401 research outputs found
PAM2 (Piston Assisted Microsyringe): A New Rapid Prototyping Technique for Biofabrication of Cell Incorporated Scaffolds
No full textRapid prototyping techniques are widely used to fabricate well-defined three-dimensional structures of tissue homologs. The piston-assisted microsyringe (PAM2) is a rapid prototyping technology specifically developed for low-shear stress extrusion of viscous hydrogel solutions containing cells. In this article the working parameters of the system were established to guarantee the realization of spatially controlled hydrogel scaffolds. Moreover the shear stresses acting on the cell membrane during extrusion was investigated through a computational fluid-dynamic analysis. The computational models show that the shear stress on the cells is of the order of 100 Pa during the extrusion process. HepG2 cells encapsulated in alginate were then extruded into spatially organized hepatic lobule-like architectures and their viability and function were evaluated. The results show that the metabolic fingerprint of the cells is preserved with respect to controls and the cells are uniformly distributed through the gel scaffold
Development of a novel micro-ablation system to realise micrometric and well-defined hydrogel structures for tissue engineering applications
No full textPurpose
– This paper aims to develop a novel micro-ablation system to realise micrometric and well-defined hydrogel structures. To engineer a tissue it is necessary to evaluate several aspects, such as cell-cell and cell-substrate interactions, its micro-architecture and mechanical stimuli that act on it. For this reason, it is important to fabricate a substrate which presents a microtopology similar to natural tissue and has chemical and mechanical properties able to promote cell functions. In this paper, well-defined hydrogel structures embedding cells were microfabricated using a purposely developed technique, micro-laser ablation, based on a thulium laser. Its working parameters (laser power emission, stepper motor velocity) were optimised to produce shaded “serpentine” pattern on a hydrogel film.
Design/methodology/approach
– In this study, initially, swelling/contraction tests on agarose and alginate hydrogel in different solutions of main components of cell culture medium were performed and were compared with the MECpH model. This comparison matched with good approximation experimental measurements. Once known how hydrogel changed its topology, microstructures with a well-defined topology were realised using a purposely developed micro-laser ablation system design. S5Y5 neuroblastoma cell lines were embedded in hydrogel matrix and the whole structure was ablated with a laser microfabrication system. The cells did not show damages due to mechanical stress present in the hydrogel matrix and to thermal increase induced by the laser beam.
Findings
– The hydrogel structure is able to reproduce extracellular matrix. Initially, the hydrogel swelling/contraction in different solutions, containing the main components of the most common cell culture media, was analysed. This analysis is important to evaluate if cell culture environment could alter microtopology of realised structures. Then, the same topology was realised on hydrogel film embedding neuronal cells and the cells did not show damages due to mechanical stress present in the hydrogel matrix and to thermal increase induced by the laser beam. The interesting obtained results could be useful to realise well-defined microfabricated hydrogel structures embedding cells to guide tissue formation
Originality/value
– The originality of this paper is the design and realisation of a 3D microfabrication system able to microfabricate hydrogel matrix embedding cells without inducing cell damage. The ease of use of this system and its potential modularity render this system a novel potential device for application in tissue engineering and regenerative medicine area
Optical response and ultrafast carrier dynamics of silicene on silver
No full textSilicene can be stabilized in various forms on Ag(111) surface and was recently integrated in field-effect transistors (FET) showing high mobility when Ag is withdrawn. However, strong hybridization effects in silicene superstructures on silver have been invoked as responsible for the disruption of its peculiar electronic properties.
We investigate the role of the Ag(111) metallic support in determining the physical properties of the Si/Ag interface, by means of theoretical calculations of the optical response of the supported system. Ab initio simulations based on density functional theory show that the silicene/Ag(111) absorption spectra are strongly non-additive, while the presence of the silicene layer still produces a clear signature. Individual contributions to the spectra are singled out, allowing us to quantify the role of electronic transitions involving silver and silicon states. Silver states, in particular, are found to provide a huge contribution to the optical absorption of silicene on silver, compatible with a strong Si-Ag hybridization. The same conclusions are derived for amorphous two-dimensional Si layers. The results point to a dimensionality-driven peculiar dielectric response of the silicon/silver interface, which is confirmed by means of measurements by Transient-Reflectance spectroscopy. These observations show a metallic-like carrier dynamics, both for silicene and ultra-thin amorphous silicon, hence providing an optical demonstration of the strong hybridization arising in silicene/Ag(111) systems [1].
[1] E. Cinquanta, G. Fratesi, S. dal Conte, C. Grazianetti, F. Scotognella, S. Stagira, C. Vozzi, G. Onida, and A. Molle, Phys. Rev. B 92, 165427 (2015
Study of the crosstalk between hepatocytes and endothelial cells using a novel multicompartmental bioreactor: a comparison between connected cultures and cocultures
No full textThe liver and other organs are connected to each other through the bloodstream. Therefore, the connection between tissues is generally mediated by soluble molecules able to cross the endothelial wall of capillaries. We developed a multicompartmental device, multicompartmental bioreactor (MCB), designed to mimic the connection between different tissues in which crosstalk is mediated by soluble molecules transported through the blood. A comparative study of the crosstalk between hepatocytes (HepG2) and endothelial cells (human umbilical vein endothelial cells) in connected culture in the MCB and in a traditional static coculture system was performed by analyzing glucose consumption and secretion of albumin, urea, and nitric oxide. When hepatocytes and endothelial cells were cultured together, the production of albumin and urea increased, and the increase was higher in the MCB than in traditional static coculture. In spite of this enhanced metabolic activity, the crosstalk between hepatocytes and endothelial cell leads to decreased glucose consumption with respect to hepatocytes alone, both in static and in dynamic conditions. However, the dynamic connected culture has a higher rate of metabolite synthesis and secretion with respect to cocultures. This means a more efficient use of energetic substrates and enhanced hepatocyte function in the MCB
- …
