ABSTRACT In an effort to design biomaterials that may promote repair of the central nervous system, 3-dimensional scaffolds made of electrospun poly lactic acid nanofibers with interconnected pores were fabricated. These scaffolds were functionalized with polyallylamine to introduce amine groups by wet chemistry. Experimental conditions of the amination protocol were thoroughly studied and selected to introduce a high amount of amine group while preserving the mechanical and structural properties of the scaffold. Subsequent covalent grafting of epidermal growth factor was then performed to further tailor these aminated structures. The scaffolds were then tested for their ability to support Neural Stem-Like Cells (NSLCs) culture. Of interest, NSLCs were able to proliferate on these EGF-grafted substrates and remained viable up to 14 d even in the absence of soluble growth factors in the medium.
Glass ionomer cements (GIC) are known as a non-bioactive dental cement. During setting the GIC have an acidic pH, driven by the acrylic acid component. It is a challenge to make GIC alkaline without disturbing its mechanical properties. One strategy was to add slowly reacting systems with an alkaline pH. The aim of the present study is to investigate the possibility of forming a bioactive dental material based on the combination of glass ionomer cement and calcium silicates. Two types of GIC were used as control. Wollastonite (CS also denoted β-CaSiO3) or Mineral Trioxide Aggregate (MTA) was incorporated into the 2 types of GIC. The material formulations' setting time, compressive strength, pH and bioactivity were compared between modified GIC and GIC control. Apatite crystals were found on the surfaces of the modified cements but not on the control GIC. The compressive strength of the cement remained with the addition of 20% calcium silicate or 20% MTA after one day immersion. In addition, the compressive strength of GIC modified with 20% MTA had been increased during the 14 d immersion (p < 0 .05).
ABSTRACT With the increasing elderly population an increase in the number of bony fractures associated to age-related diseases such as osteoporosis also follows. The relatively high stiffness of the acrylic bone cements used in these patients has been suggested to give raise to a suboptimal load distribution surrounding the cement in vivo, and hence contribute to clinical complications, such as additional fractures. The aim of this study was to develop a low-modulus bone cement, based on currently used, commercially available poly(methyl methacrylate) (PMMA) cements for vertebroplasty. To this end, acrylate end-functionalized oligo(trimethylene carbonate) (oTMC) was incorporated into the cements, and the resulting compressive mechanical properties were evaluated, as well as the cytotoxic and handling properties of selected formulations. Sixteen wt%oTMC was needed in the vertebroplastic cement Osteopal V to achieve an elastic modulus of 1063 MPa (SD 74), which gave a corresponding compressive strength of 46.1 MPa (SD 1.9). Cement extracts taken at 1 and 12 hours gave a reduced MG-63 cell viability in most cases, while extracts taken at 24 hours had no significant effect on cell behavior. The modification also gave an increase in setting time, from 14.7 min (SD 1.7) to 18.0 min (SD 0.9), and a decrease in maximum polymerization temperature, from 41.5°C (SD 3.4) to 30.7°C (SD 1.4). While further evaluation of other relevant properties, such as injectability and in vivo biocompatibility, remains to be done, the results presented herein are promising in terms of approaching clinically applicable bone cements with a lower stiffness.
ABSTRACT Pure iron has been demonstrated as a potential candidate for biodegradable metal stents due to its appropriate biocompatibility, suitable mechanical properties and uniform biodegradation behavior. The competing parameters that control the safety and the performance of BMS include proper strength-ductility combination, biocompatibility along with matching rate of corrosion with healing rate of arteries. Being a micrometre-scale biomedical device, the mentioned variables have been found to be governed by the average grain size of the bulk material. Thermo-mechanical processing techniques of the cold rolling and annealing were used to grain-refine the pure iron. Pure Fe samples were unidirectionally cold rolled and then isochronally annealed at different temperatures with the intention of inducing different ranges of grain size. The effect of thermo-mechanical treatment on mechanical properties and corrosion rates of the samples were investigated, correspondingly. Mechanical properties of pure Fe samples improved significantly with decrease in grain size while the corrosion rate decreased marginally with decrease in the average grain sizes. These findings could lead to the optimization of the properties to attain an adequate biodegradation-strength-ductility balance.
