Hybrid Sponge Research Articles

Modulating stability and mechanical properties of silica–gelatin hybrid by incorporating epoxy‐terminated polydimethylsiloxane oligomer

ABSTRACTSilica‐gelatin hybrids, particularly GT‐G hybrids prepared by crosslinking gelatin (G) with γ‐glycidoxypropyltrimethoxysilane (GT), have attracted much attention in tissue engineering for diverse applications in hard or soft tissue regeneration; however, scaffolds with tunable properties are needed to meet specific requirements. In this work, a silica‐gelatin hybrid (ES/GT‐G) was synthesized by incorporating epoxy‐terminated polydimethylsiloxane oligomer (ES) to modulate the properties of GT‐G hybrid. The ES/GT‐G hybrid sponge presented a 3D network structure with porosity 86.4% ± 0.9%, determined by the liquid displacement method, and average pore size 340 ± 36 μm, determined by SEM observation. Compared with GT‐G hybrid material, the prepared ES/GT‐G hybrid wet film showed a decrease of tensile strength from 2.79 ± 0.04 MPa to 1.87 ± 0.12 MPa, with an increase of elongation at break from 19.96 ± 0.66% to 29.86 ± 0.87%, and the ES/GT‐G hybrid sponge exhibited a decline of compressive yield strength from 1.21 ± 0.04 MPa to 0.72 ± 0.06 MPa, based on the tensile and compression tests respectively. The introduction of ES enhanced the thermal denaturing temperature of GT‐G by 5°C as determined by a DSC study, and increased in vitro biodegradation slightly, without significantly changing surface wettability and swelling behavior. These findings suggest that silica‐gelatin hybrids with tunable properties are promising for applications from hard to soft tissue regeneration. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43059.

Complete tissue coverage achieved by scaffold-based tissue engineering in the fetal sheep model of Myelomeningocele

Myelomeningocele (MMC) is the most severe form of spina bifida, one of the most common congenital anomalies. Although open fetal surgical repair of the MMC defect has been shown to result in improved outcomes, a less invasive approach applicable earlier in gestation than the current open surgical approach between 19 and 26 weeks of gestation is desirable for further improvement of neurological symptoms, as well as reduction of maternal and fetal risks. We previously reported the therapeutic potential of a scaffold-based tissue engineering approach in a fetal rat MMC model. The objective of this study was to confirm the long-term efficacy of this approach in the surgically created fetal sheep MMC model. Gelatin-based or gelatin/collagen hybrid sponges were prepared with and without basic fibroblast growth factor (bFGF) incorporation. The defect was covered by a sponge and secured by a supporting sheet with adhesive at 100 days of gestation or the gelatin/collagen hybrid with bFGF was secured with adhesive without the sheet. Although sheets were found detached at term (140 days' gestation), both gelatin-based and gelatin/collagen hybrid sponges had integrated within the newly formed granulation tissue, resulting in complete coverage of the MMC defect. The release of bFGF from sponges resulted in enhanced formation of granulation tissue and epithelialization. There was also evidence of improved preservation of the spinal cord with less associated damage on histological analysis and reversal of hindbrain herniation. These experiments provide important proof-of-principle evidence of the efficacy of scaffold-based tissue engineered coverage for the prenatal treatment of MMC.

Covalently bonded nitrogen-doped carbon-nanotube-supported Ag hybrid sponges: Synthesis, structure manipulation, and its application for flexible conductors and strain-gauge sensors

Flexible strain-gauge sensors are an essential component in electronic devices, and pressure sensing is also an important function. Here, we report an ultrastable and highly sensitive sensor based on covalently bonded nitrogen-doped carbon-nanotube-supported Ag (N-CNT/Ag) hybrid sponges with hierarchical binary-network architectures via a unidirectional freezing technique. The covalent bonding utilizing hyperbranched polyglycerol (HPG) as bridges endows the sponges with structural stability under compression, oscillation, and bending modes. Moreover, a large number of Ag nanoparticles (NPs) decorated using HPG as templates could also enable the N-CNTs/Ag sponges to possess linear current–voltage behavior. Furthermore, the Ag NPs on the compartmental films can be considered as interlocked nanodomes, which not only enhance compression stress but also generate huge variation of resistance through variation of contact area under mechanical deformation. These novel designs featuring interlocked geometry and covalent bonding allow the hybrid sponges to act as strain-gauge sensors with high gauge factor (1.4) and excellent stability.

