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Silver nanoparticles (AgNPs) decorated filter papers combining solid-phase extraction (SPE) with surface enhanced Raman spectroscopy (SERS) achieved rapid collection of analytes and in situ detection. The AgNPs were fabricated by cellulose self-sacrificing reduction. Aqueous Ag(NH3)2OH was reduced by hydroxyl groups in cellulose under alkaline conditions. The AgNPs were highly uniform and firmly adhered to the microfibers. Reaction conditions were optimized by the probe molecule p-aminothiophenol (PATP) to attain the best Raman enhancement. Methylene blue trihydrate (MB) and 6-thioguanine (6-TG) were detected by flow-through method. The results exhibited outstanding SERS effect and an obvious improvement in detection limit was observed compared to common immersion methods. SERS detection was quantitative as the log-log plot of Raman intensity against MB and 6-TG concentrations showed a linear relationship. The SERS-active paper is degradable because it could be burned after analyte detection. [ABSTRACT FROM AUTHOR]

As inspired by the Dot blot analysis, a well known technique in molecular biology and genetics for detecting biomolecules, a new paper-based platform for colorimetric detection of specific DNA sequences employing peptide nucleic acid (PNA) as a probe has been developed. In this particular study, a pyrrolidinyl PNA bearing a conformationally rigid d-prolyl-2-aminocyclopentanecarboxylic acid backbone (acpcPNA) was used as a probe. The filter paper was modified to be positively charged with grafted polymer brushes of quaternized poly(dimethylamino)ethyl methacrylate (QPDMAEMA) prepared by surface-initiated polymerization of 2-(dimethylamino)ethyl methacrylate from the filter paper via ARGET ATRP followed by quaternization with methyl iodide. Following the Dot blot format, a DNA target was first immobilized via electrostatic interactions between the positive charges of the QPDMAEMA brushes and negative charges of the phosphate backbone of DNA. Upon hybridization with the biotinylated pyrrolidinyl peptide nucleic acid (b-PNA) probe, the immobilized DNA can be detected by naked eye observation of the yellow product generated by the enzymatic reaction employing HRP-labeled streptavidin. It has been demonstrated that this newly developed assay was capable of discriminating between complementary and single base mismatch targets at a detection limit of at least 10 fmol. In addition, the QPDMAEMA-grafted filter paper exhibited a superior performance to the commercial membranes, namely Nylon 66 and nitrocellulose. [ABSTRACT FROM AUTHOR]

We exploit the combinatorial advantage of electrokinetics and tortuosity of a cellulose-based paper network on laboratory grade filter paper for the development of a simple, inexpensive, yet extremely robust (shows constant performance for 12 days) ‘paper-and-pencil’-based device for energy harvesting applications. We successfully achieve harvesting of a maximum output power of ∼640 pW in a single channel, while the same is significantly improved (by ∼100 times) with the use of a multichannel microfluidic array (maximum of up to 20 channels). Furthermore, we also provide theoretical insights into the observed phenomenon and show that the experimentally predicted trends agree well with our theoretical calculations. Thus, we envisage that such ultra-low cost devices may turn out to be extremely useful in energizing analytical microdevices in resource limited settings, for instance, in extreme point of care diagnostic applications. [ABSTRACT FROM AUTHOR]

An improved paper-based analytical device (PAD) using color screening to enhance device performance is described. Current detection methods for PADs relying on the distance-based signalling motif can be slow due to the assay time being limited by capillary flow rates that wick fluid through the detection zone. For traditional distance-based detection motifs, analysis can take up to 45 min for a channel length of 5 cm. By using a color screening method, quantification with a distance-based PAD can be achieved in minutes through a “dip-and-read” approach. A colorimetric indicator line deposited onto a paper substrate using inkjet-printing undergoes a concentration-dependent colorimetric response for a given analyte. This color intensity-based response has been converted to a distance-based signal by overlaying a color filter with a continuous color intensity gradient matching the color of the developed indicator line. As a proof-of-concept, Ni quantification in welding fume was performed as a model assay. The results of multiple independent user testing gave mean absolute percentage error and average relative standard deviations of 10.5% and 11.2% respectively, which were an improvement over analysis based on simple visual color comparison with a read guide (12.2%, 14.9%). In addition to the analytical performance comparison, an interference study and a shelf life investigation were performed to further demonstrate practical utility. The developed system demonstrates an alternative detection approach for distance-based PADs enabling fast (∼10 min), quantitative, and straightforward assays. [ABSTRACT FROM AUTHOR]

The transport of molecules and particles across adjacent flow streams is a key process in several operations implemented in microfluidic paper-based analytical devices (μPADs). Here, the transverse dispersion of analytes was quantitatively evaluated by theory and experiments. Different tests were carried out to independently measure the coefficients of both Brownian diffusion and mechanical dispersion under capillary-driven flow. The dispersion width was found to be independent of fluid velocity and analyte properties, and fully determined by the dispersivity coefficient, which is a characteristic of the paper microstructure. This information introduces a change of paradigm for the design of mixers, diluters, and concentration gradient generators on μPADs; therefore, efforts were made to rationalize these operations on paper. The research reveals that mixers and concentration gradient generators can be much more efficient than their counterparts made on conventional microchannels; in contrast, separators such as the H-filter need to be appropriately engineered on paper, because the working principle can be hindered by mechanical dispersion. The knowledge gained throughout this work would contribute to the design of μPADs with a new level of precision and control over the formation of localized concentration profiles. [ABSTRACT FROM AUTHOR]

