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1.
Carbohydr Polym ; 153: 619-630, 2016 Nov 20.
Article in English | MEDLINE | ID: mdl-27561534

ABSTRACT

Novel Cellulose (Cel) reinforced polyvinyl alcohol (PVA)-Silica (Si) composite which has good stability and in vitro degradation was prepared by lyophilization technique and implanted using N(3+) ions of energy 24keV in the fluences of 1×10(15), 5×10(15) and 1×10(16)ions/cm(2). SEM analysis revealed the formation of microstructures, and improved the surface roughness on ion implantation. In addition to these structural changes, the implantation significantly modified the luminescent, thermal and mechanical properties of the samples. The elastic modulus of the implanted samples has increased by about 50 times compared to the pristine which confirms that the stiffness of the sample surface has increased remarkably on ion implantation. The photoluminescence of the native cellulose has improved greatly due to defect site, dangling bonds and hydrogen passivation. Electric conductivity of the ion implanted samples was improved by about 25%. Hence, low energy ion implantation tunes the mechanical property, surface roughness and further induces the formation of nano structures. MG63 cells seeded onto the scaffolds reveals that with the increase in implantation fluence, the cell attachment, viability and proliferation have improved greatly compared to pristine. The enhancement of cell growth of about 59% was observed in the implanted samples compared to pristine. These properties will enable the scaffolds to be ideal for bone tissue engineering and imaging applications.


Subject(s)
Cellulose/chemistry , Polyvinyl Alcohol/chemistry , Silicon Dioxide/chemistry , Tissue Scaffolds/chemistry , Biocompatible Materials/chemistry , Cell Adhesion , Cell Line , Elastic Modulus , Electric Conductivity , Gossypium/chemistry , Humans , Ions/chemistry , Luminescence , Luminescent Agents/chemistry , Porosity , Surface Properties
2.
Mater Sci Eng C Mater Biol Appl ; 61: 651-8, 2016 Apr 01.
Article in English | MEDLINE | ID: mdl-26838893

ABSTRACT

This study examines a biocompatible scaffold series of random copolymer networks P(EA-HEA) made of Ethyl Acrylate, EA, and 2-Hydroxyl Ethyl Acrylate, HEA. The P(EA-HEA) scaffolds have been synthesized with varying crosslinking density and filled with a Poly(Vinyl Alcohol), PVA, to mimic the growing cartilaginous tissue during tissue repair. In cartilage regeneration the scaffold needs to have sufficient mechanical properties to sustain the compression in the joint and, at the same time, transmit mechanical signals to the cells for chondrogenic differentiation. Mechanical tests show that the elastic modulus increases with increasing crosslinking density of P(EA-HEA) scaffolds. The water plays an important role in the mechanical behavior of the scaffold, but highly depends on the crosslinking density of the proper polymer. Furthermore, when the scaffold with hydrogel is tested it can be seen that the modulus increases with increasing hydrogel density. Even so, the mechanical properties are inferior than those of the scaffolds with water filling the pores. The hydrogel inside the pores of the scaffolds facilitates the expulsion of water during compression and lowers the mechanical modulus of the scaffold. The P(EA-HEA) with PVA shows to be a good artificial cartilage model with mechanical properties close to native articular cartilage.


Subject(s)
Acrylic Resins/chemistry , Cartilage , Tissue Scaffolds/chemistry , Porosity
3.
Biomaterials ; 67: 254-63, 2015 Oct.
Article in English | MEDLINE | ID: mdl-26231916

ABSTRACT

The aim of this paper is to present a method to produce macroporous thin membranes made of poly (ethyl acrylate-co-hydroxyethyl acrylate) copolymer network with varying cross-linking density for cell transplantation and prosthesis fabrication. The manufacture process is based on template techniques and anisotropic pore collapse. Pore collapse was produced by swelling the membrane in acetone and subsequently drying and changing the solvent by water to produce 100 microns thick porous membranes. These very thin membranes are porous enough to hold cells to be transplanted to the organism or to be colonized by ingrowth from neighboring tissues in the organism, and they present sufficient tearing stress to be sutured with surgical thread. The obtained pore morphology was observed by Scanning Electron Microscope, and confocal laser microscopy. Mechanical properties were characterized by stress-strain experiments in tension and tearing strength measurements. Morphology and mechanical properties were related to the different initial thickness of the scaffold and the cross-linking density of the polymer network. Seeding efficiency and proliferation of mesenchymal stem cells inside the pore structure were determined at 2 h, 1, 7, 14 and 21 days from seeding.


