Substrates For Tissue Engineering Research Articles

2D imprinted substrates and 3D electrospun scaffolds revolutionize biomedicine.

Momentous advances in engineering in the 1980s and 1990s reduced significantly the manufacturing cost of equipment that can produce nano to low microscale materials. This was a key milestone in the field of biomedicine, as from the early 2000s, we entered the era of nanobiomedicine. Essentially, with very low capital cost, every laboratory in the world could develop cell culture substrates and/or implantable devices with morphological features down to the nanometer scale. The rationale of using such small dimensional features derives from the fact that the extracellular space is comprised of nanoto microscale supramolecular assemblies. Further, cells employ probing filopodia extensions and contractile intracellular machinery to gather topographical, spatial, mechanical and chemical information from the extracellular environment, which consequently determines cell functionality, lineage commitment and fate. Among the various fabrication technologies, lithography constitutes the most popular 2D top-down method, while electrospinning represents the most widely used 3D bottomup method [1–7]. The produced 2D and 3D constructs have enabled the study of cell and tissue responses at previously economical and technological prohibiting small scales and the rational design thereof for a specific application/clinical indication. Key to the design tenant is that topographical features and morphological structures should promote cellular polarization and organized extracellular matrix assembly, resembling the natural conformation of tissues. Using photolithography back in 1983, microscale V-shape grooves were created to study human gingival and porcine epithelial cell response [8]. By 1997, we were in a position to fabricate substrates with feature (square) accuracy down to 14 nm (depth) to study Xenopus neurites outgrowth using electron-beam lithography [9,10]. To date, we have successfully imprinted various gratings and geometric shapes along different scales onto thermoplastic polymers to create biologically relevant topographical interfaces. Data obtained from these and other studies clearly illustrate that topographical features are powerful modulators of cell morphology and differential function [11–15]. Further, nanoand microscale arrays have been shown to be potent tools in maintaining the phenotype fidelity of permanently differentiated cells and in differentiating stem cells toward specific lineages [16,17]. Multiple topographic arrays have also been used as high-throughput systems to elucidate the cell–surface interactions and enable identification of improved surfaces for optimal/required cell response [18,19]. Specifically, topographical features have been shown to directly modulate cell–material interaction and to affect the composition, orientation and conformation of adsorbed extracellular matrix components [20,21]. Further, nanoimprinted materials have been shown to either 2D imprinted substrates and 3D electrospun scaffolds revolutionize biomedicine

An Ultra-thin Amniotic Membrane as Carrier in Corneal Epithelium Tissue-Engineering.

Amniotic membranes (AMs) are widely used as a corneal epithelial tissue carrier in reconstruction surgery. However, the engineered tissue transparency is low due to the translucent thick underlying AM stroma. To overcome this drawback, we developed an ultra-thin AM (UAM) by using collagenase IV to strip away from the epithelial denuded AM (DAM) some of the stroma. By thinning the stroma to about 30 μm, its moist and dry forms were rendered acellular, optically clear and its collagen framework became compacted and inerratic. Engineered rabbit corneal epithelial cell (RCEC) sheets generated through expansion of limbal epithelial cells on UAM were more transparent and thicker than those expanded on DAM. Moreover, ΔNp63 and ABCG2 gene expression was greater in tissue engineered cell sheets expanded on UAM than on DAM. Furthermore, 2 weeks after surgery, the cornea grafted with UAM based cell sheets showed higher transparency and more stratified epithelium than the cornea grafted with DAM based cell sheets. Taken together, tissue engineered corneal epithelium generated on UAM has a preferable outcome because the transplanted tissue is more transparent and better resembles the phenotype of the native tissue than that obtained by using DAM for this procedure. UAM preserves compact layer of the amniotic membrane and maybe an ideal substrate for corneal epithelial tissue engineering.

