Properties Of Cryogels Research Articles

Synergetic effects of water-soluble polysaccharides for intensifying performances of oleogels fabricated by oil-absorbing cryogels

Oleogels were prepared by the cryogel-templated method from porous cryogels, which were co-structured using hydroxypropyl-methylcellulose and structural enhancers (such as flaxseed gum, κ-carrageenan, carboxymethyl-cellulose, arabic gum, and guar gum). The hardness, network density, pore size, pore volume, and SEM micrographs of cryogels showed that κ-carrageenan and flaxseed gum could keep the integrity of aqueous foams during freeze-drying and endow cryogels with the high hardness and content to hold oils (>98%). Oil absorption curves indicated that flaxseed gum and guar gum-enhanced cryogels provided the fastest oil absorption rate due to bigger pores. The absorption model was fitted well with all experimental data. Physical and mechanical properties of cryogels were positively related to the rheological property and oil bonding capacity of oleogels. κ-carrageenan and flaxseed gum were more suitable as structural enhancers to improve hydroxypropyl-methylcellulose-based cryogels for preparing oleogels to replace plastic fats in foods.

Biocompatible cryogels: preparation and application

Polymer cryogels are very promising for producing functional materials. Their porous structure makes them indispensable for some areas of medicine, catalysis, and biotechnology. In this review we focused on methods for producing cryogels based on biopolymers, interpolyelectrolyte complexes of biopolymers, and composite cryogels based on them. First, the properties of cryogels and brief theoretical information about the production of cryogels based on biopolymers were considered. The second section summarizes the latest advances in the production of cryogels based on complexes of biopolymers and composite cryogels. The features of the synthesis and the factors affecting the final properties of materials were considered. In the final part the fields of application of cryogels of the considered types in biotechnology, catalysis and medicine were studied in detail. In biotechnology cryogels are used to immobilize molecules and cells, as a basis for cell growth, and as chromatographic materials for cell separation. In catalysis cryogels are used as a matrix for the immobilization of metal nanoparticles, as well as for the immobilization of enzymes. Biocompatible cryogels and their composites are widely used in medicine for bone and cartilage tissue regeneration, drug delivery, providing a long-term profile of drug release in the body.

Water Uptake as a Crucial Factor on the Properties of Cryogels of Gelatine Cross-Linked by Dextran Dialdehyde.

We investigated the water sorption properties of macroporous cryogels of gelatine (Gel) and dextran dialdehyde (DDA) prepared via cryogelation at 260 K and following the freeze drying processes. Water vapour sorption isotherms for aerogels were studied at 293 K by two independent methods: static-gravimetric and dynamic vapour sorption (DVS) over a water activity range of 0.11–1.0. Experimental data were fitted by use of the Brunauer–Emmett–Teller (BET) and Guggenheim–Anderson–de Boer (GAB) models. The BET model (for a water activity range of 0.1 ≤ p/po ≤ 0.5) was used to calculate the sorption parameters of the studied cryogels (the monolayer capacity, surface area and energy of interaction). In comparison with BET, the GAB model can be applied for the whole range of water activities (0.1 ≤ p/po ≤ 0.95). This model gave an almost perfect correlation between the experimental and calculated sorption isotherms using nonlinear least squares fitting (NLSF). Confocal Laser Scanning Microscopy (CLSM) was used to confirm the structural differences between various DDA:Gel cryogel compositions. Thermogravimetric analysis and DSC data for aerogels DDA:Gel provided information regarding the bonded water loss, relative remaining water content of the material and the temperature of decomposition. Estimation of the amount of bound water in the cryogels after the freeze drying process as well as after the cycle of treatment of cryogels with high humidity and drying was performed using DSC. The results of the DSC determinations showed that cryogels with higher gelatin content had higher levels of bonded water.

Chitin Cryogels Prepared by Regeneration from Phosphoric Acid Solutions.

