Towards a Novel Cost-Effective and Versatile Bioink for 3D-Bioprinting in Tissue Engineering

3D-bioprinting for tissue regeneration relies on, among other things, hydrogels with favorable rheological properties. These include shear thinning for cell-friendly extrusion, post-printing structural stability as well as physiologically relevant elastic moduli needed for optimal cell attachment, proliferation, differentiation and tissue maturation. This work introduces a cost-efficient gelatin-methylcellulose based hydrogel whose rheological properties can be independently optimized for optimal printability and tissue engineering. Hydrogel viscosities were designed to present three different temperature regimes: low viscosity for eased cell suspension and printing with minimal shear stress, form fidelity directly after printing and long term structural stability during incubation. Enzymatically crosslinked hydrogel scaffolds with stiffnesses ranging from 5 to 50 kPa were produced, enabling the hydrogel to biomimic cell environments for different types of tissues. The bioink showed high intrinsic cytocompatibility and tissues fabricated by embedding and bioprinting NIH 3T3 fibroblasts showed satisfactory viability. This novel hydrogel uses robust and inexpensive technology, which can be adjusted for implementation in tissue regeneration, e.g., in myocardial or neural tissue engineering

Nanocomposites in 3D Bioprinting for Engineering Conductive and Stimuli-Responsive Constructs Mimicking Electrically Sensitive Tissue

Rebuilding damaged or diseased tissue by means of biological additive manufacturing has recently gained lot of attention and shown very promising result. Using biofabrication techniques to mimic and replicate natural tissue as well as cell environment is a very capable way to achieve physiologically relevant conditions. Especially in electrophysiological human tissue like cardiac or neural tissue, proper signal transduction is of paramount importance for appropriate function and cell maturation as well as differentiation. Precisely, these conductive properties are challenging to engineer. However, a lot of outstanding work has been done recently. Therefore, this review focuses on additives, i.e., nanocomposites with intrinsic conductive properties, to the usually nonconductive hydrogels used in 3D-bioprinting. Recent work on exploiting the properties of these nanocomposites, such as metal nanoparticles (NPs), carbon nanotubes (CNTs), graphene, or MXenes, to alter the nanoenvironment of the manufactured construct toward conductive tissues is presented. An overview of responsiveness to external stimuli, a second intrinsic property of such nanocomposites is provided as well. Furthermore, these materials are critically analyzed concerning their electrophysiology, i.e., cell–scaffold interaction, their biocompatibility as well as their toxicological properties

Support Possibilities Export of Services in the Czech Republic

The thesis is focused on the area of export support services in the Czech Republic - specifically for the international transport. Its principal aim is analysis of selected company engaged in export of services and proposing specific measures and recommendations for this company from area support export of services in the Czech Republic. Partial aim of the thesis is analysis and evaluation the use of instruments of support export of services in the Czech Republic on business entities engaged in international transport. For filling of partial aim was performed survey by questionnaires. In the analysis of selected company operating in international road transport was performed financial analysis, competition analysis - Porter´s model, STEP analysis, SWOT analysis and finally structured guided interview with company representative. Based on an analysis of selected company was performed proposal specific recommendations for this company from area support export of services in the Czech Republic

Inkjet-printed hemispherical microcapsules and silicon chip embedding

Planar lithography techniques are not effective for precise fabrication of microdevices with hemispherical shapes. Drop-on-demand (DOD) inkjet printing (IJP) of photo-curable ink is a more appropriate fabrication approach as it takes advantage of the surface tension as well as of the delivery of a well-defined ink volume. Described is a DOD IJP technique onto geometrically-patterned silicon substrates enabling the controlled fabrication of SU-8 hemispherical microcapsules. Open half capsules of 100 µm in diameter with inner cavity volumes of 5, 20 and 45 pl with a printing yield above 96% are demonstrated. The same technique is directly adapted to the fabrication of microcapsules embedding silicon microchips. The reported findings open new paths for controlled encapsulation of liquids into smart microsystems.info:eu-repo/semantics/publishe

