Acute intoxication incidents due to neurotoxic organophosphate (OP) insecticides are occasionally reported, related either to suicidal attempts or occupational exposure due to the misuse of protective equipment. Among them, chlorpyrifos is a compound related to great controversy, which is still authorized and easily accessible in many countries around the world. However, to screen for its exposure markers, instrumental methods are commonly applied, which cannot enable rapid monitoring at an early stage of an intoxication. Therefore, in this study, a microfluidic paper-based analytical device (μPAD) able to rapidly screen for chlorpyrifos-oxon, the toxic chlorpyrifos metabolite, in human serum was developed and fully validated. The μPAD combines wax-printed butyrylcholinesterase (BChE) paper sensors, a lab-on-a-chip (LOC) prototype injector and a smartphone as the analytical detector. In principle, the wax-printed strips with adsorbed BChE are embedded into LOC injectors able to deliver samples and reagents on-demand. A smartphone reader was used to monitor the color development on the strips providing binary qualitative results. μPAD method performance characteristics were thoroughly evaluated in terms of specificity, detection capability (CCβ) and ruggedness. The developed analytical platform is rapid (results within 10 min), cost-efficient (0.70 €), potentially applicable at the point-of-need and attained a low CCβ (10 μg L-1 in human serum). Finally, μPAD characteristics were critically compared to well-established methods, namely an in-house BChE microplate assay and liquid chromatography tandem mass spectrometry.

• Klíčová slova
• Chlorpyrifos, Chlorpyrifos-oxon, Lab-on-a-chip, Microfluidic paper-based analytical device, Smartphone readout, Wax-printing,
• MeSH
• chytrý telefon MeSH
• dursban * MeSH
• laboratoř na čipu MeSH
• lidé MeSH
• mikrofluidika MeSH
• mikrofluidní analytické techniky * MeSH
• papír MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• dursban * MeSH

Chloride (Cl-) is an inorganic anion present in a broad range of samples (e.g. biological, environmental, food, water, etc.), the determination of which is of widespread significance. In this work, we translate the well-established traditional argentometric method (Mohr's precipitation titration) into a small, simple, portable, and low-cost paper-based microfluidic diagnostic device, which provides rapid and quantitative analysis. The developed device enables the determination of chloride sample volumes as small as 5 μL. A distance-based detection method is implemented providing fully instrument-free quantitation. The beneficial effects of channel geometry (variable widths with constant heights) on analytical parameters were investigated. Trapezoidal channels (channel width changes linearly with height) were used to create a gradient of paper surface (titrant) available for the reaction, compared to the typical uniform rectangular channels (constant channel width). The trapezoid with increasing width offered higher sensitivity and lower detection limits (i.e. 0.05 mM vs 0.1 mM from the rectangular channel) for chloride determination across the concentration range of 0.05-25 mM. In addition, the effect of concentration of the deposited reagent on the obtained distance signals was investigated using varying concentrations of titrant (AgNO3), which allowed determination of chloride across a wider dynamic range (up to 200 mM). The utility of the paper devices was demonstrated by determination of chloride in a variety of matrices including body fluids (sweat, serum, and urine) and water samples (drinking, mineral, river water).

• Klíčová slova
• Argentometric determination, Asymmetric trapezoidal microfluidic channels, Chloride determination, Distance-based measurement, Microfluidic paper-based analytical device,
• MeSH
• chloridy analýza   MeSH
• lidé MeSH
• mikrofluidní analytické techniky * MeSH
• papír * MeSH
• povrchové vlastnosti MeSH
• tělesné tekutiny chemie   MeSH
• voda chemie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chloridy MeSH
• voda MeSH

