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Gels, Volume 3, Issue 2 (June 2017) – 12 articles

Cover Story (view full-size image): Solvent evaporation from droplets can be used to guide dispersed colloidal particles into assembled superstructures, so-called supraparticles. If done on a super-repellant surface, these supraparticles are easily collected and isolated for further use. Due to the adaptive nature of this process, numerous kinds of materials can be easily combined to create complex functional devices with defined structures for various kinds of applications, such as photonics, catalysis, sensing, and many more. View the paper here.
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16029 KiB  
Article
Transcription of Nanofibrous Cerium Phosphate Using a pH-Sensitive Lipodipeptide Hydrogel Template
by Mario Llusar, Beatriu Escuder, Juan De Dios López-Castro, Susana Trasobares and Guillermo Monrós
Gels 2017, 3(2), 23; https://doi.org/10.3390/gels3020023 - 10 Jun 2017
Cited by 8 | Viewed by 5469
Abstract
A novel and simple transcription strategy has been designed for the template-synthesis of CePO4·xH2O nanofibers having an improved nanofibrous morphology using a pH-sensitive nanofibrous hydrogel (glycine-alanine lipodipeptide) as structure-directing scaffold. The phosphorylated hydrogel was employed as a template to [...] Read more.
A novel and simple transcription strategy has been designed for the template-synthesis of CePO4·xH2O nanofibers having an improved nanofibrous morphology using a pH-sensitive nanofibrous hydrogel (glycine-alanine lipodipeptide) as structure-directing scaffold. The phosphorylated hydrogel was employed as a template to direct the mineralization of high aspect ratio nanofibrous cerium phosphate, which in-situ formed by diffusion of aqueous CeCl3 and subsequent drying (60 °C) and annealing treatments (250, 600 and 900 °C). Dried xerogels and annealed CePO4 powders were characterized by conventional thermal and thermogravimetric analysis (DTA/TG), and Wide-Angle X-ray powder diffraction (WAXD) and X-ray powder diffraction (XRD) techniques. A molecular packing model for the formation of the fibrous xerogel template was proposed, in accordance with results from Fourier-Transformed Infrarred (FTIR) and WAXD measurements. The morphology, crystalline structure and composition of CePO4 nanofibers were characterized by electron microscopy techniques (Field-Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy/High-Resolution Transmission Electron Microscopy (TEM/HRTEM), and Scanning Transmission Electron Microscopy working in High Angle Annular Dark-Field (STEM-HAADF)) with associated X-ray energy-dispersive detector (EDS) and Scanning Transmission Electron Microscopy-Electron Energy Loss (STEM-EELS) spectroscopies. Noteworthy, this templating approach successfully led to the formation of CePO4·H2O nanofibrous bundles of rather co-aligned and elongated nanofibers (10–20 nm thick and up to ca. 1 μm long). The formed nanofibers consisted of hexagonal (P6222) CePO4 nanocrystals (at 60 and 250 °C), with a better-grown and more homogeneous fibrous morphology with respect to a reference CePO4 prepared under similar (non-templated) conditions, and transformed into nanofibrous monoclinic monazite (P21/n) around 600 °C. The nanofibrous morphology was highly preserved after annealing at 900 °C under N2, although collapsed under air conditions. The nanofibrous CePO4 (as-prepared hexagonal and 900 °C-annealed monoclinic) exhibited an enhanced UV photo-luminescent emission with respect to non-fibrous homologues. Full article
(This article belongs to the Special Issue Gels as Templates for Transcription)
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5707 KiB  
Article
Cyclodextrin-Based Nanohydrogels Containing Polyamidoamine Units: A New Dexamethasone Delivery System for Inflammatory Diseases
by Monica Argenziano, Chiara Dianzani, Benedetta Ferrara, Shankar Swaminathan, Amedea Manfredi, Elisabetta Ranucci, Roberta Cavalli and Paolo Ferruti
Gels 2017, 3(2), 22; https://doi.org/10.3390/gels3020022 - 08 Jun 2017
Cited by 15 | Viewed by 5152
Abstract
Glucocorticoids are widely prescribed in treatment of rheumatoid arthritis, asthma, systemic lupus erythematosus, lymphoid neoplasia, skin and eye inflammations. However, well-documented adverse effects offset their therapeutic advantages. In this work, novel nano-hydrogels for the sustained delivery of dexamethasone were designed to increase both [...] Read more.
