Hybrid composite scaffolds prepared by sol–gel method for bone regeneration

This study reports the synthesis and characterization of hydroxyapatite (HA)/polycaprolactone (PCL) hybrid composite materials synthesized by sol–gel method. The fabrication of scaffolds was performed by salt-leaching technique using NaCl as porogen agent. In the first step, the physico-chemical characterization of composite material was performed to evaluate the composition and the interaction between the organic/inorganic phases. In the second step, optimized scaffolds were bioactivated on the surface. The combined effect of scaffold morphology and surface bioactivity is ideal for bone tissue engineering, supporting bone cells adhesion, proliferation and differentiation. Here, a combined strategy involving biomimetic approach, using a supersaturated Simulated Body Fluid (SBF), and salt-leaching technique has been developed to grow hydroxyapatite in composite scaffolds able to regenerate the natural bone.     

An ordered electrospun polycaprolactone–collagen–silk fibroin scaffold for hepatocyte culture

Nanofiber scaffolds are widely used as the platform for three-dimensional culture of hepatocytes in vitro. The pore size of scaffolds plays an important role in promoting the infiltration and proliferation of hepatocyte. We show that the average pore size of electrospun scaffold increases from ~ 7.6 to 13.2 μm, while the average fiber diameter decreases from ~ 2.0 to 1.5 μm when collected by probe array collectors. Though increase in pore size decreases the tensile stress of scaffolds, it leads to enhance the proliferation and attachment of hepatocytes. Specifically, a 6 × 6 array scaffold which was prepared by probe collector was orderly arrayed. Compared with the conventional scaffold, the pore size of the arrayed scaffold doubled and the hydrophilicity was improved. When HepG₂ cells were seeded on the arrayed scaffold, cells showed superior adhesion ability, better cell morphology and three-dimensional growth. These results indicated that the ordered 6 × 6 array scaffold has the potential as a suitable substratum for in vitro culture of hepatocytes.     

Preparation and comparative characterization of keratin–chitosan and keratin–gelatin composite scaffolds for tissue engineering applications

We report fabrication of three dimensional scaffolds with well interconnected matrix of high porosity using keratin, chitosan and gelatin for tissue engineering and other biomedical applications. Scaffolds were fabricated using porous Keratin–Gelatin (KG), Keratin–Chitosan (KC) composites. The morphology of both KG and KC was investigated using SEM. The scaffolds showed high porosity with interconnected pores in the range of 20–100 μm. They were further tested by FTIR, DSC, CD, tensile strength measurement, water uptake and swelling behavior. In vitro cell adhesion and cell proliferation tests were carried out to study the biocompatibility behavior and their application as an artificial skin substitute. Both KG and KC composite scaffolds showed similar properties and patterns for cell proliferation. Due to rapid degradation of gelatin in KG, we found that it has limited application as compared to KC scaffold. We conclude that KC scaffold owing to its slow degradation and antibacterial properties would be a better substrate for tissue engineering and other biomedical application.     

Effect of eggshell and silk fibroin on styrene–ethylene/butylene–styrene as bio-filler

SEBS (poly(styrene-b-ethylene/butylene-b-styrene)) biodegradable composites reinforced with various eggshell contents and silk fibroin are prepared by melt processing technique followed by different characterization techniques. Compare with SEBS/eggshell composites, the SEBS/eggshell/silk composites exhibit the reduction in particle size and increase interface interaction within the matrix. Thermal stability also increases in quantity.     

