Hydrogel Template Research Articles

Dexamethasone Controlled Release on TGF-β1 Treated Vocal Fold Fibroblasts.

Corticosteroids may be beneficial in treating vocal fold scarring. Current drug delivery methods do not permit controlled corticosteroid release. Here we investigate the effects of poly-lactic-co-glycolic acid (PLGA) microparticles loaded with the corticosteroid dexamethasone in reducing collagen synthesis and inflammation in vocal fold fibroblasts treated with and without TGF-β1. Experimental, in vitro study. PLGA microparticles of differing molecular weight and terminating moieties were synthesized using a hydrogel template method. The release of dexamethasone was characterized from these microparticles over 4 days. Based on the release studies, ester-terminated low molecular weight PLGA microparticles were loaded with dexamethasone and applied to TGF-β1 treated vocal fold fibroblasts for 4 days. Quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assays (ELISAs) were used to assess the effects of released dexamethasone on collagen synthesis and inflammatory mediators. COL3A1 and COL1A2 were significantly down-regulated after exposure to ester-terminated low molecular weight PLGA microparticles loaded with dexamethasone. The loaded microparticles also reduced interleukin-6 synthesis. These data show promise in using a PLGA microparticle-based delivery system to control dexamethasone release over 4 days. Our findings lay the groundwork for developing more effective treatments for vocal fold scarring.

Hydrogel nanomembranes as templates for patterned deposition of nanoparticles on arbitrary substrates.

Patterns of nanoparticles (NPs) on solid supports are usually restricted to a particular substrate or a class of substrates. Here we present a procedure that decouples the patterning step from the target substrate, enabling the fabrication of custom designed NP assemblies on nearly any solid support, including nonflat ones. The procedure relies on a hydrogel template prepared on the primary, conductive substrate and transferred to the target support as a sacrificial nanomembrane. The template is structured by electron beam lithography (EBL) which seals predefined areas of poly(ethylene glycol) based hydrogel film, making them inert to NP deposition in contrast to pristine areas that adsorb NPs in high densities. The deposition of NPs, occurring from an aqueous solution into the transferred membrane, follows EBL generated structure, delivering the desired NP pattern on the target support after removal of the organic matrix. Efficiency and flexibility of the procedure is illustrated by creating a variety of representative submicrometer patterns of densely packed gold and silver NPs on glass, including a useful pattern of a miniaturized quick-response code. The arrangement of NPs in these patterns corresponds to the negative image of EBL generated template. This significantly reduces the exposure time for designs where large areas covered with NPs are separated by thin, NP-free stripes.

A Facile Approach to Prepare Rattle/Hollow-Type α-Fe2O3 Submicron Spheres with a Thin Carbon Layer for High-Performance Lithium Ion Battery Anodes

Recently, the hollow structures of various transition metal oxide materials (cobalt oxides [1], iron oxides [2], nickel oxides [3]) have received particular attention for use in lithium-ion batteries (LIBs) because they not only have a higher theoretical capacity than commercial graphite (372 mAh g-1), but also possess a large void space that can accommodate huge changes in volume during electrochemical reactions. In our previous report, hollow Fe3O4 microspheres exhibited the improvement of cyclability. Although the hollow Fe3O4 microspheres show remarkable improvement in cycling stability, most still exhibited capacity fading at high current rates due to their poor electrical conductivity. In order to improve cycling performance at high current rates, we have prepared rattle/hollow-type α-Fe2O3 submicron spheres with thin carbon layer through the diffusion of metal ions into the hydrogel template. In this synthetic process, an additional carbon coating process is not necessary such as two-step hydrothermal process and chemical vapour deposition (CVD). In addition, we report a strategic synthesis method to control the internal structures of α-Fe2O3 submicron spheres. Of the two types of samples, the rattle-type α-Fe2O3 submicron spheres have a high surface area (1415 m2 g-1) because α-Fe2O3 nano-grains are formed in polymer networks. During removal process of template particles by heat treatment, because the cross-linked networks surrounding tiny Fe metal precursors act as a barrier to prevent particle growth, the rattle structured α-Fe2O3 submicron spheres consisting of nano-sized grains with a high surface area can be formed. In this process, the thin carbon layer is formed on the inside surface as well as outer surface of the α-Fe2O3 nano-grains, which was generated from a decomposition of the polymer templates. These rattle/hollow α-Fe2O3 submicron spheres with thin carbon layer exhibit excellent cyclability at high current rates (~10C). We demonstrated that the void space and thin carbon layer covering most of the α-Fe2O3 surface acts as buffer layer to accommodate variation in the volume of α-Fe2O3 and improves charge transfer at high current rates.