Incorporation of chitosan nanoparticles into silk fibroin-based porous scaffolds: Chondrogenic differentiation of stem cells

ABSTRACTA silk fibroin-chondroitin sulfate-sodium alginate (SF-CHS-SA) porous scaffold containing chitosan nanoparticles (NPs) was investigated. The proliferation of adipose-derived stem cells (ASCs) was studied by SEM, fluorescent microscopy, alcian blue staining, dimethylmethylene blue assay, and real-time polymerization chain reaction. The results showed that incorporation of NPs into the scaffold improved compressive modulus (5.6 ± 0.15 MPa). The amount of glycosaminoglycan expression of the ASCs was reached to 8.9 ± 0.3 µg/mL. The gene expressions of aggrecan, collagen II, and SOX9 of the ASCs were significantly improved. This study revealed that the prepared scaffold can be used as a substrate for cartilage tissue engineering.

Preparation and characterization of poly (hydroxy butyrate)/chitosan blend scaffolds for tissue engineering applications.

Background:Poly (hydroxy butyrate) (PHB) is a biodegradable and biocompatible polymer with good mechanical properties. This polymer could be a promising material for scaffolds if some features improve.Materials and Methods:In the present work, new PHB/chitosan blend scaffolds were prepared as a three-dimensional substrate in cartilage tissue engineering. Chitosan in different weight percent was added to PHB and solved in trifluoroacetic acid. Statistical Taguchi method was employed in the design of experiments.Results:The Fourier-transform infrared spectroscopy test revealed that the crystallization of PHB in these blends is suppressed with increasing the amount of chitosan. Scanning electron microscopy images showed a thin and rough top layer with a nodular structure, supported with a porous sub-layer in the surface of the scaffolds. In vitro degradation rate of the scaffolds was higher than pure PHB scaffolds. Maximum degradation rate has been seen for the scaffold with 90% wt. NaCl and 40% wt. chitosan.Conclusions:The obtained results suggest that these newly developed PHB/chitosan blend scaffolds may serve as a three-dimensional substrate in cartilage tissue engineering.

Core-shell polyurethane nanofibers with shape memory for drug release applications

Event Abstract Back to Event Core-shell polyurethane nanofibers with shape memory for drug release applications Ewa Kijeńska1, Monika Bil1, Mariusz Uchman2 and Wojciech Swieszkowski1 1 Warsaw University of Technology, Faculty of Materials Science and Engineering, Poland 2 Charles University in Prague, Faculty of Science, Czechia Introduction: Coaxially electrospun polymeric nanofibers are promising carriers for versatile bio-active agents, growth factors and drugs, allowing for their control release. On the other hand shape memory polyurethanes have excellent thermal shape memory effect and demonstrate high biocompatibility. Thus recently core-shell nanofibers based on this kind of polymers have gained much attention in various biomedical applications like cardiovascular stents. In this study preliminary investigation of electrospun fibers made of polyurethane and polyurethane/gelatine with encapsulated microspheres towards drug release and shape memory was performed. Materials and Methods: Polyurethane PCL/PLLA with shape memory based on PCL and PLLA was synthesized by polymerization in our laboratory. PCL-PEO nanoparticles ere prepared according to the protocol: 10mg of each copolymer was added to 90% THF/water mixtures and left shaken overnight till full dissolution copolymers was achieved. Then solutions were added drop-by-drop to water under vigorous stirring. Finally the solutions were dialyzed against water. In our experiments, for comparison, core –shell fibers with PCL/PLLA; PCL/PLLA:Gelatin [90:10], PCL/PLLA:Gelatin [80:20] in HFP as a shell and microspheres in water as a core, were prepared using the co-axial electrospinning. Results and Discussion: Electrospun uniform and bead free fibrous structures were successfully fabricated using co-axial electrospinning. SEM micrographs (Fig.1) of electrospun mesh revealed porous, beadless, fibrous topography. TEM investigation confirmed core-shell character of obtained fibers. Contact angle measurements data supported the fact that the incorporation of gelatin made meshes more hydrophillic compared fibers with pure polyurethane shell, thus more sufficient for biomedical applications. Release studies showed potential of use of this types of fibers for encapsulation of the drug loaded microspheres. Conclusions: Our studies suggest the potential application of co-axially electrospun PCL/PLLA polyurethane fibrous carriers with encapsulated drug loaded microspheres as a suitable substrate for target tissue engineering and indicate co-axial electrospinning technique as a promising method for fabrication of polyurethane fibers with improved functionality. The authors would like to thank the National Centre for Research and Development (Grant no: LIDER/037/673/L-4/12/NCBR/2013) for providing financial support to this project. Keywords: nanofiber, Polymeric material, medical application, Biofunction Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Electrospinning and related technologies Citation: Kijeńska E, Bil M, Uchman M and Swieszkowski W (2016). Core-shell polyurethane nanofibers with shape memory for drug release applications. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.02867 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Ewa Kijeńska Monika Bil Mariusz Uchman Wojciech Swieszkowski Google Ewa Kijeńska Monika Bil Mariusz Uchman Wojciech Swieszkowski Google Scholar Ewa Kijeńska Monika Bil Mariusz Uchman Wojciech Swieszkowski PubMed Ewa Kijeńska Monika Bil Mariusz Uchman Wojciech Swieszkowski Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Direct cellular organization with ring-shaped composite polymers and glass substrates for urethral sphincter tissue engineering.