There has been a recent resurgence in the use of paper as a substrate for developing point-of-care medical diagnostic tests, possibly triggered by expiring patents published in the 1990s. A hallmark of this resurgence has been the development of advanced shapes and structures made from paper to conduct multi-step fluidic operations using the wicking action of porous materials. Such devices indicate a distinct improvement over lateral flow immunoassays, which are restricted to conducting one-step operations. New developments in paper-based diagnostic devices have triggered interest in the development of paper-based point-of-care nucleic acid amplification tests (NAATs). NAATs can identify extremely low levels of specific nucleic acid sequences from clinical samples and are the most sensitive of all available tests for infectious disease diagnosis. Because traditional PCR-based NAATs require expensive instruments, the development of portable paper-based NAAT's has become an exciting field of research. This article aims to review and analyse the current state of development of paper-based NAATs. We project paper-based NAATs as miniaturized chemical processes and shed light on various schemes of operation used for converting the multiple steps of the chemical processes into paper microfluidic devices. We conclude by elaborating on the challenges that must be overcome in the near future so that progress can be made towards the development of fully functional and commercial paper-based NAATs. [ABSTRACT FROM AUTHOR]

Fluorescent paper sensors are widely used in the assays of environment, food and medicine; however, their applications usually have been limited due to the narrow color-change range and insensitivity of the color variation to dosage of target analytes. In this paper, we report a ratiometric fluorescent probe-based paper sensor regulated by the optimum proportion of gold nanoclusters stabilized by bovine serum albumin and fluorescent graphene oxide to achieve the maximum consecutive color change for visual determination of glucose in human serum. The oxidation of hydrogen peroxide produced by glucose quenches the red fluorescence emission of gold nanoclusters and unveils a consecutive color change from pink to blue with the corresponding dosage of glucose. This colorimetric paper sensor printed with the probe ink exhibits a dosage-sensitive allochromatic capability for the blood glucose concentration of 4–10 mM in human serum (normal concentration: 4.4–6.6 mM). The method reported here can open a window in predicting diseases related to abnormal glucose levels. [ABSTRACT FROM AUTHOR]

We present a novel microfluidic paper-based analytical device (μPAD) which utilizes the native high electroosmotic flow (EOF) in nitrocellulose to achieve stationary isotachophoresis (ITP) focusing. This approach decouples sample accumulation from the length of the channel, resulting in significant focusing over short channel lengths. We provide a brief theory for EOF-balanced ITP focusing under continuous injection from a depleting reservoir and present the design of a short (7 mm) paper-based microfluidic channel, which allows a 200 μL sample to be processed in approximately 6 min, resulting in a 20 000-fold increase in concentration – a full order of magnitude improvement compared to previous paper-based ITP devices. We show the stability of the assay over longer (40 min) durations of time, and using Morpholino probes, we present the applicability of the device for amplification-free detection of nucleic acids, with a limit-of-detection (LoD) of 5 pM in 10 min. Finally, we utilize the small footprint of the channel and show a multiplexed platform in which 12 assays operate in parallel in a 24-well plate format. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based analytical devices (μPADs) are a versatile and inexpensive point-of-care (POC) technology, but their widespread adoption has been limited by slow flow rates and the inability to carry out complex in field analytical measurements. In the present work, we investigate multilayer μPADs as a means to generate enhanced flow rates within self-pumping paper devices. Through optical and electrochemical measurements, the fluid dynamics are investigated and compared to established flow theories within μPADs. We demonstrate a ∼145-fold increase in flow rate (velocity = 1.56 cm s−1, volumetric flow rate = 1.65 mL min−1, over 5.5 cm) through precise control of the channel height in a 2 layer paper device, as compared to archetypical 1 layer μPAD designs. These design considerations are then applied to a self-pumping sequential injection device format, known as a three-dimensional paper network (3DPN). These 3DPN devices are characterized through flow injection analysis of a ferrocene complex and anodic stripping detection of cadmium, exhibiting a 5× enhancement in signal compared to stationary measurements. [ABSTRACT FROM AUTHOR]

Paper-based microfluidic devices with screen-printed electrodes (SPEs) for electrochemical sensing are popular for low-cost point-of-care diagnostics. The electroactive sensing area in these devices is always the irregular, bottom-SPE surface which is in contact with the analyte flowing within the paper substrate. Unfortunately, this results in an electroactive area which varies widely from sensor to sensor. In this paper, we present a three-dimensional paper-based analytical device with a hollow 3D fluid reservoir which allows for use of a more uniform top-SPE surface as the electroactive sensing area. The use of this isolated reservoir eliminates the need for dielectric inks used in conventional SPEs on paper. Our sensors are fabricated using a combination of wax-printing, screen-printing and simple folding via a cleanroom free process without the need for expensive equipment. Additionally, for the first time, we demonstrate an electrochemical paper-based analytical device with a custom designed potentiostat integrated circuit (IC) as a miniaturized reader. The versatility of the sensor is demonstrated through voltammetric, amperometric and potentiometric measurements of important biochemical analytes such as dopamine, glucose and pH. The 3D ePAD together with a custom CMOS potentiostat demonstrates a low-cost, versatile, self-contained system suitable for point-of-care diagnostic devices. [ABSTRACT FROM AUTHOR]