Bioactive microspheres produced from gelatin–siloxane hybrids for bone regeneration

In this study, we produced a novel microsphere with a hybridized composition of gelatin and siloxane which is bioactive and degradable for the applications in bone regeneration fields. A solution of gelatin organic and siloxane inorganic containing calcium chloride was formulated into microspheres in an oil bath mediated by a surfactant. Following the processes of hydration, gelation and solidification, well-shaped spherical particles were produced with sizes of a few to hundreds of micrometers (68 μm on average). The obtained microspheres were highly stable in an aqueous solution due to the in situ cross-linking of the siloxane with gelatin chains, which eliminated the additional cross-linking step generally used in pure gelatin. The hybridized microspheres exhibited rapid induction of apatite-like crystals on their surface with incubation in a simulated body fluid, suggesting an excellent bone bioactivity in vitro. It is considered that the newly developed organic–inorganic microspheres may be useful for the regeneration of skeletal defects.     

Electrospun fibrous web of collagen–apatite precipitated nanocomposite for bone regeneration

Electrospinning is regarded as a facile tool to generate biomaterials into a nanofibrous structure. Herein a nanofibrous web constituted of collagen and hydroxyapatite (HA) was produced from their co-precipitated nanocomposite solution by using the electrospinning method. The co-precipitated sol was freeze-dried and the dried product was dissolved in an organic solvent for the electrospinning. The electrospun web showed a well-developed nanofibrous structure with HA contents of up to 20 wt%. The internal structure of the collagen-20 wt%HA nanofiber revealed highly elongated apatite nanocrystallines precipitated within the collagen matrix. However, above the HA content of 30 wt% the nanofibrous structure could not be preserved due to the formation of beads. The MC3T3-E1 osteoblastic cells were shown to adhere and grow actively on the collagen-HA nanofibrous web. The alkaline phosphatase (ALP) activity expressed by the cells on the collagen-20 wt%HA nanofiber was lower at day 7, but was higher at day 14 than that on the pure collagen nanofiber. Based on the study, the newly-developed collagen-HA nanofiber may be useful as a cell supporting substrate in bone regeneration area.     

Preparation of regenerated silk sericin/silk fibroin blend microparticles by emulsification–diffusion method for controlled release drug delivery

This study reports drug-loaded silk sericin (SS)/silk fibroin (SF) blend microparticles being fabricated by the water-in-oil emulsion solvent diffusion of a SS/SF aqueous blend solution. Blue dextran was used as the water-soluble drug model. The influence of the SS/SF blend ratio on the characteristics and drug release behavior of the blend microparticles was investigated. The blend microparticles were analyzed by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and UV-vis spectroscopy. The blend microparticles were nearly spherical in shape as determined from SEM micrographs. The FTIR and TG results demonstrated that interactions between SS and SF molecules had occurred. The blend microparticles showed very high drug loading efficiency (94–98%) for all blend ratios. The in vitro drug release significantly decreased with decreasing SS blend ratio. The results demonstrated that the SS/SF blend microparticles could be used as biocompatible and biodegradable microparticles for controlled release drug delivery applications.     

Fabrication of glycidyl methacrylate-modified silk fibroin/poly(L-lactic acid-co-ε-caprolactone)–polyethylene glycol diacrylate hybrid 3D nanofibrous scaffolds for tissue engineering

In order to provide a biomimetic natural extracellular matrix microenvironment with excellent mechanical capacity for tissue regeneration, a novel porous hybrid glycidyl methacrylate-modified silk fibroin/poly(L-lactic acid-co-ε-caprolactone)–polyethylene glycol diacrylate (SFMA/P(LLA-CL)–PEGDA) hybrid three-dimensional (3D) nanofibrous scaffolds was successfully fabricated through the combination of 3D nanofibrous platforms and divinyl PEGDA based photocrosslinking, and then further improved water resistance by ethanol vapor post-treatment. Scanning electron microscopy and micro-computed tomography results demonstrated significant PEGDA hydrogel-like matrices bonded nanofibers, which formed a 3D structure similar to that of “steel bar (nanofibers)‒cement (PEGDA)”, with proper pore size, high porosity, and high pore connectivity density. Meanwhile, the hybrid 3D nanofibrous scaffolds showed outstanding swelling properties as well as improved compressive and tensile properties. Furthermore, these hybrid 3D nanofibrous scaffolds could provide a biocompatible microenvironment, capable of inducing the material‒cell hybrid and regulating human umbilical vein endothelial cells proliferation. They thus present significant potential in tissue regeneration.     

