Publications by authors named "Juan F Miravet"

58 Publications

Broad-Spectrum Photo-Antimicrobial Polymers Based on Cationic Polystyrene and Rose Bengal.

Front Med (Lausanne) 2021 24;8:641646. Epub 2021 May 24.

Departamento de Química Inorgánica y Orgánica, Universitat Jaume I, Castellón, Spain.

New strategies to fight bacteria and fungi are necessary in view of the problem of iatrogenic and nosocomial infections combined with the growing threat of increased antimicrobial resistance. Recently, our group has prepared and described two new readily available materials based on the combination of Rose Bengal (singlet oxygen photosensitizer) and commercially available cationic polystyrene (macroporous resin Amberlite® IRA 900 or gel-type resin IRA 400). These materials showed high efficacy in the antimicrobial photodynamic inactivation (aPDI) of . Here, we present the photobactericidal effect of these polymers against an extended group of pathogens like , and the opportunistic yeast using green light. The most interesting finding is that the studied materials are able to reduce the population of both Gram-positive and Gram-negative bacteria with good activity, although, for , in a moderate manner. In view of the results achieved and especially considering the inexpensiveness of these two types of photoactive polymers, we believe that they could be used as the starting point for the development of coatings for self-disinfecting surfaces.
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http://dx.doi.org/10.3389/fmed.2021.641646DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8180575PMC
May 2021

Photodynamic Inactivation of Biofilms Using a Hexanuclear Molybdenum Complex Embedded in Transparent polyHEMA Hydrogels.

ACS Biomater Sci Eng 2020 12 19;6(12):6995-7003. Epub 2020 Nov 19.

Departamento de Química Inórganica y Orgánica, Universitat Jaume I, Av. Sos Baynat s/n, 12071 Castellón, Spain.

Three new photoactive polymeric materials embedding a hexanuclear molybdenum cluster (BuN)[MoI(CHCOO)] () have been synthesized and characterized by means of Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and emission spectroscopy. The materials are obtained in the format of transparent and thin sheets, and the formulations used to synthesize them are comprised of 2-hydroxyethyl methacrylate (HEMA), as a polymerizable monomer, and ethylene glycol dimethacrylate (EGDMA) or poly(ethylene glycol)dimethacrylate (PEGDMA), as cross-linkers. All the polymeric hydrogels generate singlet oxygen (O) upon irradiation with visible light (400-700 nm), as demonstrated by the reactivity toward two chemical traps of this reactive species (9,10-dimethylanthracene and 1,5-dihydroxynaphthalene). Some differences have been detected between the photoactive materials, probably attributable to variations in the permeability to solvent and oxygen. Notably, one of the materials resisted up to 10 cycles of photocatalytic oxygenation reactions of 1,5-dihydroxynaphthalene. All three of the polyHEMA hydrogels doped with are efficient against biofilms when irradiated with blue light (460 nm). The material made with the composition of 90% HEMA and 10% PEGDMA () is especially easy to handle, because of its flexibility, and it achieves a notable level of bacterial population reduction (3.0 log CFU/cm). The embedding of in cross-linked polyHEMA sheets affords a protective environment to the photosensitizer against aqueous degradation while preserving the photochemical and photobactericidal activity.
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http://dx.doi.org/10.1021/acsbiomaterials.0c00992DOI Listing
December 2020

A cost-effective combination of Rose Bengal and off-the-shelf cationic polystyrene for the photodynamic inactivation of Pseudomonas aeruginosa.

Mater Sci Eng C Mater Biol Appl 2020 Dec 24;117:111302. Epub 2020 Jul 24.

Universitat Jaume I, Departamento de Química Inorgánica y Orgánica, Avda. Sos Baynat s/n, 12071 Castellón, Spain. Electronic address:

Two new photoactive materials have been prepared, characterized and tested against Pseudomonas aeruginosa bacteria (planktonic suspension). The synthesis of the polymeric photosensitizers can be made at a multigram scale, in few minutes, starting from inexpensive and readily available materials, such as Rose Bengal (photosensitizer) and ion exchange resins Amberlite® IRA 900 (macroporous) or IRA 400 (gel-type) as cationic polystyrene supports. The most notable feature of these systems is their notable bactericidal activity in the dark (4-5 log CFU/mL reduction of the population of P. aeruginosa) which becomes enhanced upon irradiation with visible light (to reach a total reduction of 8 log CFU/mL for the macroporous polymer at a fluence of 120 J/cm using green light of 515 nm).
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http://dx.doi.org/10.1016/j.msec.2020.111302DOI Listing
December 2020

Photobehavior of the antipsychotic drug cyamemazine in a supramolecular gel protective environment.

J Photochem Photobiol B 2020 Jan 6;202:111686. Epub 2019 Nov 6.