Cryogelation is a developing technique for the production of polysaccharide materials for biomedical applications. The formation of a macroporous structure during the freeze-drying of polysaccharide solutions creates biomaterials suitable for tissue engineering. Due to its availability, biocompatibility, biodegradability, and non-toxicity, chitin is a promising natural polysaccharide for the production of porous materials for tissue engineering; however, its use is limited due to the difficulty of dissolving it. This work describes the preparation of cryogels using phosphoric acid as the solvent. Compared to typical chitin solvents phosphoric acid can be easily removed from the product and recovered. The effects of chitin dissolution conditions on the structure and properties of cryogels were studied. Lightweight (ρ 0.025–0.059 g/cm3), highly porous (96–98%) chitin cryogels with various heterogeneous morphology were produced at a dissolution temperature of 20 ± 3 °C, a chitin concentration of 3–15%, and a dissolution time of 6–25 h. The crystallinity of the chitin and chitin cryogels was evaluated by 13C CP-MAS NMR spectroscopy and X-ray diffractometry. Using FTIR spectroscopy, no phosphoric acid esters were found in the chitin cryogels. The cryogels had compressive modulus E values from 118–345 kPa and specific surface areas of 0.3–0.7 m2/g. The results indicate that chitin cryogels can be promising biomaterials for tissue engineering.

Chondroitin Sulfate-Based Cryogels for Biomedical Applications.

Cryogels attained from natural materials offer exceptional properties in applications such as tissue engineering. Moreover, Halloysite Nanotubes (HNT) at 1:0.5 weight ratio were embedded into CS cryogels to render additional biomedical properties. The hemolysis index of CS cryogel and CS:HNT cryogels was calculated as 0.77 ± 0.41 and 0.81 ± 0.24 and defined as non-hemolytic materials. However, the blood coagulation indices of CS cryogel and CS:HNT cryogels were determined as 76 ± 2% and 68 ± 3%, suggesting a mild blood clotting capability. The maximum% swelling capacity of CS cryogel was measured as 3587 ± 186%, 4014 ± 184%, and 3984 ± 113%, at pH 1.0, pH 7.4 and pH 9.0, respectively, which were reduced to 1961 ± 288%, 2816 ± 192, 2405 ± 73%, respectively, for CS:HNT cryogel. It was found that CS cryogels can hydrolytically be degraded 41 ± 1% (by wt) in 16-day incubation, whereas the CS:HNT cryogels degraded by 30 ± 1 wt %. There is no chelation for HNT and 67.5 ± 1% Cu(II) chelation for linear CS was measured. On the other hand, the CS cryogel and CS:HNT cryogel revealed Cu(II) chelating capabilities of 60.1 ± 12.5%, and 43.2 ± 17.5%, respectively, from 0.1 mg/mL Cu(II) ion stock solution. Additionally, at 0.5 mg/mL CS, CS:HNT, and HNT, the Fe(II) chelation capacity of 99.7 ± 0.6, 86.2 ± 4.7% and only 11.9 ± 4.5% were measured, respectively, while no Fe(II) was chelated by linear CS chelated Fe(II). As the adjustable and controllable swelling properties of cryogels are important parameters in biomedical applications, the swelling properties of CS cryogels, at different solution pHs, e.g., at the solution pHs of 1.0, 7.4 and 9.0, were measured as 3587 ± 186%, 4014 ± 184%, and 3984 ± 113%, respectively, and the maximum selling% values of CS:HNT cryogels were determined as 1961 ± 288%, 2816 ± 192, 2405 ± 73%, respectively, at the same conditions. Alpha glucosidase enzyme interactions were investigated and found that CS-based cryogels can stimulate this enzyme at any CS formulation.

Tuning the Mechanical and Thermal Properties of Hydroxypropyl Methylcellulose Cryogels with the Aid of Surfactants.

