Fluorescent polymers for sensing and imaging

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Applications".

Deadline for manuscript submissions: closed (20 June 2019) | Viewed by 65122

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Guest Editor
Graduate School of Pharmaceutical Sciences, University of Tokyo, Bunkyo City, Tokyo 113-8654, Japan
Interests: fluorescent probe; functional polymer; analytical chemistry;photochemistry; logic gate

Special Issue Information

Dear Colleagues,

Nowadays, all scientists recognize that fluorescent probes play important roles in wide research areas, from chemistry to biology. By combining this fact with specific functional benefits from synthetic polymers, fluorescent polymeric probes are occasionally superior to small organic and inorganic fluorescent (or luminescent) probes in terms of sensitivity, robustness, and multiple functionality. For instance, exceptional sensitivity is conquered by either an amplification effects with concentrated fluorophores in a polymer particle or utilization of a stimulus-responsive polymer. The targets of fluorescent polymeric probes have extended from chemical species (e.g., ions and molecules) to physical parameter (e.g., temperature and viscosity). In addition to an environmental analysis with a glass cuvette or a microplate, biological cells are the spaces where the fluorescent polymeric probes extensively work. The ability to enter living cells and non-cytotoxicity are possible advantages of fluorescent polymeric probes in biological applications.

This Special Issue is a platform for all researches to develop a novel fluorescent polymeric probe and to establish a new analytical method using a conventional fluorescent polymeric probe. Related researches, e.g., fluorometric investigation of functional polymers, are also welcome. Well-balanced review articles with personal viewpoints are another encouraged contribution to the Special Issue.

Dr. Seiichi Uchiyama
Guest Editor

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Keywords

  • Fluorescence
  • Polymer
  • Gel
  • Nanoparticles
  • Ion
  • Live cell imaging
  • Luminescence

Published Papers (16 papers)

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Editorial

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4 pages, 159 KiB  
Editorial
The Magical Combination of Polymer Science and Fluorometry
by Seiichi Uchiyama
Polymers 2020, 12(4), 876; https://doi.org/10.3390/polym12040876 - 10 Apr 2020
Cited by 1 | Viewed by 1971
Abstract
I am very pleased to announce the publication of “Fluorescent Polymers for Sensing and Imaging” [...] Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)