Departamento de Química/Instituto de Tecnología Química UPV-CSIC, Universitat Politècnica de València, Camino de Vera s/n, 46022, Valencia, Spain. Electronic address:

In this work, a molecular hydrogel made of gelator (S)-4-((3-methyl-1-(nonylamino)-1-oxobutan-2-yl)amino)-4-oxobutanoic acid (SVN) has been employed as soft container to modify the photochemical and photophysical behavior of the antipsychotic drug cyamemazine (CMZ). The interaction of CMZ with the gel network has been evidenced by fluorescence spectroscopy through a hypsochromic shift of the emission band (from λ = 521 nm in solution to λ = 511 nm in the gel) and an increase of the fluorescence lifetime (5.6 ns in PBS vs. 7.2 ns in the gel). In the laser flash photolysis experiments on CMZ/SVN systems, the CMZ triplet excited state (CMZ*), monitored at λ = 320 nm, has been more efficiently generated and became much longer-lived than in solution (2.7 μs vs. 0.7 μs); besides, photochemical ionization leading to the radical cation CMZ was disfavored. In the steady-state experiments, photooxidation of CMZ to afford the N,S-dioxide derivative CMZ-SONO has been retarded in the gel, which provides a more lipophilic and constrained microenvironment. Both the photophysical properties and the photoreactivity are in agreement with CMZ located in a less polar domain when entrapped in the supramolecular gel, as result of the interaction of the drug with the fibers of the supramolecular SVN gel.
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http://dx.doi.org/10.1016/j.jphotobiol.2019.111686DOI Listing
January 2020

Liposome-Enveloped Molecular Nanogels.

Langmuir 2019 10 4;35(41):13375-13381. Epub 2019 Oct 4.

Departament de Química Inorgànica i Orgànica , Universitat Jaume I , Avda. Sos Baynat s/n , 12071 Castelló de la Plana , Spain.

Novel [email protected] particles were prepared by pH-triggered molecular gel formation inside of liposomes loaded with a low-molecular weight gelator derived from l-valine (). Liposome formation was carried out using l-α-phosphatidylcholine (PC) and cholesterol as components of the lipid bilayer. Molecular hydrogelator and pyranine, a ratiometric fluorescent pH probe, were entrapped in the liposomes at pH 9 and posterior acidification with d-glucono-1,5-lactone to pH 5-6 provoked intraliposomal gel formation. Removal of the lipid bilayer with sodium dodecyl sulfate yielded naked nanogel particles. The systems were characterized by transmission electron microscopy and dynamic light scattering. The [email protected] were loaded with doxorubicin, showing a similar release than that observed for liposomes. The hybrid particles described here are the first case of nonpolymeric [email protected] systems reported. This type of nanocarriers merges the benefits of liposomal vehicles with the inherent stimuli responsiveness and enhanced biocompatibility of hydrogels formed by low-molecular weight molecules, foretelling a potential use in environmentally sensitive drug release.
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http://dx.doi.org/10.1021/acs.langmuir.9b02282DOI Listing
October 2019

Self-Assembly Controls Reactivity with Nitric Oxide: Implications for Fluorescence Sensing.

ACS Omega 2018 Nov 15;3(11):15538-15545. Epub 2018 Nov 15.

Departamento de Química Inorgánica y Orgánica, Universitat Jaume I, Avda. Sos Baynat s/n, 12071 Castellón, Spain.

Three molecules containing the fluorophore 4-amino-1,8-naphthalimide (ANI) and showing different tendencies to self-assembly in aqueous environment have been prepared and fully characterized. The fluorescence emissions of two of these compounds in aqueous solutions are efficiently quenched in the presence of nitric oxide (NO) in aerated medium. Nuclear magnetic resonance and mass spectrometry techniques indicate that NO/O induces deamination of the ANI fluorophore, resulting in nonemissive 1,8-naphtalimide derivatives. It is found that the reactivity toward NO/O is regulated by the different aggregation modes presented by the molecules in aqueous medium. In this way, the molecules displaying fluorescence response toward NO/O are those with weak self-association properties whereas the compound with a high hydrophobic character (self-assembling into large nanoparticles) is insensitive to this species. Ultimately, the results described here could not only set the basis for the design of fluorescent bioprobes for NO/O based on ANI derivatives or other monoamino compounds but also could raise awareness about the importance of supramolecular interactions for the design of chemosensors.
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http://dx.doi.org/10.1021/acsomega.8b01869DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6643459PMC
November 2018

Photoactive Hexanuclear Molybdenum Nanoclusters Embedded in Molecular Organogels.

Inorg Chem 2019 Jul 5;58(14):8900-8905. Epub 2019 Jul 5.