The mechanical and thermal properties of cryogels depend on their microstructure. In this study, the microstructure of hydroxypropyl methylcellulose (HPMC) cryogels was modified by the addition of ionic (bis (2-ethylhexyl) sodium sulfosuccinate, AOT) and non-ionic (Kolliphor® EL) surfactants to the precursor hydrogels (30 g/L). The surfactant concentrations varied from 0.2 mmol/L to 3.0 mmol/L. All of the hydrogels presented viscous behavior (G″ > G′). Hydrogels containing AOT (c > 2.0 mmol/L) led to cryogels with the lowest compressive modulus (13 ± 1 kPa), the highest specific surface area (2.31 m2/g), the lowest thermal conductivity (0.030 W/(m·°C)), and less hygroscopic walls. The addition of Kolliphor® EL to the hydrogels yielded the stiffest cryogels (320 ± 32 kPa) with the lowest specific surface area (1.11 m2/g) and the highest thermal conductivity (0.055 W/(m·°C)). Density functional theory (DFT) calculations indicated an interaction energy of −31.8 kcal/mol due to the interaction between the AOT sulfonate group and the HPMC hydroxyl group and the hydrogen bond between the AOT carbonyl group and the HPMC hydroxyl group. The interaction energy between the HPMC hydroxyl group and the Kolliphor® EL hydroxyl group was calculated as −7.91 kcal/mol. A model was proposed to describe the effects of AOT or Kolliphor® EL on the microstructures and the mechanical/thermal properties of HPMC cryogels.

A Biomimetic Macroporous Hybrid Scaffold with Sustained Drug Delivery for Enhanced Bone Regeneration.

Bone regeneration is a highly complex physiological process regulated by several factors. In particular, bone-mimicking extracellular matrix and available osteogenic growth factors such as bone morphogenetic protein (BMP) have been regarded as key contributors for bone regeneration. In this study, we developed a biomimetic hybrid scaffold (CEGH) with sustained release of BMP-2 that would result in enhanced bone formation. This hybrid scaffold, composed of BMP-2-loaded cryoelectrospun poly(ε-caprolactone) (PCL) (CE) surrounded by a macroporous gelatin/heparin cryogel (GH), is designed to overcome the drawbacks of the relatively weak mechanical properties of cryogels and poor biocompatibility and hydrophobicity of electrospun PCL. The GH component of the hybrid scaffold provides a hydrophilic surface to improve the biological response of the cells, while the CE component increases the mechanical strength of the scaffold to provide enhanced mechanical support for the defect area and a stable environment for osteogenic differentiation. After analyzing characteristics of the hybrid scaffold such as hydrophilicity, pore difference, mechanical properties, and surface charge, we confirmed that the hybrid scaffold shows enhanced cell proliferation rate and apatite formation in simulated body fluid. Then, we evaluated drug release kinetics of CEGH and confirmed the sustained release of BMP-2. Finally, the enhanced osteogenic differentiation of CEGH with sustained release of BMP-2 was confirmed by Alizarin Red S staining and real-time PCR analysis.

The research advances of three dimensional porous cryogel for tissue engineering

Cryogels are a type of hydrogel material which are fabricated by cryopolymerization at subzero temperature. Due to their unique macroporous structure, shape memory properties and injectability, cryogels have gained significant interest in the fields of tissue engineering for encouraging the repair and regeneration of injured tissues. In this review, the basic concepts relevant to cryogels are introduced, and then the fabrication principle, the process parameters and the unique properties of cryogel are discussed. Next, the latest advances of cryogels as three-dimensional scaffold for various tissue engineering applications are given. Finally, this review summarizes the current limitations of cryogels, and strategies to further improve their properties for tissue engineering. The purpose of this article is to provide a reference guide for the researchers in related fields.