Chiral Arrangement of Achiral Au Nanoparticles by Supramolecular Assembly of Helical Nanofiber Templates

Chiral materials composed of organized nanoparticle superstructures have promising applications to photonics and sensing. Reliable customization of the chiroptical properties of these materials remains an important goal; hence, we report a customizable scheme making use of modular gelator components for controlling the helicity and formation of nanofibers over long length scales resulting in hydrogel templates. Controlled growth of gold nanoparticles at spatially arranged locations along the nanofiber is achieved by UV reduction of Au(I) ions on the supramolecular templates. The resulting materials were found to have significant interparticle interactions and well-defined helicity to provide high quality, chiroptically active materials. With this novel approach, the tailored assembly of nanoparticle superstructures with predictable chiroptical properties can be realized in high yield, which we expect to allow rapid advancement of chiral nanomaterials research.

Highly Efficient Surface-Enhanced Raman Scattering Substrate Formulation by Self-Assembled Gold Nanoparticles Physisorbed on Poly(N-isopropylacrylamide) Thermoresponsive Hydrogels

Employing thermoresponsive hydrogels as scaffolding material for noble metal surface loading might be useful for the fabrication of surface-enhanced Raman scattering (SERS) surfaces. Here, we report on a new, reproducible, and simple approach to engineer poly(N-isopropylacrylamide) (PNIPAAm) hydrogel surfaces optimized for physisorption of gold nanoparticles (AuNPs). The advantage of this approach consists of the simple mechanism by which AuNPs are adsorbed on hydrogel templates, without sophisticated chemical treatments for their conjugation with the hydrogel. The resulting PNIPAAm-40 nm AuNP modes demonstrate that this approach gives the capability to tune the interparticle distance and, therefore, to control and modulate SERS affinity upon temperature changing.

Individual SERS substrate with core–satellite structure decorated in shrinkable hydrogel template for pesticide detection

Individual Au@PNIPAM/Ag composite has been designed and fabricated as surface‐enhanced Raman scattering (SERS) substrate in this paper. Because of the high porosity of the polymer shell and the driving force of the Au core to Ag+(H2O)n (n = 1–4) in aqueous solution, chemical reactions can be carried out while aggregation is completely avoided. Also, this makes the formation of vast and monodisperse Ag nanoparticles within PNIPAM and increases the colloidal stability. The Au cores with different sizes and the vast Ag nanoparticles then form core–satellite structures that can generate plasmon resonance. Moreover, this kind of individual Au@PNIPAM/Ag composite can be seen directly through Raman optical microscope, and uncertain effects on SERS signals resulting from variability of the configurations are minimized because these individual composite particles are relatively uniform. Importantly, the gaps between the Au and Ag nanoparticles can decrease because the PNIPAM shrinks from swollen to collapse state, so the substrate can also be used for inspecting pesticide residues accurately and rapidly. Copyright © 2014 John Wiley & Sons, Ltd.

Hollow hydroxyapatite spheres fabrication with three-dimensional hydrogel template

Flower-like porous hollow HAp spheres were obtained by diffusion of phosphate ions into PAAm hydrogels containing calcium ions by both an electrophoresis approach and an ion diffusion method.