Departamento de Química Inorgánica y Orgánica , Universitat Jaume I , Avenida Sos Baynat s/n , Castellón 12071 , Spain.

Hexanuclear molybdenum clusters are attractive species because of their outstanding photonic properties, and in the past they have been attached to a variety of supports such as organic polymers and inorganic nanoparticles, as described in the recent literature. Here, a cluster of the formula TBA[MoIAc] (TBA = tetrabutylammonium; Ac = acetate) has been supported on molecular organogels for the first time, resulting in a new soft material with remarkable photoactivity. Electron and confocal microscopic analyses showed the alignment of the nanoclusters to 1D self-assembled fibers formed by the organic gelator, and emission spectroscopy corroborated the interaction of the emissive clusters with such fibrillary structures. The new hybrid system is a deep-red emissive material (phosphorescence maximum at ca. 680 nm), with chromatic coordinates = 0.725 and = 0.274, capable of efficiently generating singlet oxygen (O) upon illumination with white light, as demonstrated by the photooxygenation of 9,10-dimethylanthracene and 1,5-dihydroxynaphthalene. The organogels can been made in dichloromethane and toluene and in both solvents display phosphorescence emission and photocatalytic properties.
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http://dx.doi.org/10.1021/acs.inorgchem.9b00916DOI Listing
July 2019

Self-assembled multivalent (SAMul) ligand systems with enhanced stability in the presence of human serum.

Biomater Sci 2019 Aug;7(9):3812-3820

Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.

Self-assembled cationic micelles are an attractive platform for binding biologically-relevant polyanions such as heparin. This has potential applications in coagulation control, where a synthetic heparin rescue agent could be a useful replacement for protamine, which is in current clinical use. However, micelles can have low stability in human serum and unacceptable toxicity profiles. This paper reports the optimisation of self-assembled multivalent (SAMul) arrays of amphiphilic ligands to bind heparin in competitive conditions. Specifically, modification of the hydrophobic unit kinetically stabilises the self-assembled nanostructures, preventing loss of binding ability in the presence of human serum - cholesterol hydrophobic units significantly outperform systems with a simple aliphatic chain. It is demonstrated that serum albumin disrupts the binding thermodynamics of the latter system. Molecular simulation shows aliphatic lipids can more easily be removed from the self-assembled nanostructures than the cholesterol analogues. This agrees with the experimental observation that the cholesterol-based systems undergo slower disassembly and subsequent degradation via ester hydrolysis. Furthermore, by stabilising the SAMul nanostructures, toxicity towards human cells is decreased and biocompatibility enhanced, with markedly improved survival of human hepatoblastoma cells in an MTT assay.
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http://dx.doi.org/10.1039/c9bm00745hDOI Listing
August 2019

In between molecules and self-assembled fibrillar networks: highly stable nanogel particles from a low molecular weight hydrogelator.

Soft Matter 2019 Apr;15(17):3565-3572

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, Avda. Sos Baynat s/n, 12071 Castelló, Spain.

The preparation of molecular, non-polymeric nanogels from a low molecular weight hydrogelator is reported. The molecular nanogels are expected to overcome issues associated with the use of polymeric nanogels in biomedicine such as biodegradability, stimuli responsiveness, polydispersity, and batch-to-batch reproducibility. Nanogels formed by compound 1 were reproducibly prepared by sonication of a xerogel in PBS, with a total concentration of ca. 2 mM. The intensity averaged diameter of ca. 200 nm was determined by DLS. Electron microscopy (TEM and cryo-TEM) showed spherical particles. Light scattering (SALS) indicates that water is the main component of the nanoparticles, and the concentration of 1 in the nanogels is ca. 3 mg mL-1. These particles can be considered to constitute an intermediate state between free molecules and self-assembled fibrillar networks. The nanogels present excellent temporal and thermal stability and accessible hydrophobic domains, as demonstrated by the incorporation of the fluorescent dye Nile Red.
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http://dx.doi.org/10.1039/c9sm00252aDOI Listing
April 2019

Insights into the aggregation-induced emission of 1,8-naphthalimide-based supramolecular hydrogels.

Nanoscale 2018 Sep;10(36):17060-17069

Universitat Jaume I, Departamento de Química Inorgánica y Orgánica, Avda. Sos Baynat s/n, 12071, Castellón, Spain.

