Molecules

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17 pages, 5027 KiB

Open AccessArticle

Swellable Copolymers of N-isopropylacrylamide and Alkyl Acrylic Acids for Optical pH Sensing

by Barry K. Lavine, Sandhya R. Pampati, Kaushalya S. Dahal, Mariya Kim, U. D. Nuwan T. Perera, Marcus Benjamin and Richard A. Bunce

Molecules 2020, 25(6), 1408; https://doi.org/10.3390/molecules25061408 - 19 Mar 2020

Cited by 2 | Viewed by 1880

Abstract

Swellable polymers that respond to pH (including a portion of the physiological pH range) have been prepared from N-isopropylacrylamide (NIPA) copolymerized with acrylic acid, methacrylic acid, ethacrylic acid or propacrylic acid by dispersion polymerization. When the swellable polymer particles are dispersed in [...] Read more.

Swellable polymers that respond to pH (including a portion of the physiological pH range) have been prepared from N-isopropylacrylamide (NIPA) copolymerized with acrylic acid, methacrylic acid, ethacrylic acid or propacrylic acid by dispersion polymerization. When the swellable polymer particles are dispersed in a polyvinyl alcohol (PVA) hydrogel membrane, large changes occur in the turbidity of the membrane (which is measured using an absorbance spectrometer) as the pH of the buffer solution in contact with the hydrogel membrane is varied. The swelling of the NIPA copolymer is nonionic, as the ionic strength of the buffer solution in contact with the PVA membrane was increased from 0.1 to 1.0 M without a decrease in the swelling. For many of these NIPA copolymers, swelling was also reversible in both low- and high ionic strength pH-buffered media and at ambient and physiological temperatures. The composition of the formulation used to prepare these copolymers of NIPA can be correlated to the enthalpy and entropy of the pH-induced swelling. Full article

(This article belongs to the Special Issue Selective and Sensitive Detection of Biological and Chemical Species)

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11 pages, 2348 KiB

Open AccessArticle

A Cataluminescence Sensor Based on NiO Nanoparticles for Sensitive Detection of Acetaldehyde

by Run-Kun Zhang, Die Wang, Yan-Jun Wu, Yi-Han Hu, Jian-Yu Chen, Jin-Can He and Jing-Xin Wang

Molecules 2020, 25(5), 1097; https://doi.org/10.3390/molecules25051097 - 01 Mar 2020

Cited by 10 | Viewed by 2762

Abstract

Sensitive and selective detection of harmful gas is an important task in environmental monitoring. In this work, a gas sensor based on cataluminescence (CTL) for detection of acetaldehyde was designed by using nano-NiO as the sensing material. The sensor shows sensitive response to [...] Read more.

Sensitive and selective detection of harmful gas is an important task in environmental monitoring. In this work, a gas sensor based on cataluminescence (CTL) for detection of acetaldehyde was designed by using nano-NiO as the sensing material. The sensor shows sensitive response to acetaldehyde at a relatively low working temperature of 200 °C. The linear range of CTL intensity versus acetaldehyde concentration is 0.02–2.5 mg/L, with a limit of detection of 0.006 mg/L at a signal-to-noise ratio of three. Mechanism study shows that electronically excited CO₂ is the excited intermediate for CTL emission during the catalytic oxidation of acetaldehyde on the NiO surface. The proposed sensor has promising application in monitoring acetaldehyde in residential buildings and in the workplace. Full article

(This article belongs to the Special Issue Selective and Sensitive Detection of Biological and Chemical Species)

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10 pages, 2934 KiB

Open AccessArticle

A Reversible Colorimetric and Fluorescence “Turn-Off” Chemosensor for Detection of Cu²⁺ and Its Application in Living Cell Imaging

by Yun Hu, Aiqian Chen, Zhuo Kong and Demeng Sun

Molecules 2019, 24(23), 4283; https://doi.org/10.3390/molecules24234283 - 25 Nov 2019

Cited by 15 | Viewed by 3534

Abstract

Dual-function chemosensors that combine the capability of colorimetric and fluorimetric detection of Cu²⁺ are still relatively rare. Herein, we report that a 3-hydroxyflavone derivative (E)-2-(4-(dimethylamino)styryl)-3-hydroxy-4H-chromen-4-one (4), which is a red-emitting fluorophore, could serve as a reversible [...] Read more.