Three-dimensional α-Fe2O3/carbon nanotube sponges as flexible supercapacitor electrodes

The porous, flexible and compressible CNT@Fe2O3 sponges show high specific capacitance (>300 F g−1).

Rational design and fabrication of graphene/carbon nanotubes hybrid sponge for high-performance capacitive deionization

A graphene/carbon nanotubes sponge was fabricated by a freeze-drying and annealing method for capacitive deionization with an ultrahigh electrosorption capacity.

Three-dimensional CNT/graphene–sulfur hybrid sponges with high sulfur loading as superior-capacity cathodes for lithium–sulfur batteries

A facile method is presented to synthesize three-dimensional carbon nanotube/graphene–sulfur (3DCGS) sponge with a high sulfur loading of 80.1%.

CHITOSAN/SULFATED GRIFOLA FRONDOSA POLYSACCHARIDE HYBRID SPONGE ACCELERATED WOUND HEALING

The essential role and function of a dressing is to provide an environment that promotes wound healing. In this study, the development and characterization of novel polymer hybrid sponge based on chitosan-Grifola frondosa polysaccharide and cross-linked by freeze-thaw method for possible use in a variety of biomedical application is reported. A water-soluble sulfated derivative G. frondosa polysaccharide was obtained from G. frondosa polysaccharide with 98% of concentrated sulfuric acid. To make effective wound healing accelerator, a chitosan/sulfated G. frondosa polysaccharides hybrid sponge was prepared. To evaluate the wound healing effect, full thickness skin excision was performed on the backs of the rats and then the sponge was applied in the wounds, respectively. After 7 days and 14 days, gross and histological examination was performed. Grossly, untreated control group revealed that the wound had well-defined margin and was covered by crust. The testing group treated with sponge appeared to be nearly completely healed. Histology of each group was well correlated to gross findings. The testing group shows nearly complete regeneration of appendage structure similar to normal in the dermis in contrast to control group with absence and less number of skin appendages. It hints that the sponge can accelerate wound healing. The result indicates that the chitosan/sulfated G. frondosa polysaccharide hybrid sponge is a promising dressing for wound healing.

Facile in situ synthesis of hierarchical porous Ni/Ni(OH)₂ hybrid sponges with excellent electrochemical energy-storage performances for supercapacitors.

Herein, we report the in situ growth of single-crystalline Ni(OH)2 nanoflakes on a Ni support by using facile hydrothermal processes. The as-prepared Ni/Ni(OH)2 sponges were well-characterized by using X-ray diffraction (XRD), SEM, TEM, and X-ray photoelectron spectroscopy (XPS) techniques. The results revealed that the nickel-skeleton-supported Ni(OH)2 rope-like aggregates were composed of numerous intercrossed single-crystal Ni(OH)2 flake-like units. The Ni/Ni(OH)2 hybrid sponges served as electrodes and displayed ultrahigh specific capacitance (SC=3247 F g(-1)) and excellent rate-capability performance, likely owing to fast electron and ion transport, sufficient Faradic redox reaction, and robust structural integrity of the Ni/Ni(OH)2 hybrid electrode. These results support the promising application of Ni(OH)2 nanoflakes as advanced pseudocapacitor materials.