Osteoporosis is marked by accelerated bone resorption than bone formation and is currently treated with suboptimal drugs associated with severe off-target effects. More robust in vitro models are n ...
Tissue engineering scaffolds are often designed without appropriate consideration for the translational potential of the material. Solid scaffolds implanted into central nervous system (CNS) tissue to promote regeneration may require tissue resection to accommodate implantation. Or alternatively, the solid scaffold may be cut or shaped to better fit an irregular injury geometry, but some features of the augmented scaffold may fail to integreate with surrounding tissue reducing regeneration potential. To create a biomaterial able to completely fill the irregular geometry of CNS injury and yet still provide sufficient cell migratory cues, an injectable, hybrid scaffold was created to present the physical architecture of electrospun fibers in an agarose/methylcellulose hydrogel. When injected into the rat striatum, infiltrating macrophages/microglia and resident astrocytes are able to locate the fibers and utilize their cues for migration into the hybrid matrix. Thus, hydrogels containing electrospun fibers may be an appropriate platform to encourage regeneration of the injured brain.
The present study investigated the influence of granule size of 2 biphasic bone substitutes (BoneCeramic® 400-700 μm and 500-1000 μm) on the induction of multinucleated giant cells (MNGCs) and implant bed vascularization in a subcutaneous implantation model in rats. Furthermore, degradation mechanisms and particle phagocytosis of both materials were examined by transmission electron microscopy (TEM). Both granule types induced tissue reactions involving primarily mononuclear cells and only small numbers of MNGCs. Higher numbers of MNGCs were detected in the group with small granules starting on day 30, while higher vascularization was observed only at day 10 in this group. TEM analysis revealed that both mono- and multinucleated cells were involved in the phagocytosis of the materials. Additionally, the results allowed recognition of the MNGCs as the foreign body giant cell phenotype. Histomorphometrical analysis of the size of phagocytosed particles showed no differences between the 2 granule types. The results indicate that granule size seems to have impact on early implant bed vascularization and also on the induction of MNGCs in the late phase of the tissue reaction. Furthermore, the results revealed that a synthetic bone substitute material can induce tissue reactions similar to those of some xenogeneic materials, thus pointing to a need to elucidate their "ideal" physical characteristics. The results also show that granule size in the range studied did not alter phagocytosis by mononuclear cells. Finally, the investigation substantiates the differentiation of material-induced MNGCs, which are of the foreign body giant cell type.
We describe direct effects of strontium ranelate on the interaction of osteoblastic cells with different titanium substrates. Our goal was to better understand the potential of this drug for improving the efficacy of bone implants. Treatment was done with 0.12 and 0.5 mM Sr(2+) of strontium ranelate in cell culture. We analyzed cell response to the drug on titanium substrates with surface topographies obtained using acid etching, electro-erosion processing, sandblasting, and machine-tooling. Treatment preserved the initial cell adhesion to the substrates, cell shape parameters (area, aspect ratio, circularity, and solidity), and the orientation of cells on grooved surfaces. However, both concentrations of the drug increased cell proliferation in all substrates. Moreover, a dose-dependent increase in alkaline phosphatase activity and in the production of mineralized matrix with typical features of bone tissue was shown. The observed effects were similar in the different substrates. In conclusion, strontium ranelate improved the interaction of osteoblastic cells with titanium substrates, increasing cell proliferation and differentiation into mature osteoblasts and the production of bone-like mineralized matrix for all substrates. This study highlights a promising role of strontium ranelate on enhancing the clinical success of bone implants, particularly in patients with osteoporosis.