Research

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11 pages, 2685 KiB  
Article
Exploring NIR Aza-BODIPY-Based Polarity Sensitive Probes with ON-and-OFF Fluorescence Switching in Pluronic Nanoparticles
by Bahar Saremi, Venugopal Bandi, Shahrzad Kazemi, Yi Hong, Francis D’Souza and Baohong Yuan
Polymers 2020, 12(3), 540; https://doi.org/10.3390/polym12030540 - 02 Mar 2020
Cited by 21 | Viewed by 6287
Abstract
Because of their deep penetration capability in tissue, red or near infrared (NIR) fluorophores attract much attention in bio-optical imaging. Among these fluorophores, the ones that respond to the immediate microenvironment (i.e., temperature, polarity, pH, viscosity, hypoxia, etc.) are highly desirable. We studied [...] Read more.
Because of their deep penetration capability in tissue, red or near infrared (NIR) fluorophores attract much attention in bio-optical imaging. Among these fluorophores, the ones that respond to the immediate microenvironment (i.e., temperature, polarity, pH, viscosity, hypoxia, etc.) are highly desirable. We studied the response of six NIR aza-BODIPY-based and structurally similar fluorophores to polarity and viscosity for incorporation inside Pluronic nanoparticles as switchable fluorescent probes (SFPs). Based on our results, all of these fluorophores were moderately to strongly sensitive to the polarity of the microenvironment. We concluded that attaching amine groups to the fluorophore is not necessary for having strong polarity sensitive probes. We further studied the response of the fluorophores when embedded inside Pluronic nanoparticles and found that four of them qualified as SFPs. We also found that the switching ratio of the fluorophore-encapsulated Pluronic nanoparticles (ION-to-IOFF) is related to the length of the hydrophobic chain of the Pluronic tri-block copolymers. As such, the highest switching ratio pertained to F-68 with the lowest hydrophobic block poly (propylene oxide) (PPO chain of only 30 units). Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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13 pages, 2650 KiB  
Article
A Cu(II) Indicator Platform Based on Cu(II) Induced Swelling that Changes the Extent of Fluorescein Self-Quenching
by Feifei Wang, Roy P. Planalp and W. Rudolf Seitz
Polymers 2019, 11(12), 1935; https://doi.org/10.3390/polym11121935 - 25 Nov 2019
Cited by 8 | Viewed by 3124
Abstract
In this study, we established a new fluorescent indicator platform. The responsive element consists of poly(N-isopropylacrylamide) nanospheres that include small percentages of fluorescein and a ligand, anilinodiacetate (phenylIDA). Nanosphere diameters were determined to be in the range from 50 to 90 nm by [...] Read more.
In this study, we established a new fluorescent indicator platform. The responsive element consists of poly(N-isopropylacrylamide) nanospheres that include small percentages of fluorescein and a ligand, anilinodiacetate (phenylIDA). Nanosphere diameters were determined to be in the range from 50 to 90 nm by scanning electron microscopy. They were entrapped in a polyacrylamide gel to prevent nanosphere aggregation. At pH 6, the ligand is negatively charged in the absence of metal ions. Charge-charge repulsion causes the nanosphere to swell. Dynamic light scattering measurements show that these nanospheres do not shrink and aggregate at high temperature. Cu(II) binding neutralizes the charge causing the particles to shrink. This brings fluoresceins closer together, increasing the degree of self-quenching. The intensity decreases by 30% as Cu(II) concentration increases. To rule out the possibility that the observed decrease in intensity was due to Cu(II) quenching of fluorescence, we also added Zn(II) and observed a decrease in intensity. This approach can be adapted to sense different metal ions and different concentrations of Cu(II) by changing the ligand. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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12 pages, 3958 KiB  
Article
Cationic Fluorescent Nanogel Thermometers based on Thermoresponsive Poly(N-isopropylacrylamide) and Environment-Sensitive Benzofurazan
by Teruyuki Hayashi, Kyoko Kawamoto, Noriko Inada and Seiichi Uchiyama
Polymers 2019, 11(8), 1305; https://doi.org/10.3390/polym11081305 - 04 Aug 2019
Cited by 7 | Viewed by 3833
Abstract
Cationic nanogels of N-isopropylacrylamide (NIPAM), including NIPAM-based cationic fluorescent nanogel thermometers, were synthesized with a cationic radical initiator previously developed in our laboratory. These cationic nanogels were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential measurements and fluorescence [...] Read more.
Cationic nanogels of N-isopropylacrylamide (NIPAM), including NIPAM-based cationic fluorescent nanogel thermometers, were synthesized with a cationic radical initiator previously developed in our laboratory. These cationic nanogels were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential measurements and fluorescence spectroscopy, as summarized in the temperature-dependent fluorescence response based on the structural change in polyNIPAM units in aqueous solutions. Cellular experiments using HeLa (human epithelial carcinoma) cells demonstrated that NIPAM-based cationic fluorescent nanogel thermometers can spontaneously enter the cells under mild conditions (at 25 °C for 20 min) and can show significant fluorescence enhancement without cytotoxicity with increasing culture medium temperature. The combination of the ability to enter cells and non-cytotoxicity is the most important advantage of cationic fluorescent nanogel thermometers compared with other types of fluorescent polymeric thermometers, i.e., anionic nanogel thermometers and cationic/anionic linear polymeric thermometers. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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9 pages, 3020 KiB  