Cellulose cryogels prepared by regeneration from phosphoric acid solutions

The supermacroporous structure and ease of preparation of polysaccharide-based cryogels have led to their wide use in many areas and make them promising biomaterials for tissue engineering. One polysaccharide of particular interest for the production of tissue engineering scaffolds is cellulose, a natural biocompatible and nontoxic polymer. However, the complex supramolecular structure of cellulose creates difficulties in its dissolution and further processing into biomedical products. Conventional cellulose solvents have significant disadvantages, including poor removal from the resulting products. Therefore, this work proposes the preparation of cellulose-based cryogels using orthophosphoric acid, which can be easily removed and recovered. The effect of cellulose dissolution conditions on the structure and properties of cryogels were studied. Highly porous (88.3–93.4%) and light (ρ 0.091–0.161 g/cm3) cryogels with complex hierarchical morphologies were produced using a dissolution temperature of (20 ± 2) °C, a cellulose concentration in the solution > 3%, a dissolution time of 24–48 h (depending on the cellulose concentration), and precipitation with water or acetone. 13C CP-MAS NMR spectroscopy results confirmed that the regenerated cellulose is predominantly amorphous, with a crystallinity of 6.8–30.6% in the structure of cellulose II. The compressive modulus E for cryogels was from 330 to 3675 kPa. FTIR spectroscopy results showed that the regenerated cellulose had an increased number of aldehyde groups and a decreased number of hydrogen bonds decreases, indicating a decrease in crystallinity. No phosphoric acid esters of cellulose were detected in the cryogels by FTIR spectroscopy. These results pave the way for the easy preparation of biomaterials for tissue engineering.

Cryogel Carriers Comprising β‐Cyclodextrin Moieties for Improved Solubilization and Delivery of Aripiprazole

AbstractAripiprazole is a second‐generation atypical antipsychotic used for the treatment of schizophrenia, bipolar disorder, tic disorders, major depressive disorder, etc. However, aripiprazole is poorly soluble in water and many efforts are focused on developing delivery systems which can improve the solubility and the therapeutic activity of aripiprazole. In this contribution, the fabrication of novel cryogel carriers comprising β‐cyclodextrin (β‐CD) moieties for improved solubilization of aripiprazole is reported. Cryogels are synthesized by photochemical crosslinking of N,N‐dimethylacrylamide (DMA) and β‐CD triacrylate (β‐CD‐Ac3) in frozen aqueous system using H2O2 as initiator. The effect of DMA/β‐CD‐Ac3 mass ratio on the reaction efficiency, physico‐mechanical properties of cryogel, and drug loading efficiency is evaluated. The cryogel carriers are loaded with aripiprazole via procedure favoring inclusion of drug molecules into the hydrophobic cavity of β‐CD. The release of aripiprazole from PDMA/β‐CD carriers at pH 1.2 and 6.8 is studied and compared to the pure PDMA carriers.

Semi-interpenetrating polymer network cryogels based on poly(ethylene glycol) diacrylate and collagen as potential off-the-shelf platforms for cancer cell research.

In the present work, we investigated the potential of novel semi-interpenetrating polymer network (semi-IPN) cryogels, obtained through ultraviolet exposure of aqueous mixtures of poly(ethylene glycol) diacrylate and type I collagen, as tunable off-the-shelf platforms for 3D cancer cell research. We synthesized semi-IPN cryogels with variable collagen amounts (0.1% and 1% w/v) and assessed the effect of collagen on key cryogel properties for cell culture, for example, porosity, degradation rate and mechanical stiffness. Then, we investigated the ability of the cryogels to sustain the long-term growth of two pancreatic ductal adenocarcinoma (PDAC) cell populations, the parenchymal Panc1 cells and their derived cancer stem cells. Results revealed that both cell lines efficiently infiltrated, attached and expanded in the cryogels over a period of 14 days. However, only when grown in the cryogels with the highest collagen concentration, both cell lines reproduced their characteristic growth pattern previously observed in collagen-enriched organotypic cultures, biomimetic of the highly fibrotic PDAC stroma. Cellular preembedding in Matrigel, that is, the classical approach to develop/grow organoids, interfered with an efficient intra-scaffold migration and growth. Although preliminary, these findings highlight the potential of the proposed cryogels as reproducible and tunable cancer cell research platforms.

