Silica Hydrogel Research Articles

Silica Hydrogels as Platform for Delivery of Hyaluronic Acid.

Hyaluronic acid (HA) is chondroprotective and anti-inflammatory drug used clinically for treatment of inflammatory disorders (arthritis, skin diseases, bowel diseases, etc.). In addition, HA is a crucial ingredient in the cosmetic products used to eliminate the unpleasant consequences of inflammatory skin diseases. The main disadvantages that limit its use are its low mechanical properties and its rapid biodegradation. In this paper, silica hydrogels are considered as a promising matrix for HA to improve its properties. The hybrid HA-silica hydrogels were synthesized by the sol-gel method. Morphology of the hydrogels was investigated by optical microscopy and scanning electron microscopy methods. Taking into account their potential applications for topical and injectable delivery, much attention was paid to investigation of deformation properties of the hydrogels under shear, compression, and tension. Their resistance to enzymatic degradation in vitro was estimated. Kinetics and mechanisms of HA release from the hybrid hydrogels in vitro were also studied. It was found that the indicated properties can be controlled by synthesis conditions, HA molecular weight, and its loading in the hydrogels. Silica hydrogels are a prospective platform for the development of new soft formulations and cosmetic compositions of HA with improved pharmacological and consumer properties.

Development of novel silica hydrogels with improved structure properties to support growth of entrapped microalgae

Development of novel silica hydrogels with improved structure properties to support growth of entrapped microalgae

Effect of silica source on zeolite MFI crystallization in fluoride media and its physicochemical and catalytic properties

A series of MFI zeolites were synthesized in fluoride media from fumed silica hydrogel, fumed silica and TEOS to elucidate the influence of silica source on the physicochemical and catalytic properties of MFI zeolites. The materials obtained were characterized by nitrogen adsorption, XRD, SEM, TPD and 27Al NMR MAS methods and evaluated in MTO and hexane/3-methyl pentane cracking catalytic reactions. It has been demonstrated that crystallization proceeds via solution-mediated mechanism independently on silica source. However, the nature of silica source substantially affects the crystallization rate, the crystal size, the dynamics of Al incorporation into the MFI framework and Al distribution in the zeolite crystals. The application of fumed silica hydrogel and fumed silica with high polymerization degree yields crystals with an Al-enriched core and a siliceous shell. These materials demonstrate faster deactivation in the MTO reaction and higher selectivity to ethylene as compared to the MFI obtained from TEOS with a uniform Al distribution in the crystals. The effect observed is attributed to a longer diffusion path length of the reagent to active sites located mainly in the crystal core and the reaction products outside from the crystal core, resulting in a higher contribution of secondary reactions.

Experimental evaluation of a solar-driven adsorption desalination system using solid adsorbent of silica gel and hydrogel.

Nowadays, the world is facing a shortage of fresh water. Utilizing adsorbent materials to adsorb air moisture is a suitable method for producing freshwater, especially combining the adsorption desalination system with solar energy devices such as solar collectors. The low temperature of solar collectors has caused some water to remain in the adsorbents in the desorption process and has reduced the possibility of using these systems. In this research, for the first time, an evacuated tube collector (ETC) is used as an adsorbent bed so that the temperature of the desorption process reaches higher values and as a result, more fresh water is expected to produced. In this study, two adsorption desalination systems (ADS) are experimentally investigated. In the first system, a laboratory experimental setup using silica gel and hydrogel adsorbents is used to investigate freshwater production using each of the two adsorbents. The effect of different parameters such as variable adsorption and desorption time, variable temperature and humidity of inlet air, and variable adsorbent mesh sizes on the desalination process is evaluated. Then, in the second system, an innovative configuration of the solar-driven adsorption desalination system with an ETC full of silica gel is studied. In the laboratory experimental setup, the maximum amount of water produced by silica gel is 0.36 L/kg and by hydrogel is 0.58 L/kg. In the solar-driven adsorption desalination system, the largest amount of accumulated water production, daily efficiency, and cost per liter (CPL) of produced water are 1.518kg/m2 day, 11.25%, and 0.0699 $/L, respectively. Therefore, this new configuration for an adsorption desalination system seems feasible.