Article
Ratiometric Luminescent Nanoprobes Based on Ruthenium and Terbium-Containing Metallopolymers for Intracellular Oxygen Sensing
by Wu-xing Zhao, Chao Zhou and Hong-shang Peng
Polymers 2019, 11(8), 1290; https://doi.org/10.3390/polym11081290 - 02 Aug 2019
Cited by 9 | Viewed by 4286
Abstract
A collection of luminescent metal complexes have been widely used as oxygen probes in the biomedical field. However, single intensity-based detection approach usually suffered from errors caused by the signal heterogeneity or fluctuation of the optoelectronic system. In this work, respective ruthenium (II) [...] Read more.
A collection of luminescent metal complexes have been widely used as oxygen probes in the biomedical field. However, single intensity-based detection approach usually suffered from errors caused by the signal heterogeneity or fluctuation of the optoelectronic system. In this work, respective ruthenium (II) and terbium (III) complexes were chosen to coordinate a bipyridine-branched copolymer, so that to produce oxygen-sensitive metallopolymer (Ru-Poly) and oxygen-insensitive metallopolymer (Tb-Poly). Based on the hydrophobic Ru-Poly and Tb-Poly, a ratiometric luminescent oxygen nanoprobe was facilely prepared by a nanoprecipitation method. The nanoprobes have a typical size of ~100 nm in aqueous solution, exhibiting a green-red dual-wavelength emission under the excitation of 300 nm and 460 nm, respectively. The red emission is strongly quenched by dissolved oxygen while the green one is rather stable, and the ratiometric luminescence was well fitted by a linear Stern–Volmer equation. Using the ratiometric biocompatible nanoprobes, the distribution of intracellular oxygen within three-dimensional multi-cellular tumor spheroids was successfully imaged. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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17 pages, 3686 KiB  
Article
Application of PEG-Covered Non-Biodegradable Polyelectrolyte Microcapsules in the Crustacean Circulatory System on the Example of the Amphipod Eulimnogammarus verrucosus
by Ekaterina Shchapova, Anna Nazarova, Anton Gurkov, Ekaterina Borvinskaya, Yaroslav Rzhechitskiy, Ivan Dmitriev, Igor Meglinski and Maxim Timofeyev
Polymers 2019, 11(8), 1246; https://doi.org/10.3390/polym11081246 - 27 Jul 2019
Cited by 10 | Viewed by 5387
Abstract
Layer-by-layer assembled microcapsules are promising carriers for the delivery of various pharmaceutical and sensing substances into specific organs of different animals, but their utility in vivo inside such an important group as crustaceans remains poorly explored. In the current study, we analyzed several [...] Read more.
Layer-by-layer assembled microcapsules are promising carriers for the delivery of various pharmaceutical and sensing substances into specific organs of different animals, but their utility in vivo inside such an important group as crustaceans remains poorly explored. In the current study, we analyzed several significant aspects of the application of fluorescent microcapsules covered by polyethylene glycol (PEG) inside the crustacean circulatory system, using the example of the amphipod Eulimnogammarus verrucosus. In particular, we explored the distribution dynamics of visible microcapsules after injection into the main hemolymph vessel; analyzed the most significant features of E. verrucosus autofluorescence; monitored amphipod mortality and biochemical markers of stress response after microcapsule injection, as well as the healing of the injection wound; and finally, we studied the immune response to the microcapsules. The visibility of microcapsules decreased with time, however, the central hemolymph vessel was confirmed to be the most promising organ for detecting the spectral signal of implanted microencapsulated fluorescent probes. One million injected microcapsules (sufficient for detecting stable fluorescence during the first hours after injection) showed no toxicity for six weeks, but in vitro amphipod immune cells recognize the PEG-coated microcapsules as foreign bodies and try to isolate them by 12 h after contact. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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12 pages, 4210 KiB  
Article
Synthesis of Silane-Based Poly(thioether) via Successive Click Reaction and Their Applications in Ion Detection and Cell Imaging
by Zhiming Gou, Xiaomei Zhang, Yujing Zuo and Weiying Lin
Polymers 2019, 11(8), 1235; https://doi.org/10.3390/polym11081235 - 25 Jul 2019
Cited by 7 | Viewed by 3209
Abstract
A series of poly(thioether)s containing silicon atom with unconventional fluorescence were synthesized via successive thiol click reaction at room temperature. Although rigid π-conjugated structure did not exist in the polymer chain, the poly(thioether)s exhibited excellent fluorescent properties in solutions and showed visible blue [...] Read more.