PLLA–collagen and PLLA–gelatin hybrid scaffolds with funnel-like porous structure for skin tissue engineering

Abstract

In skin tissue engineering, a three-dimensional porous scaffold is necessary to support cell adhesion and proliferation and to guide cells moving into the repair area in the wound healing process. Structurally, the porous scaffold should have an open and interconnected porous architecture to facilitate homogenous cell distribution. Moreover, the scaffolds should be mechanically strong to protect deformation during the formation of new skin. In this study, the hybrid scaffolds were prepared by forming funnel-like collagen or gelatin sponge on a woven poly(l-lactic acid) (PLLA) mesh. The hybrid scaffolds combined the advantages of both collagen or gelatin (good cell-interactions) and PLLA mesh (high mechanical strength). The hybrid scaffolds were used to culture dermal fibroblasts for dermal tissue engineering. The funnel-like porous structure promoted homogeneous cell distribution and extracellular matrix production. The PLLA mesh reinforced the scaffold to avoid deformation. Subcutaneous implantation showed that the PLLA–collagen and PLLA–gelatin scaffolds promoted the regeneration of dermal tissue and epidermis and reduced contraction during the formation of new tissue. These results indicate that funnel-like hybrid scaffolds can be used for skin tissue regeneration.     

PLLA–collagen and PLLA–gelatin hybrid scaffolds with funnel-like porous structure for skin tissue engineering

In skin tissue engineering, a three-dimensional porous scaffold is necessary to support cell adhesion and proliferation and to guide cells moving into the repair area in the wound healing process. Structurally, the porous scaffold should have an open and interconnected porous architecture to facilitate homogenous cell distribution. Moreover, the scaffolds should be mechanically strong to protect deformation during the formation of new skin. In this study, the hybrid scaffolds were prepared by forming funnel-like collagen or gelatin sponge on a woven poly(l-lactic acid) (PLLA) mesh. The hybrid scaffolds combined the advantages of both collagen or gelatin (good cell-interactions) and PLLA mesh (high mechanical strength). The hybrid scaffolds were used to culture dermal fibroblasts for dermal tissue engineering. The funnel-like porous structure promoted homogeneous cell distribution and extracellular matrix production. The PLLA mesh reinforced the scaffold to avoid deformation. Subcutaneous implantation showed that the PLLA–collagen and PLLA–gelatin scaffolds promoted the regeneration of dermal tissue and epidermis and reduced contraction during the formation of new tissue. These results indicate that funnel-like hybrid scaffolds can be used for skin tissue regeneration.     

Citicoline–liposome/polyurethane composite scaffolds regulate the inflammatory response of microglia to promote nerve regeneration

Journal of Materials Science - Regulating the immune microenvironment around the central neurons is a difficult problem. To address this critical matter, drug-loading scaffolds are promising ways...     

In vitro and in vivo evaluation of chitosan–gelatin scaffolds for cartilage tissue engineering

