Research

15 pages, 4301 KiB

Open AccessArticle

Novel Crown Ether Amino Acids as Fluorescent Reporters for Metal Ions

by Patrícia M. R. Batista, Cátia D. F. Martins, M. Manuela M. Raposo and Susana P. G. Costa

Molecules 2023, 28(8), 3326; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28083326 - 09 Apr 2023

Cited by 3 | Viewed by 1369

Unnatural amino acids with enhanced properties, such as increased complexing ability and luminescence, are considered to be highly attractive building blocks for bioinspired frameworks, such as probes for biomolecule dynamics, sensitive fluorescent chemosensors, and peptides for molecular imaging, among others. Therefore, a novel [...] Read more.

Unnatural amino acids with enhanced properties, such as increased complexing ability and luminescence, are considered to be highly attractive building blocks for bioinspired frameworks, such as probes for biomolecule dynamics, sensitive fluorescent chemosensors, and peptides for molecular imaging, among others. Therefore, a novel series of highly emissive heterocyclic alanines bearing a benzo[d]oxazolyl unit functionalized with different heterocyclic π-spacers and (aza)crown ether moieties was synthesized. The new compounds were completely characterized using the usual spectroscopic techniques and evaluated as fluorimetric chemosensors in acetonitrile and aqueous mixtures in the presence of various alkaline, alkaline-earth, and transition metal ions. The different crown ether binding moieties as well as the electronic nature of the π-bridge allowed for fine tuning of the sensory properties of these unnatural amino acids towards Pd²⁺ and Fe³⁺, as seen by spectrofluorimetric titrations. Full article

(This article belongs to the Special Issue Recent Advancements in Organic Fluorophores Preparation and Applications in Chemical Biology and Functional Materials)

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11 pages, 2052 KiB

Open AccessArticle

Controlled Assembly of Fluorophores inside a Nanoliposome

by Hiroaki Konishi, Eiji Nakata, Futa Komatsubara and Takashi Morii

Molecules 2023, 28(2), 911; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28020911 - 16 Jan 2023

Cited by 1 | Viewed by 1511

Abstract

Cellular compartmentalization plays an essential role in organizing the complex and multiple biochemical reactions in the cell. An artificial compartment would provide powerful strategies to develop new biochemical tools for material production and diagnosis, but it is still a great challenge to synthesize [...] Read more.

Cellular compartmentalization plays an essential role in organizing the complex and multiple biochemical reactions in the cell. An artificial compartment would provide powerful strategies to develop new biochemical tools for material production and diagnosis, but it is still a great challenge to synthesize the compartments that encapsulate materials of interest while controlling their accurate locations, numbers, and stoichiometry. In this study, we evaluated chemical characteristics of a liposome-encapsulated compartment, which has great potential to locate various materials of interest with precise control of their locations and numbers in the compartment. A nanoliposome was constructed inside a ring-shaped DNA origami skeleton according to the method of Yang et al., and further equipped with a double-stranded DNA platform to assemble molecules of interest in the nanoliposome. Upon formation of the nanoliposome, a pH-sensitive fluorophore on the bridged platform showed little or no response to the pH change of the outer buffer, ensuring that the molecules assembled on the platform are effectively shielded from the outer environment. The ring-shaped DNA skeleton equipped with a double-stranded DNA platform allows spatial assembly of several functional molecules inside the nanoliposome to isolate them from the outer environment. Full article

(This article belongs to the Special Issue Recent Advancements in Organic Fluorophores Preparation and Applications in Chemical Biology and Functional Materials)

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20 pages, 4441 KiB

Open AccessArticle

Tuning the Photophysics of Two-Arm Bis[(dimethylamino)styryl]benzene Derivatives by Heterocyclic Substitution

by Letizia Mencaroni, Alessio Cesaretti, Benedetta Carlotti, Martina Alebardi, Fausto Elisei, Ana Ratković, Irena Škorić and Anna Spalletti

Molecules 2022, 27(24), 8725; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27248725 - 09 Dec 2022

Cited by 2 | Viewed by 1624

Abstract

The identification of novel molecular systems with high fluorescence and significant non-linear optical (NLO) properties is a hot topic in the continuous search for new emissive probes. Here, the photobehavior of three two-arm bis[(dimethylamino)styryl]benzene derivatives, where the central benzene was replaced by pyridine, [...] Read more.

