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Tissue engineering is a promising approach for obtaining lifetime durability in biological heart valves. Basic questions with respect to the selection of suitable cell populations as well as scaffolds remain unsolved. The purpose of this... more
Tissue engineering is a promising approach for obtaining lifetime durability in biological heart valves. Basic questions with respect to the selection of suitable cell populations as well as scaffolds remain unsolved. The purpose of this study was to develop a tissue-like substitute in vitro for replacement of diseased valves in vivo. Smooth-muscle cells (SMCs) were isolated from human and porcine aortic tissue using the 'explant technique' and endothelial cells from collagenase digestion. Seeding and cultivation of isolated cells was performed on a type-I collagen matrix. The scaffold-cell specimen was investigated using light and electron microscopy. Cupromeronic blue and immunoprecipitation were used for ultracytochemical staining. SMCs were allowed to grow to multilayers and migrate into the collagen network. We found a tissue-like morphology in these samples characterised by several layers of cells, spaces between the cell layers filled with newly formed extracellular matrix components, compartmentalisation of proteoglycans and their association with fibrilar matrix and the cell surface. Endothelium cells covered the SMCs of the scaffold with a histological topography similar to heart valves. This is an approach for in vitro modelling of tissue-like substitutes and preparing plane multicellular tissues as substitutes for heart valves. This model may also be used for cell biological investigations of cell-matrix interactions.
Research Interests: Electron Microscopy, Tissue Engineering, Cell Biology, Transmission Electron Microscopy, Medicine, and 13 moreExtracellular Matrix, In Vitro, Humans, Collagen, Animals, Vascular endothelium, Decellularization, Elastin, Swine, prosthesis Design, Heart Valve, Collagenase, and Cardiovascular medicine and haematology
Stem cells are of widespread interest in regenerative medicine due to their capability of self-renewal and differentiation, which is regulated by their three-dimensional microenvironment. In this study, a computer-aided biofabrication... more
Stem cells are of widespread interest in regenerative medicine due to their capability of self-renewal and differentiation, which is regulated by their three-dimensional microenvironment. In this study, a computer-aided biofabrication technique based on laser-induced forward transfer (LIFT) is used to generate grafts consisting of mesenchymal stem cells (MSCs). We demonstrate that (i) laser printing does not cause any cell damage; (ii) laser-printed MSC grafts can be differentiated toward bone and cartilage; (iii) LIFT allows printing of cell densities high enough for the promotion of chondrogenesis; (iv) with LIFT three-dimensional scaffold-free autologous tissue grafts can be fabricated keeping their predefined structure, and (v) predifferentiated MSCs survived the complete printing procedure and kept their functionality. We believe that our results will find important applications in stem cell biology and tissue engineering.
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Fibrous materials based on polyvinylidene fluoride and trifluoroethylene copolymers have been obtained by blend electrospinning and modified with polyconjugated polymer polypyrrole. The composite structure formed is a dielectric fiber in... more
Fibrous materials based on polyvinylidene fluoride and trifluoroethylene copolymers have been obtained by blend electrospinning and modified with polyconjugated polymer polypyrrole. The composite structure formed is a dielectric fiber in a conductive shell. The results indicate that by varying the degree of polypyrrole doping-up it is possible to change the character of the conductivity of the composite reversibly from inductive to capacitive.