Protein chromatography by molecular imprinted cryogels

Molecularly imprinted cryogels for protein recognition have received much attention in recent years with the development of supermacroporous polymer systems. Molecularly imprinted cryogels, which offer great advantages for the selective and effective purification and separation of biomacromolecules from their sources, have become an important candidate for affinity matrix. Cryogels with their macroporous structure give rise to use them in different applications, such as tissue engineering, protein recognition and separation fields and environmental issues. This review highlights the principles of molecular imprinting technology, the preparation and properties of cryogels, the recent developments and applications of molecularly imprinted cryogels especially in protein chromatography.

Dielectric properties of CdSe quantum dots-loaded cryogel for potential future electronic applications

Cryogels are an outstanding class of materials with special and functionalized physical properties in various fields and privileges for different industrial applications. Due to unique properties of quantum dots, properties of cryogels can be engineered by adding quantum dots in. In this study, both p(HEMA)-based cryogel and CdSe QDs synthesized and characterized, separately. Then, CdSe QDs were loaded into p(HEMA) cryogels by immersing cryogel into QDs solutions. FTIR-ATR, SEM and TGA characterizations were performed to ensure that CdSe QDs penetrate p(HEMA) cryogels effectively. Dielectric properties of CdSe QDs-loaded cryogel were investigated using Electrical Impedance Spectroscopy (EIS). Real and imaginary parts of dielectric constants were decreased significantly at low frequencies in QD-loaded cryogels. While real part of impedance was increased in CdSe QDs-loaded cryogel at low frequencies. In addition, at high frequencies, those parameters were observed to be same in both cases.

Transparent polyvinyl-alcohol cryogel as immobilisation matrix for continuous biohydrogen production by phototrophic bacteria

BackgroundPhototrophic purple non-sulfur bacteria (PNSB) have gained attention for their ability to produce a valuable clean energy source in the form biohydrogen via photofermentation of a wide variety of organic wastes. For maturation of these phototrophic bioprocesses towards commercial feasibility, development of suitable immobilisation materials is required to allow continuous production from a stable pool of catalytic biomass in which energy is not diverted towards biomass accumulation, and optimal hydrogen production rates are realised. Here, the application of transparent polyvinyl-alcohol (PVA) cryogel beads to immobilisation of Rhodopseudomonas palustris for long-term hydrogen production is described. PVA cryogel properties are characterised and demonstrated to be well suited to the purpose of continuous photofermentation. Finally, analysis of the long-term biocompatibility of the material is illustrated.ResultsThe addition of glycerol co-solvent induces favourable light transmission properties in normally opaque PVA cryogels, especially well-suited to the near-infrared light requirements of PNSB. Material characterisation showed high mechanical resilience, low resistance to diffusion of substrates and high biocompatibility of the material and immobilisation process. The glycerol co-solvent in transparent cryogels offered additional benefit by reinforcing physical interactions to the extent that only a single freeze–thaw cycle was required to form durable cryogels, extending utility beyond only phototrophic bioprocesses. In contrast, conventional PVA cryogels require multiple cycles which compromise viability of entrapped organisms. Hydrogen production studies of immobilised Rhodopseudomonas palustris in batch photobioreactors showed higher specific hydrogen production rates which continued longer than planktonic cultures. Continuous cultivation yielded hydrogen production for at least 67 days from immobilised bacteria, demonstrating the suitability of PVA cryogel immobilisation for long-term phototrophic bioprocesses. Imaged organisms immobilised in cryogels showed a monolithic structure to PVA cryogels, and demonstrated a living, stable, photofermentative population after long-term immobilisation.ConclusionTransparent PVA cryogels offer ideal properties as an immobilisation matrix for phototrophic bacteria and present a low-cost photobioreactor technology for the further advancement of biohydrogen from waste as a sustainable energy source, as well as development of alternative photo-bioprocesses exploiting the unique capabilities of purple non-sulfur bacteria.