Glucocorticoids are widely prescribed in treatment of rheumatoid arthritis, asthma, systemic lupus erythematosus, lymphoid neoplasia, skin and eye inflammations. However, well-documented adverse effects offset their therapeutic advantages. In this work, novel nano-hydrogels for the sustained delivery of dexamethasone were designed to increase both bioavailability and duration of the administered drug and reducing the therapeutic dose. Hydrogels are soft materials consisting of water-swollen cross-linked polymers to which the insertion of cyclodextrin (CD) moieties adds hydrophobic drug-complexing sites. Polyamidoamines (PAAs) are biocompatible and biodegradable polymers apt to create CD moieties in hydrogels. In this work, β or γ-CD/PAA nanogels have been developed. In vitro studies showed that a pretreatment for 24–48 h with dexamethasone-loaded, β-CD/PAA nanogel (nanodexa) inhibits adhesion of Jurkat cells to human umbilical vein endothelial cells (HUVEC) in conditions mimicking inflammation. This inhibitory effect was faster and higher than that displayed by free dexamethasone. Moreover, nanodexa inhibited COX-2 expression induced by PMA+A23187 in Jurkat cells after 24–48 h incubation in the 10−8–10−5 M concentration range, while dexamethasone was effective only at 10−5 M after 48 h treatment. Hence, the novel nanogel-dexamethasone formulation combines faster action with lower doses, suggesting the potential for being more manageable than the free drug, reducing its adverse side effects. Full article
(This article belongs to the Special Issue Micro- and Nanogels)
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10522 KiB  
Article
Temperature-Triggered Colloidal Gelation through Well-Defined Grafted Polymeric Surfaces
by Jan Maarten Van Doorn, Joris Sprakel and Thomas E. Kodger
Gels 2017, 3(2), 21; https://doi.org/10.3390/gels3020021 - 03 Jun 2017
Cited by 4 | Viewed by 4808
Abstract
Sufficiently strong interparticle attractions can lead to aggregation of a colloidal suspension and, at high enough volume fractions, form a mechanically rigid percolating network known as a colloidal gel. We synthesize a model thermo-responsive colloidal system for systematically studying the effect of surface [...] Read more.
Sufficiently strong interparticle attractions can lead to aggregation of a colloidal suspension and, at high enough volume fractions, form a mechanically rigid percolating network known as a colloidal gel. We synthesize a model thermo-responsive colloidal system for systematically studying the effect of surface properties, grafting density and chain length, on the particle dynamics within colloidal gels. After inducing an attraction between particles by heating, aggregates undergo thermal fluctuation which we observe and analyze microscopically; the magnitude of the variance in bond angle is larger for lower grafting densities. Macroscopically, a clear increase of the linear mechanical behavior of the gels on both the grafting density and chain length arises, as measured by rheology, which is inversely proportional to the magnitude of local bond angle fluctuations. This colloidal system will allow for further elucidation of the microscopic origins to the complex macroscopic mechanical behavior of colloidal gels including bending modes within the network. Full article
(This article belongs to the Special Issue Colloid Chemistry)
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2664 KiB  
Review
Bioengineering Microgels and Hydrogel Microparticles for Sensing Biomolecular Targets
by Edmondo Battista, Filippo Causa and Paolo Antonio Netti
Gels 2017, 3(2), 20; https://doi.org/10.3390/gels3020020 - 30 May 2017
Cited by 21 | Viewed by 8423
Abstract
Hydrogels, and in particular microgels, are playing an increasingly important role in a diverse range of applications due to their hydrophilic, biocompatible, and highly flexible chemical characteristics. On this basis, solution-like environment, non-fouling nature, easy probe accessibility and target diffusion, effective inclusion of [...] Read more.
Hydrogels, and in particular microgels, are playing an increasingly important role in a diverse range of applications due to their hydrophilic, biocompatible, and highly flexible chemical characteristics. On this basis, solution-like environment, non-fouling nature, easy probe accessibility and target diffusion, effective inclusion of reporting moieties can be achieved, making them ideal substrates for bio-sensing applications. In fact, hydrogels are already successfully used in immunoassays as well as sensitive nucleic acid assays, also enabling hydrogel-based suspension arrays. In this review, we discuss key parameters of hydrogels in the form of micron-sized particles to be used in sensing applications, paying attention to the protein and oligonucleotides (i.e., miRNAs) targets as most representative kind of biomarkers. Full article
(This article belongs to the Special Issue Micro- and Nanogels)
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3506 KiB  
Article
A Controlled Antibiotic Release System for the Development of Single-Application Otitis Externa Therapeutics
by Bogdan A. Serban, Kristian T. Stipe, Jeremy B. Alverson, Erik R. Johnston, Nigel D. Priestley and Monica A. Serban
Gels 2017, 3(2), 19; https://doi.org/10.3390/gels3020019 - 17 May 2017
Cited by 13 | Viewed by 5031
Abstract
Ear infections are a commonly-occurring problem that can affect people of all ages. Treatment of these pathologies usually includes the administration of topical or systemic antibiotics, depending on the location of the infection. In this context, we sought to address the feasibility of [...] Read more.
