Gel Monomers Research Articles

Engineering Cyborg Pathogens through Intracellular Hydrogelation.

Synthetic biology primarily focuses on two kinds of cell chassis: living cells and nonliving systems. Living cells are autoreplicating systems that have active metabolism. Nonliving systems, including artificial cells and nanoparticles, are nonreplicating systems typically lacking active metabolism. In recent work, Cyborg bacteria that are nonreplicating-but-metabolically active have been engineered through intracellular hydrogelation. Intracellular hydrogelation is conducted by infusing gel monomers and photoactivators into cells, followed by the activation of polymerization of the gel monomers inside the cells. However, the previous work investigated only Escherichia coli cells. Extending the Cyborg-Cell method to pathogenic bacteria could enable the exploitation of their pathogenic properties in biomedical applications. Here, we focus on different strains of Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae. To synthesize the Cyborg pathogens, we first reveal the impact of different hydrogel concentrations on the metabolism, replication, and intracellular gelation of Cyborg pathogens. Next, we demonstrate that the Cyborg pathogens are taken up by macrophages in a similar magnitude as wild-type pathogens through confocal microscopy and real-time PCR. Finally, we show that the macrophage that takes up the Cyborg pathogen exhibits a similar phenotypic response to the wild-type pathogen. Our work generalizes the intracellular hydrogelation approach from lab strains of E. coli to bacterial pathogens. The new Cyborg pathogens could be applied in biomedical applications ranging from drug delivery to immunotherapy.

Fabrication of anisotropic nanocomposite hydrogels by magnetic field‐induced orientation for mimicking cardiac tissue

AbstractThe ordered structure of biological tissues is a precondition for the development of high performance in these tissues. Hydrogels with anisotropic structures provide a good starting point for studying their biomimetic applications. In this work, a hydrogel that mimics the endogenous anisotropic structure of heart tissue was reported. The gel consists of acrylamide (AM) and 2‐Acrylamide‐2‐methylpro panesulfonic acid (AMPS) as gel monomers, α‐ketoglutaric acid as photoinitiator, and modified magnetic nanoparticles (Fe3O4‐RS) as crosslinking agent. Thus, AM, AMPS and Fe3O4‐Rs was called AAF for short. In the system, the orientation of Fe3O4‐Rs was arranged by an external magnetic field. Under ultraviolet (UV) irradiation, the precursor solution was polymerized in situ to form an AAF hydrogel. The structure, pore distribution, rheological properties, mechanical performance, swelling property, and biocompatibility of the prepared anisotropic AAF hydrogel were studied in this paper. Results showed that the mechanical performance of the AAF hydrogels was remarkably enhanced in comparison with the isotropic ones. The tensile strength of AAF hydrogel could reached 184 kPa in the direction of the parallel Orientation of Fe3O4‐Rs, and 80 kPa in the direction of the vertical Orientation of Fe3O4‐Rs under 25% strain (no magnetic field was applied during all test). Moreover, the anisotropic tensile ratio of AAF hydrogel also reached 2.3. The strength and modulus of anisotropic hydrogels were similar to cardiac tissue (anisotropic tensile ratio was 2.5), which has great potential for application in cardiac tissue engineering.

A Wetting-Enabled-Transfer (WET) Strategy for Precise Surface Patterning of Organohydrogels.

The ability to manipulate water and oil phases in a designable manner is of great significance in widespread fields from art paintings to materials science. However, achieving precise and stable surface patterns for two immiscible phases of water and oil remains a challenge. Herein, a general wetting-enabled-transfer (WET) strategy is reported to construct discretionary shape-defined surface patterns of organohydrogels along with their monolithic formation either from flat to curved surfaces or from the microscale to the macroscale. Locally differentiated wettability induces hydrophilic monomers and hydrophobic monomers from an emulsion system onto the wettability-matching regions of the prepatterned substrates, subsequently forming corresponding hydrogel and organogel patterns on the organohydrogel surface after in situ photopolymerization. The precision of the surface patterns can be controlled by optimizing the gel monomers, emulsion droplet size, and surface chemical composition of the prepatterned substrates. This finding may provide a feasible strategy for precisely patterning functional materials from two-immiscible-phase systems.