The study of aggregation-induced emission (AIE) of a series of 1,8-naphthalimide derivatives in aqueous media is reported herein. Some of these molecules constitute the first examples of 1,8-naphthalimide-containing amino acid derivatives that form hydrogels with excellent photophysical and mechanical properties. The present study provides further insights for the rational design of water-compatible stimuli-responsive photonic materials presenting AIE. AIE was quantitatively evaluated by measuring the fluorescence quantum yields of the molecules. Gelators 1 and 2 exhibit self-assembled fibrillar morphologies and present the best performance regarding the AIE effect, showing a remarkable enhancement in fluorescence intensity of 4700% and reaching a notable fluorescence quantum yield (Φf) of 30%. Non-gelator molecules 6 and 7 form nanoparticles, which also present AIE, but with emissions corresponding to their excimers. Therefore, the AIE intensity and wavelength are regulated by the type of aggregate morphology: fibers, nanoparticles or soluble species.
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http://dx.doi.org/10.1039/c8nr03755hDOI Listing
September 2018

Synthesis, spectroscopic studies and biological evaluation of acridine derivatives: The role of aggregation on the photodynamic efficiency.

Bioorg Med Chem Lett 2018 03 3;28(5):869-874. Epub 2018 Feb 3.

Universitat Jaume I, Departamento de Química Inorgánica y Orgánica, Avda. Sos Baynat s/n, 12071 Castellón, Spain. Electronic address:

Two new photoactive compounds (1 and 2) derived from the 9-amidoacridine chromophore have been synthesized and fully characterized. Their abilities to produce singlet oxygen upon irradiation have been compared. The synthesized compounds show very different self-aggregating properties since only 1 present a strong tendency to aggregate in water. Biological assays were conducted with two cell types: hepatoma cells (Hep3B) and human umbilical vein endothelial cells (HUVEC). Photodynamic therapy (PDT) studies carried out with Hep3B cells showed that non-aggregating compound 2 showed photoxicity, ascribed to the production of singlet oxygen, being aggregating compound 1 photochemically inactive. On the other hand suspensions of 1, characterized as nano-sized aggregates, have notable antiproliferative activity towards this cell line in the dark.
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http://dx.doi.org/10.1016/j.bmcl.2018.02.005DOI Listing
March 2018

Sizing Down a Supramolecular Gel into Micro- and Nanoparticles.

Langmuir 2017 10 25;33(39):10322-10328. Epub 2017 Sep 25.

Departament de Química Inorgànica i Orgànica, Universitat Jaume I , Avda. Sos Baynat s/n, 12071 Castellón, Spain.

A low molecular weight gelator with a fluorescent 1,8-naphthalimide unit forms micro- and nanoparticles in aqueous media. Slow addition of a DMSO solution of the gelator into water affords either a self-assembled fibrillar network, sheaf-like microparticles, or nanoparticles depending to the concentration used in the experiment. The micro- and nanoparticles were characterized by dynamic light scattering (DLS), electron microscopy, and fluorescence measurements. In an initial assay of particle loading, Rose Bengal and Rhodamine 123 were shown to be incorporated in the particles. Light-promoted singlet oxygen generation capabilities of Rose Bengal were modulated by its incorporation in the particles. Additionally, the particles were found to promote the transport of Rhodamine 123 into human lung carcinoma live cells. These results indicate that nanoparticles arising from low molecular weight gelators may represent a new type of nanocarriers, being a potential alternative to polymeric nanogels used in nanomedicine.
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http://dx.doi.org/10.1021/acs.langmuir.7b02440DOI Listing
October 2017

Superior performance of macroporous over gel type polystyrene as a support for the development of photo-bactericidal materials.

J Mater Chem B 2017 Aug 20;5(30):6058-6064. Epub 2017 Jul 20.

Universitat Jaume I, Departamento de Química Inorgánica y Orgánica, Avda. Sos Baynat s/n, 12071, Castellón, Spain.

A hexanuclear molybdenum cluster [MoIAc] (1) has been ionically bound onto macroporous (P) and gel-type (P) resins and their performance as materials for the photodynamic inactivation of microorganisms has been studied. It has been found that [email protected] in combination with light is able to reduce 99.999999% of the population of Gram-positive Staphylococcus aureus whereas the activity of [email protected] is limited to a 99.99% reduction at the same light dose. The same trend is observed with Gram-negative Pseudomonas aeruginosa. A comprehensive study of both materials has been performed using confocal laser scanning microscopy, thermogravimetric analysis, nitrogen porosimetry, steady state and time resolved fluorometries and diffuse reflectance spectroscopy. The photochemical generation of singlet oxygen (O) has been assessed using 9,10-dimethylanthracene as a trap for this reactive oxygen species. It can be concluded that the nature of the polymeric support is of paramount importance for the development of surfaces with bactericidal properties.
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http://dx.doi.org/10.1039/c7tb01478cDOI Listing
August 2017

Thermally Regulated Reversible Formation of Vesicle-Like Assemblies by Hexaproline Amphiphiles.

J Phys Chem B 2017 08 2;121(31):7443-7446. Epub 2017 Aug 2.

Department of Chemistry, University of Reading, Whiteknights , Reading RG6 6AD, U.K.