Polymeric hemispherical pL micro cups fabricated by inkjet printing

The fabrication of precise hemispherical shape is challenging with standard planar lithography techniques. A suitable alternative is the fabrication by inkjet printing. This paper presents a method based on drop-on-demand inkjet printing on pre-patterned silicon substrates allowing the controlled fabrication of SU-8 hemispherical cup-like structures with inner cavities of sub-nano-liter volumes. Examples are given for cups of 100μm in diameter with inner cavity volumes of 5pL, 20pL and 45pL. Arrays of 360 hemispherical SU-8 cups have been fabricated with a yield above 96%. The 4% of exceptions are also described and shown as a method for achieving almost complete SU-8 spheres.info:eu-repo/semantics/publishe

Inkjet printing for microlenses, microcapsules and MEMS-like chip embedding

Inkjet printing (IJP) is a flexible technique for the fabrication of spherical profiles benefiting from the localized surface tension effects. Combining IJP with top-down well established lithographic approaches enables fabricating spherical shapes with predefinable aspect ratios [1]. In this work, drop-on-demand (DOD) IJP of epoxy inks (InkEpo [2], micro resist technology GmbH) onto specific confinement platforms is presented for three applications: (1) microlens, (2) microcapsules with inner cavities, and (3) microcapsules embedding microchips.info:eu-repo/semantics/nonPublishe

Rapid carbon nanotubes suspension in organic solvents using organosilicon polymers

A strategy for a simple dispersion of commercial multi-walled carbon nanotubes (MWCNTs) using two organosilicones, polycarbosilane SMP10 and polysilazane Ceraset PSZ20, in organic solvents such as cyclohexane, tetrahydrofuran (THF), m-xylene and chloroform is presented. In just a few minutes the combined action of sonication and the presence of Pt(0) catalyst is sufficient to obtain a homogeneous suspension, thanks to the rapid hydrosilylation reaction between SiH groups of the polymer and the CNT sidewall. The as-produced suspensions have a particle size distribution <1μm and remain unchanged after several months. A maximum of 0.47 and 0.50mg/ml was achieved, respectively, for Ceraset in THF and SMP10 in chloroform. Possible applications as polymeric and ceramic thin films or aerogels are presented

Directional Submicrofiber Hydrogel Composite Scaffolds Supporting Neuron Differentiation and Enabling Neurite Alignment

Cell cultures aiming at tissue regeneration benefit from scaffolds with physiologically relevant elastic moduli to optimally trigger cell attachment, proliferation and promote differentiation, guidance and tissue maturation. Complex scaffolds designed with guiding cues can mimic the anisotropic nature of neural tissues, such as spinal cord or brain, and recall the ability of human neural progenitor cells to differentiate and align. This work introduces a cost-efficient gelatin-based submicron patterned hydrogel&ndash;fiber composite with tuned stiffness, able to support cell attachment, differentiation and alignment of neurons derived from human progenitor cells. The enzymatically crosslinked gelatin-based hydrogels were generated with stiffnesses from 8 to 80 kPa, onto which poly(&epsilon;-caprolactone) (PCL) alignment cues were electrospun such that the fibers had a preferential alignment. The fiber&ndash;hydrogel composites with a modulus of about 20 kPa showed the strongest cell attachment and highest cell proliferation, rendering them an ideal differentiation support. Differentiated neurons aligned and bundled their neurites along the aligned PCL filaments, which is unique to this cell type on a fiber&ndash;hydrogel composite. This novel scaffold relies on robust and inexpensive technology and is suitable for neural tissue engineering where directional neuron alignment is required, such as in the spinal cord

Influence of carbon enrichment on electrical conductivity and processing of polycarbosilane derived ceramic for MEMS applications

An analysis about the effect of carbon enrichment of allylhydridopolycarbosilane SMP10® with divinylbenzene (DVB) as a promising material for electrical conductive micro-electrical mechanical systems (MEMS) is presented. The liquid precursors can be micropipetted and cured in polytetrafluoroethylene (PTFE) molds to produce 14 mm diameter disc shaped samples. The effect of pyrolysis temperature and carbon content on the electrical conductivity is discussed. The addition of 28.7 wt.% of DVB was found to be the optimum amount. Carbon was preserved in the microstructure during pyrolysis and the ceramic yield increased from 77.5 to 80.5 wt.%. The electrical conductivity increased from 10−6 to 1 S/cm depending on the annealing temperature. Furthermore, the ceramic samples obtained with this composition were found to be in many cases crack free or with minimal cracks in contrast with the behavior of pure SMP10. Using the same process we demonstrate that also microsized ceramic samples can be produced