Silica hydrogel composites as a platform for soft drug formulations and cosmetic compositions

In this work, silica hydrogels are considered as potential basis for the development of new soft drug formulations and cosmetic products. For this purpose, the hydrogel drug-silica composites having pH ∼7 were synthesized by two-step sol-gel method under different synthesis conditions (concentration of acidic catalyst, addition of co-solvent (DMSO), drug loading). Lipoamide, a powerful antioxidant, was used as the drug. Since biomedical functionality of the hydrogel materials is largely determined by their mechanical properties, response of the hydrogels to deformation under compression, tension and shear was measured, and their thixotropic behavior was also studied. The release kinetics of the drug from the hydrogel composites was investigated in vitro. It was shown that the synthesis conditions influenced significantly on the indicated properties of the synthesized hydrogels. The compression Young's moduli and the thixotropic indexes decreased with increasing catalyst concentration and drug loading due to the destabilizing effect of these factors on microstructure of the hydrogels. However, DMSO promoted improvement of the mechanical properties of the hydrogels. The tensile properties of the hydrogels were very low. It was found that the drug release from the hydrogel composites followed zero order kinetic for two days due to mechanism of anomalous diffusion. The drug release from the hydrogel composites prepared using the highest catalyst concentration and high drug loading is characterized by higher rate constants.

Silica Hydrogels as Entrapment Material for Microalgae.

Despite being a promising feedstock for food, feed, chemicals, and biofuels, microalgal production processes are still uneconomical due to slow growth rates, costly media, problematic downstreaming processes, and rather low cell densities. Immobilization via entrapment constitutes a promising tool to overcome these drawbacks of microalgal production and enables continuous processes with protection against shear forces and contaminations. In contrast to biopolymer gels, inorganic silica hydrogels are highly transparent and chemically, mechanically, thermally, and biologically stable. Since the first report on entrapment of living cells in silica hydrogels in 1989, efforts were made to increase the biocompatibility by omitting organic solvents during hydrolysis, removing toxic by-products, and replacing detrimental mineral acids or bases for pH adjustment. Furthermore, methods were developed to decrease the stiffness in order to enable proliferation of entrapped cells. This review aims to provide an overview of studied entrapment methods in silica hydrogels, specifically for rather sensitive microalgae.

Preparation of monolithic amorphous silica aerogel through promising valorization of silicomanganese slag

Monolithic silica aerogels were successfully synthesized from silicomanganese slag by a highly efficient hydrometallurgical extraction process followed by solvent exchanges and ambient pressure drying. The silica content of the silicomanganese slag was first extracted by a facile and economical acid digestion-gelation process. The extracted silica hydrogel was then converted to silica aerogel through three-step solvent exchange, aging, and ambient pressure drying. No surface modifier was used. The characterization results revealed that the obtained silica aerogel had an amorphous structure having a low bulk density of ∼0.08 g/cm3, high specific surface area (∼509 m2/g), large pore volume (∼0.97 cm3/g), and an average pore diameter of ∼7.5 nm. Overall, the results showed that the proposed valorization process is a promising method to prepare monolithic silica aerogel from a cheap silica resource under ambient pressure drying without the use of any surface modification.