Peptides composed of hexaproline and glutamic acid (PE) or lysine (PK) as C-terminal units show thermally promoted aggregation, affording vesicle-like assemblies upon heating to 80 °C. The aggregation is analyzed by dynamic light scattering (DLS), with number-averaged diameters of ca. 600 and 300 nm, respectively, for PE and PK. NMR studies reveal that upon heating the amount of NMR-visible species is reduced to ca. 50% and that an important conformational change is experienced by the molecules in solution. Circular dichroism (CD) shows that at 20 °C the peptides present a polyproline II (PP-II) conformation which is disorganized upon heating. Scanning electron microscopy for samples which were fast frozen at 80 °C reveals vesicle-like assemblies. Using pyrene as a fluorescence probe, a critical aggregation concentration of ca. 30 μM was estimated for PE, while that of PK was above 0.6 mM. The aggregation process is found to be fully reversible and could serve as a basis for development of stimuli responsive carriers.
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http://dx.doi.org/10.1021/acs.jpcb.7b06167DOI Listing
August 2017

Deamidation of pseudopeptidic molecular hydrogelators and its application to controlled release.

J Colloid Interface Sci 2017 Nov 3;505:1111-1117. Epub 2017 Jul 3.

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, 12071 Castelló, Spain. Electronic address:

Hypothesis: The incorporation of a succinic acid-derived moiety in amino acid derivatives would favor an intramolecular catalysis of a deamidation reaction. Such reaction would permit controlled disassembly of molecular hydrogelators and the use of the hydrogels for controlled release of actives.

Experimental: Low molecular weight hydrogelators containing a succinic acid-derived moiety were prepared by conventional organic synthesis procedures. Hydrogels were examined by electron microscopy and HNMR studies were carried out to evaluate the solubility in water of the hydrogelators and the deamidation reaction. Liberation of Rose Bengal entrapped in the hydrogels was monitored by UV-Vis spectroscopy.

Findings: Molecular hydrogels formed by pseudopeptidic derivatives of l-valine suffer a thermal deamidation reaction, leading to partial disassembly. The succinic acid-derived moiety present in the gelators is responsible of intramolecular catalysis of a deamidation reaction. Such neighboring group effect is reminiscent of biochemical processes such as protein deamidation and self-excision of inteins. It has been found that the thermodynamic equilibrium of the deamidation reaction is regulated by the efficiency of hydrogelation. As a proof of concept, the thermally promoted deamidation is applied to controlled release of Rose Bengal.
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http://dx.doi.org/10.1016/j.jcis.2017.07.003DOI Listing
November 2017

Peptide-Based Molecular Hydrogels as Supramolecular Protein Mimics.

Chemistry 2017 Jan 17;23(5):981-993. Epub 2016 Aug 17.

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, Av. Sos Baynat, s/n, 12071, Castelló, Spain.

This Minireview concerns recent advances in the design, synthesis, and application of low molecular-weight peptidic hydrogelators. The sequence-specific combinations of amino acid side chain functionalities combined with hydrogen bonding of amide backbones and hydrophobic (aromatic) capping groups give these peptidic molecules the intrinsic tendency to self-assemble. The most prevalent designs include N-capped amino acid residues, bolamphiphilic peptides, and amphipathic peptides. Factors such as hydrophobic effects, the Hofmeister effect, and tunable ionization influence their aggregation properties. The self-assembly of simple bio-inspired building blocks into higher organized structures allows comparisons to be drawn with proteins and their complex functionalities, providing preliminary insights into complex biological functions and also enabling their application in a wide range of fields including catalysis, biomedical applications, and mimicry of natural dissipative systems. The Minireview is concluded by a short summary and outlook, highlighting the advances and steps required to bridge the gaps in the understanding of such systems.
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http://dx.doi.org/10.1002/chem.201602624DOI Listing
January 2017

Sucrose-fueled, energy dissipative, transient formation of molecular hydrogels mediated by yeast activity.

Chem Commun (Camb) 2016 Apr;52(31):5398-401

Departament de Química Inorgánica i Orgànica, Universitat Jaume I, Avda. Sos Baynat s/n, 12071 Castelló, Spain.

A biologically mediated, energy dissipative, reversible formation of fibrillar networks is reported. The process of gelation is linked to sucrose-fueled production of CO2 by baker's yeast (Saccharomyces cerevisiae). Continuous fueling of the system is required to maintain the self-assembled fibrillar network.
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http://dx.doi.org/10.1039/c6cc01183gDOI Listing
April 2016

Improved Efficiency of Molecular-Gel Formation by Adjusting Preorganization of Amino-Acid-Derived Flexible Molecules: A NMR and Thermodynamic study.