The identification of novel molecular systems with high fluorescence and significant non-linear optical (NLO) properties is a hot topic in the continuous search for new emissive probes. Here, the photobehavior of three two-arm bis[(dimethylamino)styryl]benzene derivatives, where the central benzene was replaced by pyridine, furan, or thiophene, was studied by stationary and time-resolved spectroscopic techniques with ns and fs resolution. The three molecules under investigation all showed positive fluorosolvatochromism, due to intramolecular charge-transfer (ICT) dynamics from the electron-donor dimethylamino groups, and significant fluorescence quantum yields, because of the population of a planar and emissive ICT state stabilized by intramolecular hydrogen-bond-like interactions. The NLO properties (hyperpolarizability coefficient and TPA cross-section) were also measured. The obtained results allowed the role of the central heteroaromatic ring to be disclosed. In particular, the introduction of the thiophene ring guarantees high fluorescent quantum yields irrespective of the polarity of the medium, and the largest hyperpolarizability coefficient because of the increased conjugation. An important and structure-dependent involvement of the triplet state was also highlighted, with the intersystem crossing being competitive with fluorescence, especially in the thiophene derivative, where the triplet was found to significantly sensitize molecular oxygen even in polar environment, leading to possible applications in photodynamic therapy. Full article

(This article belongs to the Special Issue Recent Advancements in Organic Fluorophores Preparation and Applications in Chemical Biology and Functional Materials)

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10 pages, 2777 KiB

Open AccessArticle

A Novel Fluorescent Probe for Determination of pH and Viscosity Based on a Highly Water-Soluble 1,8-Naphthalimide Rotor

by Ventsislav V. Bakov, Nikolai I. Georgiev and Vladimir B. Bojinov

Molecules 2022, 27(21), 7556; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27217556 - 04 Nov 2022

Cited by 8 | Viewed by 1850

Abstract

A novel highly water-soluble 1,8-naphthalimide with pH and viscosity-sensing fluorescence was synthesized and investigated. The synthesized compound was designed as a molecular device in which a molecular rotor and molecular “off-on” switcher were integrated. In order to obtain a TICT driven molecular motion [...] Read more.

A novel highly water-soluble 1,8-naphthalimide with pH and viscosity-sensing fluorescence was synthesized and investigated. The synthesized compound was designed as a molecular device in which a molecular rotor and molecular “off-on” switcher were integrated. In order to obtain a TICT driven molecular motion at C-4 position of the 1,8-naphthalimide fluorophore, a 4-methylpiperazinyl fragment was introduced. The molecular motion was confirmed after photophysical investigation in solvents with different viscosity; furthermore, the fluorescence-sensing properties of the examined compound were investigated in 100% aqueous medium and it was found that it could be used as an efficient fluorescent probe for pH. Due to the non-emissive deexcitation nature of the TICT fluorophore, the novel system showed low yellow–green emission, which represented “power-on”/“rotor-on” state. The protonation of the methylpiperazine amine destabilized the TICT process, which was accompanied by fluorescence enhancement indicating a “power-on”/“rotor-off” state of the system. The results obtained clearly illustrated the great potential of the synthesized compound to serve as pH- and viscosity-sensing material in aqueous solution. Full article

(This article belongs to the Special Issue Recent Advancements in Organic Fluorophores Preparation and Applications in Chemical Biology and Functional Materials)

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14 pages, 3225 KiB

Open AccessArticle

Imidazo[1,5-a]pyridine-Based Fluorescent Probes: A Photophysical Investigation in Liposome Models

by Giacomo Renno, Francesca Cardano, Giorgio Volpi, Claudia Barolo, Guido Viscardi and Andrea Fin

Molecules 2022, 27(12), 3856; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27123856 - 16 Jun 2022

Cited by 4 | Viewed by 1912

Abstract

Imidazo[1,5-a]pyridine is a stable scaffold, widely used for the development of emissive compounds in many application fields (e.g., optoelectronics, coordination chemistry, sensors, chemical biology). Their compact shape along with remarkable photophysical properties make them suitable candidates as cell membrane probes. The [...] Read more.

