Sol-gel State Research Articles

Microneedle created in skin in situ forming gels depot; an alternate approach to the sustained transdermal delivery of colchicine

Colchicine (CLC) is a commonly used medication in prevention and treatment of acute gout condition via oral route. However its oral administrations pose several gastrointestinal (GI) adverse effects. In current study, an alternate combinatorial approach of microneedles patch and in skin forming gel depots were evaluated for sustained CLC delivery through skin using CLC loaded non-ionic amphiphilic triblock pluronic-127 thermoresponsive poloxamers. In first phase, to validate the development of in situ forming depots, the phase transition of pluronic-127 from the sol-gel state was examined using AR2000 rheometer. In second phase, microneedles patches (MAPs) were fabricated via casting method utilizing (19 × 19) laser-engineered silicone micromoulds from varied biocompatible polymer blends such as Gantrez S-97, Poly-vinyl alcohol, Polyethelene glycol 10000 and Poly (vinylpyrollidone) at various concentrations. For optimized MAPs, the mechanical strength, in skin dissolution kinetics and moisture contents were determined. From mechanical testing PVP and PVA MAPs showed more brittle nature and highest loss of MAPs reduction in comparison to Gantrez® MAPs. Optimized MAPs (Gantrez®) based on high mechanical strength were utilized as a microporation source in rabbit skin. In comparison to PVA and PVP, Gantrez® MAPs showed slow dissolution kinetics and resist dissolution for 540 s. Optical coherence tomography (OCT) quantified the penetration depth of Gantrez® MAPs in newborn rabbit skin at 591 μm. Increased in TEWL values after Gantrez® MAPs treatment confirmed the pores formation in skin. Ex-vivo permeation analysis showed that 25 % w/w CLC loaded PF127® gel showed controlled and prolonged drug permeation across microporated skin for 84 h in comparison to untreated skin. The distribution of PF127 gel solution in treated skin samples was confirmed by tracking fluorescence using confocal microscopy. Results shows that MAPs created in skin micropores can be used as CLC depots and sustained effects can be achieved by successfully avoiding oral route and GI adverse effects.

Influence of Sol-Gel State in Smectite Aqueous Dispersions on Drying Patterns of Droplets.

The sol-gel state of smectite clay dispersions varies with the volume fraction of clay and electrolyte concentration. In this study, it was elucidated that the drying patterns of droplets from four types of smectite clay dispersions vary according to their sol-gel states. Droplets in the sol state exhibited a ring-shaped pattern, while those in the gel state showed a bump-shaped pattern. Near the boundary between the sol and gel states, patterns featuring both ring and bump structures were observed regardless of whether the droplets were on the sol or gel side. When guest particles or molecules were introduced into the clay dispersion, they dispersed uniformly within the system, and the drying pattern depended on the sol-gel state of the droplets. These findings suggest that the presence or absence of convection within the droplets during drying governs the drying pattern.

Enhanced Electrical and Optical Properties of Bismuth Tantalum Oxide Thin Films through Graphene Oxide Doping.

In this study, a hybrid thin film was fabricated by doping graphene oxide in a bismuth tantalum oxide solution in the sol-gel state. The thin film was produced by a brush-coating process. The graphene oxide doping ratios used were 0, 5, and 15 wt %. In the process of producing the thin film, the prepared sol-gel solution generates contraction forces, owing to the shear stress from the bristles of the brush, forming a microgroove structure. This structure was confirmed through atomic force microscopy, transmission electron microscopy, and energy-dispersive spectroscopy analyses. As a result of line profile analysis in atomic force microscopy, the groove heights of the thin film surface at 0, 5, and 15 wt % doping were 110, 130, and 160 nm, respectively, and the width of all grooves was 1 μm. The width of all thin films was approximately 1 μm, and microgrooves were confirmed. Moreover, the hybrid thin-film formation was confirmed by X-ray photoelectron spectroscopy. By comparing the electrical properties of the bismuth tantalum oxide thin film without graphene oxide doping and the thin film doped with 15 wt % graphene oxide, it was demonstrated that the electro-optical properties increased excellently with graphene oxide doping. Typically, the threshold voltage was reduced by approximately 0.26 V. Based on these observations, graphene oxide doped bismuth tantalum oxide hybrid thin films can be considered as promising candidates for thin-film applications in next-generation displays.