Corrosion inhibition of magnesium by combined zirconia silica sol–gel films

The inhibition of Mg (AZ91D) corrosion by thin sol–gel films was studied. The sol–gel films were prepared by the traditional acid or base-catalyzed hydrolysis and condensation, and finally deposited by dip coating. Two different sol–gel monomers were used: phenyltrimethoxysilane (PTMOS) and zirconium(IV)tetra-1-propoxide (ZrTPO). Films were made of each of the individual monomers and by depositing first a PTMOS film followed by ZrTPO-based film. The corrosion inhibition of the films and their characterization were examined by different methods including potentiodynamic polarization, contact angle measurement, adhesion test, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). We found that while the ZrTPO-based film did not show a significant corrosion inhibition, the PTMOS-based film provided moderate protection. Interestingly, the combined film exhibited superior corrosion inhibition as compared with the other films.

On the Development of the VIPAR Polymer Gel Dosimeter for Three-Dimensional Dose Measurements

Summary: The new polymer gel dosimeter, based on the modification of the VIPAR gel composition, is described for the purpose of radiation dose distribution measurement in radiotherapy. It features increased concentration of the two VIPAR substrates: N-vinylpyrrolidone (8%) and gelatine (7.5%) (N,N′-methylenebisacrylamide was maintained at 4%), and the addition of copper sulphate (0.0008%) and ascorbic acid (0.007%) in order to facilitate the preparation through elimination of the need for deoxygenation of the gel. Following the exposure to ionizing radiation, polymerisation and cross-linking of the new gel monomers occurs retaining the spatial distribution of absorbed dose and causing opacity of the gel. Quantitative parameters of the new gel dose response were studied using magnetic resonance imaging to relate polymerisation induced physicochemical changes of the gel to dose. The dose threshold is found significantly lower than that of the original VIPAR gel. The linear part of measured spin-spin relaxation rate R2(D) ( = 1/T2(D)) reaches up to 35 Gy. Its slope and an intercept are slightly higher relative to the original VIPAR. The efficiency of the new polymer gel-magnetic resonance imaging dosimeter was also tested for dose verification of a 3D dose distribution planned by a commercially available treatment planning software (Eclipse External Beam v.6.5) and delivered by a 6 MV medical linear accelerator. The new polymer gel is proposed to be called, VIPARnd (after VIPAR-normoxic-double).

On the Development of the VIPAR Polymer Gel Dosimeter for Three‐Dimensional Dose Measurements

AbstractSummary: The new polymer gel dosimeter, based on the modification of the VIPAR gel composition, is described for the purpose of radiation dose distribution measurement in radiotherapy. It features increased concentration of the two VIPAR substrates: N‐vinylpyrrolidone (8%) and gelatine (7.5%) (N,N′‐methylenebisacrylamide was maintained at 4%), and the addition of copper sulphate (0.0008%) and ascorbic acid (0.007%) in order to facilitate the preparation through elimination of the need for deoxygenation of the gel. Following the exposure to ionizing radiation, polymerisation and cross‐linking of the new gel monomers occurs retaining the spatial distribution of absorbed dose and causing opacity of the gel. Quantitative parameters of the new gel dose response were studied using magnetic resonance imaging to relate polymerisation induced physicochemical changes of the gel to dose. The dose threshold is found significantly lower than that of the original VIPAR gel. The linear part of measured spin‐spin relaxation rate R2(D) ( = 1/T2(D)) reaches up to 35 Gy. Its slope and an intercept are slightly higher relative to the original VIPAR. The efficiency of the new polymer gel‐magnetic resonance imaging dosimeter was also tested for dose verification of a 3D dose distribution planned by a commercially available treatment planning software (Eclipse External Beam v.6.5) and delivered by a 6 MV medical linear accelerator. The new polymer gel is proposed to be called, VIPARnd (after VIPAR‐normoxic‐double).