Chemphyschem 2016 07 30;17(13):2008-12. Epub 2016 Mar 30.

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, Avda. Sos Baynat s/n, 12071, Castellón, Spain.

The efficiency of the formation of molecular gels of simple derivatives of l-valine and l-isoleucine is greatly improved in different organic solvents when a hexyl fragment is replaced by a bulkier cyclohexyl one. A study using NMR and IR spectroscopy provides information on the preferred conformations of the molecules, indicating that the cyclohexyl moiety precludes intramolecular H bonding and preorganises the system for intermolecular interactions, which are responsible for fiber formation. NMR data of the gels provides thermodynamic data on fibrillization, revealing that the origin of this effect is mainly entropic. Electron microscopy (SEM and TEM) images show fibrillar and tape-like objects, which are observed commonly in molecular gels. Rheological measurements reveal significant differences between cyclohexyl and hexyl appended gelators. These findings could contribute to the rational design of small, flexible, building blocks for self-assembly.
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http://dx.doi.org/10.1002/cphc.201600015DOI Listing
July 2016

Dynamic Peptide Library for the Discovery of Charge Transfer Hydrogels.

ACS Appl Mater Interfaces 2015 Nov 16;7(46):25946-54. Epub 2015 Nov 16.

WestCHEM/Department of Pure and Applied Chemistry, University of Strathclyde , Thomas Graham Building, 295 Cathedral Street, Glasgow G1 1XL, United Kingdom.

Coupling of peptide self-assembly to dynamic sequence exchange provides a useful approach for the discovery of self-assembling materials. In here, we demonstrate the discovery and optimization of aqueous, gel-phase nanostructures based on dynamically exchanging peptide sequences that self-select to maximize charge transfer of n-type semiconducting naphthalenediimide (NDI)-dipeptide bioconjugates with various π-electron-rich donors (dialkoxy/hydroxy/amino-naphthalene or pyrene derivatives). These gel-phase peptide libraries are characterized by spectroscopy (UV-vis and fluorescence), microscopy (TEM), HPLC, and oscillatory rheology and it is found that, of the various peptide sequences explored (tyrosine Y-NDI with tyrosine Y, phenylalanine F, leucine L, valine V, alanine A or glycine G-NH2), the optimum sequence is tyrosine-phenylalanine in each case; however, both its absolute and relative yield amplification is dictated by the properties of the donor component, indicating cooperativity of peptide sequence and donor/acceptor pairs in assembly. The methodology provides an in situ discovery tool for nanostructures that enable dynamic interfacing of supramolecular electronics with aqueous (biological) systems.
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http://dx.doi.org/10.1021/acsami.5b08968DOI Listing
November 2015

Selective Interaction of Dopamine with the Self-Assembled Fibrillar Network of a Molecular Hydrogel Revealed by STD-NMR.

Chemistry 2015 Sep 19;21(40):13925-9. Epub 2015 Aug 19.

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, Avenida Sos Baynat, s/n; 12071 Castellón (Spain).

A molecular hydrogel formed by a derivative of L-valine with pendant isonicotinoyl moieties interacts selectively with protonated dopamine in the presence of related compounds such as 3-methylcatechol, and protonated or neutral phenethylamine. A two-point interaction with the gel fibers is postulated to explain the results. The conclusions are obtained from nuclear magnetic resonance saturation transfer experiments (STD-NMR), illustrating how this technique is perfectly suited to monitor the interaction of substrates with the fibrillar network of a molecular gel.
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http://dx.doi.org/10.1002/chem.201502018DOI Listing
September 2015

Insight into the esterase like activity demonstrated by an imidazole appended self-assembling hydrogelator.

Chem Commun (Camb) 2015 Aug;51(67):13213-6

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, 12071 Castelló, Spain.

A low molecular weight hydrogelator with a covalently appended imidazole moiety is reported. Capable of percolating water in the pH range of 6 to 8, it proves to be an efficient catalyst upon self-assembly, showing Michaelis-Menten type kinetics. Activities at different pH values correlated with dramatic structural changes were observed. It can hydrolyse p-nitrophenyl acetate (pNPA) as well as inactivated esters, and L and D-phenylalanine methyl esters. The enhanced activity can be related to the conglomeration of catalytic groups upon aggregation resulting in their close proximity and the formation of hydrophobic pockets.
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http://dx.doi.org/10.1039/c5cc04281jDOI Listing
August 2015

Structural insight into the aggregation of L-prolyl dipeptides and its effect on organocatalytic performance.

Org Biomol Chem 2015 Jan 10;13(2):592-600. Epub 2014 Nov 10.

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, Avda. SosBaynat s/n, Castelló, 12071, Spain.

