Early and on-site detection of environmental contaminations and physicochemical parameters of seawater is increasingly preferred to guarantee hazard minimization in many settings. In this paper, we ...describe a combination of microfluidic paper-based sensors (µPADs) and an Android-based smartphone application (App) for simultaneous on-site quantification of phosphate (PO
4
-P), silicate (SiO
3
-Si) and nitrite (NO
2
-N) in coastal seawater samples. The developed App can on-site capture, process, and quantify the µPAD colorimetric outputs. This App uses an image processing algorithm for quantifying color intensity and relating the RGB components to the analyte concentrations. The GPS-tagged data can be stored on the smartphone or sent via social networks. The significant factors affecting the detection of the analytes were optimized using Box–Behnken design. Under optimized parameters, the proposed method presented the linear ranges between 5 and 100 µg L
−1
for phosphate (R
2
= 0.9909), 5 to 100 µg L
−1
(R
2
= 0.9819) for nitrite and 10 to 600 µg L
−1
(R
2
= 0.9933) for silicate. The LODs of the method for detection of phosphate, nitrite and silicate were 1.52 µg L
−1
, 0.61 µg L
−1
and 3.74 µg L
−1
, respectively. The device was successfully used to simultaneous analyze and map the PO
4
-P, SiO
3
-Si and NO
2
-N of Bushehr coastal seawater samples (Iran). The results were confirmed by the lab-based conventional colorimetric methods using spectrophotometer.
In this study, electrochemical microfluidic paper-based analytical nanosensor (EμPAN) was used as a sensitive, selective, fast, and low cost technique for dopamine detection. The wax-based stamping ...technique was used for patterning of microfluidic structure on chromatography paper. A mixture of graphite-chitosan-poly ethylene glycol (PEG) was used as bare working electrode and counter electrode and silver ink was employed as quasi-reference electrode. The electrochemical behavior of these electrodes was investigated using 5 mM K3Fe(CN)6 in 0.5 M KCl. To enhance the sensitivity and selectivity of the microfluidic-based sensor towards dopamine, multiwall carbon nanotube (CNT), graphene, and Fe3O4 nanoparticles were studied. Compare to other nanomaterials, dopamine was selectively determined using graphene and sodium dodecyl sulfate (SDS) surfactant. The linear range and limit of detection of dopamine were 0.5–120 μM and 0.01 μM, respectively. To show the applicability of the EμPAN, this device was applied for determination of dopamine in blood and urine samples. Keywords: Electrochemical microfluidic paper-based analytical nanosensor, Dopamine, Blood and urine, Sodium dodecyl sulfate
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•We report in-tube magnetic solid phase microextraction of fluoroquinolones from water and urine samples based on the use of Fe3O4 nanoparticles packed tube.•Experimental design was ...employed for screening the variables significantly affecting the extraction efficiency.•Easy automation, rapid analysis, high sensitivity, possibility of fully sorbent collection after analysis and wide linear range were the main advantages of this method.
In-tube magnetic solid phase microextraction (in-tube MSPME) of fluoroquinolones from water and urine samples based on the use of sodium dodecyl sulfate (SDS) coated Fe3O4 nanoparticles packed tube has been reported. After the preparation of Fe3O4 nanoparticles (NPs) by a batch synthesis, these NPs were introduced into a stainless steel tube by a syringe and then a strong magnet was placed around the tube, so that the Fe3O4 NPs were remained in the tube and the tube was used in the in-tube SPME-HPLC/UV for the analysis of fluoroquinolones in water and urine samples. Plackett–Burman design was employed for screening the variables significantly affecting the extraction efficiency. Then, the significant factors were more investigated by Box–Behnken design. Calibration curves were linear (R2>0.990) in the range of 0.1–1000μgL−1 for ciprofloxacin (CIP) and 0.5–500μgL−1 for enrofloxacin (ENR) and ofloxacin (OFL), respectively. LODs for all studied fluoroquinolones ranged from 0.01 to 0.05μgL−1. The main advantages of this method were rapid and easy automation and analysis, short extraction time, high sensitivity, possibility of fully sorbent collection after analysis, wide linear range and no need to organic solvents in extraction.