On the example of a colorimetric sodium assay, this work demonstrates the implementation of a classical cation-exchange optode relying on an ionophore-doped plasticized PVC membrane into a paper-based analytical device (PAD). An ion-selective optode (ISO) system has been arranged into a vertically-assembled PAD (vPAD) integrating a pH-buffering function. Capillary force-driven sample liquid transportation through the paper matrix enabled pH-adjustment prior to the optical detection of the analyte cation. Functionalized paper layers with inkjet-deposited ISO membranes were combined with whole device lamination to attain a stable ion-exchange equilibrium required for the theoretical behavior of ISOs. Whole device lamination limited rapid evaporation of sample liquid on vPADs to avoid an increase of target concentration. Sigmoidal response curves between 10−5 and 1 M of Na+ at pH 5.0–7.0 have been confirmed on vPADs, following the theory defined by the cation-exchange equilibrium reaction. Finally, the influence of the cellulosic paper substrate matrix acting as a cation-exchanger on the optode response behavior has been evaluated and compared with conventional plastic film optodes. [ABSTRACT FROM AUTHOR]

The transport efficiency during capillary flow-driven sample transport on microfluidic paper-based analytical devices (μPADs) made from filter paper has been investigated for a selection of model analytes (Ni2+, Zn2+, Cu2+, PO43−, bovine serum albumin, sulforhodamine B, amaranth) representing metal cations, complex anions, proteins and anionic molecules. For the first time, the transport of the analytical target compounds rather than the sample liquid, has been quantitatively evaluated by means of colorimetry and absorption spectrometry-based methods. The experiments have revealed that small paperfluidic channel dimensions, additional user operation steps (e.g. control of sample volume, sample dilution, washing step) as well as the introduction of sample liquid wicking areas allow to increase analyte transport efficiency. It is also shown that the interaction of analytes with the negatively charged cellulosic paper substrate surface is strongly influenced by the physico-chemical properties of the model analyte and can in some cases (Cu2+) result in nearly complete analyte depletion during sample transport. The quantitative information gained through these experiments is expected to contribute to the development of more sensitive μPADs. [ABSTRACT FROM AUTHOR]

In this study, a piece of filter paper with good flexibility and hygroscopicity was used to support catalysts after a pencil drawing process. A layer of thin Ni film was deposited on the surface of the conductive graphite layer using an electrochemical method at a negative potential. Pd nanoparticles with high electrocatalytic activity for NaBH4 oxidation were introduced by immersing the Ni film-graphite-filter paper (NGF) in PdCl2 solution to obtain a Pd-NGF (PNGF) electrode. The morphology and phase structure of PNGF were characterized using scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and an X-ray diffractometer (XRD). The PNGF electrode was used as the anode in direct borohydride fuel cells (DBFCs), and the electrochemical properties for NaBH4 oxidation were determined by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The oxidation current density reaches 550 mA cm−2 at −0.4 V when the electrolyte contains 2 mol dm−3 NaOH and 0.10 mol dm−3 NaBH4. [ABSTRACT FROM AUTHOR]

In this study, we present a selective paper-based method for the detection of l-Cys in serum using DTNB-modified Ag nanoprisms (AgP-DTNB). This method is based on the principle that l-Cys reacts with DTNB in AgP-DTNB to release a TNB2− chromophore and etches simultaneously AgP-DTNB to form Ag nanodisks, hence resulting in ratiometric changes of absorbance. Different biothiols have different affinities to etch the AgP surface and cause nanodisks of different sizes, which have slightly different resonance wavelengths. Thus, l-Cys can be discriminated with different biothiols on the basis of the different absorption spectral changes and different absorbance ratios. The linear dynamic range for the determination of l-Cys was 1–1750 μM, and the correlation coefficient (R2) was 0.9968 (y = 3.0859 × 10−4 [Cys] + 0.9376). The limit of detection for l-Cys was calculated to be 0.87 μM from 3 times the standard deviation of the blanks to the slope of the calibration curve. Compared with the other nanoparticle-based sensors in solution and on paper, AgP-DTNB possesses a much wider linear range and a comparable detection limit for l-Cys. This paper-based sensor exhibits selectivity, a wide linear sensing range, low-volume sampling, miniaturization, portability, and disposability. [ABSTRACT FROM AUTHOR]

This study reports a simple, rapid, low-cost, robust, and multiplexed barcoded paper-based assay (BPA) compatible with mobile devices. An inkjet printer and an XYZ dispensing platform were used to realize mass-manufacturing of barcoded paper-based analytical devices (BPADs) with high precision and efficiency. We designed a new group of barcodes and developed an application (APP) for the reading of the new code. The new barcodes possess a 16 times higher coding capacity than the standard Codabar code in our experiment on drug residue detection. The BPA system allows applications in the assays of blood-transmitted infections, drug residues in milk and multiplex nucleic acids. The whole detection process and the readout of the results can be completed within 10 minutes. The limit of detection for enrofloxacin (ENR) (8 ng mL−1) satisfies the requirements of drug residue monitoring. Its high rapidity, simplicity, efficiency and selectivity make the BPA system extremely suitable to be applied in rapid and on-site detection. [ABSTRACT FROM AUTHOR]