Although fundamental efforts have been made to engineer circular smooth muscle layers in vitro, engineering structured skeletal muscle tissue equivalents acting as sphincters remains to be investigated. Groove patterned substrates made of homogeneous materials usually lead to cell monolayers instead of patterned cell sheets while patterned matrices failed to generate circular myotubes because cell chirality blocks the end-to-end cellular sequence corresponding to pattern directions. In this paper, we proposed concentric circular and elliptical microgroove patterned substrates with glass substrates as grooves and polymers as ridges to direct ring-shaped myoblast patterns and maximize cell alignment with respect to constraint directions, which are essential for circular myotube generation towards sphincter tissue engineering. Our results showed that our substrates direct myoblasts to proliferate in and orient along the directions of glass grooves, leading to a higher cell alignment degree than homogeneous substrates can achieve. We also found that the cell alignment degree depends on dimensions and parallelism rather than the curvature of the constraint. On the basis of these findings, we proposed finite element models that quantitatively account for our experimental data and emphasized the role of intercellular forces in cell alignment modulation. These results suggest that narrow curved constraints with parallel boundaries can favourably maximize myoblast alignment and facilitate myogenic differentiation regardless of constraint curvature, which will underpin the design of substrates and scaffolds for urethral sphincter or other hollow tissue engineering applications.

Bio-Functionalized N-Isopropylacrylamide-Co-Glycidylmethacrylate as a Customized Thermoresponsive Substrate for Corneal Tissue Engineering

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Photocurable gelatin hydrogels for cell encapsulation