In this study, two important biomarkers, namely glucose and uric acid, were detected in different biological fluids using a highly sensitive and selective chitosan-/nano-based electrochemical ...microfluidic paper-based analytical device (µPAD). A graphite/chitosan/polyethylene glycol (PEG) mixture was used as bare working electrode and counter electrode with silver ink being used as quasi-reference electrode. Graphene, multiwall carbon nanotubes, and Fe
3
O
4
nanoparticles were used to improve sensitivity as well as selectivity of the working electrodes. The developed chitosan-/nano-based microfluidic analytical system showed apparent redox peaks, and all the three types of nanomaterials improved the performance of the bare graphite/chitosan/PEG electrode with the Fe
3
O
4
-modified electrode exhibiting the sharpest signals with the highest selectivity. The linear ranges of glucose and uric acid were 0.01–30 mM and 0.05–15 mM, respectively, where the limits of detection (LOD) were 5 µM and 20 µM for glucose and uric acid, respectively. In comparison with most of previous data reported on μPADs and due to high surface area/volume ratio of NPs and faster electron transfer promoted by chitosan and NPs, the better LODs were found in the current study. The fast, efficient, and low-cost µPADs were successfully applied to highly sensitive and selective detection of glucose and uric acid in serum and urine samples and noninvasive glucose detection in tear samples.
Graphic abstract
Abstract
A novel metal-doped Zn/Cl carbon quantum dots (Zn/Cl-CQDs) was developed successfully as ratiometric fluorescent probes for the sequential on-off-on detection of riboflavin, Cu
2+
ion and ...thiamine. The excellent catalytic performance of the Zn/Cl-CQDs nanozyme serves as an ideal platform for sensitive detection of thiamine. Due to the addition of riboflavin to the Zn/Cl-CQDs, the blue emission peak of Zn/Cl-CQDs at 440 nm remains unaffected and used as an internal reference approach, while the green emission peak of riboflavin at 520 nm appeared and increased remarkably. Following the presence of Cu
2+
, a quenching blue fluorescence signal of Zn/Cl-CQDs was observed which resulted in consequent fluorescent ‘turn-off’ response toward Cu
2+
ion. Finally, upon the addition of thiamine to the above solution under alkaline condition, the blue emission of Zn/Cl-CQDs was gradually recovered. The prepared Zn/Cl-CQDs could act as a nanozyme catalyst for directly catalyzing the oxidation of non-fluorescent substrate of thiamine to produce highly fluorescent substrate of thiochrome. As a result, the blue fluorescence emission peak at 440 nm was recovered. Eventually, the sequential detection properties of ratiometric probes for riboflavin, Cu
2+
ion and thiamine were successfully applied in VB2 tablets, drinking water and VB1 tablet with good recoveries of 96.21%, 98.25% and 98.44%, respectively.
A dual-mode fluorescence and colorimetric biosensor based on nitrogen-boron co-doped carbon quantum dot (N-B CQDs) for rapid and sensitive detection of dopamine (DA) was developed. The quantum dot ...luminescent materials, N-B CQDs, were prepared by a one-step microwave-assisted method. The N-B CQDs were characterized using SEM, HR-TEM, XRD, FT-IR, Raman, fluorescence, and UV-Vis techniques. The dual-mode assays of fluorescence and colorimetric methods were used for detection of DA. The high fluorescent N-B CQDs mediated turn-off assay for the facile room temperature detection of dopamine via inner filter effect (IFE) and Forster resonance energy transfer (FRET) processes at basic pH. The colorimetric detection of DA was also developed via in-house android application using a smartphone and N-B CQD solution-based nanosensor. The smartphone-based colorimetric biosensors generated more reliable information for quantitative analysis of color changes than the naked eye. Furthermore, a smartphone application with N-B CQD solution-based nanosensor was integrated to monitor the color changes through the DA addition. Wide linear ranges were achieved for DA in the ranges 0.25–50 μM and 5–500 μM with fluorescence and smartphone-based method, respectively. The satisfactory results of the dual-mode detection of DA, not only in aqueous solution, but also in human urine and serum biological sample demonstrated its potential application in biosensing, as a point of care diagnostic tool.
Graphical abstract
Organ-on-a-chip systems are miniaturized microfluidic 3D human tissue and organ models designed to recapitulate the important biological and physiological parameters of their in vivo counterparts. ...They have recently emerged as a viable platform for personalized medicine and drug screening. These in vitro models, featuring biomimetic compositions, architectures, and functions, are expected to replace the conventional planar, static cell cultures and bridge the gap between the currently used preclinical animal models and the human body. Multiple organoid models may be further connected together through the microfluidics in a similar manner in which they are arranged in vivo, providing the capability to analyze multiorgan interactions. Although a wide variety of human organ-on-a-chip models have been created, there are limited efforts on the integration of multisensor systems. However, in situ continual measuring is critical in precise assessment of the microenvironment parameters and the dynamic responses of the organs to pharmaceutical compounds over extended periods of time. In addition, automated and noninvasive capability is strongly desired for long-term monitoring. Here, we report a fully integrated modular physical, biochemical, and optical sensing platform through a fluidics-routing breadboard, which operates organ-on-a-chip units in a continual, dynamic, and automated manner. We believe that this platform technology has paved a potential avenue to promote the performance of current organ-on-a-chip models in drug screening by integrating a multitude of real-time sensors to achieve automated in situ monitoring of biophysical and biochemical parameters.