Micro array patch assisted transdermal delivery of high dose, ibuprofen sodium using thermoresponsive sodium alginate/poly (vinylcaprolactam) in situ gels depot

Current study reports the combined technique of microneedle array patches and thermoresponsive gels. Microneedles array patch mediated insitu skin depots were evaluated for sustain drug delivery using sodium alginate/Poly (vinylcaprolactam) thermoresponsive gels. Their phase transition property from sol-gel state was monitored with AR2000 rheometer. Ibuprofen sodium was loaded in optimized formulations. The non-soluble cross-linked microneedle array patches (MAPs) were prepared from variable biocompatible polymers using silicone micromoulds. The fabricated MAPs were evaluated for mechanical stability, inskin dissolution, insertion forces and moisture contents. The penetration depth of MAPs in neonatal rabbit skin was tracked by optical coherence tomography. The optimized MAPs (GP10000) were used as microporation source in skin owing to their stable nature. Pores formation in skin samples after MAPs treatment was confirmed by optical coherence tomography, dye binding and skin integrity analysis. The invitro permeation of Ibuprofen sodium from formulations was studied using Franz cells across intact skin and MAPs applied skin. It was concluded from the results that Ibuprofen sodium permeation was observed for longer time through MAPs treated skin as compared to intact skin. Confocal study confirmed the diffusion of drug loaded formulations in deeper tissues with higher intensity.

Formation and stability of fibers obtained by cold gelation of pea protein isolate aggregates in a hydrodynamic spinning process

Using plant protein sources in the formulation of food products is an important option to reduce the overall carbon footprint of the human diet. However, the ability to convert plant proteins into functional ingredients can hamper their use by the food industry. Our objective was to assemble pea protein isolate (PPI) aggregates into edible fibers. They were obtained by co-injection of a suspension of PPI aggregates with a solution of calcium chloride by means of physico-chemical bonds, i.e. in the absence of thermal treatment or chemical reaction. As soon as specific hydrodynamic conditions were met, homogeneous fibers of few hundreds μm diameter and few cm length were obtained. Small angle X-ray scattering showed that the building blocks of these fibers were dense aggregates of 400 nm radius. Calcium and PPI concentrations required for the processing of fibers were roughly given by the sol-gel state diagram of PPI aggregates. Compared to their dairy protein based equivalent, PPI fibers were obtained with a low mass fraction of protein (3% w/w) and were stable regardless of the concentration of calcium chloride used. We concluded that the robustness of the hydrodynamic spinning process was attributed to the strong reactivity of PPI aggregates with calcium ions and the low tendency of PPI gels to syneresis.

Effect of pH and electrolyte concentration on sol–gel state of semi-dilute aqueous cellulose nanofiber suspension: an interpretation based on angle-dependent DLVO theory

Effect of pH and electrolyte concentration on sol–gel state of semi-dilute aqueous cellulose nanofiber suspension: an interpretation based on angle-dependent DLVO theory

A novel electronic assay based on a sol-gel transition reaction and a thin-film transistor of supramolecular hydrogels to detect alkaline phosphatase activity