Event Abstract Back to Event Photocurable gelatin hydrogels for cell encapsulation Timothy Hughes1*, Lingli Li1, 2*, Conglie Lu2*, Mei Chen2*, Huixiang Ma2*, Lei Wang3*, Xiaojuan Hao1*, Keith Mclean1* and Chen Hao2, 3* 1 CSIRO, Manufacturing, Australia 2 Wenzhou Medical University, Wenzhou Eye Hospital, China 3 Wenzhou Institute of Biomaterials and Engineering, China Introduction: Tissue engineering requires the implantation of cells along with a supportive scaffold. As such, degradable support scaffolds that are amenable to minimally invasive implantation are attractive. With this in mind, we have explored the use of phototriggered thiol-ene reactions as a method to produce injectable and photocurable cell supportive scaffolds that can be cured in the presence of cells (Figure 1). Figure 1: Conceptual diagram of in situ cured scaffold in the presence of cells Materials and Methods: Type A Porcine skin (Bloom 100) Gelatin (Sigma Aldrich) was used for experiments. Vinyl functionalised gelatines were produced from gelatine and vinyl anhydrides (eg: acrylate and pentanoic anhydride)[1]. While thiolylated gelatin was prepared from gelatin and cysteine with EDC and NHS[1]. The products were purified by dialysis (1 kDa MWCO) and freeze dried before being reconstituted with saline (0.9 %). Light triggered thiol-ene reactions were used to crosslink the vinyl functionalised gelatins with multifunctional thiols included thiolated gelatin. The rheological properties of the precursor formulations as well as the final gels and their cure profiles were measured using photorheology. The effect of solids content, ratio of components and light intensity were investigated. The water content, optical transparency and mechanical properties and microscopic morphologies of the gels were also measured. The ability of bovine corneal endothelial cells (bCECs) and fibroblast cells (L929) to grow on the gels was investigated. The in situ curing of gels in the presence of living cells was also explored. Finally a gelatin hydrogel was cured in situ to fill corneal defects in rabbits(trephine, 3 mm diameter by 200 μm deep) to assess the corneal biocompatibility of the hydrogels. Results and Discussion: Thiol-ene crosslinked gelatins were able to be cured within 2 min. of exposure to 365 nm light resulting in optically transparent gels with water contents about 80-85 %. The resulting soft gels possessed high viability of both L929 and bCECs (>80 %). The mechanical properties of the gels could be tuned by altering the feed ratio of the components and the light intensity used during the cure. Live/Dead staining confirmed that both bCEC and L929 retained high cell viability in culture following in situ cure of the gelatin hydrogels containing the cells (Figure 2). Moreover, laser confocal imaging indicated that the cells were evenly distributed within the hydrogel. Figure 2: 3D Laser confocal fluorescent imaging of L929 cells pre stained with DilC(3) after 7 days of cell culture in a hydrogel matrix prepared from a formulation of 150 mg/ml 2:1 Gel-LA to Gel-SH + Irgacure 2959 (0.5 %) cured with 100 mW/cm2 for 1min Corneal defects in rabbit corneas were filled with in situ cured gelatine hydrogel and the wounded cornea re-epithelialized in 3 to 7 days with minimal inflammation (Figure 3). Figure 3: Slit lamp microscope images of corneal defects at day 1 (left) and 7 (right) stained with fluorescein filled with gelatin hydrogel matrix prepared from a formulation of 150 mg/ml 2:1 Gel-LA to Gel-SH + Irgacure 2959 (0.5 %) cured with 100 mW/cm2 for 1min Conclusions: Phototriggered thiol-ene reactions are rapid and facile methods of forming crosslinked gelatin hydrogels. They resulted in transparent gels with mechanical properties suitable for soft tissue replacements. In addition, they could be cured in the presence of living cells which maintained high viability for over 7 days post crosslinking. Moreover, the in situ cured gels were able to heal rabbit corneal defects in vivo with low inflammation and rapid re-epithelialization. Therefore, the resulting materials are promising candidates for corneal tissue engineering substrates. This study is supported by Chinese Scholarship Council, the International Scientific and Technological Cooperation Project (No. 2012DFB30020) and High-end Foreign Experts Recruitment Program (China, No.GDW20133300101).

Biomimetic polyurethane – Based fibrous scaffolds

The design of biomimetic scaffolds that reproduce the biochemical, mechanical and structural functions of the ECM is a fundamental requirement to develop functional substrate for tissue engineering. To this aim, materials which combine the easy processability and mechanical properties of synthetic polymers with the biochemical cues provided by natural materials, develop positive interaction with cells, enabling tissue regrowth in vivo. In this work, a polyester urethane (NS-BC2000) was synthesised using poly (ε-caprolactone) diol (PCL) as macrodiol, 1,4-diisocyanatobutane (BDI) as diisocyanate and N-Boc serinol as chain extender. After Boc cleavage (S-BC2000) to expose free amino groups, a S-BC2000/PEO (80/20wt./wt.) solution was successfully electrospun fabricating aligned nanofibres with a fibre size of 2.8±0.6µm.The aligned nanofibres were then functionalised with IKVAV peptide that was covalently bound exploiting the presence of free amino groups on S-BC2000 chains.

Nanocomposite scaffold with enhanced stability by hydrogen bonds between collagen, polyvinyl pyrrolidone and titanium dioxide

In this study, three-dimensional (3D) nanocomposite scaffolds, as potential substrates for skin tissue engineering, were fabricated by freeze drying the mixture of type I collagen extracted from porcine skin and polyvinyl pyrrolidone (PVP)-coated titanium dioxide (TiO2) nanoparticles. This procedure was performed without any cross-linker or toxic reagents to generate porosity in the scaffold. Both morphology and thermal stability of the nanocomposite scaffold were examined. The swelling behavior, mechanical properties and hydrolytic degradation of the composite scaffolds were carefully investigated. Our results revealed that collagen, PVP and TiO2 are bonded together by four main hydrogen bonds, which is an essential action for the formation of nanocomposite scaffold. Using Coasts–Redfern model, we were able to calculate the thermal degradation apparent activation energy and demonstrated that the thermal stability of nanocomposites is dependent on amount of PVP incorporated. Furthermore, SEM images showed that the collagen fibers are wrapped and stabilized on scaffolds by PVP molecules, which improve the ultimate tensile strength (UTS). The UTS of PVP-contained scaffold is four times higher than that of scaffold without PVP, whereas ultimate percentage of elongation (UPE) is decreased, and PVP can enhance the degradation resistance.