Characterization of polyacrylamide gels as an elastic model for food gels

Serving as an elastic model system for food gels, characteristics of polyacrylamide (PAAm) gels were investigated using small amplitude and large deformation rheological tests. The PAAm gels displayed elastic or viscoelastic behavior depending on network crosslink density. For elastic PAAm gels, the rheological properties obeyed the theory of rubber elasticity; whereas for viscoelastic PAAm gels, shear modulus depended on temperature. The elastic PAAm gel fracture parameters did not change with deformation rate (0.2–5.5 s−1), indicating insignificant viscous flow during deformation. Fracture stress was correlated with gel monomer concentration, whereas the fracture strain remained constant regardless of the monomer concentration. In addition, the stress was linearly proportioned with strain up to fracture, indicating that PAAm gels did not experience finite network chain extensibility during large deformation. Consequently, the fracture of PAAm gels did not result from the extensional limitation of network chains, nor did gel fracture result from the nonlinear force–distance relationship between polymer connections. Purportedly, the fracture of PAAm gels was caused by external force overcoming the gel cohesive forces, and low strength of PAAm gels compared to rubbers caused fracture prior to experiencing nonlinear stress-strain deformation.

An amperometric hydrogen peroxide biosensor based on immobilizing horseradish peroxidase to a nano-Au monolayer supported by sol–gel derived carbon ceramic electrode

A novel strategy for fabricating horseradish peroxidase (HRP)-based H 2O 2 sensor has been developed by combining the merits of carbon sol–gel supporting matrix and nano-scaled particulate gold (nano-Au) mediator. The thiol functional group-derived carbon ceramic electrode (CCE) was first constructed using (3-mercaptopropyl) trimethoxy silane as sol–gel monomer. Then, the stable nano-Au monolayer was obtained through covalent linkage between nano-Au and thiol group on the surface of CCE. The experimental results showed that nano-Au monolayer formed not only could steadily immobilize HRP but also efficiently retain its bioactivity. Hydrogen peroxide was detected with the aid of hydroquinone mediator to transfer electrons between the electrode and HRP. The process parameters for the fabrication of the enzyme electrode and various experimental variables such as the operating potential, mediator concentration and pH of background electrolyte were explored for optimum analytical performance of the enzyme electrode. The biosensor had a fast response of less than 8 s with linear range of 1.22×10 −5 to 1.10×10 −3mol l −1 and a detection limit of 6.1×10 −6mol l −1. The sensitivity of the sensor for H 2O 2 was 0.29 A l mol −1 cm −2. The activation energy for enzyme reaction was calculated to be 10.1 kJ mol −1. The enzyme electrode retained 75% of its initial activity after 5 weeks storage in phosphate buffer at pH 7.

An amperometric hydrogen peroxide biosensor based on immobilizing horseradish peroxidase to a nano-Au monolayer supported by sol?gel derived carbon ceramic electrode

A novel strategy for fabricating horseradish peroxidase (HRP)-based H 2 O 2 sensor has been developed by combining the merits of carbon sol–gel supporting matrix and nano-scaled particulate gold (nano-Au) mediator. The thiol functional group-derived carbon ceramic electrode (CCE) was first constructed using (3-mercaptopropyl) trimethoxy silane as sol–gel monomer. Then, the stable nano-Au monolayer was obtained through covalent linkage between nano-Au and thiol group on the surface of CCE. The experimental results showed that nano-Au monolayer formed not only could steadily immobilize HRP but also efficiently retain its bioactivity. Hydrogen peroxide was detected with the aid of hydroquinone mediator to transfer electrons between the electrode and HRP. The process parameters for the fabrication of the enzyme electrode and various experimental variables such as the operating potential, mediator concentration and pH of background electrolyte were explored for optimum analytical performance of the enzyme electrode. The biosensor had a fast response of less than 8 s with linear range of 1.22×10 −5 to 1.10×10 −3 mol l −1 and a detection limit of 6.1×10 −6 mol l −1 . The sensitivity of the sensor for H 2 O 2 was 0.29 A l mol −1 cm −2 . The activation energy for enzyme reaction was calculated to be 10.1 kJ mol −1 . The enzyme electrode retained 75% of its initial activity after 5 weeks storage in phosphate buffer at pH 7.