Ti2AlC has been investigated for several decades, but much less attention has been paid to its delamination and potential energy storage applications, mainly due to the difficulty of delamination and its oxidation features. Herein, a new path to enhance exfoliation and delamination of two-dimensional (2D) Ti2CTx MXene is used. By using an etchant of HCl + LiF, multilayer Ti2CTx is easy to obtain. With only the assistance of mild sonication for 1.5 h without any additional intercalation, two-dimensional (2D) Ti2CTx flake suspensions are produced. Subsequently, the as-fabricated stable suspensions of delaminated Ti2CTx flakes are combined with carbon nanotubes. After filtration, a two-dimensional layered Ti2CTx/carbon nanotube (CNT) nanocomposite “paper” is prepared. Owing to the larger specific area of MXene flakes, which is caused by the complete exfoliation of MXene, with carbon nanotubes assisting with structural support between layers to prevent restacking, this structure provides a rapid charge transfer path during electrochemical reactions. When the nanocomposite paper is used as a lithium ion battery anode, it exhibits a higher capacitance and better cycling stability (a reversible capacity of 155.5 mA h g−1 at 100 mA g−1 after 200 cycles). Moreover, the “paper” can be directly used for electrodes in supercapacitors; the calculated capacitances are 515.3 F g−1 and 694 F cm−3 at a scanning rate of 2 mV s−1. The facile synthesis of layered Ti2C MXene/carbon nanotube nanocomposite paper provides a more secure and easy way to fabricate promising energy storage materials, and creates wider opportunities for exploiting the potential of other MXenes. [ABSTRACT FROM AUTHOR]

Proof-of-concept is shown for two-phase countercurrent flow on paper. The device consists of two paper layers, one of which has been modified with a sizing agent to be hydrophobic. The layers exhibit different wetting behavior for water and octanol. Both phases dominate wetting in one of the layers and can be made to move in different directions along the interface to achieve liquid–liquid extraction. [ABSTRACT FROM AUTHOR]

A concept integrating sampling and protein digestion is introduced here combining fast and simple fabrication by wax printing on filter paper with trypsin immobilized polymer beads. The paper reactors showed promising results with a high degree of protein digestion within fifty minutes in model protein mixtures as well as in human blood. The model protein mixture was used for the evaluation of performance both with and without a reduction and alkylation step. The paper reactors without reduction and alkylation showed between 46% and 75% protein sequence coverage and between five and 20 high confidence peptides (one and five zero missed cleavage peptides, respectively). Compared to a conventional in-solution approach, the paper reactor showed 10% less protein sequence coverage, 29% fewer high confidence peptides and 19% fewer high confidence peptides with zero missed cleavages. Placement of the protein reduction and alkylation step (before or after protein digestion) was shown to be of low importance. The storage stability of the paper reactors with (six weeks) and without (twelve weeks) tryptic peptides was satisfactory. The ability of the paper reactors to digest complex biological samples was investigated by comparison with human whole blood samples prepared using a conventional dried blood spot (DBS) procedure with overnight digestion in non-targeted analysis. The reactors showed a comparable performance with 75 ± 25 for the protein groups compared to 76 ± 5 for the DBS samples. Additionally, 267 ± 72 and 335 ± 11 unique peptides (high confidence) were identified for on-paper digestion and DBS, respectively. [ABSTRACT FROM AUTHOR]

The development of point-of-care bioassays for sensitive screening of protein-based cancer biomarkers would improve the opportunity for early stage diagnosis. A strategy for a fluorescence resonance energy transfer (FRET)-based bioassay has been investigated that makes use of modified cellulose paper for the detection of an epithelial cell adhesion molecule (EpCAM), which is a transmembrane glycoprotein that is overexpressed in several tumors of epithelial origin. The paper matrix was a substrate for immobilized aptamer-linked quantum dots (QDs-Apt) and Cy3 labeled complementary DNA (cDNA), which served as a donor and an acceptor, respectively. Competitive binding of EpCAM displaced the cDNA, resulting in the reduction of FRET. The paper-based bioassay was able to detect EpCAM in buffer solution as well as in 10% bovine serum solution using a reaction time of no more than 60 minutes. The dynamic range was 1–100 nM in buffer with a precision better than 4%, and the limit of detection was 250 pM in buffer and 600 pM in 10% serum. [ABSTRACT FROM AUTHOR]

In vitro models for screening new cancer chemotherapeutics often rely on two-dimensional cultures to predict therapeutic potential. Unfortunately, the predictive power of these models is limited, as they fail to recapitulate the complex three-dimensional environments in tumors that promote a chemoresistant phenotype. In this study, we describe the preparation and characterization of paper-based cultures (PBCs) engineered to assess chemotherapeutic effectiveness in three dimensional, diffusion-limited environments. Similar environments are found in poorly vascularized tumors. Monotonic gradients develop across these cultures, which are assembled by stacking cell-laden paper scaffolds to yield thick tissue-like structures, and provide distinct chemical environments for each scaffold. After prolonged incubation, the scaffolds can simply be peeled apart and analyzed. Through fluorescence imaging, we determined that viable and proliferative cell populations were most abundant in scaffolds close to the nutrient-rich medium. By adjusting the cell density, we modulated the spatiotemporal evolution of oxygen gradients across the cultures and correlated these environmental changes with cellular sensitivity to SN-38 exposure. From these results, we showed that differences in the oxygen gradients produced cellular populations with significantly different chemosensitivities. Through this work, we highlight PBCs ability to serve as an analytical model capable of determining chemotherapeutic effectiveness under a range of chemical environments. [ABSTRACT FROM AUTHOR]