The deposition of chemical reagent inks on paper is a crucial step in the development and fabrication of microfluidic paper-based analytical devices (μPADs). A pen-plotting approach, delivering chemical ink deposition using technical pens filled with reagents and inserted into a desktop electronic plotter, is shown herein to be a versatile, low-cost, simple, rapid, reproducible, and high-throughput solution. The volume of the deposited ink was quantified gravimetrically, confirming that nanoliter volumes of reagents can be deposited reproducibly (e.g. 7.55 ± 0.37 nL/mm for a plotting speed of 10 cm/s) in detection zones of μPADs, typically spatially defined using wax printing. This approach was further investigated with regard to deposition of reagents in different geometrical forms (circular and linear), so demonstrating its applicability for preparation of μPADs with flexible design and application. By adjusting the plotting speed for linear deposition, lines with a relatively large range of widths (≈628-1192 μm) were created. Circular deposition was also demonstrated via delivery of reagents within wax printed circular fluidic barriers of a range of diameters (inner diameter = 1.5-7 mm). These capabilities were practically demonstrated via the fabrication of μPADs, based upon differing detection principles for determination of aluminum in natural waters using Morin as the fluorescent reagent. Traditional μPADs based on digital image colorimetry (DIC) were produced using circular deposition, whilst distance-based μPADs exploited linear deposition. Both types of μPADs developed using this method showed excellent precision for determination of trace concentrations of aluminium (average RSDs = 3.38% and 6.45%, and LODs = 0.5 ng (0.25 ppm) and 2 ng (0.5 ppm), for traditional and distance-based detection, respectively).

• Klíčová slova
• Aluminium determination, Distance-based detection, Microfluidic paper-based analytical device, Plotter, Reagent deposition, Technical pen,
• Publikační typ
• časopisecké články MeSH

Distance-based detection methods, as used in development of microfluidic paper analytical devices (μPADs), rely on the dynamic formation of a colored band along the length of the paper microfluidic channels. The color change is driven by the reaction of chromogenic reagents (typically water-insoluble) that are bound to the paper, thus not subject to being washed away by the sample flow along the detection channel. Here, we introduce the use of an anion-exchange filter paper (as a replacement for standard, unmodified filter paper) for distance-based detection in μPADs, in order to immobilize the water-soluble anionic reagents upon the paper detection channels based on ion-exchange interactions of the oppositely charged paper (protonated tertiary amine groups) and the anionic groups of the reagents. The ion-exchange (IE) paper was initially characterized and its properties were compared with standard cellulose paper. The IE paper was shown to be capable of strong retention of anionic reagents exhibiting acidic functional groups (carboxylic, sulfonic), which become deprotonated and negatively charged when in contact with the IE paper. The effect of the ionic strength (10-250 mM Cl-) and pH (1-13) on the immobilization of the investigated reagents were also determined. The IE-μPADs were then modified with anionic chromogenic reagents and applied to distance-based determination of total calcium (LOD = 0.03 mM) and total acidity (LOD = 2.5 mM) content in serum and wine samples, respectively. The detailed mechanisms of the developed assays on the IE paper are also discussed. We propose that IE-μPADs represent a useful new addition to the distance-based detection toolbox and considerably enhance the applicability of such a detection method.

• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

This work presents an affordable distance-based microfluidic paper-based device (μPAD), using polydiacetylene (PDA) liposome as a chromogenic substance with a smartphone-based photo editor, for rapid and in-field analysis of quaternary ammonium compounds (QACs) (e.g., didecyldimethylammonium chloride (DDAC), benzyldimethyltetradecyl ammonium chloride (BAC), and cetylpyridinium chloride (CPC)). In-field analysis of these compounds is important to ensure their antimicrobial activity and user safety since they are widely utilized as disinfectants in households and hospitals. The μPAD featured a thermometer-like shape consisting of a sample reservoir and a microchannel as the detection zone, which was pre-deposited with PDA liposome. The color change from blue to red appeared in the presence of QACs and the color bar lengths were proportional to the QAC concentrations. Reactions of QACs with the PDA required a specific pH range (from pH 4.0 to 10.0) and a readout time of 7 min. Analytical performance characteristics of the device were tested with DDAC, BAC, and CPC showing acceptable specificity, accuracy (96.1-109.4%), and precision (%RSDs ≤ 9.3%). Limits of detection and quantitation were in the ranges of 20 to 80 and 70 to 250 μM, respectively. Feasibility of the newly developed device was demonstrated for in-field analysis of QACs in fumigation solution providing comparable results with those obtained from a colorimetric assay (P > 0.05). The proposed device shows potentials for further applications of other analytes since it offers speed, simplicity, and affordability for in-field analysis, especially in remote areas where expertise, resources, and infrastructures are limited. Graphical abstract.