Subject(s)
Cell Transplantation/methods , Membranes, Artificial , Regenerative Medicine/methods , Actin Cytoskeleton/drug effects , Actin Cytoskeleton/metabolism , Animals , Cell Proliferation/drug effects , Cross-Linking Reagents/pharmacology , DNA/metabolism , Fluorescent Antibody Technique , Mechanical Phenomena , Mesenchymal Stem Cells/cytology , Mesenchymal Stem Cells/drug effects , Porosity , Sus scrofa , Tissue Scaffolds/chemistry , Vinculin/metabolism
4.
J Mech Behav Biomed Mater ; 48: 60-69, 2015 Aug.
Article in English | MEDLINE | ID: mdl-25913609

ABSTRACT

In tissue engineering the design and optimization of biodegradable polymeric scaffolds with a 3D-structure is an important field. The porous scaffold provide the cells with an adequate biomechanical environment that allows mechanotransduction signals for cell differentiation and the scaffolds also protect the cells from initial compressive loading. The scaffold have interconnected macro-pores that host the cells and newly formed tissue, while the pore walls should be micro-porous to transport nutrients and waste products. Polycaprolactone (PCL) scaffolds with a double micro- and macro-pore architecture have been proposed for cartilage regeneration. This work explores the influence of the micro-porosity of the pore walls on water permeability and scaffold compliance. A Poly(Vinyl Alcohol) with tailored mechanical properties has been used to simulate the growing cartilage tissue inside the scaffold pores. Unconfined and confined compression tests were performed to characterize both the water permeability and the mechanical response of scaffolds with varying size of micro-porosity while volume fraction of the macro-pores remains constant. The stress relaxation tests show that the stress response of the scaffold/hydrogel construct is a synergic effect determined by the performance of the both components. This is interesting since it suggests that the in vivo outcome of the scaffold is not only dependent upon the material architecture but also the growing tissue inside the scaffold׳s pores. On the other hand, confined compression results show that compliance of the scaffold is mainly controlled by the micro-porosity of the scaffold and less by hydrogel density in the scaffold pores. These conclusions bring together valuable information for customizing the optimal scaffold and to predict the in vivo mechanical behavior.


Subject(s)
Cartilage/chemistry , Compressive Strength/physiology , Mechanotransduction, Cellular/physiology , Tissue Engineering/methods , Tissue Scaffolds/chemistry , Water/metabolism , Biocompatible Materials , Hydrogel, Polyethylene Glycol Dimethacrylate , Materials Testing , Permeability , Polyesters/chemistry , Porosity
5.
J Biomech ; 48(7): 1310-7, 2015 May 01.
Article in English | MEDLINE | ID: mdl-25814177

ABSTRACT

The aim of this experimental study is to predict the long-term mechanical behavior of a porous scaffold implanted in a cartilage defect for tissue engineering purpose. Fatigue studies were performed by up to 100,000 unconfined compression cycles in a polycaprolactone (PCL) scaffold with highly interconnected pores architecture. The scaffold compliance, stress-strain response and hysteresis energy have been measured after different number of fatigue cycles, while the morphology has been observed by scanning electron microscopy at the same fatigue times. To simulate the growing tissue in the scaffold/tissue construct, the scaffold was filled with an aqueous solution of polyvinyl alcohol (PVA) and subjected to repeating cycles of freezing and thawing that increase the hydrogel stiffness. Fatigue studies show that the mechanical loading provokes failure of the dry scaffold at a smaller number of deformation cycles than when it is immersed in water, and also that 100,000 compressive dynamic cycles do not affect the scaffold/gel construct. This shows the stability of the scaffold implanted in a chondral defect and gives a realistic simulation of the mechanical performance from implantation of the empty scaffold to regeneration of the new tissue inside the scaffold's pores.


