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Biosensors & Bioelectronics Oct 2018The ability to interact with plants, both to sense and to actuate, would open new opportunities for precision agriculture. These interactions can be achieved by using...
The ability to interact with plants, both to sense and to actuate, would open new opportunities for precision agriculture. These interactions can be achieved by using the plant as part of the sensing system. The present work demonstrates real-time monitoring of β-glucuronidase (GUS) expression in transgenic tobacco plants using its activity as a biomarker for functional sensing. As "proof of concept", we demonstrated GUS enzyme biosensing under constitutive expression in Msk8 tomato cells and transgenic tobacco plants and in heat shock inducible BY2 tobacco cells and tobacco plants. The sensing was done using a three-electrode microchip in Msk8 or BY2 cell culture or in tobacco plant leaves. The electrode microchip was used to transduce the expression of the GUS enzyme by chronoamperometry to a measurable electrical current signal. For the constitutive expression of GUS in Msk8 cells, the system sensitivity was 0.076 mA/mM-cm and the limit of detection was 0.1 mM. For the heat shock inducible BY2 cells the GUS enzyme activity was detected 12-26 h after the heat shock was applied (40 °C for 2 h) using two different substrates: p-nitrophenyl-β-glucuronide (with sensitivity of 0.051 mA/mM-cm) and phenolphthalein-β-glucuronide (with sensitivity of 0.029 mA/mM-cm).
Topics: Biosensing Techniques; Cells, Cultured; Electrophysiological Phenomena; Gene Expression Regulation, Plant; Glucuronidase; Lab-On-A-Chip Devices; Limit of Detection; Solanum lycopersicum; Plant Leaves; Plants, Genetically Modified; Stress, Physiological; Nicotiana
PubMed: 29982119
DOI: 10.1016/j.bios.2018.06.045 -
Analytical Sciences : the International... Mar 2019We propose the creation of reusable indicator-sorbed-solids, using anion-exchange resins or kaolin as supports, with the aim to reduce chemical use towards green...
We propose the creation of reusable indicator-sorbed-solids, using anion-exchange resins or kaolin as supports, with the aim to reduce chemical use towards green analytical chemistry. Indicators (phenolphthalein, thymol blue and butterfly pea flower extract as a natural indicator) sorbed on a solid support, were employed in acid-base titration, in both homogenous aqueous and heterogenous aqueous organic phases. Applications of the developed techniques to some real samples, such as vinegar, colored fruit juice and vegetable oil, have been demonstrated.
Topics: Acetic Acid; Adsorption; Anion Exchange Resins; Food Analysis; Fruit and Vegetable Juices; Green Chemistry Technology; Indicators and Reagents; Kaolin; Plant Oils; Titrimetry
PubMed: 30344207
DOI: 10.2116/analsci.18N019 -
The Analyst Nov 2018Since different quenching mechanisms can endow carbon dots (CDs) with diverse responsive manners, multi-mode sensing can in principle be achieved by a single...
Since different quenching mechanisms can endow carbon dots (CDs) with diverse responsive manners, multi-mode sensing can in principle be achieved by a single carbon-dot-based sensor. In this work, green emissive CDs were prepared by simple hydrothermal pyrolysis of phenolphthalein and ethylenediamine at 180 °C for 5 h, with a quantum yield of 17%. The as-prepared CDs can be selectively quenched by Hg2+ due to their specific binding affinity causing photo-induced electron transfer (PET). Due to the inner filter effect (IFE), the CDs also showed intensive fluorescent response to lemon yellow dye. Moreover, the CDs responded to Fe2+ or H2O2 selectively in the presence of H2O2 or Fe2+ owing to oxidative quenching (OQ) by hydroxyl radicals resulting from the Fenton reaction. Via the diverse responsive manners of PET, IFE and OQ, multi-mode sensing for Hg2+, lemon yellow and Fe2+, H2O2 was thus achieved by a single green emissive carbon-dot-based sensor. Accordingly, the linear ranges for the selective detection of Hg2+, lemon yellow, Fe2+ and H2O2 were found to be 0.0-500.0, 0.0-20.0, 0.0-90.0 and 0.0-50.0 μM, with the limits of detection as low as 5.8, 0.5, 1.2 and 1.1 μM, respectively.
PubMed: 30358772
DOI: 10.1039/c8an01552j -
ACS Applied Materials & Interfaces Dec 2016Self-assembled and cross-linked chitosan/cellulose glutaraldehyde composite materials (CGC) were prepared with enhanced surface area and variable morphology. FTIR, CHN,...