Abstract Herein, we developed an extended floating-gate thin-film transistor (EFG-TFT) together with various sol-gel phases to determine alkaline phosphatase (ALP) activity. The EFG-TFT was fabricated with ZnO as the channel material and YOX as the dielectric layer, which provided an extended area for sensing the analyte interacting with the designed hydrogelator. A peptide-based supramolecular hydrogel material, i.e., 2-naphthylacetic acid- l -phenylalanine- l -phenylalanine- l -O-phosphor tyrosine (named Nap-FF-Yp) was synthesized as our sensing platform to detect ALP activity and the sol-gel state. Nap-FF-Yp could be cleaved by ALP during hydrolysis, leading to π-π stacking, and finally changed to a hydrogel. Due to the difference in the potential drop between the liquid phase and gel phase of the hydrogel, the sol-gel transition reaction could be monitored by the electrical signal. The greater the extent of hydrogelation, the smaller the threshold voltage (Vth) variation, and the threshold voltage shifted to the left. Under the device’s optimal conditions with oxygen plasma treatment, the limit of detection (LOD) reached 0.024 U/L. The development of this novel sol-gel state for a high-speed screening sensing platform with an excellent electrical response demonstrates the potential capabilities of future high-speed response sensors.

Simulation of polarization data using modified Glazounov equation (T & E simultaneously) of barium titanate based normal and relaxor ferroelectrics

In the present study, simulation of polarization data using modified Glazounov equation (T & E simultaneously) of Barium Titanate based normal and relaxor ferroelectrics (i.e. BaTiO3 and Ba(NdxTi(1-2x)Nbx)O3) as proposed by us was carried out. These materials were prepared through sol-gel and solid state double sintering route. Modified Glazounov equation describes and model the experimental PE data in terms of dipole moment and activation energy for thermally activated dipoles present the ceramic materials. This equation best fit to the experimental PE data. The increase and decrease of activation energy with temperature and composition was attributed to the degree of disorderness of dipoles.

Chirality Transfer in Carbon Dot-Composited Sol-Gel Systems for Excitation-Dependent Circularly Polarized Luminescence.

In situ control of a circularly polarized luminescent (CPL) signal is desirable but rarely addressed. Even to compare with traditional chemical regulations, controlling the CPL signal at the material level using simple physical manipulation (such as photoexcitation) can be more convenient and preferable. In this work, we have constructed carbon dot-based composite luminescent materials with CPL activity. The materials can exist in the sol-gel state in a mixture solvent by chiral co-assembly, and chirality transfer occurred in the supramolecular assemblies and induced the CPL activity. Owing to the unique luminescent properties of the carbon dot component, the obtained CPL signal of the composite system is therefore excitation-dependent. The control ability of the CPL signal may allow the composite materials to find potential usage in advanced chirality-related fields.

INVESTIGATION OF THE TEMPERATURE-SENSITIVE CHARACTERISTIC OF GRAFTED GELATIN-PLURONIC HYDROGEL WITH INCORPORATION CALOPHYLLUM INOPHYLLUM OIL EXTRACT APPLIED FOR WOUND HEALING

Temperature-sensitive hydrogels were synthesized from gelatin-pluronic F127 with Calophyllum inophyllum oil extract incorporated as the the active ingredient by ultrasonic waves to increase the healing effect of wound treatments. The temperaturesensitive nature of the hydrogels were determined using the inversion tube method along with rheological property measurements. The sol-gel state of the hydrogels were found to change with temperature, at low-temperatures hydrogel gelatin - pluronic F127 is found to be in a liquid state, and when the temperature raised due to body temperature the hydrogel became a gel film. In addition, the hydrogel containing Calophyllum inophyllum oil has the ability to heal burns in the second degree after 10days of treatment. These results showed the potential application of the biomaterial in tissue regeneration.

Kinetic Stabilization of the Sol-Gel State in Perovskites Enables Facile Processing of High-Efficiency Solar Cells.