NMR and organocatalytic studies of four dipeptides derived from L-proline are described. Results indicate that important conformational changes around the catalytic L-proline moiety are observed for free dipeptides upon changing the adjacent amino acid. Also, an aggregation process is detected as the concentration increases. The self-association of the dipeptides has been fitted to a cooperative binding model. All the compounds have been assayed as catalysts for the conjugated addition of cyclohexanone to trans-β-nitrostyrene in toluene. In agreement with the structural studies, noticeable changes in the catalytic performance are detected upon changing the catalyst concentration, as the catalyst is activated by self-aggregation.
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http://dx.doi.org/10.1039/c4ob02003kDOI Listing
January 2015

Rational design of heat-set and specific-ion-responsive supramolecular hydrogels based on the Hofmeister effect.

Chemistry 2014 Oct 12;20(44):14465-72. Epub 2014 Sep 12.

Departament de Química Inorgánica I Orgánica, Universitat Jaume I, 12071 Castelló (Spain); Current address: Laboratorio de Polímeros Terapéuticos, Centro de Investigación Principe Felipe, Valencia (Spain).

Smart supramolecular hydrogels have been prepared from a bolaamphiphilic L-valine derivative in aqueous solutions of different salts. The hydrogels respond selectively to different ions and are either reinforced or weakened. In one case, in contrast to conventional systems, the hydrogels are formed upon heating of the system. The use of the hydrogels in the controlled release of an entrapped dye is described as a proof of the potential applications of these systems. The responsive hydrogels were rationally designed by taking into account the noticeable effect of different ions from the Hofmeister series in the solubility of the hydrogelator, which was assessed by using NMR experiments. On the one hand, kosmotropic anions such as sulfate produce a remarkable solubility decrease in the gelator, which is associated with gel reinforcement, as measured by rheological experiments. On the other hand, chaotropic species such as perchlorate weaken the gel. A dramatic effect was observed in the presence of guanidinium chloride, which boosted the solubility of the gelator, in accordance with its chaotropic behaviour reported in protein science. In this case, a direct interaction of the guanidinium species with the carbonyl groups of the hydrogelator is detected by (13) C NMR spectroscopy. The weakening of this interaction upon a temperature increase allows for the preparation of heat-set hydrogelating systems.
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http://dx.doi.org/10.1002/chem.201402547DOI Listing
October 2014

Freezing capture of polymorphic aggregates of bolaamphiphilic (L)-valine-based molecular hydrogelators.

Chemistry 2014 May 26;20(19):5762-7. Epub 2014 Mar 26.

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, 12071 Castelló (Spain), Fax: (+34) 964728214.

Nanostructured xerogels have been prepared by the freeze-drying of hydrogels and aggregates formed by bolaamphiphilic L-valine derivatives after aging under different environmental conditions. A wide variety of shapes and sizes has been achieved by a simple methodology. These nanostructures have been studied by SEM and WAXD and a dramatic influence of structural flexibility on the kinetics of aggregation has been observed. Such flexibility and a modulation of the hydrophobic effect have shown a profound influence in the packing of these compounds and revealed a high degree of polymorphism.
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http://dx.doi.org/10.1002/chem.201400346DOI Listing
May 2014

Tetrapeptidic molecular hydrogels: self-assembly and co-aggregation with amyloid fragment Aβ1-40.

Chemistry 2014 Jan 11;20(4):1023-31. Epub 2013 Dec 11.

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, 12071 Castelló (Spain), Fax: (+34) 964728214.

A new family of isomeric tetrapeptides containing aromatic and polar amino acid residues that are able to form molecular hydrogels following a smooth change in pH is described. The hydrogels have been studied by spectroscopic and microscopic techniques showing that the peptide primary sequence has an enormous influence on the self-assembly process. In particular, the formation of extended hydrophobic regions and the appearance of π-stacking interactions have been revealed as the driving forces for aggregation. Moreover, the interaction of these compounds with amyloid peptidic fragment Aβ1-40 has been studied and some of them have been shown to act as templates for the aggregation of this peptide into non-β-sheet fibrillar structures. These compounds could potentially be used for the capture of toxic, soluble amyloid oligomers.
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http://dx.doi.org/10.1002/chem.201302651DOI Listing
January 2014

In situ synthesis-gelation at room temperature vs. heating-cooling procedure. Fine tuning of molecular gels derived from succinic acid and L-valine.

J Colloid Interface Sci 2013 Dec 18;412:65-71. Epub 2013 Sep 18.

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, 12071 Castelló, Spain.

Hypothesis: The reaction between succinic anhydride and a diamine derived from L-valine should afford efficiently a molecular gelator. Based on this reaction, it should be feasible to prepare molecular gels at room temperature, avoiding the conventional thermal treatment required for the solubilization of the gelator, by in situ, simultaneous, synthesis and gelation. The gels prepared by in situ and conventional heating-cooling protocols could present important differences relevant for potential practical applications of these materials.