Amperometric immunosensor for probing complement III (C 3) based on immobilizing C 3 antibody to a nano-Au monolayer supported by sol–gel-derived carbon ceramic electrode

An electrochemical immunosensor based on nano-size particulate gold (nano-Au) monolayer as sensing interface has been developed for probing complement III (C 3). The thiol functional group-derived carbon ceramic electrode (CCE) was firstly constructed using (3-mercaptopropyl) trimethoxy silane (MPTMOS) as sol–gel monomer. The stable nano-Au monolayer was obtained resulting from covalent combination between nano-Au and thiol group on the surface of CCE. The nano-Au monolayer formed was utilized as a sensing platform for the immobilization of C 3 antibody (anti-C 3) and subsequent immunoreaction. A competitive immunoassay format was adopted with horseradish peroxidase (HRP)–C 3 as a tracer, hydroquinone and hydrogen peroxide as the enzymatic substrates. The dynamic concentration range for C 3 is 0.08–5.6 μg ml −1. The feasibility of regenerating nano-Au monolayer for consecutive assays was demonstrated by a simple chemical treatment after each determination. The high stability of formed nano-Au monolayer, readily adsorptive immobilization of antibody on nano-Au monolayer, efficient activity retention of loading immunoreactants as well as the simple operation for the formation of nano-Au monolayer make proposed methodology an attractive alternative for the designing new-type immunosensors.

Effect of residual acrylamide monomer from two-dimensional gels on matrix-assisted laser desorption/ionization peptide mass mapping experiments.

Residual acrylamide can cause severe suppression of signal intensity during matrix-assisted laser desorption/ionization (MALDI) peptide mass mapping experiments. This suppression phenomenon can compromise the ability to detect low picomole and subpicomolar amounts of peptides extracted from two-dimensional gels. A rapid and simple method that exploits the use of pipette tips incorporating C18 packing materials for the enhancement of MALDI signal intensity is presented. The utility of the method is demonstrated with peptide solutions incorporating residual acrylamide and/or gel monomer components.

A facile sol–gel method for the encapsulation of gold nanoclusters in silica gels and their optical properties

A novel process consisting of a synthesis of gold hydrosol using tetrakis (hydroxymethyl) phosphonium chloride (THPC) reduction and a sol–gel process using tetramethylorthosilicate (TMOS) for the encapsulation of gold nanoparticles (Au/SiO 2: 0.1–1 wt% Au) in a matrix of silica gel without the aid of any external stabilizing agent or organically modified sol–gel monomers is described. The optical absorption spectra showed the typical surface plasmon resonance for Au at around 530 nm, corroborated by X-ray photoelectron spectroscopy. Transmission electron microscopy revealed the existence of spherical Au particles in the matrix. The mean diameter of Au nanoparticles in gels varied from 10 to 20 nm, supported by X-ray diffraction data. The third-order optical non-linearity ( χ 3) determined by the degenerate four-wave mixing (DFWM) method exhibited a value of 4.6 × 10 −11 esu for a gel with 0.1 wt% Au.

Highly Efficient Organic/Inorganic Hybrid Nonlinear Optic Materials via Sol−Gel Process: Synthesis, Optical Properties, and Photobleaching for Channel Waveguides