Dual-function chemosensors that combine the capability of colorimetric and fluorimetric detection of Cu²⁺ are still relatively rare. Herein, we report that a 3-hydroxyflavone derivative (E)-2-(4-(dimethylamino)styryl)-3-hydroxy-4H-chromen-4-one (4), which is a red-emitting fluorophore, could serve as a reversible colorimetric and fluorescence “turn-off” chemosensor for the detection of Cu²⁺. Upon addition of Cu²⁺ to 4 in neutral aqueous solution, a dramatic color change from yellow to purple-red was clearly observed, and its fluorescence was markedly quenched, which was attributed to the complexation between the chemosensor and Cu²⁺. Conditions of the sensing process had been optimized, and the sensing studies were performed in a solution of ethanol/phosphate buffer saline (v/v = 3:7, pH = 7.0). The sensing system exhibited high selectivity towards Cu²⁺. The limit of naked eye detection of Cu²⁺ was determined at 8 × 10⁻⁶ mol/L, whereas the fluorescence titration experiment showed a detection limit at 5.7 × 10⁻⁷ mol/L. The complexation between 4 and Cu²⁺ was reversible, and the binding constant was found to be 3.2 × 10⁴ M⁻¹. Moreover, bioimaging experiments showed that 4 could penetrate the cell membrane and respond to the intracellular changes of Cu²⁺ within living cells, which indicated its potential for biological applications. Full article

(This article belongs to the Special Issue Selective and Sensitive Detection of Biological and Chemical Species)

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17 pages, 4681 KiB

Open AccessArticle

The Design and Synthesis of Fluorescent Coumarin Derivatives and Their Study for Cu²⁺ Sensing with an Application for Aqueous Soil Extracts

by Bin Qian, Linda Váradi, Adrian Trinchi, Suzie M. Reichman, Lei Bao, Minbo Lan, Gang Wei and Ivan S. Cole

Molecules 2019, 24(19), 3569; https://doi.org/10.3390/molecules24193569 - 02 Oct 2019

Cited by 7 | Viewed by 2991

Abstract

A series of fluorescent coumarin derivatives 2a–e were systematically designed, synthesized and studied for their Cu²⁺ sensing performance in aqueous media. The sensitivities and selectivities of the on-to-off fluorescent Cu²⁺ sensing signal were in direct correlation with the relative [...] Read more.

A series of fluorescent coumarin derivatives 2a–e were systematically designed, synthesized and studied for their Cu²⁺ sensing performance in aqueous media. The sensitivities and selectivities of the on-to-off fluorescent Cu²⁺ sensing signal were in direct correlation with the relative arrangements of the heteroatoms within the coordinating moieties of these coumarins. Probes 2b and 2d exhibited Cu²⁺ concentration dependent and selective fluorescence quenching, with linear ranges of 0–80 μM and 0–10 μM, and limits of detection of 0.14 μM and 0.38 μM, respectively. Structural changes of 2b upon Cu²⁺ coordination were followed by fluorescence titration, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), mass spectrometry, and single crystal X-ray diffraction on the isolated Cu²⁺-coumarin complex. The results revealed a 1:1 stoichiometry between 2b and Cu²⁺, and that the essential structural features for Cu²⁺-selective coordination are the coumarin C=O and a three-bond distance between the amide NH and heterocyclic N. Probe 2b was also used to determine copper (II) levels in aqueous soil extracts, with recovery rates over 80% when compared to the standard soil analysis method: inductively coupled plasma-mass spectrometry (ICP-MS). Full article

(This article belongs to the Special Issue Selective and Sensitive Detection of Biological and Chemical Species)