The use of biomolecules as coatings on biomaterials is recognized to constitute a promising approach to modulate the biological response of the host. In this work, we propose a coating composed by 2 biomolecules susceptible to provide complementary properties for cardiovascular applications: fibronectin (FN) to enhance endothelialization, and phosphorylcholine (PRC) for its non thrombogenic properties. Polytetrafluoroethylene (PTFE) was selected as model substrate mainly because it is largely used in cardiovascular applications. Two approaches were investigated: 1) a sequential adsorption of the 2 biomolecules and 2) an adsorption of the protein followed by the grafting of phosphorylcholine via chemical activation. All coatings were characterized by immunofluorescence staining, X-Ray Photoelectron Spectroscopy and Scanning Electron Microscopy analyses. Assays with endothelial cells showed improvement on cell adhesion, spreading and metabolic activity on FN-PRC coatings compared with the uncoated PTFE. Platelets adhesion and activation were both reduced on the coated surfaces when compared with uncoated PTFE. Moreover, clotting time tests exhibited better hemocompatibility properties of the surfaces after a sequential adsorption of FN and PRC. In conclusion, FN-PRC coating improves cell adhesion and non-thrombogenic properties, thus revealing a certain potential for the development of this combined deposition strategy in cardiovascular applications.
Tissue engineering is a rapidly advancing technology in the field of regenerative medicine. For the transplantation of cell sheets, a carrier must maintain the shape of a cell sheet from a culture dish to affected sites as well as release the sheet easily onto the lesion. In this study, we examined the utility of a novel, poly(lactic acid)-based carrier for cell sheets transplantation to the cornea of dogs and the skin of rats. The poly(lactic acid)-based carrier easily picked a cell sheet up from the dish, fit to the shape of the transplantation sites, and saved time for cell sheets detachment comparing to a conventional carrier. Thus, the poly(lactic acid)-based carrier would be useful for easy cell sheet transplantations.
Magnetic force microscopy (MFM) is an atomic force microscopy (AFM) based technique in which an AFM tip with a magnetic coating is used to probe local magnetic fields with the typical AFM spatial resolution, thus allowing one to acquire images reflecting the local magnetic properties of the samples at the nanoscale. Being a well established tool for the characterization of magnetic recording media, superconductors and magnetic nanomaterials, MFM is finding constantly increasing application in the study of magnetic properties of materials and systems of biological and biomedical interest. After reviewing these latter applications, three case studies are presented in which MFM is used to characterize: (i) magnetoferritin synthesized using apoferritin as molecular reactor; (ii) magnetic nanoparticles loaded niosomes to be used as nanocarriers for drug delivery; (iii) leukemic cells labeled using folic acid-coated core-shell superparamagnetic nanoparticles in order to exploit the presence of folate receptors on the cell membrane surface. In these examples, MFM data are quantitatively analyzed evidencing the limits of the simple analytical models currently used. Provided that suitable models are used to simulate the MFM response, MFM can be used to evaluate the magnetic momentum of the core of magnetoferritin, the iron entrapment efficiency in single vesicles, or the uptake of magnetic nanoparticles into cells.
As an alternative technique for calcium phosphate coating on titanium alloys, we propose to functionalize the metal surface with anionic bath containing chlorides of palladium or silver as activators. This new deposition route has several advantages such as controlled conditions, applicability to complex shapes, no adverse effect of heating, and cost effectiveness. A mixture of hydroxyapatite and calcium phosphate hydrate is deposited on the surface of Ti–6Al–4V. Calcium phosphate coating is built faster compared with the one by Simulated Body Fluid. Cell morphology and density are comparable to the control one; and the results prove no toxic compound is released into the medium during the previous seven days of immersion. Moreover, the cell viability is comparable with cells cultivated with the virgin medium. These experimental treatments allowed producing cytocompatible materials potentially applicable to manufacture implantable devices for orthopedic and oral surgeries.
