Search results for "OLDS"
showing 10 items of 602 documents
Phenotypic redifferentiation and cell cluster formation of cultured human articular chondrocytes in a three-dimensional oriented gelatin scaffold in …
2013
Modern tissue engineering strategies comprise three elemental parameters: cells, scaffolds and growth factors. Articular cartilage represents a highly specialized tissue which allows frictionless gliding of corresponding articulating surfaces. As the regenerative potential of cartilage is low, tissue engineering-based strategies for cartilage regeneration represent a huge challenge. Prostaglandins function as regulators in cartilage development and metabolism, especially in growth plate chondrocytes. In this study, it was analyzed if prostaglandin E2 (PGE2) has an effect on the phenotypic differentiation of human chondrocytes cultured in a three-dimensional (3D) gelatin-based scaffold made …
Morphogenetically active scaffold for osteochondral repair (Polyphosphate/alginate/N,O-carboxymethyl chitosan)
2016
Here we describe a novel bioinspired hydrogel material that can be hardened with calcium ions to yield a scaffold material with viscoelastic properties matching those of cartilage. This material consists of a negatively charged biopolymer triplet, composed of morphogenetically active natural inorganic polyphosphate (polyP), along with the likewise biocompatible natural polymers N,O-carboxymethyl chitosan (N,O-CMC) and alginate. The porosity of the hardened scaffold material obtained after calcium exposure can be adjusted by varying the pre-processing conditions. Various compression tests were applied to determine the local (nanoindentation) and bulk mechanical properties (tensile/compressio…
Multipotential Role of Growth Factor Mimetic Peptides for Osteochondral Tissue Engineering
2022
Articular cartilage is characterized by a poor self-healing capacity due to its aneural and avascular nature. Once injured, it undergoes a series of catabolic processes which lead to its progressive degeneration and the onset of a severe chronic disease called osteoarthritis (OA). In OA, important alterations of the morpho-functional organization occur in the cartilage extracellular matrix, involving all the nearby tissues, including the subchondral bone. Osteochondral engineering, based on a perfect combination of cells, biomaterials and biomolecules, is becoming increasingly successful for the regeneration of injured cartilage and underlying subchondral bone tissue. To this end, recently,…
κ-Carrageenan and PVA blends as bioinks to 3D print scaffolds for cartilage reconstruction.
2022
3D printing of polymeric scaffolds and autologous stem cells is a promising tool for damaged facial cartilage reconstruction surgeries. To this end, suitable bioinks are needed to generate scaffolds with the required morphological and functional features. We formulated hydrogel bioinks using k-Carrageen (kC) and poly(vinyl alcohol) (PVA) in three different weight ratios. The kC gives the systems the ability to undergo rapid sol-to-gel transitions upon cooling from 60 °C and above to body temperature, while the PVA is used as rheology modifier and porogen. The latter is crosslinked after molding or printing by freeze-thaw cycling for 1 day (FT1) or 5 days (FT5). To select the most suitable f…
Implantation of a polycaprolactone scaffold with subchondral bone anchoring ameliorates nodules formation and other tissue alterations
2015
Purpose: Articular cartilage has limited repair capacity. Two different implant devices for articular cartilage regeneration were tested in vivo in a sheep model to evaluate the effect of subchondral bone anchoring for tissue repair. Methods: The implants were placed with press-fit technique in a cartilage defect after microfracture surgery in the femoral condyle of the knee joint of the sheep and histologic and mechanical evaluation was done 4.5 months later. The first group consisted of a biodegradable polycaprolactone (PCL) scaffold with double porosity. The second test group consisted of a PCL scaffold attached to a poly(L-lactic acid) (PLLA) pin anchored to the subchondral bone. Result…
Polyphosphate, the physiological metabolic fuel for corneal cells: a potential biomaterial for ocular surface repair
2019
The regeneration of the epithelium, covering the avascular cornea, involves the processes of differentiation, proliferation and migration of cells originating from the corneal epithelial stem cells. We ask the question if these energy-consuming processes can be fueled by the physiological, inorganic polyphosphate (polyP), the main energy storage/donor molecule in the extracellular space. The ex vivo results reveal that addition of polyP, in the form of soluble Na-polyP, to the culture medium elicits a strong stimulatory effect on cell viability/growth and migration of corneal epithelial cells. Microscopic analyses of partially denuded cornea specimens show that in the presence of polyP, but…
Dynamic processes involved in the pre-vascularization of silk fibroin constructs for bone regeneration using outgrowth endothelial cells
2009
For successful bone regeneration tissue engineered bone constructs combining both aspects, namely a high osteogenic potential and a rapid connection to the vascular network are needed. In this study we assessed the formation of pre-vascular structures by human outgrowth endothelial cells (OEC) from progenitors in the peripheral blood and the osteogenic differentiation of primary human osteoblasts (pOB) on micrometric silk fibroin scaffolds. The rational was to gain more insight into the dynamic processes involved in the differentiation and functionality of both cell types depending on culture time in vitro. Vascular tube formation by OEC was assessed quantitatively at one and 4 weeks of cul…
Effect of bioglass on growth and biomineralization of SaOS-2 cells in hydrogel after 3D cell bioprinting.
2014
We investigated the effect of bioglass (bioactive glass) on growth and mineralization of bone-related SaOS-2 cells, encapsulated into a printable and biodegradable alginate/gelatine hydrogel. The hydrogel was supplemented either with polyphosphate (polyP), administered as polyP • Ca2+-complex, or silica, or as biosilica that had been enzymatically prepared from ortho-silicate by silicatein. These hydrogels, together with SaOS-2 cells, were bioprinted to computer-designed scaffolds. The results revealed that bioglass (nano)particles, with a size of 55 nm and a molar ratio of SiO2 : CaO : P2O5 of 55 : 40 : 5, did not affect the growth of the encapsulated cells. If silica, biosilica, or polyP …
Flows and mixing in channels with misaligned superhydrophobic walls.
2014
Aligned superhydrophobic surfaces with the same texture orientation reduce drag in the channel and generate secondary flows transverse to the direction of the applied pressure gradient. Here we show that a transverse shear can be easily generated by using superhydrophobic channels with misaligned textured surfaces. We propose a general theoretical approach to quantify this transverse flow by introducing the concept of an effective shear tensor. To illustrate its use, we present approximate theoretical solutions and Dissipative Particle Dynamics simulations for striped superhydrophobic channels. Our results demonstrate that the transverse shear leads to complex flow patterns, which provide a…
Stability of melt flow due to a traveling magnetic field in a closed ampoule
2004
The linear three-dimensional instability of the flow due to a low frequency traveling magnetic field in a regular cylinder is studied numerically for height-to-diameter ratios in the range [0.5:2.5]. The first instability has the form of an azimuthal wave with wave numbers between 1 and 6 depending on the aspect ratio. It is shown that the flow is stable if the Reynolds number is below 290. Even stronger stationary flows may be obtained in a flattened cylinder.