Surface topography effect on fibroblasts population on epiclon-based polyimide films

A polyimide based on alicyclic units, such as epiclon (5-(2,5-dioxotetrahydrofurfuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride), was investigated from the point of view of its surface features to check their suitability for cell culture applications. Atomic force microscopy data revealed fractal and isotropic surfaces with nanoscale roughness and peaks placed at much smaller distances comparing to the cell size scale, favoring a good compatibility of the synthesized material with the biological medium, particularly after plasma treatment. Surface tension properties were determined in order to evaluate the interactions at the bio-interface affecting the adherence behavior of cell-binding proteins to the sample surface. In vitro experiments regarding the cytocompatibility and population tendency reveal that polyimide allows cells to adhere and to proliferate onto the surface. These tests indicate that the studied epiclon-based polyimide is not cytotoxic and can be recommended as good candidate for cell culture substrate in tissue engineering, especially after plasma treatment.

Mineralization on polylactide/gelatin composite nanofibers using simulated body fluid containing amino acid

From physiological point of view, organic–inorganic composite nanofibers are envisioned promising substrates for bone tissue engineering. Biomineralization on polymeric nanofibers using simulated body fluid (SBF) is a common technique to obtain the composite nanofibers. Many factors, however, will affect the nucleation and crystal growth of deposited apatite, such as the additives like amino acids in SBF. In this study, electrospun composite nanofibers consisting of poly(l-lactide) (PLLA, 50wt%) and gelatin (50wt%) were soaked in 2.5 times SBF (2.5SBF) for different time periods (1, 2, 3, 5 and 7 days) to perform the biomineralization. Three amino acids (glycine, aspartic acid, or arginine) of different charge characteristics were introduced into the SBF, and their effects on nucleation and transformation of calcium phosphate depositions were systematically investigated. The results revealed that amino acids could take part in the early stage formation of pre-nucleation clusters, leading to different assemblies dependent closely on the feature of amino acid. In comparison with normal 2.5SBF, the presence of amino acid was able to enhance the preferred orientation of hydroxyapatite (HA) crystal along c axis and the transformation from amorphous calcium phosphate to hierarchical HA. The incorporation of glycine had promoted the formation of the well-evolved needle-like HA crystals in comparison with aspartic acid or arginine. It was suggested that the addition of amino acids into SBF might be a useful tool to regulate the biomineralizaiton for preparing organic–inorganic composite nanofibers.

Simultaneous electrospun‐electrosprayed biocomposite nanostructured substrates for bone tissue engineering

The objective of this study is to fabricate PLACL, silk fibroin (SF) and hydroxyapatite (HA) biocomposite nanofibrous scaffolds for bone tissue engineering. The fabricated nanofibrous scaffolds have been characterized by SEM, contact angle, functional groups analysis, porosity, mechanical properties and TEM. Hydroxyapatite nanoparticles were electrosprayed on the surface of electrospun nanofibers to achieve rough surface morphology of biocomposite scaffolds for the growth and differentiation of MSCs into osteogenesis. The fabricated scaffolds showed better pore size (1.5-7.8 µm), highly porous (68-93%) with fiber diameterobtained around 213±78 to 340 ± 52 nm and FT-IR analysis observed amide groups, carbonate and phosphate groups in the biocomposite nanofibrous scaffolds. The obtained PLACL/SF/HA (blend) and (spray) scaffolds were hydrophilic having a water contact angle of 35.90±3.42° and 24.57±2.45° compared to PLACL (127.70±3.67°) scaffolds. MSCs cultured on these scaffolds underwent osteogenic differentiation in the presence of SF/HA for mineralization in bone tissue regeneration. Osteogenic differentiation of MSCs was confirmed by alkaline phosphatase activity, mineralization and osteocalcin expression. The observed results proved that the SF/HA loaded biocomposite nanofibrous scaffolds improved the biological functions for the proliferation of cells, ALP activity, differentiation of MSCs into osteogenesis and mineralization for bone tissue engineering.