Subject(s)
Hydrogel, Polyethylene Glycol Dimethacrylate/chemistry , Polyesters/chemistry , Tissue Engineering/methods , Tissue Scaffolds , Calorimetry, Differential Scanning , Cartilage , Cartilage, Articular/physiology , Compressive Strength , Humans , Materials Testing , Microscopy, Electron, Scanning , Models, Theoretical , Polyvinyl Alcohol , Porosity , Prostheses and Implants , Regeneration , Tissue Engineering/instrumentation
6.
J Mech Behav Biomed Mater ; 32: 125-131, 2014 Apr.
Article in English | MEDLINE | ID: mdl-24447878

ABSTRACT

A model is proposed to assess mechanical behavior of tissue engineering scaffolds and predict their performance "in vivo" during tissue regeneration. To simulate the growth of tissue inside the pores of the scaffold, the scaffold is swollen with a Poly (Vinyl alcohol) solution and subjected to repeated freezing and thawing cycles. In this way the Poly (Vinyl alcohol) becomes a gel whose stiffness increases with the number of freezing and thawing cycles. Mechanical properties of the construct immersed in water are shown to be determined, in large extent, by the water mobility constraints imposed by the gel filling the pores. This is similar to the way that water mobility determines mechanical properties of highly hydrated tissues, such as articular cartilage. As a consequence, the apparent elastic modulus of the scaffold in compression tests is much higher than those of the empty scaffold or the gel. Thus this experimental model allows assessing fatigue behavior of the scaffolds under long-term dynamic loading in a realistic way, without recourse to animal experimentation.


Subject(s)
Biocompatible Materials , Cartilage, Articular/cytology , Materials Testing , Prostheses and Implants , Tissue Scaffolds , Animals , Elastic Modulus , Humans , Mechanical Phenomena , Polyvinyl Alcohol , Porosity , Rabbits , Stress, Mechanical , Viscosity
7.
J Biomater Appl ; 28(9): 1304-15, 2014 May.
Article in English | MEDLINE | ID: mdl-24108064

ABSTRACT

Polycaprolactone scaffolds modified with cross-linked hyaluronic acid were prepared in order to establish whether a more hydrophilic and biomimetic microenvironment benefits the progenitor cells arriving from bone marrow in a cell-free tissue-engineering approach. The polycaprolactone and polycaprolactone/hyaluronic acid scaffolds were characterized in terms of morphology and water absorption capacity. The polycaprolactone and polycaprolactone/hyaluronic acid samples were implanted in a chondral defect in rabbits; bleeding of the subchondral bone was provoked to generate a spontaneous healing response. Repair at 1, 4, 12, and 24 weeks was assessed macroscopically using the International Cartilage Repair Society score and the Oswestry Arthroscopy Score and microscopically using immunohistological staining for collagen type I and type II, and for Ki-67. The presence of hyaluronic acid improves scaffold performance, which supports a good repair response without biomaterial pre-seeding.


Subject(s)
Hyaluronic Acid/chemistry , Polyesters/chemistry , Tissue Engineering , Tissue Scaffolds , Animals , Cell-Free System , Microscopy, Electron, Scanning , Rabbits , Thermogravimetry
8.
J Biomed Mater Res B Appl Biomater ; 101(6): 991-7, 2013 Aug.
Article in English | MEDLINE | ID: mdl-23529953

ABSTRACT

The aim of this paper is to quantify the adhered fibronectin (FN; by adsorption and/or grafting) and the exposure of its cell adhesive motifs (RGD and FNIII7-10) on poly(ethyl acrylate) (PEA) copolymers whose chemical composition has been designed to increase wettability and to introduce acid functional groups. FN was adsorbed to PEA, poly(ethyl acrylate-co-hydroxyethyl acrylate), poly(ethyl acrylate-co-acrylic acid), and poly(ethyl acrylate-co-methacrylic acid) copolymers, and covalently cross-linked to poly(ethyl acrylate-co-acrylic acid) and poly(ethyl acrylate-co-methacrylic acid) copolymers. Amount of adhered FN and exhibition of RGD and FNIII7- 10 fragments involved in cell adhesion were quantified with enzyme-linked immunosorbent assay tests. Even copolymers with a lower content of the hydrophilic component showed a decrease in water contact angle. In addition, FN was successfully fixed on all surfaces, especially on the hydrophobic surfaces. However, it was demonstrated that exposure of its cell adhesion sequences, which is the key factor in cell adhesion and proliferation, was higher for hydrophilic surfaces.


Subject(s)
Acrylic Resins/chemistry , Coated Materials, Biocompatible/chemistry , Fibronectins/chemistry , Acrylates/chemistry , Adsorption , Amino Acid Motifs , Cell Adhesion , Cells, Cultured , Humans , Materials Testing , Methacrylates/chemistry , Oligopeptides/chemistry , Surface Properties , Wettability
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