Microparticles produced by the hydrogel template method for sustained drug delivery

Polymeric microparticles have been used widely for sustained drug delivery. Current methods of microparticle production can be improved by making homogeneous particles in size and shape, increasing the drug loading, and controlling the initial burst release. In the current study, the hydrogel template method was used to produce homogeneous poly(lactide-co-glycolide) (PLGA) microparticles and to examine formulation and process-related parameters. Poly(vinyl alcohol) (PVA) was used to make hydrogel templates. The parameters examined include PVA molecular weight, type of PLGA (as characterized by lactide content, inherent viscosity), polymer concentration, drug concentration and composition of solvent system. Three model compounds studied were risperidone, methylprednisolone acetate and paclitaxel. The ability of the hydrogel template method to produce microparticles with good conformity to template was dependent on molecular weight of PVA and viscosity of the PLGA solution. Drug loading and encapsulation efficiency were found to be influenced by PLGA lactide content, polymer concentration and composition of the solvent system. The drug loading and encapsulation efficiency were 28.7% and 82% for risperidone, 31.5% and 90% for methylprednisolone acetate, and 32.2% and 92% for paclitaxel, respectively. For all three drugs, release was sustained for weeks, and the in vitro release profile of risperidone was comparable to that of microparticles prepared using the conventional emulsion method. The hydrogel template method provides a new approach of manipulating microparticles.

Sound absorption properties of porous composites fabricated by a hydrogel templating technique

Abstract

Synthesis of multiple-shell porous CeO2 hollow spheres by a hydrogel template method

CeO2 hollow spheres with porous multiple-shell were synthesized via a simple electric-current assisted template method. Dense polyacrylamide network, as the template, plays an important role in the formation of the porous and hollow CeO2 spheres, such as providing favorable nucleation sites for the formation of Ce(OH)3 nanocrystals, controlling the size of the aqueous domains, and limiting crystal arrangement in the domains. Furthermore, the interaction between Ce3+ ions and amide groups of the polyacrylamide was the driving force for the self-assembly of the crystals, resulting in the porous Ce(OH)3 hollow spheres. The effects of the reaction parameters on the morphology, size and number of the shells of the porous hollow structures were investigated, and the formation mechanism of the hierarchical porous CeO2 hollow spheres was proposed.

Development of an in Vitro 3D Tumor Model to Study Therapeutic Efficiency of an Anticancer Drug

The importance and advantages of three-dimensional (3D) cell cultures have been well-recognized. Tumor cells cultured in a 3D culture system as multicellular tumor spheroids (MTS) can bridge the gap between in vitro and in vivo anticancer drug evaluations. An in vitro 3D tumor model capable of providing close predictions of in vivo drug efficacy will enhance our understanding, design, and development of better drug delivery systems. Here, we developed an in vitro 3D tumor model by adapting the hydrogel template strategy to culture uniformly sized spheroids in a hydrogel scaffold containing microwells. The in vitro 3D tumor model was to closely simulate an in vivo solid tumor and its microenvironment for evaluation of anticancer drug delivery systems. MTS cultured in the hydrogel scaffold are used to examine the effect of culture conditions on the drug responses. Free MTS released from the scaffold are transferred to a microfluidic channel to simulate a dynamic in vivo microenvironment. The in vitro 3D tumor model that mimics biologically relevant parameters of in vivo microenvironments such as cell-cell and cell-ECM interactions, and a dynamic environment would be a valuable device to examine efficiency of anticancer drug and targeting specificity. These models have potential to provide in vivo correlated information to improve and optimize drug delivery systems for an effective chemotherapy.

Assembly of complex cell microenvironments using geometrically docked hydrogel shapes

Cellular communities in living tissues act in concert to establish intricate microenvironments, with complexity difficult to recapitulate in vitro. We report a method for docking numerous cellularized hydrogel shapes (100-1,000 µm in size) into hydrogel templates to construct 3D cellular microenvironments. Each shape can be uniquely designed to contain customizable concentrations of cells and molecular species, and can be placed into any spatial configuration, providing extensive compositional and geometric tunability of shape-coded patterns using a highly biocompatible hydrogel material. Using precisely arranged hydrogel shapes, we investigated migratory patterns of human mesenchymal stem cells and endothelial cells. We then developed a finite element gradient model predicting chemotactic directions of cell migration in micropatterned cocultures that were validated by tracking ∼2,500 individual cell trajectories. This simple yet robust hydrogel platform provides a comprehensive approach to the assembly of 3D cell environments.