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9 pages, 4291 KiB

Open AccessCommunication

Ratiometric Polymer Probe for Detection of Peroxynitrite and the Application for Live-Cell Imaging

by Hio Kuan Lao, Jingyun Tan, Chunfei Wang and Xuanjun Zhang

Molecules 2019, 24(19), 3465; https://doi.org/10.3390/molecules24193465 - 24 Sep 2019

Cited by 2 | Viewed by 2371

Abstract

Peroxynitrite (ONOO⁻) is one of the sources of oxidation stress involved in many biological signaling pathways. The role of ONOO⁻ being a double-edged sword in biological systems drives the development of effective detection tools. In this work, a boronate-based polymeric [...] Read more.

Peroxynitrite (ONOO⁻) is one of the sources of oxidation stress involved in many biological signaling pathways. The role of ONOO⁻ being a double-edged sword in biological systems drives the development of effective detection tools. In this work, a boronate-based polymeric fluorescent probe PB-PVA was synthesized and the probe performance was evaluated. The probe exhibits ratiometric sensing of ONOO⁻ in a range of 0–6 µM. There is good linear relationship between the probe fluorescence intensity ratio and ONOO⁻ concentration. The probe also displays moderate selectivity towards ONOO⁻ over other ROS. Moreover, it is water-soluble and possesses good biocompatibility which aids the imaging of ONOO⁻ in living cells. These properties could make the probe a promising tool in in vitro study related to ONOO⁻. Full article

(This article belongs to the Special Issue Selective and Sensitive Detection of Biological and Chemical Species)

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14 pages, 4614 KiB

Open AccessArticle

Pharmacokinetic and Metabolism Studies of Monomethyl Auristatin F via Liquid Chromatography-Quadrupole-Time-of-Flight Mass Spectrometry

by Min-Ho Park, Byeong ill Lee, Jin-Ju Byeon, Seok-Ho Shin, Jangmi Choi, Yuri Park and Young G. Shin

Molecules 2019, 24(15), 2754; https://doi.org/10.3390/molecules24152754 - 29 Jul 2019

Cited by 12 | Viewed by 4280

Abstract

A simple liquid chromatography–quadrupole-time-of-flight–mass spectrometric assay (LC-TOF-MS/MS) has been developed for the evaluation of metabolism and pharmacokinetic (PK) characteristics of monomethyl auristatin F (MMAF) in rat, which is being used as a payload for antibody-drug conjugates. LC-TOF-MS/MS method was qualified for the quantification [...] Read more.

A simple liquid chromatography–quadrupole-time-of-flight–mass spectrometric assay (LC-TOF-MS/MS) has been developed for the evaluation of metabolism and pharmacokinetic (PK) characteristics of monomethyl auristatin F (MMAF) in rat, which is being used as a payload for antibody-drug conjugates. LC-TOF-MS/MS method was qualified for the quantification of MMAF in rat plasma. The calibration curves were acceptable over the concentration range from 3.02 to 2200 ng/mL using quadratic regression. MMAF was stable in various conditions. There were no significant matrix effects between rat and other preclinical species. The PK studies showed that the bioavailability of MMAF was 0% with high clearance. Additionally, the metabolite profiling studies, in vitro/in vivo, were performed. Seven metabolites for MMAF were tentatively identified in liver microsome. The major metabolic pathway was demethylation, which was one of the metabolic pathways predicted by MedChem Designer. Therefore, these results will be helpful to understand the PK, catabolism, and metabolism behavior of MMAF comprehensively when developing antibody-drug conjugates (ADCs) in the future. Full article

(This article belongs to the Special Issue Selective and Sensitive Detection of Biological and Chemical Species)

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11 pages, 2304 KiB

Open AccessArticle

Whole Slide Imaging for High-Throughput Sensing Antibiotic Resistance at Single-Bacterium Level and Its Application to Rapid Antibiotic Susceptibility Testing

by Donghui Song, Haomin Liu, Huayi Ji and Yu Lei

Molecules 2019, 24(13), 2441; https://doi.org/10.3390/molecules24132441 - 03 Jul 2019

Cited by 9 | Viewed by 3788

Abstract

Since conventional culture-based antibiotic susceptibility testing (AST) methods are too time-consuming (typically 24–72 h), rapid AST is urgently needed for preventing the increasing emergence and spread of antibiotic resistant infections. Although several phenotypic antibiotic resistance sensing modalities are able to reduce the AST [...] Read more.