A novel low-cost, compact and sensitive paper-based platform for the accurate monitoring of glucose in biological fluids is presented. Paper-based working and reference electrodes are combined to build a whole potentiometric cell, which also fits a sampling module for simple and fast determination of glucose in a single drop of blood. The working electrode is built using a platinized filter paper coated with a Nafion membrane that entraps the enzyme glucose oxidase; the reference electrode is made by casting a polyvinylbutyral-based membrane onto a conductive paper. The system works by detecting the hydrogen peroxide generated as a result of the enzymatic reaction. Selectivity is achieved due to the permselective behaviour of Nafion, while a significant enhancement of the sensitivity is reached by exploiting the Donnan-coupled formal potential. Under optimum conditions, a sensitivity of −95.9 ± 4.8 mV per decade in the 0.3–3 mM range is obtained. Validation of the measurements has been performed against standard methods in human serum and blood. Final integration with a wireless reader allows for truly in situ measurements with a less than 2 minute procedure including a two-point calibration, washing and measurement. This low-cost analytical device opens up new prospects for rapid diagnostic results in non-laboratory settings. [ABSTRACT FROM AUTHOR]

Cellular invasion is the gateway to metastasis, which is the leading cause of cancer-related deaths. Invasion is driven by a number of chemical and mechanical stresses that arise in the tumor microenvironment. In vitro assays are needed for the systematic study of cancer progress. To be truly predictive, these assays must generate tissue-like environments that can be experimentally controlled and manipulated. While two-dimensional (2D) monolayer cultures are easily assembled and evaluated, they lack the extracellular components needed to assess invasion. Three-dimensional (3D) cultures are better suited for invasion studies because they generate cellular phenotypes that are more representative of those found in vivo. This feature article provides an overview of four invasion platforms. We focus on paper-based cultures, an emerging 3D culture platform capable of generating tissue-like structures and quantifying cellular invasion. Paper-based cultures are as easily assembled and analyzed as monolayers, but provide an experimentally powerful platform capable of supporting: co-cultures and representative extracellular environments; experimentally controlled gradients; readouts capable of quantifying, discerning, and separating cells based on their invasiveness. With a series of examples we highlight the potential of paper-based cultures, and discuss how they stack up against other invasion platforms. [ABSTRACT FROM AUTHOR]

3D CoNi2S4 and cross-linked NiCo2S4 arrays have been grown on carbon paper (CP) using a one-step hydrothermal method. The 3D cross-linked structure provides a convenient channel for electron and lithium-ion (Li+) transport and performs a facile strain relaxation during cycling, exhibits high capacity, excellent rate capability and superior cycle performance. [ABSTRACT FROM AUTHOR]

A novel silica coated paper substrate is developed through a facile vacuum filtration method by using the commercially available silica particles as the coating material and corn starch as the adhesive agent. Unlike the commercial silica coated paper (namely grade SG81 paper), the resulting paper substrate was covered by a layer of silica particles on the top side of the paper, and no cellulosic fibers were exposed at its surface. After loading a solution sample on its surface, the coated silica particles allowed the target analytes to remain at the top side rather than penetration through the substrate. Owing to this effect and the special interactions with analytes, the as-prepared silica coated paper demonstrated superior performance in the analysis of different pesticides in milk using paper spray mass spectrometry to the uncoated filter paper and grade SG81 paper. Compared to the other two papers, paper spray analysis using the as-prepared paper improved the estimated lower limit of quantitation of seven pesticides (alachlor, acetochlor, pretilachlor, butachlor, metolachlor, napropamid and benzeneacetamide) in milk by a factor of 2 to 19-fold depending on the pesticide. This study offers a novel paper substrate for paper spray in high sensitivity analysis of target analytes in a complex foodstuff matrix without any pretreatment. [ABSTRACT FROM AUTHOR]

Microfluidic-based integrated molecular diagnostic systems, which are automated, sensitive, specific, user-friendly, robust, rapid, easy-to-use, and portable, can revolutionize future medicine. Current research and development largely relies on polydimethylsiloxane (PDMS) to fabricate microfluidic devices. Since the transition from the proof-of-principle phase to clinical studies requires a vast number of integrated microfluidic devices, there is a need for a high-volume manufacturing method of silicone-based microfluidics. Here we present the first roll-to-roll (R2R) thermal imprinting method to fabricate integrated PDMS–paper microfluidics for molecular diagnostics, which allows production of tens of thousands of replicates in an hour. In order to validate the replicated molecular diagnostic platforms, on-chip amplification of viral ribonucleic acid (RNA) with loop-mediated isothermal amplification (LAMP) was demonstrated. These low-cost, rapid and accurate molecular diagnostic platforms will generate a wide range of applications in preventive personalized medicine, global healthcare, agriculture, food, environment, water monitoring, and global biosecurity. [ABSTRACT FROM AUTHOR]

A new and simple fluorescent probe bearing mono-sulfur (1) and tetra-sulfur (2) tetrahydrodibenzo phenanthridine derivatives were synthesized and examined for their cation recognition abilities towards different cations in aqueous acetonitrile solution and paper strips. Both the probes showed high selectivity and sensitivity with strong affinity towards Hg2+ ions over other cations, such as Cu2+, Ca2+, Co2+, Cd2+, Pb2+, Zn2+, Ni2+, Mg2+, Mn2+, Al3+, Fe3+, La3+, Ag+, K+, Na+ and Li+. The binding stoichiometry ratios of 1–Hg2+ and 2–Hg2+ are recognized as 1 : 1 according to the UV-Vis absorption spectra, fluorescence measurements and computational (DFT) studies, and the possible binding mode of these receptors with Hg2+ is also proposed. The limit of detection with Hg2+ cation was found to be as low as 0.91 nM and 0.041 nM for probes 1 and 2, respectively. The results clearly indicate that the synthesised tetrahydrodibenzo phenanthridine derivatives 1 and 2 could be used as excellent chemosensors for Hg2+ detection in biological and environmental samples. [ABSTRACT FROM AUTHOR]

Designing cost-effective, highly efficient and stable electrocatalysts for oxygen evolution reaction is of paramount importance. Although extensive studies have focused on the relatively cheaper 3d transition metal oxide catalysts, the effect of trimetallic composites on the catalytic ability still remains elusive. Herein, we selected FeCo catalyst as the platform and investigated the catalytic activity of trimetallic composites, which were synthesized by incorporating Mo, W or Ni into the FeCo catalyst. The experimental results evidenced that FeCoMo/CP exhibited high catalytic activity towards water oxidation in alkaline solution, which required an overpotential of only ∼270 mV. Such impressive catalytic performance of FeCoMo/CP can be attributed to the fact that the introduction of Mo appreciably modulated the electronic structure of the Fe and Co centers, leading to an enhancement in intrinsic active sites. Benefiting from the tight contact with the highly conductive carbon paper substrate, FeCoMo/CP showed excellent stability up to 120 h. These results indicate that the surface engineering of FeCo-based catalysts by incorporating non-noble metals is a rational strategy to promote the performance of electrocatalysts. [ABSTRACT FROM AUTHOR]

In this work, an application of a design of experiments approach for the optimization of an isoniazid assay on a single-area inkjet-printed paper-based analytical device (PAD) is described. For this purpose, a central composite design was used for evaluation of the effect of device geometry and amount of assay reagents on the efficiency of the proposed device. The factors of interest were printed length, width, and sampling volume as factors related to device geometry, and amounts of the assay reagents polyvinyl alcohol (PVA), NH4OH, and AgNO3. Deposition of the assay reagents was performed by a thermal inkjet printer. The colorimetric assay mechanism of this device is based on the chemical interaction of isoniazid, ammonium hydroxide, and PVA with silver ions to induce the formation of yellow silver nanoparticles (AgNPs). The in situ-formed AgNPs can be easily detected by the naked eye or with a simple flat-bed scanner. Under optimal conditions, the calibration curve was linear in the isoniazid concentration range 0.03–10 mmol L−1 with a relative standard deviation of 3.4% (n = 5 for determination of 1.0 mmol L−1). Finally, the application of the proposed device for isoniazid determination in pharmaceutical preparations produced satisfactory results. [ABSTRACT FROM AUTHOR]

We report a green fabrication of conductive paper based on in situ polymerization of polymerizable deep eutectic solvents (PDESs) through a screen printing process. By pre-designed circuit paths and careful integration, on-demand input/output 3D circuits can be achieved, showing its flexibility to origami electronics. [ABSTRACT FROM AUTHOR]

Chromogenic probe with oxidized bis-indolyl scaffold has been synthesized for the detection of a nerve gas mimicking agent, DCNP (diethyl cyanophosphonate) at pH 8.0 in water. The mechanism of interaction was proposed as the release of cyanide ion through the indole group mediating the hydrolysis of phosphorous-hetero atom bond and, thereafter, the Michael addition of the liberated CN− ion to the electron deficient C=C bond of the bis-indolyl moiety. The reaction featured a remarkable change in color from red to colorless at ambient condition. Then, low-cost and portable paper strips were designed for a rapid and on-site vapor phase detection of DCNP without involving any sophisticated instrument or skilled personnel. Finally, a dye assembled inorganic nanocomposite material was devised to achieve a more sensitive ‘turn-on’ detection of DCNP in water. [ABSTRACT FROM AUTHOR]

A miniaturized paper-based lab-on-chip (LoC) was developed for the facile measurement of urinary Phe (phenylalanine) level on PKU (Phenylketonuria) treated patient. This system permits the monitoring of Phe in a dynamic range concentration of 20–3000 μM. [ABSTRACT FROM AUTHOR]

In this study, a technique based on multiple headspace extraction gas chromatography (MHE-GC) was applied to determine the transfer kinetics of contaminants from paper-based packaging materials to air because of its sensitivity and safety. Mathematical equations were derived in order to calculate the desorption reaction rate constant of a contaminant. This procedure was applied to five contaminants: o-xylene, ethanol absolute, n-dodecane, diphenyl oxide, and diallyl-o-phthalate. The results indicated that the desorption reaction rate constant increased with temperature. The vapor pressure and chemical structure of the contaminants also affected the desorption reaction rate constant. Temperature had a predominant effect on the desorbing kinetics of the contaminants. The equilibrium times of desorption decreased as the temperature increased; for example, the equilibrium times of o-xylene were ≥4, 4, and 1 h at 40, 70, and 100 °C, respectively. [ABSTRACT FROM AUTHOR]

A paper/poly(methyl methacrylate) (PMMA) hybrid CD-like microfluidic SpinChip integrated with DNA probe-functionalized graphene oxide (GO) nanosensors was developed for multiplex quantitative LAMP detection (mqLAMP). This approach can simply and effectively address a major challenging problem of multiplexing in current LAMP methods. [ABSTRACT FROM AUTHOR]