탈미네랄골분이 첨가된 알지네이트 스펀지에서 조직공학적 연골 재건

알지네이트와 탈미네랄골분(DBP) 하이브리드 스펀지는 각각 DBP가 0, 10, 20, 40 및 80% 첨가된 스펀지로, 연골 재건을 위해 제작되었다. 세포의 증식은 MTT를 통해 관찰했으며, 형태학적, 조직학적, 생물학적 관찰 그리고 RT-PCR을 1, 2, 및 3 주에 실시하였다. 세포생존율에 있어서 20% DBP/알지네이트 스펀지에서 다른 스펀지보다도 가장 좋은 결과를 보였으며, 광학전자현미경 관찰에서 또한 20% 스펀지에서 가장 좋은 세포부착률과 증식률을 확인하였다. 마지막으로, 조직학적 평가에서 20% 스펀지에서 연골세포의 표현형이 가장 잘 유지됨과 동시에 산성뮤코 다당류와 제2형 콜라겐이 잘 형성된 것을 확인하였다. 이로써 DBP/알지네이트 하이브리드 스펀지는 연골 조직공학을 위한 지지체로써 활용될 수 있을 것이다. Demineralized bone particles (DBP) and alginate hybrid sponges were fabricated at 10, 20, 40 and 80% DBP/alginate hybrid ratios for seeding chondrocyte. Cell proliferation was measured via MTT assay. Morphological observation, histology, biological assay and RT-PCR were performed at each time point 1, 2 and 3 weeks. The cell viability was better in 20% DBP/alginate sponges than in other sponges. SEM results showed that more attached and more proliferated cells in the 20% DBP/alginate sponges with the lapse of time. Finally, histochemical assay results showed that the phenotype of chondrocyte was well maintained and both acidic mucopolysaccharide and type II collagen was well formed at 20% sponges. This study suggested that DBP/alginate sponge may serve as a potential cell delivery vehicle and a structural basis for tissue engineered articular cartilage.

Three-Dimensional Sulfur/Graphene Multifunctional Hybrid Sponges for Lithium-Sulfur Batteries with Large Areal Mass Loading

In this communication, we introduce the concept of three dimensional (3D) battery electrodes to enhance the capacity per footprint area for lithium-sulfur battery. In such a battery, 3D electrode of sulfur embedded into porous graphene sponges (S-GS) was directly used as the cathode with large areal mass loading of sulfur (12 mg cm−2), approximately 6–12 times larger than that of most reports. The graphene sponges (GS) worked as a framework that can provide high electronic conductive network, abilities to absorb the polysulfides intermediate, and meanwhile mechanical support to accommodate the volume changes during charge and discharge. As a result, the S-GS electrode with 80 wt.% sulfur can deliver an extremely high areal specific capacitance of 6.0 mAh cm−2 of the 11th cycle, and maintain 4.2 mAh cm−2 after 300 charge−discharge cycles at a rate of 0.1C, representing an extremely low decay rate (0.08% per cycle after 300 cycles), which could be the highest areal specific capacity with comparable cycle stability among the rechargeable Li/S batteries reported ever.

A compressible mesoporous SiO2 sponge supported by a carbon nanotube network

Applications of mesoporous silica (m-SiO2) have suffered from its fragility (monolithic m-SiO2 easily collapses under compression) and limited internal molecular exchange through small channels. Previously reported hierarchical porous m-SiO2 structures containing interconnected macropores could improve adsorption properties, but they were still intrinsically fragile without sufficient mechanical strength to sustain deformation. Here, we embed a three-dimensional carbon nanotube (CNT) skeleton into m-SiO2 to fabricate bulk, robust sponges that can be compressed to large strains (60% volume reduction) repeatedly in both air and water. This is done by directly casting a uniform m-SiO2 layer with tunable thickness onto the surface of CNTs while maintaining the original network and open porous structure, resulting in a core-shell CNT@m-SiO2 hybrid sponge. By pumping fluid through the CNT@m-SiO2 sponges under cyclic compression, the adsorption rate and efficiency of dye molecules can be significantly enhanced due to the mesoporous coating on CNTs and enhanced fluid exchange throughout internal pores. The CNT@m-SiO2 sponges may be used as robust and flexible adsorption media, and chemical and biological sensors with high performance.