• Klíčová slova
• Distance-based microfluidic paper-based device, In-field analysis, Polydiacetylene, Quaternary ammonium compounds,
• Publikační typ
• časopisecké články MeSH

Microfluidic paper-based analytical devices modified with molecularly imprinted polymers (μPADs@MIPs) were developed for fluorescent detection of targeted thiols via in situ UV-induced formation of quantum dots (μPADs@MIPs@QDs). The selectivity enhancement by the MIP layer formed on the filter paper surface was demonstrated for the isolation of L-homocysteine from wine. Followed by the addition of metal precursors solution (Zn/Cd/Cu) and UV irradiation, fluorescent quantum dots were formed thus enabling quantitative detection of the thiol (serving as a QD capping agent). The effect of different semiconductors was investigated to achieve a lower band gap and higher fluorescence intensity. Increasing fluorescence intensity in the presence of thiol groups was obtained for the following precursors mixture composition: ZnCdCu/S > ZnCd/S > ZnCu/S > ZnS. The proposed method has a good relationship between the fluorescence intensity of ZnCdCu/S QDs and L-homocysteine in a linear range from 0.74 to 7.40 μM with a limit of detection (LOD) and quantification (LOQ) of 0.51 and 1.71 μM respectively. This method was applied for the determination of L-homocysteine in white wine with RSD under 6.37%.

• Klíčová slova
• Microfluidic paper-based analytical devices, Molecularly imprinted polymers, Quantum dots, Thiol, White wine,
• MeSH
• fluorescenční barviva MeSH
• homocystein MeSH
• kvantové tečky * MeSH
• mikrofluidika MeSH
• molekulárně imprintované polymery MeSH
• molekulový imprinting * metody   MeSH
• polymery MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fluorescenční barviva MeSH
• homocystein MeSH
• molekulárně imprintované polymery MeSH
• polymery MeSH

Paper-based analysis has captivated scientists' attention in the field of analytical chemistry and related areas for the last two decades. Arguably no other area of modern chemical analysis is so broad and diverse in its approaches spanning from simple 'low-tech' low-cost paper-based analytical devices (PADs) requiring no or simple instrumentation, to sophisticated PADs and microfluidic paper-based analytical devices (μPADs) featuring elements of modern material science and nanomaterials affording high selectivity and sensitivity. Correspondingly diverse is the applicability, covering resource-limited scenarios on the one hand and most advanced approaches on the other. Herein we offer a view reflecting this diversity in the approaches and types of devices. The core idea of this article rests in dividing μPADs according to their type into two groups: A) instrumentation-free μPADs for resource-limited scenarios or developing countries and B) instrumentation-based μPADs as futuristic POC devices for e-diagnostics mainly aimed at developed countries. Each of those two groups is presented and discussed with the view of the main requirements in the given area, the most common targets, sample types and suitable detection approaches either implementing high-tech elements or low-tech low-cost approaches. Finally, a socioeconomic perspective is offered in discussing the fabrication and operational costs of μPADs, and, future perspectives are offered.