The diagnosis of infectious diseases is entering a new and interesting phase. Technologies based on paper microfluidics, coupled to developments in isothermal amplification of Nucleic Acids (NAs) raise opportunities for bringing the methods of molecular biology in the field, in a low setting environment. A lot of work has been performed in the domain over the last few years and the landscape of contributions is rich and diverse. Most often, the level of sample preparation differs, along with the sample nature, the amplification and detection methods, and the design of the device, among other features. In this review, we attempt to offer a structured description of the state of the art. The domain is not mature and there exist bottlenecks that hamper the realization of Nucleic Acid Amplification Tests (NAATs) complying with the constraints of the field in low and middle income countries. In this domain however, the pace of progress is impressively fast. This review is written for a broad Lab on a Chip audience. [ABSTRACT FROM AUTHOR]

A colorimetric point-of-care paper-based analytical device (PAD) is developed for detecting adulterated beverages using whiskey falsified with caramel color as a model. Combining principal component analysis and calibration curves facilitated identification of adulteration in samples seized by the Brazilian Federal Police, at only ∼$0.02 per sample. [ABSTRACT FROM AUTHOR]

Microfluidic platforms are an attractive option for incorporating complex fluid handling into low-cost and rapid diagnostic tests. A persistent challenge for microfluidics, however, is the mismatch in the “world-to-chip” interface – it is challenging to detect analytes present at low concentrations in systems that can only handle small volumes of sample. Here we describe a new technique termed pre-concentration by liquid intake by paper (P-CLIP) that addresses this mismatch, allowing digital microfluidics to interface with volumes on the order of hundreds of microliters. In P-CLIP, a virtual microchannel is generated to pass a large volume through the device; analytes captured on magnetic particles can be isolated and then resuspended into smaller volumes for further processing and analysis. We characterize this method and demonstrate its utility with an immunoassay for Plasmodium falciparum lactate dehydrogenase, a malaria biomarker, and propose that the P-CLIP strategy may be useful for a wide range of applications that are currently limited by low-abundance analytes. [ABSTRACT FROM AUTHOR]

Herein, a pH sensitive paper SERS chip was prepared by selecting m-cresol purple, a molecule with halochromic properties in the neutral pH range as a Raman reporter. The adsorbed m-cresol purple underwent a reversible change in its electronic configuration from a non-resonant species to a resonant species, which resulted in a significant Raman signal intensity variation due to the transformation of the sensing mode from SERS to surface-enhanced resonance Raman scattering (SERRS). The chips have a sensitive pH range of 6.0 to 8.0 and exhibited good performance for the detection of natural water samples with detection precision of approximately 0.03 pH units, suggesting great potential for environmental pH monitoring applications. [ABSTRACT FROM AUTHOR]

A new method for making superhydrophobic (SH) paper based on spraying a nanocomposite film is developed. Furthermore, manipulating the wetting characteristics of SH paper has been demonstrated through a new method, i.e.printing solid grey patterns of different intensities with simple printing technology (home or office grade ink-jet and laser printers). It has been found that for a range of ink intensities (0–85%), water drop mobility can be changed at a different rate (almost independently) from repellency. The repellency of water decreases minimally up to 85% ink intensity with a sharp decrease up to 100% ink intensity. Drop mobility remains constant up to 30% ink intensity with a steady decrease up to 100% ink intensity. It was observed that using ink-jet or laser printing would yield different results for the change of mobility or repellency with higher amounts of ink/toner used. Being able to achieve almost independent control of water drop mobility over water drop repellency on SH paper would allow inexpensive lab-on-paper devices to be used for sampling, mixing and transport of liquids. [ABSTRACT FROM AUTHOR]

We report a method for fabricating inexpensive microfluidic platforms on paper using laser treatment. Any paper with a hydrophobic surface coating (e.g., parchment paper, wax paper, palette paper) can be used for this purpose. We were able to selectively modify the surface structure and property (hydrophobic to hydrophilic) of several such papers using a CO2laser. We created patterns down to a minimum feature size of 62 ± 1 µm. The modified surface exhibited a highly porous structure which helped to trap/localize chemical and biological aqueous reagents for analysis. The treated surfaces were stable over time and were used to self-assemble arrays of aqueous droplets. Furthermore, we selectively deposited silica microparticles on patterned areas to allow lateral diffusion from one end of a channel to the other. Finally, we demonstrated the applicability of this platform to perform chemical reactions using luminol-based hemoglobin detection. [ABSTRACT FROM AUTHOR]

Two paper-based microfluidic techniques, photolithography and wax patterning, were investigated for their potential to improve upon the sensitivity, reproducibility, and versatility of paper spray mass spectrometry. The main limitation of photolithography was the significant signal (approximately three orders of magnitude) above background which was attributed to the chemicals used in the photoresist process. Hydrophobic barriers created via wax patterning were discovered to have approximately 2 orders of magnitude less background signal compared to analogous barriers created using photolithography. A minimum printed wax barrier thickness of approximately 0.3 mm was necessary to consistently retain commonly used paper spray solvents (1 : 1 water : acetonitrile/methanol) and avoid leakage. Constricting capillary flow via wax-printed channels yielded both a significant increase in signal and detection time for detection of model analytes. This signal increase, which was attributed to restricting the radial flow of analyte/solvent on paper (i.e., a concentrating effect), afforded a significant increase in sensitivity (p< 0.05) for the detection of pesticides spiked into residential tap water using a five-point calibration curve. Finally, unique mixing designs using wax patterning can be envisioned to perform on-paper analyte derivatization. [ABSTRACT FROM AUTHOR]

This document is a contents list for the journal "Dalton Transactions: An International Journal of Inorganic Chemistry." It provides a list of papers published in the latest issue of the journal, covering a wide range of topics in chemistry. The papers explore subjects such as stimuli-responsive luminescence, the synthesis and reactivity of different compounds, and the development of new sensors, luminescent materials, catalysts, and coordination compounds. The journal aims to foster connections within the global chemistry community and reinvest its profits into the field. Additionally, the document includes a correction for a previous paper. [Extracted from the article]