Cell Alignment Driven by Mechanically Induced Collagen Fiber Alignment in Collagen/Alginate Coatings.

For many years it has been a major challenge to regenerate damaged tissues using synthetic or natural materials. To favor the healing processes after tendon, cornea, muscle, or brain injuries, aligned collagen-based architectures are of utmost interest. In this study, we define a novel aligned coating based on a collagen/alginate (COL/ALG) multilayer film. The coating exhibiting a nanofibrillar structure is cross-linked with genipin for stability in physiological conditions. By stretching COL/ALG-coated polydimethylsiloxane substrates, we developed a versatile method to align the collagen fibrils of the polymeric coating. Assays on cell morphology and alignment were performed to investigate the properties of these films. Microscopic assessments revealed that cells align with the stretched collagen fibrils of the coating. The degree of alignment is tuned by the stretching rate (i.e., the strain) of the COL/ALG-coated elastic substrate. Such coatings are of great interest for strategies that require aligned nanofibrillar biological material as a substrate for tissue engineering.

Luminescence from micro-/nano-scale anodic aluminum oxide containing electrochemical etching derived nanoporous silicon

This paper reports a novel way of the fabrication of micro-/nano-anodic aluminum oxide containing electrochemical derived nanoporous Si (AAO–Si) to achieve strong co-emission of light with controllable intensities. The AAO–Si was fabricated by electrochemical anodizing of aluminum followed by spin coating of nanoporous Si particles onto AAO. The microstructure and its luminescence of micro-/nano-AAO were controlled by electrochemical anodizing times. The fabrication of micro-/nano-AAO containing nanoporous Si resulted in a light-emitting from both AAO and nanoporous Si emission under a single excitation source. These results suggest that the potential application of micro-/nano-AAO contains Si for potential application in optoelectronic and biocompatible substrates for tissue engineering.

Enhanced bioactivity of osteoblast-like cells on poly(lactic acid)/poly(methyl methacrylate)/nano-hydroxyapatite scaffolds for bone tissue engineering

Bone tissue engineering has great potential but requires an appropriate substrate with good bioactivity. In this study, poly(lactic acid) (PLA)/poly(methyl methacrylate) (PMMA)/nano-hydroxyapatite (n-HA) hybrid nanofibrous scaffolds were fabricated via electrospinning. The morphologies of the scaffolds were observed by scanning electron microscopy, transmission electron microscopy and the structures of the scaffolds were measured by fourier transform infrared spectrum. After immersion in simulated body fluid, the more deposition of ball-like apatite can be observed on the surface of the hybrid PLA/PMMA/n-HA scaffold. In vitro degradation experiments showed that the less degradation occurred in the hybrid PLA/PMMA/n-HA scaffold. The studies of cell adhesion and growth capability were investigated by incubating the osteoblast-like cells (MG-63) in the scaffolds, which verified the addition of n-HA could promote the adhesion and proliferation of the Human osteoblast-like cells (MG-63). Hence, the electrospun hybrid PLA/PMMA/n-HA nanofibrous scaffold is a promising biomaterial, propitious to be a substrate for bone tissue engineering.

In vitro degradation study of novel HEC/PVA/collagen nanofibrous scaffold for skin tissue engineering applications

The aim of this study was focused on the degradation behavior of electrospun (hydroxyethyl cellulose/poly(vinyl) alcohol) HEC/PVA and HEC/PVA/collagen nanofibrous scaffolds, as a potential substrates for skin tissue engineering in two biologically related media: phosphate buffered solution (PBS) and Dulbecco's modified Eagle's medium (DMEM) for 12 weeks incubation period. The scaffolds were characterized at different degradation times by a series of analysis including pH changes of solutions, weight loss, swelling ratio, SEM, ATR-FTIR, DSC, TGA and mechanical properties. The results indicated that HEC/PVA/collagen scaffolds were exhibited slower degradation rate in both medium as compared to HEC/PVA blend nanofibers. All fibers displayed uneven and rough surfaces towards the final week of incubation in both PBS and DMEM solution. As degradation time increased, there were little changes in the chemical structure as determined by FTIR spectra while thermal studies revealed that the melting temperatures and crystallinity of scaffolds were slightly shifted to a lower value. Both HEC/PVA and HEC/PVA/collagen fibers showed significant decrease in Young's modulus and tensile stress over 12 weeks degradation. These results show that these nanofibrous scaffold demonstrate degradation behavior that meets the requirement as potential degradable biomaterials for dermal replacement.