Silk fibroin has been widely explored for many biomedical applications, due to its biocompatibility and biodegradability. The aim of this work was to study the role of dialysis and freezing on structural conformation, thermal properties and morphology of silk fibroin hydrogels. Hydrogels were prepared after 3 and 7 days of dialysis and the effect of freezing was analyzed. For that purpose, a part of the fibroin hydrogels underwent freezing at -20 °C for 24 h, followed by lyophilization and the rest of the hydrogels were kept at 8 °C for 24 h, with further lyophilization. The fibroin hydrogels were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Measurements by XRD and FTIR indicated that silk I and silk II structures were present in the fibroin hydrogels and that the secondary structure of fibroin is transformed mostly to β-sheet during the gelation process. Thermal analysis indicated that fibroin hydrogels are thermally stable with the degradation peak at around 330–340 °C. SEM micrographs showed porous structures and the fibroin hydrogels subjected to freezing presented a much larger pore size. Results indicate that the dialysis time and freezing did not alter the material crystallinity, conformation or thermal behavior; however, hydrogel microstructure was strongly affected by dialysis time and freezing, showing controlled pores size. This study provides fundamental knowledge on silk fibroin hydrogels preparation and properties and the studied hydrogels are promising to be used in the biomaterial field.
We analyzed the interactions between human primary cells from pancreatic ductal adenocarcinoma (PDAC) and polymeric scaffolds to develop 3D cancer models useful for mimicking the biology of this tumor. Three scaffold types based on two biocompatible polymeric formulations, such as poly(vinyl alcohol)/gelatin (PVA/G) mixture and poly(ethylene oxide terephthalate)/poly(butylene terephthalate) (PEOT/PBT) copolymer, were obtained via different techniques, namely, emulsion and freeze-drying, compression molding followed by salt leaching, and electrospinning. In this way, primary PDAC cells interfaced with different pore topographies, such as sponge-like pores of different shape and size or nanofiber interspaces. The aim of this study was to investigate the influence played by the scaffold architecture over cancerous cell growth and function. In all scaffolds, primary PDAC cells showed good viability and synthesized tumor-specific metalloproteinases (MMPs) such as MMP-2, and MMP-9. However, only sponge-like pores, obtained via emulsion-based and salt leaching-based techniques allowed for an organized cellular aggregation very similar to the native PDAC morphological structure. Differently, these cell clusters were not observed on PEOT/PBT electrospun scaffolds. MMP-2 and MMP-9, as active enzymes, resulted to be increased in PVA/G and PEOT/PBT sponges, respectively. These findings suggested that spongy scaffolds supported the generation of pancreatic tumor models with enhanced aggressiveness. In conclusion, primary PDAC cells showed diverse behaviors while interacting with different scaffold types that can be potentially exploited to create stage-specific pancreatic cancer models likely to provide new knowledge on the modulation and drug susceptibility of MMPs.
High failure rates of cobalt-chromium-molybdenum (Co-Cr-Mo) metal-on-metal hip prosthesis were reported by various authors, probably due to the alloy's limited hardness and tribological properties. This thus caused the popularity of the alloy in metal-on-metal hip replacements to decrease due to its poor wear properties when compared with other systems such as ceramic-on-ceramic. S-phase surface engineering has become an industry standard when citing surface hardening of austenitic stainless steels. This hardening process allows the austenitic stainless steel to retain its corrosion resistance, while at the same time also improving its hardness and wear resistance. By coupling S-phase surface engineering, using the proprietary Kolsterising(®) treatment from Bodycote Hardiff GmbH, that is currently being used mainly on stainless steel, with Co-Cr-Mo alloys, an improvement in hardness and tribological characteristics is predicted. The objective of this paper is to analyze the biocompatibility of a Kolsterised(®) Co-Cr-Mo alloy, and to characterize the material surface in order to show the advantages gained by using the Kolsterised(®) material relative to the original untreated alloy, and other materials. This work has been performed on 3 fronts including; Material characterization, "In-vitro" corrosion testing, and Biological testing conforming to BS EN ISO 10993-18:2009 - Biological evaluation of medical devices. Using these techniques, the Kolsterised(®) cobalt-chromium-molybdenum alloys were found to have good biocompatibility and an augmented corrosion resistance when compared with the untreated alloy. The Kolsterised(®) samples also showed a 150% increase in surface hardness over the untreated material thus predicting better wear properties.