Perovskite solar cells increasingly feature mixed-halide mixed-cation compounds (FA1- x - y MAx Csy PbI3- z Brz ) as photovoltaic absorbers, as they enable easier processing and improved stability. Here, the underlying reasons for ease of processing are revealed. It is found that halide and cation engineering leads to a systematic widening of the anti-solvent processing window for the fabrication of high-quality films and efficient solar cells. This window widens from seconds, in the case of single cation/halide systems (e.g., MAPbI3 , FAPbI3 , and FAPbBr3 ), to several minutes for mixed systems. In situ X-ray diffraction studies reveal that the processing window is closely related to the crystallization of the disordered sol-gel and to the number of crystalline byproducts; the processing window therefore depends directly on the precise cation/halide composition. Moreover, anti-solvent dripping is shown to promote the desired perovskite phase with careful formulation. The processing window of perovskite solar cells, as defined by the latest time the anti-solvent drip yields efficient solar cells, broadened with the increasing complexity of cation/halide content. This behavior is ascribed to kinetic stabilization of sol-gel state through cation/halide engineering. This provides guidelines for designing new formulations, aimed at formation of the perovskite phase, ultimately resulting in high-efficiency perovskite solar cells produced with ease and with high reproducibility.

The effects of temperature, feed ratio, and reaction time on the properties of copolymer PLA-PEG-PLA

Triblock copolymers were polymerised by the ring-opening reaction of D,L-lactide in the presence of poly(ethylene glycol) (PEG), with number-average molecular weight (Mn) of 1500 and 2050 g/mol, using Sn(Oct)2 as a catalyst. The influences of the reaction time, the ratio of PEG and Poly(D,L-lactic acid) (PLA), and PEG types on structure and sol-gel phase transition of PLA-PEG-PLA triblock copolymers were investigated. Optimal polymerisation parameters were obtained, such as reaction time of 18 hours, a catalyst amount of 1.3%, and PEG/PLA ratio of 1/1.7, PEG (Mn=1500); the efficiency of the triblock synthesis was 42.3%. The properties of PLA-PEG-PLA copolymers were evaluated by analytical methods such as proton nuclear magnetic resonance H1NMR spectroscopy, gel permeation chromatography (GPC), and the sol-gel state transition at varying temperature. The results show that the triblock was successfully synthesised and its hydrogel had capability of the sol-gel state transition when the temperature changed. The PLA-PEG-PLA copolymer in aqueous solution is a thermo-sensitive hydrogel that can be used for drug and protein delivery systems or triblock denaturation applications for commercial purposes.

PH/Thermo-Dual Responsive Tunable In Situ Cross-Linkable Depot Injectable Hydrogels Based on Poly(N-Isopropylacrylamide)/Carboxymethyl Chitosan with Potential of Controlled Localized and Systemic Drug Delivery.

In the current study, cytocompatible in situ cross-linkable pH/thermo-dual responsive injectable hydrogels were prepared based on poly(N-isopropylacrylamide) and carboxymethyl chitosan, i.e., poly(CMCS-g-NIPAAm). The prepared formulations were aimed to be used as drug depot of 5-fluorouracil (5-FU) after subcutaneous administration in vivo. The phase transition from sol-gel state under physiologic temperature range was analyzed and confirmed by tube titling and optical transmittance measurements. The viscoelastic properties of gel formulations were confirmed by rheology determination via time sweep, temperature, and continuous ramp test. Oscillatory swelling cycles confirmed temperature effect and structural changes. pH and temperature sensitivity of dual responsive gels were analyzed at different pH and temperature programs. In vitro drug release profile displayed that developed formulations have the highest release in acidic pH at 25°C. The safety of blank gel formulations was evaluated against L929 cell lines via MTT assay and confirmed cytocompatibility with no detectable toxicity. In vitro cytotoxic potential of drug-loaded gels against HeLa and MCF-7 cancer cell lines confirmed that 5-FU has controlled cytotoxic potential in depot form in comparison to free 5-FU solution. The IC50 values for free 5-FU (21 ± 05μg/ml and 18 ± 66μg/ml) were found higher in comparison to the loaded form. The copolymer structure formation was confirmed by NMR and FTIR spectroscopic analysis. TG and DSC analysis proved the thermal stability and phase transition temperatures of pure and copolymer samples, while SEM analysis showed the porous nature of in situ formed hydrogels. It was concluded from the results that the developed formulations have pH/temperature sensitivity with potential of systemic and intratumoral controlled drug delivery properties.