Functionalized hybrid nanofibers to mimic native ECM for tissue engineering applications

Nanotechnology being one of the most promising technologies today shows an extremely huge potential in the field of tissue engineering to mimic the porous topography of natural extracellular matrix (ECM). Natural polymers are incorporated into the synthetic polymers to fabricate functionalized hybrid nanofibrous scaffolds, which improve cell and tissue compatibility. The present study identified the biopolymers – aloe vera, silk fibroin and curcumin incorporated into polycaprolactone (PCL) as suitable substrates for tissue engineering. Different combinations of PCL with natural polymers – PCL/aloe vera, PCL/silk fibroin, PCL/aloe vera/silk fibroin, PCL/aloe vera/silk fibroin/curcumin were electrospun into nanofibrous scaffolds. The fabricated two dimensional nanofibrous scaffolds showed high surface area, appropriate mechanical properties, hydrophilicity and porosity, required for the regeneration of diseased tissues. The nanofibrous scaffolds were characterized by Scanning electron microscope (SEM), porometry, Instron tensile tester, VCA optima contact angle measurement and FTIR to analyze the fiber diameter and morphology, porosity and pore size distribution, mechanical strength, wettability, chemical bonds and functional groups, respectively. The average fiber diameter of obtained fibers ranged from 250nm to 350nm and the tensile strength of PCL scaffolds at 4.49MPa increased upto 8.3MPa for PCL/silk fibroin scaffolds. Hydrophobicity of PCL decreased with the incorporation of natural polymers, especially for PCL/aloe vera scaffolds. The properties of as-spun nanofiber scaffolds showed their potential as promising scaffold materials in tissue engineering applications.

Metal cation cross-linked nanocellulose hydrogels as tissue engineering substrates.

The use of cellulose materials for biomedical applications is attractive due to their low cost, biocompatibility, and biodegradability. Specific processing of cellulose to yield nanofibrils further improves mechanical properties and suitability as a tissue engineering substrate due to the similarity to the fibrous structure, porosity, and size-scale of the native extracellular matrix. In order to generate the substrate, nanocellulose hydrogels were fabricated from carboxylated cellulose nanofibrils via hydrogelation using metal salts. Hydrogels cross-linked with Ca(2+) and Fe(3+) were investigated as tissue culture substrates for C3H10T1/2 fibroblast cells. Control substrates as well as those with physically adsorbed and covalently attached fibronectin protein were evaluated with X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), and enzyme linked immunosorbent assay (ELISA). Significantly more cells were attached to surfaces modified with protein, with the highest number of cells adhered to the calcium cross-linked hydrogels with covalently attached protein.

Galactose grafting on poly(ε-caprolactone) substrates for tissue engineering: a preliminary study

The grafting of galactose units onto poly(ε-caprolactone) (PCL) substrates by a wet chemistry two-step procedure is proposed. Even though a reduction of hardness from 0.58–0.31GPa to 0.12–0.05GPa is achieved, the chemical functionalization does not negatively affect the tensile modulus (332.2±31.3MPa and 328.5±34.7MPa for unmodified and surface-modified PCL, respectively) and strength (15.1±1.3MPa and 14.8±1.5MPa as assessed before and after the surface modification, respectively), as well as the mechanical behaviour evaluated through small punch test. XPS and enzyme-linked lectin assay (ELLA) demonstrate the presence, and also the correct exposition of the saccharidic epitope on PCL substrates. The introduction of carbohydrate moieties on the PCL surfaces clearly enhances the hydrophilicity of the substrate, as the water contact angle decreases from 82.1±5.8° to 62.1±4.2°. Furthermore, preliminary biological analysis shows human mesenchymal stem cell viability over time and an improvement of cell adhesion and spreading.