Self-assembled and cross-linked chitosan/cellulose glutaraldehyde composite materials (CGC) were prepared with enhanced surface area and variable morphology. FTIR, CHN, and C solid state NMR studies provided support for the cross-linking reaction between the amine groups of chitosan and glutaraldehyde; whereas, XRD and TGA studies provided evidence of cellulose-chitosan interactions for the composites. SEM, equilibrium swelling, and nitrogen adsorption studies corroborate the enhanced surface area and variable morphology of the cross-linked biopolymers. Equilibrium sorption studies at alkaline conditions with phenolic dyes, along with single component and mixed naphthenates in aqueous solution revealed variable uptake properties with the composites. The Freundlich isotherm model revealed that the composite at the highest levels of cross-linker, CGC3, had the highest sorption affinity (K; L mmol/g) for phenolphthalein (phth) followed by ortho-nitrophenyl acetic acid (ONPAA) and para-nitrophenol (PNP), as follows: Phth (5.03 × 10) > ONPAA (2.28 × 10) > PNP (8.49 × 10). The Sips isotherm model provided a good description of the sorption profile of single component and naphthenate mixtures. The monolayer uptake capacity (Q; mg g) is given in parentheses: 2-hexyldecanoic acid (S1; 115 mg/g) > 2-naphthoxyacetic acid (S3; 40.5 mg/g) > trans-4-pentylcyclohexylcarboxylic acid (S2; 13.7 mg/g). By comparison, the Q values for CGC3 with naphthenate mixtures (24.1 and 27.4 mg/g) according to UV spectroscopy and electrospray ionization mass spectrometry (ESI-HRMS). The sorbent materials generally show greater uptake with naphthenates that possess lower vs higher double bond equivalence (DBE) values. Kinetic studies revealed that the sorption of phth adopted behavior described by the pseudo-second order model, while uptake for S3 and naphthenate mixtures adopted pseudo-first order behavior. This study contributes to a greater understanding of the sorption properties of the two types of abundant biopolymers and their composites by illustrating their tunable sorption properties. The key role of hydrophobic interactions for CGC materials was evidenced by the controlled sorptive uptake of carboxylate anions with variable molecular structure.
PubMed: 27802018
DOI: 10.1021/acsami.6b11504 -
Memory (Hove, England) Oct 2023Retrieval practice typically benefits learning in children, although little is known about the benefits of retrieval practice for learning spelling. We investigated this...
Retrieval practice typically benefits learning in children, although little is known about the benefits of retrieval practice for learning spelling. We investigated this issue in three experiments with fifth-grade children from a low-income area of Brazil. In the experiments, children first read a list of words (study), and after a short interval wrote down the studied words after hearing and rereading them (copy) or after only hearing them (retrieval practice). After an interval of 4 days, spelling performance was greater for words from the retrieval practice condition than for words from the copy condition, but only when immediate corrective feedback was provided (Experiment 3). The current findings, therefore, suggest that retrieval practice followed by corrective feedback is an effective strategy to improve spelling performance of fifth-grade children.
Topics: Humans; Child; Brazil; Dioctyl Sulfosuccinic Acid; Hearing; Language; Learning; Phenolphthalein
PubMed: 37605436
DOI: 10.1080/09658211.2023.2248420 -
ACS Applied Materials & Interfaces Aug 2021In the current biosensor, the signal generation is limited to single virus detection in the reaction chamber. An adaptive strategy is required to enable the recognition...