The thermally stable second-order nonlinear optic (NLO) hybrid materials were successfully prepared by a sol−gel process using dye-attached sol−gel monomers (ormosils) of difunctionalized or trifunctionalized second-order NLO chromophores attached to silicon atoms. The dye-attached sol−gel monomers were synthesized by the coupling reaction of 3-isocyanatopropyltriethoxysilane with the corresponding functionalized NLO chromophores in DMAc. The dye-attached sol−gel monomers were homopolymerized and copolymerized with TEOS by hydrolysis and polycondensation in the presence of a slight excess amount of acidified water (pH 3), yielding the hybrid precusors (or a homogeneous solution). The hybrid precursors were spin-coated on various substrates such as ITO glass and NaCl disk. Hybrid films were further polycondensed by curing at 170 °C for 3 h. The cured hybrid materials existed in monohydroxy (T2, Q3) and nonhydroxy (T3, Q4) states, indicating the formation of a highly cross-linked silicon−oxygen polymeric network. All of the cured organic/SiO2 hybrid films are transparent. The organic/SiO2 hybrid materials were quite stable at elevated temperatures above 250 °C. The hybrid films were poled by corona discharge technique or dc contact electrode. The values of electro-optic coefficient for the organic/SiO2 hybrid materials were in the range of 3.7 to 16 pm/V at the wavelength of 1.3 μm, depending on dye-attached sol−gel monomers and poling conditions. The SG-DANS (1:2:2) film shows excellent temporal stability. The r33 signal remained at 80% of its initial value after heating even at 150 °C for 3 h. Also, the second-order nonlinear optical coefficient d31 of 72 pm/V for the SG-DANS (1:2:0) hybrid film measured by the Maker fringe technique was obtained. The refractive index was decreased after photobleaching. Using the hybrid film, a single-mode channel waveguide was also fabricated by the photobleaching method. The mode pattern confirmed that a channel waveguide was single-mode, and the optical propagation loss was measured to be less than 1 dB/cm.

Direct Synthesis and Characterization of Gold and Other Noble Metal Nanodispersions in Sol−Gel-Derived Organically Modified Silicates

A general approach to prepare nanodispersions of noble metals in organically modified silicates is presented with particular emphasis on the synthesis of gold nanodispersion and its characterization. Organically modified sol−gel monomers containing amine functional groups are used to stabilize the metal salts before the reduction step and to cap and prevent coagulation of the metal sol after reduction and through gel formation, drying, and aging. Uniform spherical metal nanodispersions of Au, Pt, and Pd with average diameter of 4−6 nm were obtained. The particle size distribution and the average size of silver nanoparticles prepared by the same method were considerably larger. This was attributed to the lower stability of the silver−amine complex and to the lower affinity of amines to silver surfaces. Stable aqueous colloidal solutions and supported metal nanodispersions in porous films and monoliths can be prepared by this route.

Direct synthesis of gold nanodispersions in sol–gel derived silicate sols, gels and films

A simple method for the preparation of stable colloidal suspensions of gold nanoparticles in silicate sols, silicate based films and monoliths is presented; organically modified sol–gel monomers containing amine functional groups are used for the stabilisation of Au ions and the metal nanocrystalline sol.

Seeing gel wells well

Indicator dyes have been incorporated in the stacking gel monomer used in acrylamide gels to render readily visible and delineate the sample wells. Some dyes, such as bromphenol blue, migrate during the electrophoresis, whereas others, such as the ortho-unsubstituted phenol red, become chemically bound to the polymerized gel. The method can be used for agarose gels.

Antibodies to proteins from yolk of immunized hens.

Immunoglobulins IgY, extracted from yolks of hens immunized against several proteins and natural mixtures of proteins were examined by the Ouchterloney gel diffusion and Laurell immuno-electrophoresis techniques. The molecular weights of the proteins ranged from 8 x 10(6) to less than 2 x 10(4). The hens produced IgY antibodies readily when injected with the high molecular antigens > 150 000 but did not react as well to antigens of relatively low molecular weight < 30 000. Optimal precipitin reactions were obtained with low molecular antigens when the agarose gel contained 1.5 M NaCl. Salt concentration (0.15-1.5 M NaCl) has no effect on the precipitin reaction in gels on the systems of high molecular antigens and their IgY antibodies apart from a displacement of the precipitin line. From the relative positions of the precipitin lines to the wells containing the reactants it would appear that the IgY formed dimers when the concentration of NaCl is 1.6 M and remain as monomers in gels containing 0.15 M NaCl. An explanation of the salt effect is offered.