A series of poly(thioether)s containing silicon atom with unconventional fluorescence were synthesized via successive thiol click reaction at room temperature. Although rigid π-conjugated structure did not exist in the polymer chain, the poly(thioether)s exhibited excellent fluorescent properties in solutions and showed visible blue fluorescence in living cells. The strong blue fluorescence can be attributed to the aggregation of lone pair electron of heteroatom and coordination between heteroatom and Si atom. In addition, the responsiveness of poly(thioether) to metal ions suggested that the selectivity of poly(thioether) to Fe3+ ion could be enhanced by end-modifying with different sulfhydryl compounds. This study further explored their application in cell imaging and studied their responsiveness to Fe3+ in living cells. It is expected that the described synthetic route could be extended to synthesize novel poly(thioether)s with superior optical properties. Their application in cell imaging and ion detection will broaden the range of application of poly(thioether)s. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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14 pages, 2649 KiB  
Article
Magnetic Fluorescence Molecularly Imprinted Polymer Based on FeOx/ZnS Nanocomposites for Highly Selective Sensing of Bisphenol A
by Xin Zhang, Shu Yang, Weijie Chen, Yansong Li, Yuping Wei and Aiqin Luo
Polymers 2019, 11(7), 1210; https://doi.org/10.3390/polym11071210 - 19 Jul 2019
Cited by 30 | Viewed by 4235
Abstract
In this study, magnetic fluorescence molecularly imprinted polymers were fabricated and used for the selective separation and fluorescence sensing of trace bisphenol A (BPA) in environmental water samples. The carboxyl-functionalized FeOx magnetic nanoparticles were conjugated with mercaptoethylamine-capped Mn2+ doped ZnS quantum [...] Read more.
In this study, magnetic fluorescence molecularly imprinted polymers were fabricated and used for the selective separation and fluorescence sensing of trace bisphenol A (BPA) in environmental water samples. The carboxyl-functionalized FeOx magnetic nanoparticles were conjugated with mercaptoethylamine-capped Mn2+ doped ZnS quantum dots to prepare magnetic FeOx and ZnS quantum dot nanoparticles (FeOx/ZnS NPs). Additionally, molecular imprinting on the FeOx/ZnS NPs was employed to synthesize core-shell molecularly imprinted polymers. The resulting nanoparticles were well characterized using transmission electron microscopy, Fourier transform infrared spectra, vibrating sample magnetometer and fluorescence spectra, and the adsorption behavior was investigated. Binding experiments showed that the molecularly imprinted FeOX/ZnS NPs (FeOx/ZnS@MIPs) exhibited rapid fluorescent and magnetic responses, and high selectivity and sensitivity for the detection of bisphenol A (BPA). The maximum adsorption capacity of FeOx/ZnS@MIPs was 50.92 mg·g−1 with an imprinting factor of 11.19. Under optimal conditions, the constructed fluorescence magnetic molecularly imprinted polymers presented good linearity from 0 to 80 ng mL−1 with a detection limit of 0.3626 ng mL−1 for BPA. Moreover, the proposed fluorescence magnetic polymers were successfully applied to on-site magnetic separation and real-time fluorescence analysis of target molecule in real samples. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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15 pages, 1484 KiB  
Article
Two-Step Energy Transfer Dynamics in Conjugated Polymer and Dye-Labeled Aptamer-Based Potassium Ion Detection Assay
by Inhong Kim, Ji-Eun Jung, Woojin Lee, Seongho Park, Heedae Kim, Young-Dahl Jho, Han Young Woo and Kwangseuk Kyhm
Polymers 2019, 11(7), 1206; https://doi.org/10.3390/polym11071206 - 19 Jul 2019
Cited by 4 | Viewed by 5102
Abstract
We recently implemented highly sensitive detection systems for photo-sensitizing potassium ions (K+) based on two-step Förster resonance energy transfer (FRET). As a successive study for quantitative understanding of energy transfer processes in terms of the exciton population, we investigated the fluorescence [...] Read more.
We recently implemented highly sensitive detection systems for photo-sensitizing potassium ions (K+) based on two-step Förster resonance energy transfer (FRET). As a successive study for quantitative understanding of energy transfer processes in terms of the exciton population, we investigated the fluorescence decay dynamics in conjugated polymers and an aptamer-based 6-carboxyfluorescein (6-FAM)/6-carboxytetramethylrhodamine (TAMRA) complex. In the presence of K+ ions, the Guanine-rich aptamer enabled efficient two-step resonance energy transfer from conjugated polymers to dyed pairs of 6-FAM and TAMRA through the G-quadruplex phase. Although the fluorescence decay time of TAMRA barely changed, the fluorescence intensity was significantly increased. We also found that 6-FAM showed a decreased exciton population due the compensation of energy transfer to TAMRA by FRET from conjugated polymers, but a fluorescence quenching also occurred concomitantly. Consequently, the fluorescence intensity of TAMRA showed a 4-fold enhancement, where the initial transfer efficiency (~300%) rapidly saturated within ~0.5 ns and the plateau of transfer efficiency (~230%) remained afterward. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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8 pages, 1567 KiB  
Article
pH Behavior of Polymer Complexes between Poly(carboxylic acids) and Poly(acrylamide derivatives) Using a Fluorescence Label Technique
by Yuriko Matsumura and Kaoru Iwai
Polymers 2019, 11(7), 1196; https://doi.org/10.3390/polym11071196 - 17 Jul 2019
Cited by 4 | Viewed by 2683
Abstract
In order to clarify the local environment during interpolymer complex formation between poly(carboxylic acids) and poly(acrylamide derivatives) with different N-substitutions, a fluorescence label technique was used. 3-(2-propenyl)-9-(4-N,N-dimethylaminophenyl) phenanthrene (VDP) was used as an intramolecular fluorescence probe. All polymers [...] Read more.