Supercapacitors based on freeze dried MnO2 embedded PEDOT: PSS hybrid sponges

The present study investigates in detail the synthesis and characterization of PEDOT: PSS/MnO2 hybrid sponge electrodes for supercapacitor/battery applications. These hybrid sponges were prepared using freeze drying technique and showed hierarchical pores ranging from micron to nanometric size. Scanning electron microscopy-energy dispersive X-ray showed uniform dispersion of MnO2 along the PEDOT: PSS matrix. Thermo gravimetric-differential thermal analysis showed higher thermal stability for these hybrid constructs compared to PEDOT: PSS sponges. From the electrochemical studies, an intrinsic correlation between overall specific capacitance, morphology and weight percentage of MnO2 in the PEDOT: PSS matrix has been defined and explained in KOH electrolyte system. High cyclic stability was observed at the end of 2000 cycles for these hybrid sponges with less than 5 % capacitance fading. These sponges exhibit mass specific capacitance values as high as 10688Fg−1 which was found to be 35% higher compare to PEDOT: PSS sponges as obtained from Weibull statistics. The application of these electrodes was explored in a fully functional asymmetric coin cell unit where an energy and power density of 200mWhkg−1 and 6.4kWkg−1, was obtained, respectively.

Hybrid sponge comprised of galactosylated chitosan and hyaluronic acid mediates the co-culture of hepatocytes and endothelial cells

When constructing an in vitro model of liver tissue to mimic the in vivo liver microenvironment, the major challenge is to preserve and maintain the hepatocyte phenotype. The aim of this study was to develop a novel intelligent hybrid sponge for use in a dense co-culture system designed to simulate the liver microenvironment. We prepared a galactosylated chitosan (GCs)/hyaluronic acid (HA) hybrid sponge using a freeze-drying technique for the co-culture of primary hepatocytes and endothelial cells. Subsequently, we investigated the biocompatibility of the GCs/HA scaffold with primary hepatocytes and endothelial cells in terms of cell attachment, morphology, bioactivity, and maintenance of specific liver functions. The GCs/HA-hybrid sponge demonstrated good biocompatibility not only with primary hepatocytes, but also with endothelial cells. In our model, primary hepatocytes exhibited superior bioactivity and higher levels of liver-specific functions in terms of hepatocyte-specific gene expression, urea production, and testosterone metabolism as compared to a monoculture system. We succeeded in constructing a liver tissue-like model using the GCs/HA-hybrid sponge. Therefore, we anticipate that GCs/HA-hybrid sponges may be a promising matrix for the co-culture of hepatocytes and endothelial cells in liver tissue engineering, and might be employed as a novel co-culture model for applications in toxicology and drug metabolism.

Photocatalytic, recyclable CdS nanoparticle-carbon nanotube hybrid sponges

Semiconducting nanoparticles with lower bandgap (e.g., CdS) are alternative photocatalysts to TiO2, since they have a potentially wider range light of absorption and improved catalytic efficiency. However, they must be securely anchored on a porous substrate for practical applications. Here, we report a hybrid porous photocatalyst fabricated by grafting 4–6 nm diameter CdS nanoparticles uniformly throughout the entire macroporous structure of a three-dimensional carbon nanotube (CNT) sponge. The unique feature of our structure is that only the CdS nanoparticles grafted on the outside surface are active in photocatalysis, while other nanoparticles are stored inside the sponge in the fresh state for use when the catalyst is recycled. Our CdS-CNT hybrid sponges show high efficiency in removing organic contaminants from water. Spectroscopic measurements show that the hybrid sponges are multifunctional, simultaneously performing organic molecular adsorption (using the inter-CNT spacing), and photocatalytic decomposition (by the CdS nanoparticles grafted on the surface), both of which contribute to water purification. Furthermore, the surface part of the sponges can be stripped off to expose inner nanoparticles for use when the catalyst is recycled, without performance degradation. Open image in new window

Culture of bovine articular chondrocytes in funnel-like collagen-PLGA hybrid sponges**This work was presented at the International Union of Materials Research Societies (International Conference in Asia) (Qingdao, China, Sep. 25–28 2010).