This document is a contents list for the New Journal of Chemistry, a publication by The Royal Society of Chemistry and the Centre National de la Recherche Scientifique. It provides a list of articles and papers featured in the latest issue of the journal, covering a diverse range of topics in chemistry. Some of the topics include enantioselective insertion of vinyl diazoacetates, building a data science toolbox for designing catalysts, and the synthesis and coordination behavior of a ferrocene phosphinostibine. The document also includes a correction to a previously published paper. [Extracted from the article]

This document is a contents list for the journal "Green Chemistry," published by the Royal Society of Chemistry. It features research papers on various topics related to sustainable chemistry, including photocatalytic upgrading of hydroxymethylfurfural, lignin extraction and nanodispersion, selenium-doped carbon materials, and the valorization of bio-renewable glycerol. The journal also includes tutorial reviews on topics such as Pickering emulsion-derived nano/microreactors and the iron ligand-to-metal charge transfer chemistry in water. Additionally, there are perspective papers, communications, and other research papers covering a range of subjects in green chemistry. The papers provide valuable insights into the development of greener and more sustainable chemical processes. [Extracted from the article]

This document is a contents list for the journal "Dalton Transactions: An International Journal of Inorganic Chemistry." It features a compilation of research papers covering various topics such as metal dioxo complexes, piezo-photocatalytic CO2 reduction, and carbonaceous materials for lithium-ion batteries. The journal aims to foster connections within the chemistry community and stimulate innovative ideas. Additionally, the document includes corrections to two previously published papers. [Extracted from the article]

With the advent of lithium-ion batteries (LIBs), the selection and application of electrode materials have been the subject of much discussion and study. Among them, graphite has been widely investigated for use as electrode materials in LIBs due to its abundant resources, low cost, safety and electrochemical diversity. While it is commonly recognized that conventional graphite materials utilized for commercial purposes have a limited theoretical capacity, there has been a steady emergence of new and improved carbonaceous materials for use as anodes in light of the progressive development of LIBs. In this paper, the latest research progress of various carbon materials in LIBs is systematically and comprehensively reviewed. Firstly, the rocking chair charging and discharging mechanism of LIBs is briefly introduced in this paper, using graphite anodes as an example. After that, the general categories of carbonaceous materials are highlighted, and the recent research on the recent progress of various carbonaceous materials (graphite-based, amorphous carbon-based, and nanocarbon-based) used in LIB anodes is presented separately based on the classification of the structural morphology, emphasizing the influence of the morphology and structure of carbon-based materials on the electrochemical performance of the batteries. Finally, the current challenges of carbonaceous materials in LIB applications and the future development of other novel carbonaceous materials are envisioned. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal "Dalton Transactions: An International Journal of Inorganic Chemistry." It includes various articles and papers on topics such as molecular transition metal catalysts, spectroscopic techniques, synthesis of materials, and studies on different compounds. The journal aims to connect the global chemistry community and invest its profits back into the field. This document is a list of research papers published in the journal Dalton Transactions. The papers cover a range of topics including electrocatalytic reduction of CO2, assembly of clusters, rechargeable batteries, and carbon nanoarchitectures. Each paper is summarized by its title and authors, providing a brief overview of the research topic. The document is a valuable resource for library patrons conducting research in various scientific fields. [Extracted from the article]

The document is a contents list for the journal "Dalton Transactions: An International Journal of Inorganic Chemistry." It includes various articles and papers on topics such as copper complexes, lanthanide-based POMs, and coordination polymers. The journal is published by The Royal Society of Chemistry, a leading chemistry community. The document also mentions approved training courses offered by the society. The given document is a list of papers published in the journal Dalton Transactions. The papers cover a range of topics in chemistry, including catalysis, phosphors, materials synthesis, and more. Each paper is identified by its title, authors, and page number. The document also includes a correction and a retraction for two previously published papers. [Extracted from the article]

The New Journal of Chemistry is a publication that focuses on the chemical sciences and aims to connect researchers worldwide. The document provided is a contents list for the journal's 2024 edition. It includes papers on various topics such as membrane modification, nanoparticle synthesis, targeted therapy, catalysis, and material properties. Two specific papers are highlighted: one discusses the use of cationic lipids in non-viral gene delivery, while the other explores the confinement of metal-organic framework (MOF) etching-induced hollow structures for enhanced activation of peroxymonosulfate. The journal is published by The Royal Society of Chemistry and the Centre National de la Recherche Scientifique. [Extracted from the article]

The document is a contents list for the journal "Dalton Transactions: An International Journal of Inorganic Chemistry." It includes various articles and papers on topics such as combatting bacterial infections, rare-earth metal-organic frameworks, and electrochemical capacitor applications. The journal is published by The Royal Society of Chemistry, a leading chemistry community. The document provides a brief overview of the articles included in the journal issue. The papers cover a range of topics in chemistry, including the synthesis of stable cyclopropenylvinyl ligands, the properties of metal-organic frameworks, the photocatalytic performance of titanium-oxide clusters, and the adsorption mechanisms of heavy metals on silica. Other topics include the synthesis of coordination polymers, the synthesis of salophen complexes, and the behavior of cyanido-bridged complexes. The papers provide valuable insights into various areas of chemical research. [Extracted from the article]