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Item does not contain fulltext Gelatin methacrylate (GelMA) is an inexpensive, photocrosslinkable, cell-responsive hydrogel which has drawn attention for a wide range of tissue engineering applications. The potential of GelMA scaffolds was demonstrated to be tunable for different tissue engineering (TE) applications through modifying the polymer concentration, methacrylation degree, or UV light intensity. Despite the promising results of GelMA hydrogels in tissue engineering, the influence of polymer concentration for bone tissue engineering (BTE) scaffolds was not established yet. Thus, in this study, we have demonstrated the effect of polymer concentration in GelMA scaffolds on osteogenic differentiation. We prepared GelMA scaffolds with 5 and 10% polymer concentrations and characterized the scaffolds in terms of porosity, pore size, swelling characteristics, and mechanical properties. Subsequent to the scaffolds characterization, the scaffolds were seeded with bone marrow derived rat mesenchymal stem cells and cultured in osteogenic media to evaluate the possible osteogenic differentiation effect exerted by the polymer concentration. After 7, 14, 21, and 28 days, DNA content, calcium deposition, and alkaline phosphatase (ALP) activity of scaffolds were evaluated quantitatively by colorimetric bioassays. Furthermore, the distribution of the calcium deposition within the scaffolds was attained qualitatively and quantitatively by microcomputer tomography (microCT). Our data suggest that GelMA hydrogels prepared with 5% polymer concentration has promoted homogeneous extracellular matrix calcification and it is a great candidate for BTE applications. (c) 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 201-209, 2018.

Cell elasticity, motility and migration are very important for understanding various biological processes. Currently, monitoring cellular traction forces is desired as new marker to monitor cell functionality. We developed a sensor system for cell force measurement based upon a polymer microchip covered with a micropillar matrix. The spring constant is chosen to enable pillar bending by cellular forces. The microchip is read out optically. Besides a transmission image to analyze pillar bending, two different fluorescence images of dye markers can be taken sequentially. Matrix with the cells is illuminated by spatially homogenized LED radiation. The focal position during long term experiments can be maintained by means of a piezo stage in order to obtain highly resolved images from the CCD imager. Sophisticated software controls the optical system and performs image registration. First, one transmission (red) as well as two fluorescence images (blue & green) are taken using appropriate CCD gain and integration times. Fluorescence information yields those pillar positions that are at least covered by a cell. The transmission image is used to calculate the magnitude and direction of pillars deflection. Therefore, detection of single pillar position and its deviation from a hexagonal grid is analyzed automatically, enabling a mapping of traction forces. The system containing transducer polymer chip, optics, and dedicated software analysis is a complete imaging system for image registration, single cell visualization and cellular force measurement. First results of cellular force measurements obtained are presented.

Chitosan is a natural polymer widely investigated and used due to its antibacterial activity, mucoadhesive, analgesic, and hemostatic properties. Its biocompatibility makes chitosan a favorable candidate for different applications in tissue engineering (TE), such as skin, bone, and cartilage tissue regeneration. Despite promising results obtained with chitosan 3D scaffolds, significant challenges persist in fabricating hydrogel structures with ordered architectures and biological properties to mimic native tissues. In this work, chitosan has been investigated aiming at designing and fabricating uniaxial scaffolds which can be proposed for the regeneration of anisotropic tissues (i.e., skin, skeletal muscle, myocardium) by 3D printing technology. Chitosan was blended with gelatin to form a polyelectrolyte complex in two different ratios, to improve printability and shape retention. After the optimization of the printing process parameters, different crosslinking conditions were investigated, and the 3D printed samples were characterized. Tripolyphosphate (TPP) was used as crosslinker for chitosan-based scaffolds. For the optimization of the printing temperature, the sol-gel temperature of the chitosan-gelatin blend was determined by rheological measurements and extrusion temperature was set to 20°C (i.e., below sol-gel temperature). The shape fidelity and surface morphology of the 3D printed scaffolds after crosslinking was dependent on crosslinking conditions. Interestingly, mechanical properties of the scaffolds were also significantly affected by the crosslinking conditions, nonetheless the stability of the scaffolds was strongly determined by the content of gelatin in the blend. Lastly, in vitro cytocompatibility test was performed to evaluate the interactions between L929 cells and the 3D printed samples. 2% w/v chitosan and 4% w/v gelatin hydrogel scaffolds crosslinked with 10% TPP, 30 min at 4°C following 30 min at 37°C have shown cytocompatible and stable characteristics, compared to all other tested conditions, showing suitable properties for the regeneration of anisotropic tissues.