Three-dimensional porous scaffolds play an important role in tissue engineering and regenerative medicine. Structurally, these porous scaffolds should have an open and interconnected porous architecture to facilitate a homogeneous cell distribution. Moreover, the scaffolds should be mechanically strong to support new tissue formation. We developed a novel type of funnel-like collagen sponge using embossing ice particulates as a template. The funnel-like collagen sponges could promote the homogeneous cell distribution, ECM production and chondrogenesis. However, the funnel-like collagen sponges deformed during cell culture due to their weak mechanical strength. To solve this problem, we reinforced the funnel-like collagen sponges with a knitted poly(D,L-lactic-co-glycolic acid) (PLGA) mesh by hybridizing these two types of materials. The hybrid scaffolds were used to culture bovine articular chondrocytes. The cell adhesion, distribution, proliferation and chondrogenesis were investigated. The funnel-like structure promoted the even cell distribution and homogeneous ECM production. The PLGA knitted mesh protected the scaffold from deformation during cell culture. Histological and immunohistochemical staining and cartilaginous gene expression analyses revealed the cartilage-like properties of the cell/scaffold constructs after in vivo implantation. The hybrid scaffold, composed of a funnel-like collagen sponge and PLGA mesh, would be a useful tool for cartilage tissue engineering.

The Development of Gelatin/Chitosan Hybrid Scaffold for Mouse Embryonic Stem Cell Line ATDC5

Functional scaffolds fabricated from biopolymers are of great importance for tissue engineering. In this paper, by mimicking the combination of two major components in Extracellular Matrix – collagen and polysaccharide respectively, we fabricated gelatin and chitosan hybrid sponge for cartilage tissue engineering. Extending previous results of gelatin/chitosan film showed that all the hybrid coating film (chitosan: gelatin= 4:1; 1:1; 1:4) can support the adhesion of ATDC5 that comparable to Tissue Culture Dish (TCD). More importantly, stem cell line ATDC5 on coating dish of chitosan: gelatin=1:4 showed enhanced differentiation rate than that on other films and TCD. For three dimensional scaffolds, we fabricated hybrid sponge scaffold of chitosan: gelatin=4:1, 2:1, 1:1, 1:2, 1:4 respectively. Morphological characterizations of the sponges showed that this kind of gelatin/chitosan hybrid scaffold is promising for application in cartilage tissue engineering.

A Novel Cylinder-Type Poly(L-Lactic Acid)–Collagen Hybrid Sponge for Cartilage Tissue Engineering

The development of porous scaffolds having both high porosity and strong mechanical strength for tissue engineering and regenerative medicine has been quite challenging. A novel hybrid poly(L-lactic acid) (PLLA)-collagen hybrid sponge was developed by enclosing collagen sponge in a cup-shaped PLLA sponge to meet the necessary requirements. Collagen sponge was formed in the center of the PLLA sponge cup, and collagen microsponges were formed in the pores of the PLLA sponge cup. The PLLA-collagen hybrid sponge showed higher mechanical strength than did those of the PLLA sponge cup and collagen sponge. The porosity of the PLLA-collagen hybrid sponge was greater than that of the PLLA sponge cup. The cup-shaped PLLA sponge skeleton provided the hybrid sponge with high mechanical strength and protected against cell leakage during cell seeding, while the central collagen sponge contributed to high porosity, and facilitated cell adhesion and distribution in the hybrid sponge. Cartilaginous tissue was successfully regenerated when chondrocytes were cultured in the hybrid sponge. This method of hybridization will provide a new technique for the preparation of functional porous scaffolds for tissue engineering.