Ear infections are a commonly-occurring problem that can affect people of all ages. Treatment of these pathologies usually includes the administration of topical or systemic antibiotics, depending on the location of the infection. In this context, we sought to address the feasibility of a single-application slow-releasing therapeutic formulation of an antibiotic for the treatment of otitis externa. Thixotropic hydrogels, which are gels under static conditions but liquefy when shaken, were tested for their ability to act as drug controlled release systems and inhibit Pseudomonas aeruginosa and Staphylococcus aureus, the predominant bacterial strains associated with outer ear infections. Our overall proof of concept, including in vitro evaluations reflective of therapeutic ease of administration, formulation stability, cytocompatibility assessment, antibacterial efficacy, and formulation lifespan, indicate that these thixotropic materials have strong potential for development as otic treatment products. Full article
(This article belongs to the Special Issue Hydrogels for Drug Delivery)
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2286 KiB  
Article
Design of Hybrid Gels Based on Gellan-Cholesterol Derivative and P90G Liposomes for Drug Depot Applications
by Nicole Zoratto, Francesca Romana Palmieri, Claudia Cencetti, Elita Montanari, Chiara Di Meo, Maria Letizia Manca, Maria Manconi and Pietro Matricardi
Gels 2017, 3(2), 18; https://doi.org/10.3390/gels3020018 - 08 May 2017
Cited by 2 | Viewed by 4948
Abstract
Gels are extensively studied in the drug delivery field because of their potential benefits in therapeutics. Depot gel systems fall in this area, and the interest in their development has been focused on long-lasting, biocompatible, and resorbable delivery devices. The present work describes [...] Read more.
Gels are extensively studied in the drug delivery field because of their potential benefits in therapeutics. Depot gel systems fall in this area, and the interest in their development has been focused on long-lasting, biocompatible, and resorbable delivery devices. The present work describes a new class of hybrid gels that stem from the interaction between liposomes based on P90G phospholipid and the cholesterol derivative of the polysaccharide gellan. The mechanical properties of these gels and the delivery profiles of the anti-inflammatory model drug diclofenac embedded in such systems confirmed the suitability of these hybrid gels as a good candidate for drug depot applications. Full article
(This article belongs to the Special Issue Micro- and Nanogels)
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4718 KiB  
Review
The Potential of Stimuli-Responsive Nanogels in Drug and Active Molecule Delivery for Targeted Therapy
by Marta Vicario-de-la-Torre and Jacqueline Forcada
Gels 2017, 3(2), 16; https://doi.org/10.3390/gels3020016 - 08 May 2017
Cited by 63 | Viewed by 9366
Abstract
Nanogels (NGs) are currently under extensive investigation due to their unique properties, such as small particle size, high encapsulation efficiency and protection of active agents from degradation, which make them ideal candidates as drug delivery systems (DDS). Stimuli-responsive NGs are cross-linked nanoparticles (NPs), [...] Read more.
Nanogels (NGs) are currently under extensive investigation due to their unique properties, such as small particle size, high encapsulation efficiency and protection of active agents from degradation, which make them ideal candidates as drug delivery systems (DDS). Stimuli-responsive NGs are cross-linked nanoparticles (NPs), composed of polymers, natural, synthetic, or a combination thereof that can swell by absorption (uptake) of large amounts of solvent, but not dissolve due to the constituent structure of the polymeric network. NGs can undergo change from a polymeric solution (swell form) to a hard particle (collapsed form) in response to (i) physical stimuli such as temperature, ionic strength, magnetic or electric fields; (ii) chemical stimuli such as pH, ions, specific molecules or (iii) biochemical stimuli such as enzymatic substrates or affinity ligands. The interest in NGs comes from their multi-stimuli nature involving reversible phase transitions in response to changes in the external media in a faster way than macroscopic gels or hydrogels due to their nanometric size. NGs have a porous structure able to encapsulate small molecules such as drugs and genes, then releasing them by changing their volume when external stimuli are applied. Full article
(This article belongs to the Special Issue Micro- and Nanogels)
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5537 KiB  
Article
Nanoparticulate Poly(glucaramide)-Based Hydrogels for Controlled Release Applications
by Erik R. Johnston, Tyler N. Smith and Monica A. Serban
Gels 2017, 3(2), 17; https://doi.org/10.3390/gels3020017 - 06 May 2017
Viewed by 4377
Abstract
In 2004, D-Glucaric acid (GA) was identified as one of the top value-added chemicals from renewable feedstocks. For this study, a patented synthetic method was used to obtain gel forming polymers through the polycondensation of GA and several aliphatic diamines. The first time [...] Read more.