Extraction of pectin from albedo of lemon peels for preparation of tissue engineering scaffolds

Pectin is a type of anionic polysaccharide naturally found in a number of fruits and vegetables. Although pectin is widely used for food industry, its biomedical applications such as wound dressing, drug delivery and cancer targeting have also been investigated. In our study, we combined extracted pectin (from albedo of lemon peels) with chitosan (as a natural polymer) to synthesize chitosan/pectin cryogels. The extracted pectin was subjected to qualitative and quantitative analyses. Chitosan/pectin spongy supermacroporous cryogels were produced by cryogelation method at different combinations (100:0, 80:20, 60:40 and 40:60, w/w). Polyelectrolyte interactions between pectin and chitosan and crosslinking of chitosan with glutaraldehyde were verified by using FTIR. The porosity, swelling ratio, degradation behaviors and mechanical properties of cryogels were determined. SEM analysis demonstrated the pore morphology and average pore diameters of cryogels. After all analysis, 40:60 chitosan/pectin cryogel was selected for cytotoxicity studies. Glioblastoma (U-87 MG) cell line was used to evaluate the in vitro cytotoxicity of scaffolds. MTT assay and SEM analyses demonstrated the scaffolds were nontoxic, and supported cell attachment and viability.

Interconnected macropores cryogel with nano-thin crosslinked network regenerated cellulose

Dissolved oil palm empty fruit bunch cellulose (EFBC) and sodium carboxymethylcellulose (NaCMC) were chemically crosslinked with epichlorohydrin (ECH) to generate designated hydrogel. After swelling process in distilled water, the swollen hydrogel was frozen and freeze-dried to form cryogel. The swelling phenomenon of hydrogel during the absorption process gave substantial effects on thinning of crosslinked network wall, pore size and volume, steadiness of cryogel skeletal structure, and re-swelling of cryogel. The swelling effects on hydrogel were confirmed via microscopic study using variable pressure scanning electron microscope (VPSEM). From the retrieved VPSEM images, nano-thin crosslinked network wall of 24.31 ± 1.97 nm and interconnected pores were observed. As a result, the amount of water, the swelling degree, and the freeze-drying process indirectly affected the VPSEM images that indicated pore size and volume, formation of interconnected pores, and re-swelling of cryogel. This study determined the intertwined factors that affected both hydrogel and cryogel properties by investigating the swelling phenomenon and its ensuing effects.

Preparation of Gelatin and Gelatin/Hyaluronic Acid Cryogel Scaffolds for the 3D Culture of Mesothelial Cells and Mesothelium Tissue Regeneration.

Mesothelial cells are specific epithelial cells that are lined in the serosal cavity and internal organs. Nonetheless, few studies have explored the possibility to culture mesothelial cells in a three-dimensional (3D) scaffold for tissue engineering applications. Towards this end, we fabricated macroporous scaffolds from gelatin and gelatin/hyaluronic acid (HA) by cryogelation, and elucidated the influence of HA on cryogel properties and the cellular phenotype of mesothelial cells cultured within the 3D scaffolds. The incorporation of HA was found not to significantly change the pore size, porosity, water uptake kinetics, and swelling ratios of the cryogel scaffolds, but led to a faster scaffold degradation in the collagenase solution. Adding 5% HA in the composite cryogels also decreased the ultimate compressive stress (strain) and toughness of the scaffold, but enhanced the elastic modulus. From the in vitro cell culture, rat mesothelial cells showed quantitative cell viability in gelatin (G) and gelatin/HA (GH) cryogels. Nonetheless, mesothelial cells cultured in GH cryogels showed a change in the cell morphology and cytoskeleton arrangement, reduced cell proliferation rate, and downregulation of the mesothelium specific maker gene expression. The production of key mesothelium proteins E-cadherin and calretinin were also reduced in the GH cryogels. Choosing the best G cryogels for in vivo studies, the cell/cryogel construct was used for the transplantation of allograft mesothelial cells for mesothelium reconstruction in rats. A mesothelium layer similar to the native mesothelium tissue could be obtained 21 days post-implantation, based on hematoxylin and eosin (H&E) and immunohistochemical staining.

Three-dimensional cryogels for biomedical applications.