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Research Interests: Materials Science, Cochlear Implant, Stiffness, Article, Radius, and 2 moreDDC and Insertion Loss(DDC and Insertion Loss)
(DDC and Insertion Loss)
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ABSTRACT In the field of cryopreservation cells are stored at cryogenic temperatures in order to maintain their quality after thawing. Lowering the temperature reduces the metabolism of cells and therefore can prevent their loss of... more
ABSTRACT In the field of cryopreservation cells are stored at cryogenic temperatures in order to maintain their quality after thawing. Lowering the temperature reduces the metabolism of cells and therefore can prevent their loss of quality over time. During the freezing process different parameters have been identified as cell damaging mechanisms [1]. Thus, a correct setting of process parameters including the cooling and warming rate, nucleation temperature (Tn), sample geometry, as well as type and concentration of cryoprotective agents can reduce cellular damage and result in high quality output after freezing. For comparison of the qualities of different biological specimens, freezing protocols and viability analyses need to be standardised. Most of the earlier studies did not account for the control of all process parameters, especially the nucleation temperature [1]. Therefore, the aim of this study was to control all possible process parameters during freezing of human endothelial cells (ECs) and mesenchymal stem cells (MSCs) of the marmoset monkey using different experimental methods. A standardised freezing protocol was developed which is based on our earlier experimental results [2]. The protocol includes a cooling rate of 5 K/min, heating rate of 100 K/min, 5% (v/v) DMSO and a nucleation temperature of −8 °C. The first method used was a μ-freezer (CM2000, Carburos Metalicos) where 1 mL cell suspensions were frozen in cryovials. For the control of the nucleation temperature a new setup was developed which is based on nucleation via Peltier elements [3]. A second method used a commercially available cryomicroscopic setup to visualise the cells in suspension which involves a LINHAM cryostage FDCS 196. and a digital camera (Retiga, QImaging). The temperature of the samples was controlled from 40 to −196 °C. The manual cell seeding process required the removal of the lid of the cryostage when a cooled copper rod touches the supercooled sample. To overcome this limitation, we developed a new seeding device for cryomicroscopic investigations of aqueous samples. This device applies a copper rod which is cooled via liquid nitrogen flushed heat exchanger. A USB camera is used to identify the position of the copper rod tip during an initial local calibration procedure which is electronically stored. Thus, the system can automatically calculate the distance to the sample. Nucleation is induced by a liquid nitrogen cooled copper rod which is positioned towards the specimen by a step motor system. The device allows for the control of the nucleation temperature at cooling rates up to 10 K/min with an accuracy of ±0.2 K. Both construction designs allow the control of the nucleation temperature and contribute to a further standardisation of freezing protocols. After cell freezing, the quality of the protocol was determined using staining methods based on trypan blue, calcein AM and ethidium homodimer. As a general quality test the absolute viability was determined which is defined as the ratio of viable cell number after freezing to the total cell number before freezing. Using this method, the viability of ECs after freezing was 90%. After thawing, MSCs were tested for proliferation and differentiation into the osteogenic and adipogenic lineage. To achieve a standardisation of freezing protocols we propose to control all process parameters including the nucleation temperature and the use of the absolute viability as a general method for quality comparison of different cellular specimens after freeze/thawing.
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ABSTRACT Cryopreservation is the only one possible way to store rare cell types for the long term. Despite this, there are still challenges to preserve stem cells. In order to improve viability and proliferation of cells after... more
ABSTRACT Cryopreservation is the only one possible way to store rare cell types for the long term. Despite this, there are still challenges to preserve stem cells. In order to improve viability and proliferation of cells after cryopreservation we encapsulated them in small alginate beads. The gel-like structure and mild environment inside alginate beads may protect encapsulated cells from cryoinjury and resist the reorganization of ice crystals during thawing. The existing encapsulation methods do not provide alginate beads with narrow size distribution and are not able to generate small beads in repeatable manner. Here we applied high voltage to encapsulate cells in alginate. Such technology has been shown to be advantageous over the commonly used air flow encapsulation [Gryshkov et al., Mater Sci Eng C Mater Biol Appl 2014]. Mesenchymal stem cells (MSCs) derived from the Common marmoset Callithrix jacchus were encapsulated in 1.6% (w/v) sterile alginate at a concentration 1*10^6 cells/ml using high voltage (15, 20, 25 kV). Air flow encapsulation was run as a control. MSCs in alginate beads were frozen either immediately after encapsulation or after 24 h of incubation. Cryopreservation was conducted with 1 K/min cooling rate down to -80 °C with 10% Me2SO. After storage beads were thawed at 37 °C with further removing of alginate using sodium citrate. The recovered MSCs were seeded for proliferation and metabolic activity assays either immediately after thawing or after 5 days of recovery. High voltage encapsulation method was able to generate alginate beads containing cells with narrow size distribution (3–7%) in repeatable manner. The incubation of encapsulated MSCs slightly reduced the proliferation after thawing. Immediately frozen cells recovered at the same rate as fresh control. Our results show an increased proliferation of MSCs frozen immediately after encapsulation. The viability and proliferation of encapsulated MSCs could be further improved by modifying the alginate to allow mammalian cell types to attach to alginate structure and resist ice crystal formation during freezing.