In order to clarify the local environment during interpolymer complex formation between poly(carboxylic acids) and poly(acrylamide derivatives) with different N-substitutions, a fluorescence label technique was used. 3-(2-propenyl)-9-(4-N,N-dimethylaminophenyl) phenanthrene (VDP) was used as an intramolecular fluorescence probe. All polymers were synthesized by free radical polymerization. Interpolymer complexation was monitored by charge transfer emission from the VDP unit. Both of the poly(carboxylic acids) formed interpolymer complexes with poly(N,N-dimethylacrylamide) (polyDMAM). The micro-environments around the VDP unit in the acidic pH region for the poly(methacrylic acid) (polyMAAc) and polyDMAM mixed systems were more hydrophobic than those of the poly(acrylic acid) (polyAAc) and polyDMAM mixed systems, as the α-methyl group of the MAAc unit contributed to hydrophobicity around the polymer chain during hydrogen bond formation. This suggests that, when the poly(carboxylic acids) and poly(acrylamide derivatives) were mixed, with a subsequent decrease in the solution pH, a hydrogen bond was partially formed, following which the hydrophobicity of the micro-environment around the polymer chains was changed, resulting in the formation of interpolymer complexes. Moreover, the electron-donating ability of the carbonyl group in the poly(acrylamide derivatives) had an effect on complexation with poly(carboxylic acids). Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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12 pages, 1731 KiB  
Article
Oxygen-Resistant Electrochemiluminescence System with Polyhedral Oligomeric Silsesquioxane
by Ryota Nakamura, Hayato Narikiyo, Masayuki Gon, Kazuo Tanaka and Yoshiki Chujo
Polymers 2019, 11(7), 1170; https://doi.org/10.3390/polym11071170 - 10 Jul 2019
Cited by 5 | Viewed by 2688
Abstract
We report the oxygen-resistant electrochemiluminescence (ECL) system from the polyhedral oligomeric silsesquioxane (POSS)-modified tris(2,2′-bipyridyl)ruthenium(II) complex (Ru-POSS). In electrochemical measurements, including cyclic voltammetry (CV), it is shown that electric current and ECL intensity increase in the mixture system containing Ru-POSS and tripropylamine (TPrA) on [...] Read more.
We report the oxygen-resistant electrochemiluminescence (ECL) system from the polyhedral oligomeric silsesquioxane (POSS)-modified tris(2,2′-bipyridyl)ruthenium(II) complex (Ru-POSS). In electrochemical measurements, including cyclic voltammetry (CV), it is shown that electric current and ECL intensity increase in the mixture system containing Ru-POSS and tripropylamine (TPrA) on the indium tin oxide (ITO) working electrode. The lower onset potential (Eonset) in CV is observed with Ru-POSS compared to tris(2,2′-bipyridyl)ruthenium(II) complex (Ru(bpy)32+). From the series of mechanistic studies, it was shown that adsorption of Ru-POSS onto the ITO electrode enhances TPrA oxidation and subsequently the efficiency of ECL with lower voltage. Moreover, oxygen quenching of ECL was suppressed, and it is proposed that the enhancement to the production of the TPrA radical could contribute to improving oxygen resistance. Finally, the ECL-based detection for water pollutant is demonstrated without the degassing treatment. The commodity system with Ru(bpy)32+ is not applicable in the absence of degassing with the sample solutions due to critical signal suppression, meanwhile the present system based on Ru-POSS was feasible for estimating the amount of the target even under aerobic conditions by fitting the ECL intensity to the standard curve. One of critical disadvantages of ECL can be solved by the hybrid formation with POSS. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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13 pages, 3105 KiB  
Article
Highly Selective Fluorescence Sensing and Imaging of ATP Using a Boronic Acid Groups-Bearing Polythiophene Derivate
by Lihua Liu, Linlin Zhao, Dandan Cheng, Xinyi Yao and Yan Lu
Polymers 2019, 11(7), 1139; https://doi.org/10.3390/polym11071139 - 03 Jul 2019
Cited by 11 | Viewed by 5927
Abstract
A boronic acid groups-bearing polythiophene derivate (L) was designed and synthesized for highly sensitive fluorescence detection of ATP based on a multisite-binding coupled with analyte-induced aggregation strategy. L has a polythiophene backbone as fluorophores and two functional side groups, i.e., quaternary [...] Read more.
A boronic acid groups-bearing polythiophene derivate (L) was designed and synthesized for highly sensitive fluorescence detection of ATP based on a multisite-binding coupled with analyte-induced aggregation strategy. L has a polythiophene backbone as fluorophores and two functional side groups, i.e., quaternary ammonium group and boronic acid group, as multibinding sites for ATP. When various structural analogues such as ADP, AMP, and various inorganic phosphates were added into the aqueous solution of L, only ATP caused a remarkable fluorescence quenching of about 60-fold accompanied by obvious color changes of solution from yellow to purple. The detection limit is estimated to be 2 nM based on 3σ/slope. With the advantage of good water solubility, low toxicity, and highly selective response to ATP, L was successfully utilized as a probe to real-time assay activity of adenylate kinase (ADK) and map fluorescent imaging of ATP in living cells. Full article
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13 pages, 4839 KiB  
Article