Imidazo[1,5-a]pyridine is a stable scaffold, widely used for the development of emissive compounds in many application fields (e.g., optoelectronics, coordination chemistry, sensors, chemical biology). Their compact shape along with remarkable photophysical properties make them suitable candidates as cell membrane probes. The study of the membrane dynamics, hydration, and fluidity is of importance to monitor the cellular health and to explore crucial biochemical pathways. In this context, five imidazo[1,5-a]pyridine-based fluorophores were synthesized according to a one-pot cyclization between an aromatic ketone and benzaldehyde in the presence of ammonium acetate and acetic acid. The photophysical features of prepared compounds were investigated in several organic solvents and probes 2–4 exhibited the greatest solvatochromic behavior, resulting in a higher suitability as membrane probes. Their interaction with liposomes as artificial membrane model was tested showing a successful intercalation of the probes in the lipid bilayer. Kinetic experiments were carried out and the lipidic phase influence on the photophysical features was evaluated through temperature-dependent experiments. The results herein reported encourage further investigations on the use of imidazo[1,5-a]pyridine scaffold as fluorescent membrane probes. Full article

(This article belongs to the Special Issue Recent Advancements in Organic Fluorophores Preparation and Applications in Chemical Biology and Functional Materials)

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19 pages, 11941 KiB

Open AccessArticle

Amphiphilicity-Controlled Localization of Red Emitting Bicationic Fluorophores in Tumor Cells Acting as Bio-Probes and Anticancer Drugs

by Alessio Cesaretti, Letizia Mencaroni, Carmela Bonaccorso, Valentina Botti, Eleonora Calzoni, Benedetta Carlotti, Cosimo Gianluca Fortuna, Nicolò Montegiove, Anna Spalletti and Fausto Elisei

Molecules 2022, 27(12), 3713; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27123713 - 09 Jun 2022

Cited by 3 | Viewed by 1440

Abstract

Small organic molecules arouse lively interest for their plethora of possible biological applications, such as anticancer therapy, for their ability to interact with nucleic acids, or bioimaging, thanks to their fluorescence emission. Here, a panchromatic series of styryl-azinium bicationic dyes, which have already [...] Read more.

Small organic molecules arouse lively interest for their plethora of possible biological applications, such as anticancer therapy, for their ability to interact with nucleic acids, or bioimaging, thanks to their fluorescence emission. Here, a panchromatic series of styryl-azinium bicationic dyes, which have already proved to exhibit high water-solubility and significant red fluorescence in water, were investigated through spectrofluorimetric titrations to assess the extent of their association constants with DNA and RNA. Femtosecond-resolved transient absorption spectroscopy was also employed to characterize the changes in the photophysical properties of these fluorophores upon interaction with their biological targets. Finally, in vitro experiments conducted on tumor cell lines revealed that some of the bicationic fluorophores had a peculiar localization within cell nuclei exerting important antiproliferative effects, others were instead found to localize in the cytoplasm without leading to cell death, being useful to mark specific organelles in light of live cell bioimaging. Interestingly, this molecule-dependent behavior matched the different amphiphilicity featured by these bioactive compounds, which are thus expected to be caught in a tug-of-war between lipophilicity, ensured by the presence of aromatic rings and needed to pass cell membranes, and hydrophilicity, granted by charged groups and necessary for stability in aqueous media. Full article

(This article belongs to the Special Issue Recent Advancements in Organic Fluorophores Preparation and Applications in Chemical Biology and Functional Materials)