In the current biosensor, the signal generation is limited to single virus detection in the reaction chamber. An adaptive strategy is required to enable the recognition of multiple viruses for diagnostics and surveillance. In this work, a nanocarrier is deployed to bring specific signal amplification into the biosensor, depending on the target viruses. The nanocarrier is designed using pH-sensitive polymeric nanoparticle-laden nanocarriers (PNLNs) prepared by sequential nanoprecipitation. The nanoprecipitation of two chromogens, phenolphthalein (PP) and thymolphthalein (TP), is investigated in three different solvent systems in which PNLNs demonstrate a high loading of the chromogen up to 59.75% in dimethylformamide (DMF)/dimethyl sulfoxide (DMSO)/ethanol attributing to the coprecipitation degree of the chromogens and the polymer. The PP-encapsulated PNLNs (PP@PNLNs) and TP-encapsulated PNLNs (TP@PNLNs) are conjugated to antibodies specific to target viruses, influenza virus A subtype H1N1 (IV/A/H1N1) and H3N2 (IV/A/H3N2), respectively. After the addition of anti-IV/A antibody-conjugated magnetic nanoparticles (MNPs) and magnetic separation, the enriched PNLNs/virus/MNPs sandwich structure is treated in an alkaline solution. It demonstrates a synergy reaction in which the degradation of the polymeric boundary and the pH-induced colorimetric development of the chromogen occurred. The derivative binary biosensor shows feasible detection on IV/A with excellent specificities of PP@PNLNs on IV/A/H1N1 and TP@PNLNs on IV/A/H3N2 with LODs of 27.56 and 28.38 fg mL, respectively. It intrigues the distinguished analytical signal in human serum with a variance coefficient of 25.8% and a recovery of 93.6-110.6% for one-step subtype influenza virus detection.
Topics: Antibodies, Immobilized; Biosensing Techniques; Blood; Chromogenic Compounds; Colorimetry; Drug Carriers; Drug Liberation; Humans; Immunomagnetic Separation; Influenza A Virus, H1N1 Subtype; Influenza A Virus, H3N2 Subtype; Limit of Detection; Magnetic Iron Oxide Nanoparticles; Phenolphthalein; Thymolphthalein; Viral Load
PubMed: 34328304
DOI: 10.1021/acsami.1c08813 -
Theranostics 2018Saliva as a sample matrix is rapidly gaining interest for disease diagnosis and point-of-care assays because it is easy to collect (non-invasive) and contains many...
Saliva as a sample matrix is rapidly gaining interest for disease diagnosis and point-of-care assays because it is easy to collect (non-invasive) and contains many health-related biomarkers. However, saliva poses particular problems relative to more common urine and blood matrices, which includes low analyte concentrations, lack of understanding of biomolecule transportation and inherent viscosity variability in human samples. While several studies have sought to improve assay sensitivity, few have addressed sample viscosity specifically. The goal of this study is to minimize the effect of sample viscosity on paper-based analytical devices (PADs) for the measurement of pH and nitrite in human saliva. PADs were used to measure salivary pH from 5.0 to 10.0 with a universal indicator consisting of chlorophenol red, phenol red and phenolphthalein. Nitrite determination was performed using the Griess reaction. Artificial saliva with viscosity values between 1.54 and 5.10 mPa∙s was tested on the proposed PAD. To ensure the proposed PADs can be tailored for use in-field analysis, the devices were shipped to Australia and tested with human specimens. Initial experiments showed that viscosity had a significant impact on the calibration curve for nitrite; however, a more consistent curve could be generated when buffer was added after the sample, irrespective of sample viscosity. The linear range for nitrite detection was 0.1 to 2.4 mg/dL using the improved method. The nitrite measurement in artificial saliva also showed a good correlation with the standard spectrophotometry method (=0.8484, paired sample -test, n=20). Measured pH values from samples with varying viscosities correlated well with the results from our pH meter. The inherent variation of salivary viscosity that impacts nitrite and pH results can be addressed using a simple washing step on the PAD without the need for complex procedures.
Topics: Australia; Chemistry Techniques, Analytical; Humans; Hydrogen-Ion Concentration; Nitrites; Paper; Saliva; Sensitivity and Specificity; Specimen Handling; Viscosity
PubMed: 30083260
DOI: 10.7150/thno.24941 -
Molecules (Basel, Switzerland) Aug 2021Water pollution by various toxic substances remains a serious environmental problem, especially the occurrence of organic micropollutants including endocrine disruptors,...