Cryogels are a subset of hydrogels synthesized under sub-zero temperatures: initially solvents undergo active freezing, which causes crystal formation, which is then followed by active melting to create interconnected supermacropores. Cryogels possess several attributes suited for their use as bioscaffolds, including physical resilience, bio-adaptability, and a macroporous architecture. Furthermore, their structure facilitates cellular migration, tissue-ingrowth, and diffusion of solutes, including nano- and micro-particle trafficking, into its supermacropores. Currently, subsets of cryogels made from both natural biopolymers such as gelatin, collagen, laminin, chitosan, silk fibroin, and agarose and/or synthetic biopolymers such as hydroxyethyl methacrylate, poly-vinyl alcohol, and poly(ethylene glycol) have been employed as 3D bioscaffolds. These cryogels have been used for different applications such as cartilage, bone, muscle, nerve, cardiovascular, and lung regeneration. Cryogels have also been used in wound healing, stem cell therapy, and diabetes cellular therapy. In this review, we summarize the synthesis protocol and properties of cryogels, evaluation techniques as well as current in vitro and in vivo cryogel applications. A discussion of the potential benefit of cryogels for future research and their application are also presented.

Polyvinyl Alcohol-Based Cryogels for the Oil Industry

The paper presents the results of studies of rheological properties of the initial viscous solutions of polyvinyl alcohol and ‘oil-in-water’ (O/W) emulsions. It is found that aqueous solutions of polymer and polymer-based colloidal systems have typical non-Newtonian properties. After the freeze-thaw cycle, the viscous liquid systems pass into a solid state of aggregation to form multicomponent cryogels with rubber-like structure. The elastic properties of two-component cryogels consisting of polyvinyl alcohol and water only, three-component compositions formed on the basis of an ‘aqueous PVA solution-mineral oil’ emulsion, and cryogels containing loose dispersed fillers are investigated. The physicochemical properties of the obtained elastic samples are studied. The prospects of application of cryogels for the oil producing well and road construction are outlined. A comparative analysis of physicomechanical properties of cryogels depending on the nature of the filler is carried out. In order to simulate the real conditions of oil field construction in the permafrost zone, samples of cryogels with solid dispersed fillers pre-wetted with oil are prepared and their mechanical and hydrophobic properties are investigated. Hydrophobic properties of cryogels make it possible to use them as waterproofing layer (membrane) in the construction of the asphalt pavement and insulation of the bottoms and walls of hydraulic structures. Cryogels can be recommended for use as polymer ‘pigs’ for removal of undesirable deposits in the pipeline during its cleaning or for pipeline pressure testing. In this case, ‘batching pigs’ are introduced to the boundary between hydrocarbon liquid and water.

Hydroxyapatite nanowire composited gelatin cryogel with improved mechanical properties and cell migration for bone regeneration

Hydrogels are normally not robust enough to meet the repairing requirements of bone defects, therefore, cryogels of higher mechanical properties are developed as the more proper candidates for the purpose. In view of the organic–inorganic composition of natural bone tissues, hydroxyapatite (HA) is envisioned as a good additive for protein cryogels to achieve biomimetic compositions, additionally, as an excellent reinforcement to increase the mechanical properties of cryogels. In this study, methacrylated gelatin (GelMA) was synthesized and corresponding 3D-structured cryogel was fabricated, followed by the incorporation of HA nanowires (HANWs) at different amounts as reinforcements. The results showed that the GelMA/HANW composite cryogels possessed highly porous structure with HANWs being homogeneously distributed. The compressive strengths and mechanical stability of the composite cryogels were improved alongside the increasing contents of HANWs. These composite cryogels were proven non-cytotoxic, able to support cell proliferation and promote osteogenic differentiation of bone mesenchymal stromal cells. More importantly, their porous structure allowed cell migration within the matrix, which was normally hard to be achieved in GelMA hydrogel. With improved performance, GelMA/HANW composite cryogels were thus possibly serving as a new type of bone repair materials.