Sol Gel vs Solid State Synthesis of the Fast Lithium-Ion Conducting Solid State Electrolyte Li7La3Zr2O12 Substituted with Iron

Two calcined products of Li6.4Fe0.2La3Zr2O12 can be synthesized via the solid state method and the sol gel method. Inhomogeneities of the iron distribution in the powder for the solid state method lead to a combination of cubic and tetragonal structure. By using the sol gel method the homogeneity can significantly been increased resulting in the desired pure phase cubic structured powders in I3d. By in situ dilatometer measurements the densification process can be comprehended for the first time for garnet type materials. The density can be significantly increased by the usage of the sol gel synthesis compared to the solid state synthesis with short sintering times of 2 h delivering pure phase pellets for both synthesis methods. Electrical impedance measurements revealed clearly divided semicircles for the bulk and the grain boundary contribution for the solid state synthesis, while the sol gel synthesis showed only one semicircle from the bulk contribution due to a large crystallite size. The total ionic conductivity for the pellet synthesized via the sol gel method is 1.82 mS/cm at 25°C which is the fastest found so far for garnet type or garnet related materials.

Controlling alginate oxidation conditions for making alginate-gelatin hydrogels

In the present work, we discuss how oxidation conditions can affect the physical properties of oxidized alginate and crosslinking it with gelatin. We show that the amount of aldehyde groups produced on oxidized alginate backbone increases by increasing alginate concentration even in constant molar ratio of sodium periodate to alginate's repeating units. Increasing the concentration of alginate solution, promote the extent of chain scission and decreases the molecular weight of oxidized alginate, which can be due to the increased possibility of molecular collisions and oxidizing two adjacent uronic acids in the chain. By changing the oxidation condition, therefore, we can produce oxidized alginate with same degree of oxidation but different molecular weights, which change the sol-gel state of alginate-gelatin mixtures. Using oxidized alginates with different molecular weights, we suggest that the aldehyde end groups in alginate chains have the dominant effect in crosslinking with gelatin.

Effect of the pH and NaCl on the microstructure and rheology of mixtures of whey protein isolate and casein micelles upon heating

Thermal gelation of aqueous solutions of micellar casein (MC), whey protein isolate (WPI) and mixtures was investigated as a function of the total protein concentration and the composition at different pH between 5.8 and 6.6. The sol-gel state diagram was determined visually and the mechanical properties of the gels were studied by oscillatory shear rheology. The evolution of the shear moduli was measured as a function of heating time at different temperatures. Strong synergy between the two types of milk proteins was observed during gelation of mixtures. MC gels are formed above a critical temperature that increases with increasing concentration. The MC gels are reinforced by co-aggregation of denatured whey proteins. Hybrid gels display stronger elastic moduli and less syneresis than pure MC gels. The microstructure of the gels was assessed using confocal laser scanning microscopy and showed that hybrid gels were more homogeneous than pure MC gels. The structure of rapidly formed MC gels was not modified by subsequent co-aggregation with denatured WPI. The effect of electrostatic interactions was probed by comparing gelation of salt free solutions with that at 0.1 M NaCl. Addition of salt led to an increase of the minimal gel concentration of MC.