Continual monitoring of secreted biomarkers from organ-on-a-chip models is desired to understand their responses to drug exposure in a noninvasive manner. To achieve this goal, analytical methods ...capable of monitoring trace amounts of secreted biomarkers are of particular interest. However, a majority of existing biosensing techniques suffer from limited sensitivity, selectivity, stability, and require large working volumes, especially when cell culture medium is involved, which usually contains a plethora of nonspecific binding proteins and interfering compounds. Hence, novel analytical platforms are needed to provide noninvasive, accurate information on the status of organoids at low working volumes. Here, we report a novel microfluidic aptamer-based electrochemical biosensing platform for monitoring damage to cardiac organoids. The system is scalable, low-cost, and compatible with microfluidic platforms easing its integration with microfluidic bioreactors. To create the creatine kinase (CK)-MB biosensor, the microelectrode was functionalized with aptamers that are specific to CK-MB biomarker secreted from a damaged cardiac tissue. Compared to antibody-based sensors, the proposed aptamer-based system was highly sensitive, selective, and stable. The performance of the sensors was assessed using a heart-on-a-chip system constructed from human embryonic stem cell-derived cardiomyocytes following exposure to a cardiotoxic drug, doxorubicin. The aptamer-based biosensor was capable of measuring trace amounts of CK-MB secreted by the cardiac organoids upon drug treatments in a dose-dependent manner, which was in agreement with the beating behavior and cell viability analyses. We believe that, our microfluidic electrochemical biosensor using aptamer-based capture mechanism will find widespread applications in integration with organ-on-a-chip platforms for in situ detection of biomarkers at low abundance and high sensitivity.
Development of an efficient, portable and simple nanosensor-based systems with reliable analytical performance for on-site monitoring of vitamin B12 (VB12) are still major problems and a challenging ...work for quality control of manufacturers. Herein, a new fluorescence, UV–Vis and smartphone triple mode nanosensors were designed for the simultaneous detection of VB12 with high sensitivity and accuracy. A novel nanosensor was synthesized through nicotinamide-functionalizing of carbon quantum dot (NA-CQDs) by an one-step microwave-assisted method with green approach. The NA-CQDs sensor showed excellent fluorescence properties and wide linear ranges from 0.1–60 µM with the detection limits of 31.7 nM. Moreover, color changes of NA-CQDs induced by the VB12 could also be detected by UV–Vis spectrophotometer and inhouse-developed application installed on smartphone as a signal reader, simultanusly. The Red, Green and Blue (RGB) intensities of the colorimetric images of NA-CQDs/VB12 system which taken by smartphone's camera converted into quantitative values by the application. A smartphone-integrated with NA-CQDs as colorimetric sensing platform displays good linear ranges (4.16 to 66.6 μM) for on-site determination of VB12 with detection limit of 1.40 μM. The method was successfully applied in the determination of VB12 in complex pharmaceutical supplement formulations without any sample pre-treatment and matrix interfering effects. The recovery results (96.52% to 105.10%) which were in agreement with the reference methods, demonstrating the capability of the smartphone-assisted colorimetric sensing platform in many on-site practical applications of quality controls.
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•Pyrrole was elctropolymerized on the inner surface of a stainless steel tube.•We report new in-tube SPME approach named electrochemically controlled in-tube SPME.•After the ...completion of EC in-tube SPME–HPLC setup, the PPy-coated tube was used as working electrode.•This approach, which combined electrochemistry and in-tube SPME, decreased the total analysis time and increased the sensitivity.•Extraction ability of the tube in presence and in absence of applied electrical potential was investigated.
We report a new in-tube solid phase microextraction approach named electrochemically controlled in-tube solid phase microextraction (EC in-tube SPME). This approach, which combined electrochemistry and in-tube SPME, led to decrease in total analysis time and increase in sensitivity. At first, pyrrole was elctropolymerized on the inner surface of a stainless steel tube. Then, the polypyrrole (PPy)-coated in-tube SPME was coupled on-line to liquid chromatography (HPLC) to achieve automated in-tube SPME–HPLC analysis. After the completion of EC-in-tube SPME–HPLC setup, the PPy-coated tube was used as working electrode for uptake of diclofenac as target analyte. Extraction ability of the tube in presence and in absence of applied electrical field was investigated. It was found that, under the same extraction conditions, the extraction efficiency could be greatly enhanced by using the constant potential. Important factors are also optimized. The detection limit (S/N=3) and precision were 0.1μgL−1 and 4.4%, respectively.
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