Silica Hydrogels as a Basis of Novel Soft Dosage Forms and Cosmetic Compositions

Silica Hydrogels as a Basis of Novel Soft Dosage Forms and Cosmetic Compositions

Changes in the Properties of Precipitated Silica Depending on the Modification Process of Silica Hydrogel Originated from Rice Husk

In this study, the changes in the properties of the prepared precipitated silica were evaluated depending on the conditions of the modification process of the silica hydrogel originated from rice husks. Rice husk silica hydrogel was prepared through a sol-gelation process after alkali soaking extraction of rice husk. The silica hydrogel was modified by adjusting the solution concentration and temperature conditions in acidic and alkali solutions. As a result, the changes in surface chemical properties and the improvement of quality characteristics such as whiteness and impurity removal were confirmed through the modification process. The modification treatment in an acidic atmosphere minimized the decrease in production yield and showed great effects on the whiteness and the removal of impurities such as alkali metals. In a alkaline condition, the improvement in the whiteness was clearly shown, but the reduction in yield increased. It was shown that the effects of the residual alkali metals and the organic substances on the properties of the precipitated silica could be controlled by the control of the modification process conditions.

Preparation and characterization of silica hydrogel nanocomposites as a drug delivery system

Preparation and characterization of silica hydrogel nanocomposites as a drug delivery system

Targeting Insect Olfaction in vivo and in vitro Using Functional Imaging.

Insects decode volatile chemical signals from its surrounding environment with the help of its olfactory system, in a fast and reliable manner for its survival. In order to accomplish this task, odorant receptors (ORs) expressed in olfactory sensory neurons (OSNs) in the fly’s antenna process such odor information. In order to study such a sophisticated process, we require access to the sensory neurons to perform functional imaging. In this article, we present different preparations to monitor odor information processing in Drosophila melanogaster OSNs using functional imaging of their Ca2+ dynamics. First, we established an in vivo preparation to image specific OSN population expressing the fluorescent Ca2+ reporter GCaMP3 during OR activation with airborne odors. Next, we developed a method to extract and to embed OSNs in a silica hydrogel with OR activation by dissolved odors. The odor response dynamics under these different conditions was qualitatively similar which indicates that the reduction of complexity did not affect the concentration dependence of odor responses at OSN level.

DEFORMATION PROPERTIES OF HYDROGEL COMPOSITESOF Α-LIPOIC ACID WITH COLLOID SILICA

Hydrogels are widely used as the basis of soft drug formulations and cosmetic compositions (ointments, creams, gels, masks, dermal fillers, etc.). Deformation properties of these products are very important from the point of view of the convenience and safety of their application, as well as optimization of their production process. In this work, inorganic silica hydrogels are considered as a promising basis for the development of new soft drug formulations and products for cosmetology. The hydrogel composites of colloid silica with α-lipoic acid which is a well-known powerful anti-oxidant used for treatment of various skin diseases were synthesized. Besides, the drug has a reju-venating effect on the skin. Taking into account the indicated potential application of the hydrogels and the methods of their administration (transdermal, injection), the hydrogels had a pH of 6.6-7.4. Pure silica hydrogels and their composites with α-lipoic acid were synthesized by a two-step sol-gel method. Using the method of optical microscopy, it was shown that they have a highly po-rous surface. The deformation properties of the synthesized hydrogels under compression, tension, and shear were determined. It is shown that the synthesized hydrogels have a certain elasticity under axial compression, thixotropy and exhibit pseudoplasticity. The effects ofthe synthesis con-ditions (concentration of the catalyst for silica sol formation, the amount of the introduced drug) on the deformation properties of the composites have been established. The effects were explained in terms of the influence of these factors on the strength of the three-dimensional silica framework of the hydrogel materials. The discovered deformation properties of silica hydrogels make them promising for the development of new soft drug formulations for topical application.

Sequential drug delivery by injectable macroporous hydrogels for combined photodynamic-chemotherapy

With hollow mesoporous silica (hMSN) and injectable macroporous hydrogel (Gel) used as the internal and external drug-loading material respectively, a sequential drug delivery system DOX-CA4P@Gel was constructed, in which combretastatin A4 phosphate (CA4P) and doxorubicin (DOX) were both loaded. The anti-angiogenic drug, CA4P was initially released due to the degradation of Gel, followed by the anti-cell proliferative drug, DOX, released from hMSN in tumor microenvironment. Results showed that CA4P was mainly released at the early stage. At 48 h, CA4P release reached 71.08%, while DOX was only 24.39%. At 144 h, CA4P was 78.20%, while DOX release significantly increased to 61.60%, showing an obvious sequential release behavior. Photodynamic properties of porphyrin endow hydrogel (ϕΔ(Gel) = 0.91) with enhanced tumor therapy effect. In vitro and in vivo experiments showed that dual drugs treated groups have better tumor inhibition than solo drug under near infrared laser irradiation, indicating the effectivity of combined photodynamic-chemotherapy.