Preparation of Fluorescent Molecularly Imprinted Polymers via Pickering Emulsion Interfaces and the Application for Visual Sensing Analysis of Listeria Monocytogenes
by Xiaolei Zhao, Yan Cui, Junping Wang and Junying Wang
Polymers 2019, 11(6), 984; https://doi.org/10.3390/polym11060984 - 04 Jun 2019
Cited by 45 | Viewed by 4212
Abstract
In this work, a novel molecularly imprinted polymer (MIP) with water-soluble CdTe quantum dots (QDs) was synthesized by oil-in-water Pickering emulsion polymerization using whole Listeria monocytogenes as the template. Listeria monocytogenes was first treated by acryloyl-functionalized chitosan with QDs to form a bacteria–chitosan [...] Read more.
In this work, a novel molecularly imprinted polymer (MIP) with water-soluble CdTe quantum dots (QDs) was synthesized by oil-in-water Pickering emulsion polymerization using whole Listeria monocytogenes as the template. Listeria monocytogenes was first treated by acryloyl-functionalized chitosan with QDs to form a bacteria–chitosan network as the water phase. This was then stabilized in an oil-in-water emulsion comprising a cross-linker, monomer, and initiator, causing recognition sites on the surface of microspheres embedded with CdTe QDs. The resulting MIP microspheres enabled selective capture of the target bacteria via recognition cavities. The target bacteria Listeria monocytogenes was detected. Scanning electron microscopy (SEM) characterization showed that the MIPs had a rough spherical shape. There was visual fluorescence detection via quenching in the presence of the target molecule, which offered qualitative detection of Listeria monocytogenes in milk and pork samples. The developed method simplified the analysis process and did not require any sample pretreatment. In addition, the fluorescence sensor provided an effective, fast, and convenient method for Listeria monocytogenes detection in food samples. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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13 pages, 1947 KiB  
Article
Fabrication of Active Polymer Optical Fibers by Solution Doping and Their Characterization
by Igor Ayesta, Mikel Azkune, Eneko Arrospide, Jon Arrue, María Asunción Illarramendi, Gaizka Durana and Joseba Zubia
Polymers 2019, 11(1), 52; https://doi.org/10.3390/polym11010052 - 31 Dec 2018
Cited by 10 | Viewed by 3480
Abstract
This paper employs the solution-doping technique for the fabrication of active polymer optical fibers (POFs), in which the dopant molecules are directly incorporated into the core of non-doped uncladded fibers. Firstly, we characterize the insertion of a solution of rhodamine B and methanol [...] Read more.
This paper employs the solution-doping technique for the fabrication of active polymer optical fibers (POFs), in which the dopant molecules are directly incorporated into the core of non-doped uncladded fibers. Firstly, we characterize the insertion of a solution of rhodamine B and methanol into the core of the fiber samples at different temperatures, and we show that better optical characteristics, especially in the attenuation coefficient, are achieved at lower temperatures. Moreover, we also analyze the dependence of the emission features of doped fibers on both the propagation distance and the excitation time. Some of these features and the corresponding ones reported in the literature for typical active POFs doped with the same dopant are quantitatively similar among them. This applies to the spectral location of the absorption and the emission bands, the spectral displacement with propagation distance, and the linear attenuation coefficient. The samples prepared in the way described in this work present higher photostability than typical samples reported in the literature, which are prepared in different ways. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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8 pages, 4811 KiB  
Communication
A Polymer-Gel Eye-Phantom for 3D Fluorescent Imaging of Millimetre Radiation Beams
by Leonard H. Luthjens, Tiantian Yao and John M. Warman
Polymers 2018, 10(11), 1195; https://doi.org/10.3390/polym10111195 - 26 Oct 2018
Cited by 12 | Viewed by 2955
Abstract
We have filled a 24 mm diameter glass sphere with a transparent polymer-gel that is radio-fluorogenic, i.e., it becomes (permanently) fluorescent when irradiated, with an intensity proportional to the local dose deposited. The gel consists of >99.9% tertiary-butyl acrylate (TBA), pre-polymerized to ~15% [...] Read more.
We have filled a 24 mm diameter glass sphere with a transparent polymer-gel that is radio-fluorogenic, i.e., it becomes (permanently) fluorescent when irradiated, with an intensity proportional to the local dose deposited. The gel consists of >99.9% tertiary-butyl acrylate (TBA), pre-polymerized to ~15% conversion, and ~100 ppm maleimido-pyrene (MPy). Its dimensions and physical properties are close to those of the vitreous body of the human eye. We have irradiated the gel with a 3 mm diameter, 200 kVp X-ray beam with a dose rate of ~1 Gy/min. A three-dimensional (3D) (video) view of the beam within the gel has been constructed from tomographic images obtained by scanning the sample through a thin sheet of UV light. To minimize optical artefacts, the cell was immersed in a square tank containing a refractive-index-matching medium. The 20–80% penumbra of the beam was determined to be ~0.4 mm. This research was a preparatory investigation of the possibility of using this method to monitor the millimetre diameter proton pencil beams used in ocular radiotherapy. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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Review