Morphological differences in BMP-2-induced ectopic bone between solid and crushed hyaluronan hydrogel templates

The possibility to affect bone formation by using crushed versus solid hydrogels as carriers for bone morphogenetic protein 2 (BMP-2) was studied. Hydrogels, based on chemical crosslinking between hyaluronic acid and poly(vinyl alcohol) derivatives, were loaded with BMP-2 and hydroxyapatite. Crushed and solid forms of the gels were analyzed both in vitro via a release study using ¹²⁵I radioactive labeling of BMP-2, and in vivo in a subcutaneous ectopic bone model in rats. Dramatically different morphologies were observed for the ectopic bone formed in vivo in the two types of gels, even though virtually identical release profiles were observed in vitro. Solid hydrogels induced formation of a dense bone shell around non-degraded hydrogel, while crushed hydrogels demonstrated a uniform bone formation throughout the entire sample. These results suggest that by crushing the hydrogel, the construct's three-dimensional network becomes disrupted. This could expose unreacted functional groups, making the fragment's surfaces reactive and enable limited chemical fusion between the crushed hydrogel fragments, leading to similar in vitro release profiles. However, in vivo these interactions could be broken by enzymatic activity, creating a macroporous structure that allows easier cell infiltration, thus, facilitating bone formation.

Rattle type α-Fe2O3 submicron spheres with a thin carbon layer for lithium-ion battery anodes

A facile method for the synthesis of rattle type α-Fe2O3 submicron spheres with a thin carbon layer using a hydrogel template is described in this paper. The high surface area, internal structure and thin carbon layer contributed to the improved cyclability of a lithium ion battery at high current rates.

Electrochemical Synthesis of Copper Sulfide Nanostructure with PAM Hydrogel Template

Flower-like, sphere and lamellar structures of copper sulfide have been prepared by an electrochemical method with PAM hydrogel as template. The unique synthetic method required no multiple growth steps typical of other methods, and just utilized the electric currents to drive the ions to realize the controlling the resultant morphology in the PAM hydrogel system. The structure of product was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The morphology of these structures could be controlled by adjusting the content of PAM in hydrogel, and the intension of electric current.

Identifying emerging trends of protein hydrogels for biological scaffolding

The strategies of bottom-up design of inorganic structures from biological templates enable cheap, eco-friendly and efficient fabrication of nano-structured materials. Here, template assembly of silica nanostructures were achieved using different protein hydrogels. Ovalbumin and fibrinogen gels were prepared by heat treatment at different pHs and protein concentrations. These hydrogels have been morphologically (SEM) and mechanically (rheology) well characterized. Next, a silica precursor is added, the condensation reaction is initiated and finally the protein hydrogel template is removed by calcination. A variety of 3D nanostructures ranging from highly porosity structures to spherical particles have been identified and characterized. Furthermore, it was observed that the fractal dimension of silica structures follow the same pattern than their corresponding templates. Consequently, the bio-scaffolding method proposed here helps the bottom-up assembly of silica precursors in nanostructures with defined three dimensional dimensions and provides a versatile route for the design of new architectures under green conditions.

Poly(acrylamide-co-vinyl sulfonic acid) p(AAm-co-VSA) hydrogel templates for Co and Ni metal nanoparticle preparation and their use in hydrogen production