IMMOBILIZATION OF PROBIOTIC CULTURES WITH ENTEROSORBENTS BASED ON HIGHLY DISPERSED SILICA

An important effectiveness factor of probiotic therapy is the survival of cells in the gastrointestinal tract and their integration into the intestinal biofilm. The possibility of creating complex preparations of enterosorbent-probiotic on the basis of dry highly dispersed silica and methyl-silicic acid hydrogel has been investigated. The survival of Streptococcus thermophilus and Bifidobacterium longum monocultures in the composition of lyophilized complex preparations, in particular under the simulated conditions of the gastrointestinal tract, was studied. The rheological and biotechnological parameters of yoghurt fermented with S. thermophilus IMV B-7249 strain immobilized in a hydrogel were evaluated. It was determined that the functional state of the culture immobilized in highly dispersed silica remained corresponded to the proper technological parameters of sour-milk yoghurt, and the effective viscosity and stability of the product increased. This makes it possible to recommend such a preparation for a use not only for enteral use but also for the production of fermented milk products.

Ultra‐Stretchable Self‐Healing Composite Hydrogels as Touch Panel

AbstractDevelopment of ultra‐stretchable and sensitive soft touch panel is of great importance for broad applications in artificial intelligence, wearable devices, and soft robotics. However, traditional human‐computer interfaces (HCIs) suffer from the discomfort and asynchronous signals in current application scenarios. Herein, a hydrogel‐based self‐healing touch panel, which is highly deformable, and both mechanically and electrically self‐healable, has been successfully developed from a poly(N,N′‐dimethylacrylamide)/silica hydrogel which possesses an ultra‐high stretchability >3800%. A surface‐capacitive touch mechanism is adopted to sense a touched position. The panel can be operated under high areal strain without sacrificing its functionalities. Skin touch panel is constructed and adhered to human skin, with the strong performance and self‐healing ability demonstrated by writing words and playing games.

Fabrication of a Nanoporous Silica Hydrogel by Cross-Linking of SiO2–H3BO3–Hexadecyltrimethoxysilane for Excellent Adsorption of Azo Dyes from Wastewater

This study reports a novel cross-linking approach to fabricate the hydrothermally neutralized silica hydrogel of SiO2-H3BO3-hexadecyltrimethoxysilane by grafting alkylsilane groups onto the nanoporous silica. The synthesized silica hydrogel possessed a large specific surface area of 51.3 m2g-1 and showed excellent dye adsorption capability of cationic dyes in neutral (pH 7) and alkaline (pH 9) medium from wastewater. The colloidal electrokinetic potential analysis revealed that the outstanding adsorption efficiency of cationic dyes over anionic dyes strongly relies on the surface charge of the hydrogels. Moreover, the hydrophobic interactions between the dye molecules and the hydrogels were studied, and it was found that the dye adsorption performance can be tuned by altering the concentration of hydrophobic reagents of the hydrogel. The dye adsorption mechanism was established, and the kinetic study suggested that the adsorption is a pseudo-second-order reaction. Adsorption isotherms at various equilibrium conditions fitted well with the Langmuir isotherm. Therefore, this strongly supports the promising and practical application of the prepared silica hydrogel. The recyclability of the hydrogel was studied, and it showed 90% adsorption efficiency by the regenerated gel up to 6 cycles, which has a high potential in wastewater treatment.