Chitosan–gelatin polyelectrolyte complexes were fabricated and evaluated as tissue engineering scaffolds for cartilage regeneration in vitro and in vivo. The crosslinker for the gelatin component was selected among glutaraldehyde, bisepoxy, and a water-soluble carbodiimide (WSC) based upon the proliferation of chondrocytes on the crosslinked gelatin. WSC was found to be the most suitable crosslinker. Complex scaffolds made from chitosan and gelatin with a component ratio equal to one possessed the proper degradation rate and mechanical stability in vitro. Chondrocytes were able to proliferate well and secrete abundant extracellular matrix in the chitosan–gelatin (1:1) complex scaffolds crosslinked by WSC (C1G1_WSC) compared to the non-crosslinked scaffolds. Implantation of chondrocytes-seeded scaffolds in the defects of rabbit articular cartilage confirmed that C1G1_WSC promoted the cartilage regeneration. The neotissue formed the histological feature of tide line and lacunae in 6.5 months. The amount of glycosaminoglycans in C1G1_WSC constructs (0.187 ± 0.095 μg/mg tissue) harvested from the animals after 6.5 months was 14 wt.% of that in normal cartilage (1.329 ± 0.660 μg/mg tissue). The average compressive modulus of regenerated tissue at 6.5 months was about 0.539 MPa, which approached to that of normal cartilage (0.735 MPa), while that in the blank control (3.881 MPa) was much higher and typical for fibrous tissue. Type II collagen expression in C1G1_WSC constructs was similarly intense as that in the normal hyaline cartilage. According to the above results, the use of C1G1_WSC scaffolds may enhance the cartilage regeneration in vitro and in vivo.     

Elastomer modified polypropylene–polyethylene blends as matrices for wood flour–plastic composites

Blends of polyethylene (PE) and polypropylene (PP) could potentially be used as matrices for wood–plastic composites (WPCs). The mechanical performance and morphology of both the unfilled blends and wood-filled composites with various elastomers and coupling agents were investigated. Blending of the plastics resulted in either small domains of the minor phase in a matrix of major phase or a co-continuous morphology if equal amounts of HDPE and PP were added. The tensile moduli and yield properties of the blends were clearly proportional to the relative amounts of HDPE and PP in the blends. However, the nominal strain at break and the notched Izod impact energies of HDPE were greatly reduced by adding as little as 25% of the PP. Adding an ethylene–propylene–diene (EPDM) elastomer to the blends, reduced moduli and strength but increased elongational properties and impact energies, especially in HDPE-rich blends. Adding wood flour to the blends stiffened but embrittled them, especially the tougher, HDPE-rich blends, though the reductions in performance could be offset somewhat by adding elastomers and coupling agents or a combination of both.     

Towards ready-to-use 3-D scaffolds for regenerative medicine: adhesion-based cryopreservation of human mesenchymal stem cells attached and spread within alginate–gelatin cryogel scaffolds

Cultivation and proliferation of stem cells in three-dimensional (3-D) scaffolds is a promising strategy for regenerative medicine. Mesenchymal stem cells with their potential to differentiate in various cell types, cryopreserved adhesion-based in fabricated scaffolds of biocompatible materials can serve as ready-to-use transplantation units for tissue repair, where pores allow a direct contact of graft cells and recipient tissue without further preparation. A successful cryopreservation of adherent cells depends on attachment and spreading processes that start directly after cell seeding. Here, we analyzed different cultivation times (0.5, 2, 24 h) prior to adhesion-based cryopreservation of human mesenchymal stem cells within alginate–gelatin cryogel scaffolds and its influence on cell viability, recovery and functionality at recovery times (0, 24, 48 h) in comparison to non-frozen control. Analysis with confocal laser scanning microscopy and scanning electron microscopy indicated that 2 h cultivation time enhanced cryopreservation success: cell number, visual cell contacts, membrane integrity, motility, as well as spreading were comparable to control. In contrast, cell number by short cultivation time (0.5 h) reduced dramatically after thawing and expanded cultivation time (24 h) decreased cell viability. Our results provide necessary information to enhance the production and to store ready-to-use transplantation units for application in bone, cartilage or skin regenerative therapy.     