Experimental: The gelator was synthesized by reaction of succinic anhydride and a diamine derived from L-valine, affording two new amide bonds. The molecular gels were studied by IR, NMR, electron microscopy, X-ray diffraction and DSC.

Findings: The results indicate that different polymorphic fibrillar networks are formed depending on the gel preparation method, highlighting how the properties of molecular gels can be tuned in this way. Significant differences between thermal and in situ gels were found in properties such as thermal stability, thixotropic behavior or release of an entrapped dye. In situ synthesis-gelation has also been shown to provide gels in media such as oleic acid which cannot be jellified by conventional heating-cooling procedures.
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http://dx.doi.org/10.1016/j.jcis.2013.08.055DOI Listing
December 2013

Substrate selective catalytic molecular hydrogels: the role of the hydrophobic effect.

Chem Commun (Camb) 2013 Nov;49(90):10608-10

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, 12071 Castelló, Spain.

A catalytic hydrogel is reported for the substrate selective direct aldol reaction of aliphatic ketones based on their hydrophobicity and on the emergence of catalytic activity only after self-assembly of the catalyst.
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http://dx.doi.org/10.1039/c3cc45623dDOI Listing
November 2013

Interplay of molecular hydrogelators and SDS affords responsive soft matter systems with tunable properties.

Langmuir 2013 Jul 17;29(30):9544-50. Epub 2013 Jul 17.

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, 12071 Castelló, Spain.

The gelation efficiency of low molecular weight bolaamphiphilic hydrogelators 1 and 2 is influenced by the presence of SDS micelles. Similarly, the critical micellar concentration value of SDS is reduced in the presence of the studied molecular hydrogelators. Rheological measurements indicate that the strength of the hydrogels can be modulated with SDS, the gels becoming weaker in the presence of micelles. This behavior has been rationalized with the help of NMR studies using diffusion measurements and NOE correlations. The results obtained clearly point to the formation of mixed micelles composed of SDS and the hydrogelators. In the case of 1, the gelator:SDS ratio in the mixed micelles has been estimated from solubility studies to be ca. 1:2.5. Electron microscopy reveals that when SDS is present, the morphology of the xerogels is modified in its appearance at the micrometer scale but fibers with diameter in the nanometer range are observed in all the cases. The interplay between the surfactant and the gelators provides with new possibilities for the modulation of both gel and micelle formation. Examples are shown to highlight the potential usefulness of this type of interconnected system. In one case the release of a gel entrapped dye is modulated by the presence of SDS and sodium chloride. In another example, an intricate system that responds to a temperature excursion by irreversible micelle disassembly is shown.
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http://dx.doi.org/10.1021/la401653bDOI Listing
July 2013

Control of molecular gelation by chemical stimuli.

Chem Soc Rev 2013 Sep 21;42(17):7086-98. Epub 2012 Dec 21.

Universitat Jaume I, Dpt. Quıímica Inorgànica i Orgànica, 12071 Castelló, Spain.

Molecular gels are formed by the self-assembly of low-molecular weight compounds by weak non-covalent interactions and thus, they may be easily disassembled in response to external stimuli. Chemically sensitive gels can be prepared by introducing in the molecular design functional groups that may interact either by covalent or non-covalent forces with other molecules present in the medium. Functional molecular gels have been reported that are sensitive to acids, bases, ions, redox-active compounds, neutral species, reactive compounds and enzymes. Here we present a broad revision of the different chemical inputs that can be used to tune gel properties through some appealing application-based selected examples.
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http://dx.doi.org/10.1039/c2cs35436eDOI Listing
September 2013

Self-assembly studies of a chiral bisurea-based superhydrogelator.

Chemistry 2012 Nov 27;18(46):14725-31. Epub 2012 Sep 27.

Departament de Química Inorgànica i Orgànica, Universitat Jaume I, Castelló, Spain.

A chiral bisurea-based superhydrogelator that is capable of forming supramolecular hydrogels at concentrations as low as 0.2 mM is reported. This soft material has been characterized by thermal studies, rheology, X-ray diffraction analysis, transmission electron microscopy (TEM), and by various spectroscopic techniques (electronic and vibrational circular dichroism and by FTIR and Raman spectroscopy). The expression of chirality on the molecular and supramolecular levels has been studied and a clear amplification of its chirality into the achiral analogue has been observed. Furthermore, thermal analysis showed that the hydrogelation of compound 1 has a high response to temperature, which corresponds to an enthalpy-driven self-assembly process. These particular thermal characteristics make these materials easy to handle for soft-application technologies.
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http://dx.doi.org/10.1002/chem.201200707DOI Listing
November 2012
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