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15 pages, 2678 KiB  
Review
A Personal Journey across Fluorescent Sensing and Logic Associated with Polymers of Various Kinds
by Chao-Yi Yao, Seiichi Uchiyama and A. Prasanna de Silva
Polymers 2019, 11(8), 1351; https://doi.org/10.3390/polym11081351 - 14 Aug 2019
Cited by 8 | Viewed by 3633
Abstract
Our experiences concerning fluorescent molecular sensing and logic devices and their intersections with polymer science are the foci of this brief review. Proton-, metal ion- and polarity-responsive cases of these devices are placed in polymeric micro- or nano-environments, some of which involve phase [...] Read more.
Our experiences concerning fluorescent molecular sensing and logic devices and their intersections with polymer science are the foci of this brief review. Proton-, metal ion- and polarity-responsive cases of these devices are placed in polymeric micro- or nano-environments, some of which involve phase separation. This leads to mapping of chemical species on the nanoscale. These devices also take advantage of thermal properties of some polymers in water in order to reincarnate themselves as thermometers. When the phase separation leads to particles, the latter can be labelled with identification tags based on molecular logic. Such particles also give rise to reusable sensors, although molecular-scale resolution is sacrificed in the process. Polymeric nano-environments also help to organize rather complex molecular logic systems from their simple components. Overall, our little experiences suggest that researchers in sensing and logic would benefit if they assimilate polymer concepts. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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