Pressure drop correlation for oil–refrigerant R134a mixture flashing flow in a small diameter tube

This paper presents an experimental investigation of the ester oil ISO VG10/refrigerant R134a mixture flashing flow in a 6.0 m long, 3.22 mm ID tube, which is one of the primary steps towards the construction of a methodology for the study of the lubrication and gas leakage in refrigeration compressors. The phase change starts with solubility reduction of the refrigerant in the oil as the pressure decreases due to the friction forces. In this flashing flow the foam pattern is observed at the end of the tube as vapor quality reaches high values, and this is a particular phenomenon of this kind of mixture flow. In order to study this pressure drop, an experimental apparatus was designed to allow the measurement of both pressure and temperature profiles along the tube as well as the visualization of the flow patterns. Pressure and temperature distribution along the flow were measured for saturation pressure ranging from 450 to 650 kPa, mass flux ranging from about 2000 to 3000 kg/(m²s), temperatures around 303 K, and inlet refrigerant concentration varying between 0.2 and 0.4 kg ref/kg mixt. An available correlation proposed to predict the frictional pressure drop for a mixture composed by the mineral oil SUNISO 1GS and refrigerant R12 flowing in small diameter tubes yielded large deviations in predicting the ester oil and refrigerant R134a mixture flow. A new correlation has been proposed that fitted the experimental data with rms deviations of 24%.     

Hydrogel–elastomer composite biomaterials: 4. Experimental optimization of hydrogel–elastomer composite fibers for use as a wound dressing

We report a novel 3-D cavity wound dressing based on a hydrogel–elastomer Interpenetrating Polymer Network (IPN) fabricated into an open-mesh architecture. IPN fibers used to form the dressing were produced by a wet spinning method and optimized in two steps. A factorial experiment was first conducted to identify key parameters that controlled fiber properties. We observed that gelatin wt% played a major role in determining fiber yield, swelling, strength and stability. Other contributing factors included coagulation solution composition, gelatin type, and pre- and post-UV irradiation time. The key factors were then further evaluated individually to achieve a condition that provided a combination of good swelling, mechanical properties and stability. The concentration of the gelatin/HydroThane^TM extrusion solution significantly affected fiber formation and properties, presumably due to the changes in solution viscosity. The effects of pre-UV irradiation were also ascribed to its impact on the solution viscosity and became negligible at higher concentrations when viscosity is mainly controlled by concentration. The composition of the coagulation bath influenced the fiber swelling and wet stress. These results, taken together with our previous studies, suggest that our biomaterial would provide a combination of mechanical and swelling properties suitable for wound dressing applications.     

Self-assembled 3D ACF–rGO–TiO2 composite as efficient and recyclable spongy adsorbent for organic dye removal

Reduced graphene oxide (rGO) nanosheets (NSs) decorated with TiO₂ nanoparticles (NPs) were bound to activated carbon fibers (ACF) forming three-dimensional (3D) macroscopic composites with nanoscale building blocks by a one-pot hydrothermal self-assembly method. The integration of adsorption capacity enhanced by rGO NSs and photocatalytic activity introduced by TiO₂ NPs in the resultant ACF–rGO–TiO₂ composite was demonstrated via the proof-of-concept application of disposing organic dyes, i.e. Rhodamine B (RhB). Moreover, the photocatalytic degradation of laden RhB dye can effectively make ACF–rGO–TiO₂ composites regenerate the adsorption capacity, promoting two practical values: (1) eliminating rather than removing dye pollutants and (2) recycling rather than consuming adsorbents. The synergistic functionalization highlights the potential of 3D ACF–rGO–TiO₂ composite as a promising massive adsorbent with photocatalytic activities for environment purifications.     

Cobalt–nickel composite films synthesized by chemical bath deposition method as an electrode material for supercapacitors

Cobalt–nickel (Co–Ni) composite thin films were fabricated on copper substrates using a simple chemical bath deposition route in an ammonia-complexed solution containing cobalt chloride and nickel chloride. The structural and morphological properties of the film confirmed that the chemically deposited Co–Ni composites formed in the hydroxide phase and were well covered with irregular shaped nano-platelets. The chemically deposited Co–Ni composite electrode exhibited a maximum specific capacitance of 324 F/g, which was much larger than that of the pristine components. The cyclic voltammetry and charge–discharge test showed that the capacitance of the chemically deposited Co–Ni composite electrode mainly consisted of a pseudocapacitance.