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20 pages, 6241 KiB

Open AccessArticle

Imaging-Guided Delivery of a Hydrophilic Drug to Eukaryotic Cells Based on Its Hydrophobic Ion Pairing with Poly(hexamethylene guanidine) in a Maleated Chitosan Carrier

by Sofia A. Zakharenkova, Marina I. Lebedeva, Alexandra N. Lebedeva, Irina A. Doroshenko, Ksenya Yu Vlasova, Anastasiya A. Bartoshevich, Vladimir M. Senyavin, Sergey S. Abramchuk, George G. Krivtsov, Alexander A. Ezhov, Tatyana A. Podrugina, Natalia L. Klyachko and Mikhail K. Beklemishev

Molecules 2021, 26(24), 7426; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26247426 - 07 Dec 2021

Cited by 3 | Viewed by 2428

Abstract

Imaging-guided delivery is developed for hydrophobic drugs, and to a much lesser extent, hydrophilic ones. In this work we have designed a novel strategy for real-time monitoring of hydrophilic drug delivery. Traditionally, the drug and the dye are covalently attached to a nanocarrier [...] Read more.

Imaging-guided delivery is developed for hydrophobic drugs, and to a much lesser extent, hydrophilic ones. In this work we have designed a novel strategy for real-time monitoring of hydrophilic drug delivery. Traditionally, the drug and the dye are covalently attached to a nanocarrier or are electrostatically adsorbed. Recently, we found an efficient way to bind the drug by ion-paring with an appropriate counter-ion to form the aggregate that embeds a hydrophobic dye with a considerable fluorescence enhancement. We synthesized a series of carbocyanine dyes of hydrophobicity sufficient for solubilization in hydrophobic ion pairs, which restores their emission in the near-infrared (NIR) region upon the formation of the ternary aggregates. To avoid using toxic surfactants, we applied an amphiphilic polymer-oligomer poly(hexamethylene guanidine) (PHMG) as a counter-ion. Сeftriaxone was used as a model hydrophilic drug ensuring the highest fluorescent signal. The so-formed drug–counter-ion–dye aggregates were encapsulated into a cross-linked maleated chitosan carrier. Confocal laser scanning microscopy (CLSM) studies have demonstrated internalization of the encapsulated model drug by breast adenocarcinoma cells at 40 min after treatment. These results suggest the potential application of hydrophobic ion pairs containing an NIR dye in imaging-guided delivery of hydrophilic compounds. Full article

(This article belongs to the Special Issue Recent Advancements in Organic Fluorophores Preparation and Applications in Chemical Biology and Functional Materials)

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14 pages, 2184 KiB

Open AccessArticle

Synthesis and Spectroscopic Characterization of Thienopyrazine-Based Fluorophores for Application in Luminescent Solar Concentrators (LSCs)

by Xheila Yzeiri, Massimo Calamante, Alessio Dessì, Daniele Franchi, Andrea Pucci, Francesco Ventura, Gianna Reginato, Lorenzo Zani and Alessandro Mordini

Molecules 2021, 26(18), 5428; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26185428 - 07 Sep 2021

Cited by 8 | Viewed by 2334

Abstract

Organic fluorophores have found broad application as emitters in luminescent solar concentrators (LSCs) for silicon photovoltaics. In particular, the preparation of organic conjugated systems with intense light-harvesting ability, emissions in the deep-red and NIR regions, and large Stokes shift values represent a very [...] Read more.

Organic fluorophores have found broad application as emitters in luminescent solar concentrators (LSCs) for silicon photovoltaics. In particular, the preparation of organic conjugated systems with intense light-harvesting ability, emissions in the deep-red and NIR regions, and large Stokes shift values represent a very challenging undertaking. Here, we report a simple and easy way to prepare three symmetrical donor–acceptor–donor (DAD) organic-emitting materials based on a thienopyrazine core. The central core in the three dyes was modified with the introduction of aromatic substituents, aiming to affect their optical properties. The fluorophores were characterized by spectroscopic studies. In all cases, visible-NIR emissions with large Stokes shifts were found, highlighting these molecules as promising materials for the application in LSCs. Full article

(This article belongs to the Special Issue Recent Advancements in Organic Fluorophores Preparation and Applications in Chemical Biology and Functional Materials)

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