P(AAM-co-VSA) hydrogel was prepared at different mole ratios form the corresponding monomers and used in absorption of metal ions such as Co and Ni from aqueous environments. Then, these bound metal ions within the hydrogel matrices were reduced to their metal nanoparticles by aqueous NaBH4 treatment. Finally, p(AAm-co-VSA)–M (M: Co or Ni) composites were used as reactor in the hydrolysis of NaBH4 for hydrogen generation. The amounts of metal ions before and after metal nanoparticle formation were determined by Atomic Absorption Spectroscopy (AAS). P(AAm-VSA) hydrogel showed greater absorption tendency for Ni(II) ions than Co(II) ions, and the metal ion binding capacity of these hydrogels was increased with an increase in the amount of VSA in the copolymeric hydrogel. It was also found that although the amount of Ni ions loaded into the hydrogel matrices were more than Co ions, Co metal nanoparticle-containing hydrogel produced hydrogen faster than Ni metal nanoparticle-containing hydrogel composites. The activation energy for the Co nanoparticle-embedded p(AAm-co-VSA) was found as 34.505 kJ mol−1k−1, and other thermodynamic parameters were also calculated. The p(AAm-co-VSA)–Co hydrogel can be used up to 5 times repetitively without any loss of yield but with 55% of catalytic activity.

Synthesis of PbSO4 crystals by hydrogel template on postprocessing strategy for secondary pollution

Pb2+ ions pose a significant threat to the environment and public health. Removal and reuse of Pb2+ ions from the environment are major focuses of waste treatment. Here the poly(acrylonitrile-acrylamide-acrylic acid) hydrogel prepared via crosslinking polymerization was introduced to capture Pb2+ ions, then as an in situ template to induce the formation of PbSO4 crystals with special morphology successfully. The absorption efficiency of Pb2+ ions by hydrogel was tested. The results show at the conditions of initial pH 5, 25°C, 1.578mg Pb2+ ions was removed by per unit hydrogel mass. PbSO4 crystals were characterized by X-ray diffraction, Raman spectrum, scanning electron microscopy, transmission electron microscopy, and fluorescence spectrometer. The results indicate that the branch-type structure crystals were excellent crystalline and mainly oriented along (101) and (231) plane. The PL spectrum show emission peaks at 380 and 400nm and indicate that the product may have applications in an electronic light device. This approach provides an inspiration on the post-processing of the secondary pollution.

Nontoxic poly(ethylene oxide phosphonamidate) hydrogels as templates for biomimetic mineralization of calcium carbonate and hydroxyapatite architectures

A simple protocol has been developed for the creation of the biomimetic hybrid materials, calcium carbonate, and hydroxyapatite, by in situ growth and mineralization in newly developed nontoxic hydrogel templates. A series of poly(ethylene oxide phosphonamidate) hydrogels with different network structures were synthesized by reacting various poly(ethylene glycol)s with phosphorous oxychloride and diamines in a one-pot protocol, which exhibits promising advantages including a short reaction time, an easy separation, and a high yield with a mass producible feasibility. The hydrogels were proven to be nontoxic according to an in vitro viability assay using human embryonic kidney 293T cells. Careful control of growth and mineralization conditions such as ions transport rate, pH, type of hydrogel, and mineralization temperature resulted in a variety of calcium carbonate and hydroxylapatite architectures including nanorods, nanowires, and well-defined hybrid structures. The resulting materials were analyzed by infrared spectroscopy, electron microscopes, energy-dispersive X-ray spectroscopy, and X-ray powder diffraction.

Synthesis of luminescent YVO4:Eu3+ submicrometer crystals through hydrogels as directing agents

The innovative hydrogel template (polyacrylamide or polyacrylic acid) directed synthesis of YVO4:Eu3+ phosphor in a controlled manner was thoroughly studied. Photoluminescence spectra show the europium(III)-doped yttrium orthovanadate could exhibit strong red emissions within the soft matrix (polyacrylamide) and remain relatively stable even when the temperature reached nearly 100 °C. After calcination process, X-ray powder diffraction patterns, SEM and DLS measurements implied that the sample was in agreement with pure tetragonal phase and the particle sizes were in the range of 100–200 nm. More importantly, YVO4:Eu3+ products prepared based on hydrogels have remarkable improvement in emission intensities compared to phosphors synthesized by conventional approach. Similar results of overall quantum efficiency also support that YVO4:Eu3+ assembled by PAM hydrogel (1.94%) is better than the routine way (0.91%).