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Co-polymer polyvinylidene fluoride-co-trifluoroethylene (PVDF-TrFE) is a promising piezoelectric material for a range of medical and industrial applications such as tissue engineering, sensors and membrane technics. In this regard, blend... more
Co-polymer polyvinylidene fluoride-co-trifluoroethylene (PVDF-TrFE) is a promising piezoelectric material for a range of medical and industrial applications such as tissue engineering, sensors and membrane technics. In this regard, blend electrospinning is an ideal method to produce suitable polymeric nano- and micro-fiber scaffolds or membranes from polymer solutions. Stable electrospinning process is strongly dependent on PVDF-TrFE solution properties. Thus, this study aimed at evaluating the effect of different suitable solvents on physical properties PVDF-TrFE polymer solutions and produced films with different solvent combinations and mixing ratios. The results indicate that solution viscosities range between 5.47 and 37.17 Pa.s. Furthermore, piezoelectric phase fraction and crystallinity of PVDF-TrFE films were characterized using Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry, respectively. All films exhibited a piezoelectric polar beta-phase formation. The crystalline beta-phase fraction of the most of the films was higher than the value of the initial material (77%). Results demonstrate the influence of solvent combinations and mixing ratios on melting temperature and crystallinity.
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Chitin as a biological material which has been identified in skeletal structures of a broad variety of unicellular (yeast, protists, diatoms) and multicellular (sponges, corals, worms, molluscs, arthropods) organisms is recognized as... more
Chitin as a biological material which has been identified in skeletal structures of a broad variety of unicellular (yeast, protists, diatoms) and multicellular (sponges, corals, worms, molluscs, arthropods) organisms is recognized as natural template with good perspectives in modern biomedicine. This chapter provides first insights into prospective applications of naturally prefabricated three-dimensional chitinous scaffolds from selected marine sponges in tissue engineering. This became possible only owing to the recent discovery of poriferan chitin which provoked renewed multidisciplinary interest driven by growing demand in novel biomimetic materials. Here, we focused on both demosponges of Verongiida order as a renewable source of chitin scaffolds with jewelry designs, and human mesenchymal stromal cells having high therapeutic potential. The chapter covers approaches for isolation of scaffolds from the chitin-bearing marine sponges, nuances of their interaction with human cells and cryopreservation potential.
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Research Interests: Medicine, Clinical Sciences, Gynecology, Degeneration, Staining, and 2 moreStain and Calcification(Stain and Calcification)
(Stain and Calcification)
Research Interests: Engineering, Materials Engineering, Materials Science, Mechanics, Heat Transfer, and 15 moreNanotechnology, Heat Exchanger, Heat and Mass Transfer, Mathematical Sciences, Physical sciences, Plate Heat Exchanger, Nanofluid, Heat transfer coefficient, Pressure Drop, Heat transfer enhancement, Applied Thermal Engineering, Nusselt Number, Airflow, Heat Sink, and heat technology
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Calcium phosphate cements (CPCs) offer a promising solution for treating bone defects due to their osteoconductive, injectable, biocompatible, and bone replacement properties. However, their brittle nature restricts their utilization to... more
Calcium phosphate cements (CPCs) offer a promising solution for treating bone defects due to their osteoconductive, injectable, biocompatible, and bone replacement properties. However, their brittle nature restricts their utilization to non-load-bearing applications. In this study, the impact of hybrid silk fibroin (SF) and kappa-carrageenan (k-CG) nanofibers as reinforcements in CPC was investigated. The CPC composite was fabricated by incorporating electrospun nanofibers in 1, 3, and 5% volume fractions. The morphology, mineralization, mechanical properties, setting time, injectability, cell adhesion, and mineralization of the CPC composites were analyzed. The results demonstrated that the addition of the nanofibers improved the CPC mixture, leading to an increase in compressive strength (14.8 ± 0.3 MPa compared to 8.1 ± 0.4 MPa of the unreinforced CPC). Similar improvements were seen in the bending strength and work fracture (WOF). The MC3T3-E1 cell culture experiments indicated ...
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Due to the increasing energy cost, the efficiency of the industrial dryer as the energy-intensive processes should be improved. The designer should optimize the design parameters of industrial drying equipment to achieve the minimum... more
Due to the increasing energy cost, the efficiency of the industrial dryer as the energy-intensive processes should be improved. The designer should optimize the design parameters of industrial drying equipment to achieve the minimum drying energy consumption. SST k-ω turbulence model is used to simulate a real geometry for industrial drying applications. For the optimization of the impinging round jet, the specific drying energy consumption is set as the objective function to be minimized. The jet to surface distance, jet to jet spacing, jet inlet velocity, jet angle, and surface velocity are chosen as the design parameters. The SHERPA search algorithm is used to search for the optimal point from the weighted sum of all objectives method. One correlation is developed and validated for the specific drying energy consumption. It is found that the SST k-ω turbulence model succeeded with reasonable accuracy in reproducing the experimental results. The minimum specific energy consumption...