In 2004, D-Glucaric acid (GA) was identified as one of the top value-added chemicals from renewable feedstocks. For this study, a patented synthetic method was used to obtain gel forming polymers through the polycondensation of GA and several aliphatic diamines. The first time characterization and a potential practical application of such hydrogels is reported herein. Our findings indicate that the physical properties and gelling abilities of these materials correlate with the chemical structure of the precursor diamines used for polymerization. The hydrogels appear to have nanoparticulate nature, form via aggregation, are thermoresponsive, and appear suitable as controlled release systems for small molecules. Overall, this study further highlights the versatility of GA as a building block for the synthesis of sustainable materials, with potential for a wide array of applications. Full article
(This article belongs to the Special Issue Hydrogels Based on Dynamic Covalent Chemistry)
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15602 KiB  
Review
Droplets, Evaporation and a Superhydrophobic Surface: Simple Tools for Guiding Colloidal Particles into Complex Materials
by Marcel Sperling and Michael Gradzielski
Gels 2017, 3(2), 15; https://doi.org/10.3390/gels3020015 - 04 May 2017
Cited by 25 | Viewed by 9527
Abstract
The formation of complexly structured and shaped supraparticles can be achieved by evaporation-induced self-assembly (EISA) starting from colloidal dispersions deposited on a solid surface; often a superhydrophobic one. This versatile and interesting approach allows for generating rather complex particles with corresponding functionality in [...] Read more.
The formation of complexly structured and shaped supraparticles can be achieved by evaporation-induced self-assembly (EISA) starting from colloidal dispersions deposited on a solid surface; often a superhydrophobic one. This versatile and interesting approach allows for generating rather complex particles with corresponding functionality in a simple and scalable fashion. The versatility is based on the aspect that basically one can employ an endless number of combinations of components in the colloidal starting solution. In addition, the structure and properties of the prepared supraparticles may be modified by appropriately controlling the evaporation process, e.g., by external parameters. In this review, we focus on controlling the shape and internal structure of such supraparticles, as well as imparted functionalities, which for instance could be catalytic, optical or electronic properties. The catalytic properties can also result in self-propelling (supra-)particles. Quite a number of experimental investigations have been performed in this field, which are compared in this review and systematically explained. Full article
(This article belongs to the Special Issue Colloid Chemistry)
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1150 KiB  
Article
Impact of Chitosan Molecular Weight and Attached Non-Interactive Chains on the Formation of α-Lactalbumin Nanogel Particles
by Juan Du, Young-Hee Cho, Ryan Murphy and Owen Griffith Jones
Gels 2017, 3(2), 14; https://doi.org/10.3390/gels3020014 - 26 Apr 2017
Cited by 4 | Viewed by 3826
Abstract
Thermal treatment of protein–polysaccharide complexes will form nanogel particles, wherein the polysaccharide controls nanogel formation by limiting protein aggregation. To determine the impact of the chitosan molecular weight and non-interactive chains on the formation of nanogels, mixtures of α-lactalbumin were prepared with selectively-hydrolyzed [...] Read more.