Since conventional culture-based antibiotic susceptibility testing (AST) methods are too time-consuming (typically 24–72 h), rapid AST is urgently needed for preventing the increasing emergence and spread of antibiotic resistant infections. Although several phenotypic antibiotic resistance sensing modalities are able to reduce the AST time to a few hours or less, concerning the biological heterogeneity, their accuracy or limit of detection are limited by low throughput. Here, we present a rapid AST method based on whole slide imaging (WSI)-enabled high-throughput sensing antibiotic resistance at single-bacterium level. The time for determining the minimum inhibitory concentration (MIC) was theoretically shortest, which ensures that the growth of each individual cell present in a large population is inhibited. As a demonstration, our technique was able to sense the growth of at least several thousand bacteria at single-cell level. Reliable MIC of Enterobacter cloacae against gentamicin was obtained within 1 h, while the gold standard broth dilution method required at least 16 h for the same result. In addition, the application of our method prevails over other imaging-based AST approaches in allowing rapid and accurate determination of antibiotic susceptibility for phenotypically heterogeneous samples, in which the number of antibiotic resistant cells was negligible compared to that of the susceptible cells. Hence, our method shows great promise for both rapid AST determination and point-of-care testing of complex clinical bacteria isolates. Full article

(This article belongs to the Special Issue Selective and Sensitive Detection of Biological and Chemical Species)

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12 pages, 5075 KiB

Open AccessArticle

Synthesis of Fluorescent Carbon Dots as Selective and Sensitive Probes for Cupric Ions and Cell Imaging

by Shu-Wei Huang, Yu-Feng Lin, Yu-Xuan Li, Cho-Chun Hu and Tai-Chia Chiu

Molecules 2019, 24(9), 1785; https://doi.org/10.3390/molecules24091785 - 08 May 2019

Cited by 51 | Viewed by 4039

Abstract

A novel sensing system has been designed for the detection of cupric ions. It is based on the quenched fluorescence signal of carbon dots (CDs), which were carbonized from poly(vinylpyrrolidone) (PVP) and L-Cysteine (CYS). Cupric ions interact with the nitrogen and sulfur atoms [...] Read more.

A novel sensing system has been designed for the detection of cupric ions. It is based on the quenched fluorescence signal of carbon dots (CDs), which were carbonized from poly(vinylpyrrolidone) (PVP) and L-Cysteine (CYS). Cupric ions interact with the nitrogen and sulfur atoms on surface of the CDs to form an absorbed complex; this results in strong quenching of the fluorescence of the CDs via a fast metal-to-ligand binding affinity. The synthesized water-soluble CDs also exhibited a quantum yield of 7.6%, with favorable photoluminescent properties and good photostability. The fluorescence intensity of the CDs was very stable in high ionic strength (up to 1.0 M NaCl) and over a wide range of pH levels (2.0–12.0). This facile method can therefore develop a sensor that offers reliable, fast, and selective detection of cupric ions with a detection limit down to 0.15 μM and a linear range from 0.5 to 7.0 μM (R² = 0.980). The CDs were used for cell imaging, observed that they were low toxicity to Tramp C1 cells and exhibited blue and green and red fluorescence under a fluorescence microscope. In summary, the CDs exhibited excellent fluorescence properties, and could be applied to the selective and sensitive detection of cupric ion and multicolor cell imaging. Full article

(This article belongs to the Special Issue Selective and Sensitive Detection of Biological and Chemical Species)

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