Water pollution by various toxic substances remains a serious environmental problem, especially the occurrence of organic micropollutants including endocrine disruptors, pharmaceutical pollutants and naphthol pollutants. Adsorption process has been an effective method for pollutant removal in wastewater treatment. However, the thermal regeneration process for the most widely used activated carbon is costly and energy-consuming. Therefore, there has been an increasing need to develop alternative low-cost and effective adsorption materials for pollutant removal. Herein, β-cyclodextrin (β-CD), a cheap and versatile material, was modified with methacrylate groups by reacting with methacryloyl chloride, giving an average degree of substitution of 3 per β-CD molecule. β-CD-methacrylate, which could function as a crosslinker, was then copolymerized with acrylamide monomer via free-radical copolymerization to form β-CD-polyacrylamide (β-CD-PAAm) hydrogel. Interestingly, in the structure of the β-CD-PAAm hydrogel, β-CD is not only a functional unit binding pollutant molecules through inclusion complexation, but also a structural unit crosslinking PAAm leading to the formation of the hydrogel 3D networks. Morphological studies showed that β-CD-PAAm gel had larger pore size than the control PAAm gel, which was synthesized using conventional crosslinker instead of β-CD-methacrylate. This was consistent with the higher swelling ratio of β-CD-PAAm gel than that of PAAm gel (29.4 vs. 12.7). In the kinetic adsorption studies, phenolphthalein, a model dye, and bisphenol A, propranolol hydrochloride, and 2-naphthol were used as model pollutants from different classes. The adsorption data for β-CD-PAAm gel fitted well into the pseudo-second-order model. In addition, the thermodynamic studies revealed that β-CD-PAAm gel was able to effectively adsorb the different dye and pollutants at various concentrations, while the control PAAm gel had very low adsorption, confirming that the pollutant removal was due to the inclusion complexation between β-CD units and pollutant molecules. The adsorption isotherms of the different dye and pollutants by the β-CD-PAAm gel fitted well into the Langmuir model. Furthermore, the β-CD-PAAm gel could be easily recycled by soaking in methanol and reused without compromising its performance for five consecutive adsorption/desorption cycles. Therefore, the β-CD-PAAm gel, which combines the advantage of an easy-to-handle hydrogel platform and the effectiveness of adsorption by β-CD units, could be a promising pollutant removal system for wastewater treatment applications.
PubMed: 34443616
DOI: 10.3390/molecules26165031 -
Molecules (Basel, Switzerland) May 2020This paper investigates the development of the alkalinity and its impact on carbon steel reinforcement embedded in alkali-activated fly ashes (AAFA) and alkali-activated...
This paper investigates the development of the alkalinity and its impact on carbon steel reinforcement embedded in alkali-activated fly ashes (AAFA) and alkali-activated fly ashes with ten percentage mass (wt%) of blast furnace slag (AAFAS)-based materials (geopolymer-GP). The pH analysis of eluates indicates a remarkable decrease of alkalinity in AAFA and AAFAS in the first hours of the geopolymerization process. Phenolphthalein solution and pore solution tests on concretes also show a sharp decrease of alkalinity with increased content in the binder due to carbonation. Micro X-ray computer tomography (µXCT) and electrochemical techniques indicate that the changed pH in the GP systems was accompanied by a decrease in the corrosion rates of steel reinforcement when compared to ordinary Portland cement (OPC) systems. In contrast to calcite and vaterite, which were detected in OPC and AAFAS after a carbonation process, only sodium carbonate natron was determined at lower levels in AAFA by X-ray diffraction (XRD).
Topics: Alkalies; Carbon; Coal Ash; Electrochemical Techniques; Hydrogen-Ion Concentration; Polymerization; Polymers; Steel; Tomography, X-Ray Computed
PubMed: 32438581
DOI: 10.3390/molecules25102359 -
Molecules (Basel, Switzerland) Jan 2023The formation of the inclusion complex between β-cyclodextrin (CD) and phenolphthalein (PP) was investigated by means of UV-Vis and FT-IR spectroscopies. The...
The formation of the inclusion complex between β-cyclodextrin (CD) and phenolphthalein (PP) was investigated by means of UV-Vis and FT-IR spectroscopies. The thermodynamic parameters were calculated in the absence and presence of LiI, KI, NaI and CsI iodide salts. The enthalpy change during the formation was found to be negative for all solutions with iodide salts. The enthalpy change was found to decrease in the sequence no salt > NaI > KI> CsI > LiI. Moreover, it was observed that with increasing salt concentration enthalpy decreases monotonically. The interaction between the two molecules was mostly attributed to hydrogen bonding and Van der Waals interactions. Thermodynamic properties revealed that electrostatic forces also contribute when LiI is present in solutions. A molecular docking study was performed to elucidate the docking between phenolphthalein and cyclodextrin. The FT-IR spectra of CD, PP and the CD-PP complex were recorded to establish the formation of the inclusion complex. Semi-empirical and DFT methods were utilized to study theoretically the complexation process and calculate the IR vibrational spectra. The adequate agreement between theoretical and experimental results supports the proposed structural model for the CD-PP complexation.
PubMed: 36770813
DOI: 10.3390/molecules28031147