Agar-gelatin hybrid sponge-induced three-dimensionalin vitro‘liver-like’ HepG2 spheroids for the evaluation of drug cytotoxicity

Agar-gelatin hybrid sponges were used as scaffolds to induce the formation of three-dimensional (3D) spheroids of HepG2 cells. Agar and gelatin in 2:1 ratio were used to make films and sponges. The cell adhesive properties of the films were evaluated by the attachment kinetics. The growth kinetics of HepG2 cells was studied using MTT assay and morphology of the 3D spheroids was observed through inverted optical microscopy. The liver cell-specific functions of the 3D spheroids were evaluated in terms of albumin secretion and urea synthesis. Paracetamol was used as a model drug to investigate the use of these 3D spheroids in the preliminary cytotoxicity evaluation of drugs. The results showed that the agar-gelatin hybrid sponges induced the formation of 3D HepG2 spheroids with significant liver-specific functions. These spheroids exhibited higher amounts of albumin and urea synthesis than the control monolayer culture. These 3D spheroids were found to be more sensitive to the drug (TCIC(50) value of 4.6 mM) than the control monolayer (TCIC(50) value of 6.2 mM). The study shows that agar-gelatin-induced HepG2 3D spheroids can be used for the preliminary evaluation of the toxicity of drugs and chemicals.

Bone differentiation of marrow-derived mesenchymal stem cells using β-tricalcium phosphate–alginate–gelatin hybrid scaffolds

The aim of the present study was to establish a 3D culture system for bone differentiation of mesenchymal stem cells (MSCs), using a new hybrid sponge. To manufacture the scaffold, a composite of beta-tricalcium phosphate-alginate-gelatin was prepared and cast as pellets of 1 cm diameter. The sponge was then fabricated by drying in freeze-dryer for 12 h. The porosity, mean pore size, compressive modulus and strength of the composite sponge fabricated in this study were 89.7%, 325.3 microm, 1.82 and 0.196 MPa, respectively. To establish a 3D culture system, the rat bone marrow-derived MSCs were suspended in 500 microl diluted collagen gel, loaded into the porous sponge and provided with medium with or without osteogenic supplements for 3 weeks. The day after loading, the cells appeared in the scaffold's internal spaces, where later some of them from either culture survived by anchoring on the surfaces. At the end of cultivation period, individually adhered cells from both cultures were observed to be replaced by cell aggregates, in which mineralized matrix was detected by alizarin red staining. Furthermore, RT-PCR analysis indicated that the bone-specific gene osteocalcin was expressed in cultures in both the presence and absence of the osteogenic supplements. Taken together, it seems that the studied scaffolds are cell-compatible and, more importantly, possess some osteo-inductive properties.

Preparation and characterization of PLA/fibroin composite and culture of HepG2 (human hepatocellular liver carcinoma cell line) cells

Through adding insoluble fibroin microparticles into polylactic acid (PLA) solution, stirring intensively and then freeze-drying the blend, we prepared a composite scaffold composed of polylactic acid (PLA) and fibroin. Observation of the PLA/fibroin composite scaffold by scanning electron microscopy (SEM) showed that fibroin microparticles uniformly distributed in PLA matrix and interconnected pore structures were formed in the scaffolds. The in vitro cell culture result showed that the HepG2 (human hepatocellular liver carcinoma cell line) cells attached and spread well on the surfaces of the composite scaffold. Compared with that on PLA scaffolds, the attachment and growth of HepG2 on the composite scaffold were greatly improved. HepG2 cells attached on the hybrid sponges and established cell–cell contacts to form aggregates with a size up to 100 μm. Considering that the PLA skeleton facilitated the desired shape formation, and fibroin microparticles improved the cell growth, the PLA/fibroin composite scaffold is a promising matrix for hepatic tissue engineering.