Thermo-responsive chitosan/silk fibroin/amino-functionalized mesoporous silica hydrogels with strong and elastic characteristics for bone tissue engineering

Amino-functionalized mesoporous silica nanoparticles with radially porous architecture were optimally synthesized, and they were used together with silk fibroin and chitosan to produce a type of covalently crosslinked composite hydrogel using genipin as a crosslinker. The optimally achieved composite gels were found to be thermo-responsive at physiological temperature and pH with well-defined injectability. They were also detected to have mechanically strong and elastic characteristics. In addition, these gels showed the ability to release bioactive Si ions suited to an effective dose range in approximately linear manners for a few weeks. Studies on the cell-gel constructs revealed that the composite gels well supported the growth of seeded MC3T3-E1 cells, and the deposition of matrix components. Results obtained from the detection of alkaline phosphatase activity and the matrix mineralization in the cell-gel constructs confirmed that these composite gels had certain osteogenic capacity. The obtained results suggest that these composite gels have promising potential in bone repair and regeneration.

Kinetics of the exchange of water absorbed in silica hydrogel with ethanol: Modelling by brouers and sotolongo-costa fractal kinetics

Isothermal kinetics of the exchange of absorbed water in a silica hydrogel (SH) with ethanol was examined. The isothermal kinetic curves of absorbed water exchange with ethanol were measured at the temperatures: T = = 297, 306 and 316 K. The rate of the exchange was analysed as a function of time. The possibility of mathematical description of the kinetics of exchange by the Brouers and Sotolongo-Costa?s (BS) fractal?s kinetics model was examined. Parameter values (n, ?, ?) of the model and their changes with temperature were calculated. By applying the method of Ozao, it was determined that the rate limiting step of the process of exchange was the rate of exchange of the absorbed water with ethanol. Values of the fractal dimension of the SH-ethanol interphase were calculated. The dependences of the effective time-dependent rate coefficient, activation energy and pre-exponential factor on time and degree of exchange were calculated and discussed. The proposed model of the mechanism of the exchange of absorbed water with ethanol was discussed.

Vortex Fluidic-Mediated Fabrication of Fast Gelated Silica Hydrogels with Embedded Laccase Nanoflowers for Real-Time Biosensing under Flow.

The fabrication of hybrid protein-Cu3(PO4)2 nanoflowers (NFs) via an intermediate toroidal structure is dramatically accelerated under shear using a vortex fluidic device (VFD), which possesses a rapidly rotating angled tube. As-prepared laccase NFs (LNFs) exhibit ≈1.8-fold increase in catalytic activity compared to free laccase under diffusion control, which is further enhanced by ≈ 2.9-fold for the catalysis under shear in the VFD. A new LNF immobilization platform, LNF@silica incorporated in a VFD tube, was subsequently developed by mixing the LNFs for 15 min with silica hydrogel resulting in gelation along the VFD tube surface. The resulting LNFs@silica coating is highly stable and reusable, which allows a dramatic 16-fold enhancement in catalytic rates relative to LNF@silica inside glass vials. Ultraviolet-visible spectroscopy-based real-time monitoring within the LNFs@silica-coated tube reveals good stability of the coating in continuous flow processing. The results demonstrate the utility of the VFD microfluidic platform, further highlighting its ability to control chemical and enzymatic processes.

Synthesis of uniformly dispersed silica/graphene oxide composite hydrogel using acid/base combinatorial catalysts system

This study involved the preparation of a sol–gel-based silica hydrogel, which incorporates uniformly dispersed graphene oxide (GO), using an acid/base combinatorial catalyst system. The gelation time of the silica hydrogel was dramatically reduced by adding the combinatorial catalyst instead of using a single catalyst system. Raman mapping confirmed that the combinatorial catalyst system considerably improved the uniformity of GO dispersion in the silica matrix. The silica/GO composite hydrogel demonstrated a very wide range of elastic moduli, compressive strength, and strain at fracture, indicating that this composite hydrogel system could potentially be used as a platform for stem cell culture or as a stretchable gel.