Thermal treatment of protein–polysaccharide complexes will form nanogel particles, wherein the polysaccharide controls nanogel formation by limiting protein aggregation. To determine the impact of the chitosan molecular weight and non-interactive chains on the formation of nanogels, mixtures of α-lactalbumin were prepared with selectively-hydrolyzed chitosan containing covalently-attached polyethylene glycol chains (PEG) and heated near the protein’s isoelectric point to induce formation of nanogels. Turbidity of heated mixtures indicated the formation of suspended aggregates, with greater values observed at higher pH, without attached PEG, and among samples with 8.9 kDa chitosan. Mixtures containing 113 kDa chitosan-PEG formed precipitating aggregates above pH 5, coinciding with a low-magnitude colloidal charge and average hydrodynamic radii > 400 nm. All other tested mixtures were stable to precipitation and possessed average hydrodynamic radii ~100 nm, with atomic force microscopy showing homogeneous distributions of spherical nanogel aggregates. Over all of the tested conditions, attached PEG led to no additional significant changes in the size or morphology of nanogels formed from the protein and chitosan. While PEG may have interfered with the interactions between protein and the 113 kDa chitosan, prompting greater aggregation and precipitation, PEG did not indicate any such interference for shorter chitosan chains. Full article
(This article belongs to the Special Issue Micro- and Nanogels)
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6710 KiB  
Article
Tacticity-Dependent Interchain Interactions of Poly(N-Isopropylacrylamide) in Water: Toward the Molecular Dynamics Simulation of a Thermoresponsive Microgel
by Gaio Paradossi and Ester Chiessi
Gels 2017, 3(2), 13; https://doi.org/10.3390/gels3020013 - 19 Apr 2017
Cited by 8 | Viewed by 5264
Abstract
The discovery that the lower critical solution temperature (LCST) of poly(N-Isopropylacrylamide) (PNIPAM) in water is affected by the tacticity opens the perspective to tune the volume phase transition temperature of PNIPAM microgels by changing the content of meso dyads in the [...] Read more.
The discovery that the lower critical solution temperature (LCST) of poly(N-Isopropylacrylamide) (PNIPAM) in water is affected by the tacticity opens the perspective to tune the volume phase transition temperature of PNIPAM microgels by changing the content of meso dyads in the polymer network. The increased hydrophobicity of isotactic-rich PNIPAM originates from self-assembly processes in aqueous solutions also below the LCST. The present work aims to detect the characteristics of the pair interaction between polymer chains, occurring in a concentration regime close to the chain overlap concentration, by comparing atactic and isotactic-rich PNIPAM solutions. Using atomistic molecular dynamics simulations, we successfully modelled the increased association ability of the meso-dyad-rich polymer in water below the LCST, and gain information on the features of the interchain junctions as a function of tacticity. Simulations carried out above the LCST display the PNIPAM transition to the insoluble state and do not detect a relevant influence of stereochemistry on the structure of the polymer ensemble. The results obtained at 323 K provide an estimate of the swelling ratio of non-stereocontrolled PNIPAM microgels which is in agreement with experimental findings for microgels prepared with low cross-linker/monomer feed ratios. This study represents the first step toward the atomistic modelling of PNIPAM microgels with a controlled tacticity. Full article
(This article belongs to the Special Issue Micro- and Nanogels)
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Article
Ultrasound- and Temperature-Induced Gelation of Gluconosemicarbazide Gelator in DMSO and Water Mixtures
by Mothukunta Himabindu and Aruna Palanisamy
Gels 2017, 3(2), 12; https://doi.org/10.3390/gels3020012 - 18 Apr 2017
Cited by 12 | Viewed by 5836
Abstract
We have developed amphiphilic supramolecular gelators carrying glucose moiety that could gel a mixture of dimethyl sulfoxide (DMSO) and water upon heating as well as ultrasound treatment. When the suspension of gluconosemicarbazide was subjected to ultrasound treatment, gelation took place at much lower [...] Read more.
We have developed amphiphilic supramolecular gelators carrying glucose moiety that could gel a mixture of dimethyl sulfoxide (DMSO) and water upon heating as well as ultrasound treatment. When the suspension of gluconosemicarbazide was subjected to ultrasound treatment, gelation took place at much lower concentrations compared to thermal treatment, and the gels transformed into a solution state at higher temperatures compared to temperature-induced gels. The morphology was found to be influenced by the nature of the stimulus and presence of salts such as KCl, NaCl, CaCl2 and surfactant (sodium dodecyl sulphate) at a concentration of 0.05 M. The gel exhibited impressive tolerance to these additives, revealing the stability and strength of the gels. Fourier transform infrared spectroscopy (FTIR) revealed the presence of the intermolecular hydrogen bonding interactions while differential scanning calorimetry (DSC) and rheological studies supported better mechanical strength of ultrasound-induced (UI) gels over thermally-induced (TI) gels. Full article
(This article belongs to the Special Issue Organogels for Biomedical Applications)
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