Chitosan (CS) is a versatile biopolymer whose morphological and chemico-physical properties can be designed for a variety of biomedical applications. Taking advantage of its electrolytic nature, cathodic polarization allows CS deposition on electrically conductive substrates, resulting in thin porous structures with tunable morphology. Here we propose an easy method to obtain CS membranes with highly oriented micro-channels for tissue engineering applications, relying on simple control of process parameters and cathodic substrate geometry. Cathodic deposition was performed on two different aluminum grids in galvanostatic conditions at 6.25 mA cm−2 from CS solution [1g L−1] in acetic acid (pH 3.5). Self-standing thin scaffolds were cross linked either with genipin or epichlorohydrin, weighted, and observed by optical and electron microscopy. Swelling properties at pH 5 and pH 7.4 have been also investigated and tensile tests performed on swollen samples at room temperature. Finally, direct and indirect assays have been performed to evaluate the cytotoxicity at 24 and 72 h. Thin scaffolds with two different oriented porosities (1000µm and 500µm) have been successfully fabricated by electrochemical techniques. Both cross-linking agents did not affected the mechanical properties and cytocompatibility of the resulting structures. Depending on the pH, these structures show interesting swelling properties that can be exploited for drug delivery systems. Moreover, thanks to the possibility of controlling the porosity and the micro-channel orientation, they should be used for the regeneration of tissues requiring a preferential cells orientation, e.g., cardiac patches or ligament regeneration.
Human umbilical vein endothelial cells (HUVECs) were successfully entrapped in polyethylene oxide (PEO) core /polycaprolactone (PCL) shell electrospun fibers thus creating a "bioactive fiber." The viability and release of biomolecules from the entrapped cells in the bioactive fibers were characterized. A key modification to the core solution was the inclusion of 50% fetal bovine serum (FBS), which improved cell viability substantially. The fluorescein diacetate (FDA) staining revealed that the entrapped cells were intact and viable immediately after the electrospinning process. A long-term cell viability assay using AlamarBlue® showed that cells were viable for over two weeks. Secreted Interleukin-8 (IL-8) was monitored as a candidate released protein, which can also act as an indicator of HUVEC stress. These results demonstrated that HUVECs could be entrapped within the electrospun scaffold with the potential of controllable cell deposition and the creation of a bioactive fibrous scaffold with extended functionality.
Thermoplastic biodegradable polymers displaying elastomeric behavior and mechanical consistency are greatly appreciated for the regeneration of soft tissues and for various medical devices. However, while the selection of a suitable base material is determined by mechanical and biodegradation considerations, it is the surface properties of the biomaterial that are responsible for the biological response. In order to improve the interaction with cells and modulate their behavior, biologically active molecules can be incorporated onto the surface of the material. With this aim, the surface of a lactide and caprolactone based biodegradable elastomeric terpolymer was modified in two stages. First, the biodegradable polymer surface was aminated by atmospheric pressure plasma treatment and second a crosslinker was grafted in order to covalently bind the biomolecule. In this study, albumin was used as a model protein. According to X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), albumin was efficiently immobilized on the surface of the terpolymer, the degree of albumin surface coverage (ΓBSA) reached ~35%. Moreover, gel permeation chromatography (GPC) studies showed that the hydrolytic degradation kinetic of the synthesized polymer was slightly delayed when albumin was grafted. However, the degradation process in the bulk of the material was unaffected, as demonstrated by Fourier transform infrared (FTIR) analyses. Furthermore, XPS analyses showed that the protein was still present on the surface after 28 days of degradation, meaning that the surface modification was stable, and that there had been enough time for the biological environment to interact with the modified material.
The distinctive physicochemical, mechanical and electrical properties of carbon nanostructures are currently gaining the interest of researchers working in bioengineering and biomedical fields. Carbon nanotubes, carbon dendrimers, graphenic platelets and nanodiamonds are deeply studied aiming at their application in several areas of biology and medicine. Here we provide a summary of the carbon nanomaterials prepared in our labs and of the fabrication techniques used to produce several biomedical utilities, from scaffolds for tissue growth to cargos for drug delivery and to biosensors.