• Klíčová slova
• Developing countries, High-tech, Instrumentation-free devices, Low-cost, Microfluidic paper-based analytical devices (μPADs), Paper-based analytical devices (PADs),
• MeSH
• laboratoř na čipu MeSH
• mikrofluidní analytické techniky * MeSH
• papír MeSH
• point of care testing MeSH
• rozvojové země MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Although the proteome of each organism is unambiguously coded in its genome, the proteome shows the real biology in action in each particular organism. New powerful tools are being developed for biochemists and biologists to analyze complex biological samples for studying the complete protein supplement of the genome, i. e., the proteome. There are several methods available for proteome analysis including 2-DE and several forms of MS. In recent years, technologies such as microfluidics and array-based systems have appeared in the field of analysis, identification, and quantification of proteins. These novel approaches might help in solving current technical challenges in proteomics. This paper presents a practical application of the first commercially available microfluidic nano-ESI device coupled with nano-LC (i. e., HPLC-chip) for the analysis of samples of some biological protein mixtures.

• MeSH
• chromatografie kapalinová * přístrojové vybavení   metody   MeSH
• čočka chemie   MeSH
• hmotnostní spektrometrie * přístrojové vybavení   metody   MeSH
• lidé MeSH
• mikrofluidní analytické techniky * přístrojové vybavení   metody   MeSH
• molekulární sekvence - údaje MeSH
• proteiny analýza   genetika   MeSH
• rýže (rod) chemie   MeSH
• semena rostlinná chemie   MeSH
• testování materiálů MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• hodnotící studie MeSH
• práce podpořená grantem MeSH
• Názvy látek
• proteiny MeSH

Distance-based detection (DbD) on paper-based microfluidic analytical devices (μPADs) has emerged as a promising, cost-effective, simple, and instrumentation-free assay method. Broadening the applicability of a new way of immobilization of reagent for DbD on μPADs (DμPADs) is presented, employing an ion exchange (IE) interaction of an anionic metallochromic reagent, 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol (5-Br-PAPS), on the anion-exchange filter paper. The IE DμPADs demonstrate superiority over standard cellulose filter paper in terms of the degree of reagent immobilization, detection sensitivity, and clear detection endpoints due to the strong retention of 5-Br-PAPS. The study investigated various parameters influencing DbD, including 5-Br-PAPS concentrations (0.25-1 mM), buffer types (acetic acid-Tris, MES), buffer concentrations (20-500 mM), and auxiliary complexing agents (acetic, formic, and glycolic acids). Subsequently, the performance of 17 metals (Ag+, Cd2+, Co2+, Cr3+, Cu2+, Fe2+, Hg2+, La2+, Mn2+, Ni2+, Pb2+, Ti2+, Zn2+, Al3+, As3+, Fe3+, and V4+) was evaluated, with color formation observed for 12 metals. Additionally, the paper surface was examined using SEM and SEM-EDX to verify the suitability of certain areas in the detection channel for reagent immobilization and metal binding. This method demonstrates quantitation limits of metals in the low μg mL-1 range, showing great potential for the rapid screening of toxic metals commonly found in herbal supplements and cosmetics regulated by the Food and Drug Administration (FDA). Thus, it holds promise for enhancing safety and regulatory compliance in product quality assessment. Furthermore, this method offers a cost-effective, environmentally sustainable, and user-friendly approach for the rapid visual quantification of heavy metals for in-field analysis, eliminating the need for complex instrumentation.

• Publikační typ
• časopisecké články MeSH

The review focuses on the design of detection cells, the use of microcontrollers for processing and evaluation of the detection signal, and the development of multi-detection systems for electromigration, liquid chromatography, flow-through and microfluidic techniques. A separate section is the introduction of modern 3D printing techniques and the use of new printing materials for the design of multidetection systems. In addition to traditional utilisation in separation techniques, new versions of contactless conductivity detectors are finding applications in FIA, SIA, portable and paper based analytical systems or as independent sensors. Applicationwise, C4Ds find new use in gas detection, segmented flow monitoring, as part of point of care devices, and in many other biomedical, environmental, agricultural and industrial applications.

• Klíčová slova
• 3D printing, Capillary electrophoresis, Contactless conductivity detection, Microcontroller, Microfluidics, Sensor,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH