high quantum yield (QY) and remarkable selectivity for Fe 3+ ions. Utilizing o-phenylenediamine as a precursor, the study achieved a straightforward and environmentally friendly synthesis method, enabling the efficient detachment of metal ions from the Cdot surface upon introducing pyrophosphate (PPi). The presence of surface hydroxyl and amino groups facilitated specific Fe 3+ recognition. Employing D-optimal response surface methodology, the study optimized Cdot synthesis parameters, identifying temperature and heating time as critical factors influencing QY. Statistical analysis confirmed the model's reliability, predicting maximum QY of 48.8 % with minimal deviation from experimental results. Characterization studies revealed the amorphous nature of Cdots through HR-TEM, XRD, and FTIR analysis. Furthermore, the proposed LAMP/PPi biosensing technique demonstrated higher sensitivity, specificity, and repeatability, with negligible interference from common anions and efficacy across varying pH levels. The limit of detection (LOD) of 0.079 (±0.01) μM and the detection range of 0.1 μM-2 mM underscore the biosensor's practical utility. This study highlights a promising direction for developing paper-based LAMP/PPi biosensors with potential diagnostics and environmental monitoring applications. Significantly, the biosensing technique is applicable to any DNA amplification method generating pyrophosphate (PPi) as a by-product., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Dinesh Prasad reports financial support was provided by Birla Institute of Technology. DINESH PRASAD reports a relationship with Birla Institute of Technology., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Digital microfluidics (DMF) is a platform that enables the automated manipulation of individual droplets of sizes ranging from nanoliter to microliter and can be coupled with numerous techniques, including colorimetry. However, although the DMF electrode architecture is highly versatile, its integration with different analytical methods often requires either changes in sample access, top plate design, or the integration of supplementary equipment into the system. As an alternative to overcome these challenges, this study proposes a simple integration between paper-based analytical devices (PADs) and DMF for automated and eco-friendly sample processing aiming at the colorimetric detection of creatinine (CR, an important biomarker for kidney disease) in artificial urine. An optimized and selective Jaffé reaction was performed on the device, and the reaction products were delivered to the PAD, which was subsequently analyzed with a bench scanner. The optimal operational parameters on the DMF platform were a reaction time of 45 s with circular mixing and image capture after 5 min. Under optimized conditions, a linear behavior was obtained for creatinine concentrations ranging from 2 to 32 mg dL -1 , with limits of detection and quantitation equal to 1.4 mg dL -1 and 2.0 mg dL -1 , respectively. For the concentration range tested, the relative standard deviation varied from 2.5 to 11.0%, considering four measurements per concentration. CR-spiked synthetic urine samples were subjected to analysis via DMF-PAD and the spectrophotometric reference method. The concentrations of CR determined using both analytical techniques were close to the theoretical values, with the resultant standard deviations of 2-9% and 1-4% for DMF-PADs and spectrophotometry, respectively. Furthermore, the recovery values were within the acceptable range, with DMF-PADs yielding 96-108% and spectrophotometry producing 95-102%. Finally, the greenness of the DMF-PAD and spectrophotometry methods was evaluated using the Analytical Greenness (AGREE) metric software, in which 0.71 and 0.51 scores were obtained, respectively. This indicates that the proposed method presents a higher greenness level, mainly due to its miniaturized characteristics using a smaller volume of reagent and sample and the possibility of automation, thus reducing user exposure to potentially toxic substances. Therefore, the DMF-PADs demonstrated great potential for application in the clinical analysis of creatinine, aiding in routine tests by introducing an automated, simple, and environmentally friendly process.

A novel type of colorimetric/fluorescent nanopaper indicator has been developed from the melt-extruded poly (vinyl alcohol-co-ethylene) nanofibers with surface anchored metal-organic frameworks (MOFs) by an interfacial coordination strategy. Specifically, the fluorescein isothiocyanate molecules could be anchored to the nanofiber surface by nickel ions and co-assembled into a hydrophilic nanocoating via a dynamic water/alcohol solvent evaporation method. Interestingly, this hydrophilic surface enables fast adsorption of moistures and interaction with biological amine vapors, resulting a saffron cake-layer of MOF nanocrystals with ultra-sensitive colorimetric/fluorescent responses based on an alkaline pH/ammonia induced competitive coordination mechanism. Finally, these porous nanofibrous matrix and active nanocoating make the nano-paper an ultra-sensitive optical platform for in-situ monitoring of the shrimp freshness from mins to weeks. Therefore, this composite film shows great potential into advanced paper-based indicators for food quality control and safety in processing industry., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The recycling of paper and board (PB) yields economic and environmental advantages compared to primary paper production. However, PB from lightweight packaging (LWP) waste is currently not comprehensively reintegrated into the paper value stream. To develop an adapted recycling process for PB from LWP, PB quantities, qualities, and fluctuations ranges in LWP are required. Currently, no sufficient database is available. Therefore, we developed a methodical approach and conducted a case study to access the PB potential in LWP sorting plants using manual analysis and sensor-based material flow monitoring. Differences resulting from seasonal variations, materials from different settlement structures, and fluctuation ranges in LWP composition over two weeks have been investigated. PB contents in the input of 6.5 wt% (ww) and 5.9 wt% (ww) were determined for winter and summer sampling campaigns, respectively. The PB product stream amounted to 5.7 wt% (ww, winter) and 4.8 wt% (ww, summer). Around 45 wt% (ww) of PB from the PB product stream was classified as misplaced by the consumer and should have been discarded in separate paper collections. Based on the determined PB quantities and qualities, a potential of usable and in the PB product stream available PB in LWP was determined. The technically available and usable PB potential in German LWP waste amounts to 89,000 to 100,000tons per year (average PB yield of around 65 wt% (ww)). The methodical approach can be adapted for sorting plant balances. The results can contribute to developing an adapted recycling process for PB from LWP., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The study examined the beneficial effects of the synergistic deinking and delignification process on the quality of recycled pulp. By utilizing a mixture of neutral sodium sulfite, sodium carbonate, and fungal hemicellulase enzyme, the research demonstrated that the paper achieved enhancements in brightness, whiteness, tensile and burst indices, while also exhibiting reduced yellowness and ERIC in comparison to paper derived from chemically deinked pulp. The high-resolution ESCA analysis demonstrated a reduction in lignin surface coverage, and enhancement in the O/C atomic ratios. FTIR spectra indicated notable alterations in the structure of fibers and the functional groups of deinked pulp fibers. XRD spectra confirmed a higher cellulose crystallinity index and FESEM micrographs illustrated a rougher surface with the emergence of new fibrils. Additionally, UV analysis of the pulp effluents indicated significant lignin absorbance, while post-bleaching with H 2 O 2 further enhanced the reactivity of the pulp and the overall quality of the paper., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Iman Akbarpour reports financial support was provided by Gorgan University of Agricultural Sciences and Natural Resources. Iman Akbarpour reports a relationship with Gorgan University of Agricultural Sciences and Natural Resources that includes: board membership and employment. This work was funded by the Gorgan University of Agricultural Sciences and Natural Resources (GUASNR) under Project Grant AGRI/4081/2023, Research Plan ID number 01-474-93. The author extends thanks to GUASNR, Golestan University, Mazandaran University, and Tehran University for providing laboratory facilities and valuable cooperationthat contributed to the successful completion of this research. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)