Thermal blooming and photoluminescence characterizations of sol–gel CdO–SiO2 with different nanocomposite

The CdO NPs was synthesized using the sol–gel method and the nanoparticles were characterized using an UV–Vis spectrophotometer, with shape and size were examined by SEM and XRD. The XRD analysis respects the Bragg’s law and confirmed the crystalline nature of CdO nanoparticles. From the XRD, the average size of CdO NPs was found to be around 41 nm. The photoluminescence spectra of the CdO NPs, as recorded at room temperature, were excited at 300 nm wavelength. The broad emission peaks were between 600 and 650 nm (orange emission). The optical limiting performance of the nanocomposite was described in the sol–gel state. Also, this study has observed and studied the diffraction rings generated in CdO NPs using the same CW laser. The number of rings increases almost exponentially with an increasing volume fraction of SiO2 in the nanocomposites. The refractive index change, Δn, and effective nonlinear refractive index, n 2, were found to be 10−4 and 10−8 cm2/W, respectively. The effective nonlinear refractive index, n 2, was determined based on the observed number of rings. The threshold values of the CdO, CdO–2SiO2 and CdO–5SiO2 nanocomposites are 7.1, 6.55 and 6.34 mW, respectively. This large nonlinearity is attributed to the thermal effect. The present studies suggest that the nanocomposite is a potential candidate for optical device applications such as the optical limiters. The thermal blooming technique was applied to evaluate the thermo-optic coefficient and thermal diffusivity of the CdO NPs. In the thermal blooming experimental setup a transistor–transistor logic modulated CW laser of wavelength 532 nm was used as the excitation source.

Evolution of Phase Structure and Micro-Morphologies of the La<sub>0.7</sub>M<sub>0.3</sub>MnO<sub>3</sub> (M=Ca, Sr) Sintered at Different Temperature

The La0.7M0.3MnO3 (M=Ca, Sr) were synthesized by combining sol-gel technique and solid state sintering method. The evolutions of phase structure and micro-morphologies of the La0.7M0.3MnO3 with final sintering temperature (950-1250°C) were investigated. The results show that the La0.7Ca0.3MnO3 compounds exhibit single perovskite phase with cubic structure and the La0.7Sr0.3MnO3 compounds exhibit single perovskite phase with rhombohedra structure. The final sintering temperature has no obvious effect on the phase structure of La0.7Ca0.3MnO3. However, the density and grain size of La0.7M0.3MnO3 (M=Ca, Sr) increase with the increase of the final sintering temperature. Moreover, the micro-morphologies of La0.7Ca0.3MnO3 are more sensitive to final sintering temperature compared with that of La0.7Sr0.3MnO3. When sintering temperature is no less than 1150°C, the La0.7Ca0.3MnO3 has hardly any pore. After sintering at no less than 1250°C, the La0.7Sr0.3MnO3 becomes dense.

Study of Effect of Doping on Grain and Grain Boundary Parameters of Sr1−2xNaxNdxBi4Ti4O15 (x = 0−0.5) Ceramics Using Impedance Spectroscopy

Detailed impedance studies are done on Sr1−2xNaxNdx­Bi4Ti4O15 (x = 0, 0.1, 0.2, 0.4 and 0.5) system prepared by both sol gel and solid state method. An effort is made to explain the different mechanisms involved in the conduction mechanism through impedance studies. Grain boundary conduction dominates over the grain conduction. Capacitance is associated with the net polarization of ferroelectric domains. Grain boundaries required higher activation energies for hopping than the grains.

Dielectric, Ferroelectric and Piezoelectric Properties of Sr0.8Na0.1Nd0.1Bi4Ti4O15 Prepared by Sol Gel and Solid State Technique

Effect of lower ionic radii (Na and Nd) substitution in A-site on the structure, dielectric, ferroelectric and piezoelectric properties of SrBi4Ti4O15 (SBT) is investigated in this paper. The samples are prepared by solid state double sintering method and sol gel method based on pechini process. Substitution of smaller ions reduced the dielectric constant and remanent polarization values. But sol gel samples showed good dielectric and ferroelectric properties. A-site substitution has resulted in improved Curie temperature and piezoelectric properties. As a result, Na and Nd modified SBT ceramics are found to be excellent high temperature piezoelectric materials.