Yazar "Ilhan-Ayisigi, Esra" seçeneğine göre listele

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    Biomimetic 3D bioprinted bilayer GelMA scaffolds for the delivery of BMP-2 and VEGF exogenous growth factors to promote vascularized bone regeneration in a calvarial defect model in vivo
    (Elsevier, 2025) Alarcin, Emine; Akguner, Zeynep Puren; Ozturk, Ayca Bal; Yasayan, Gokcen; Ilhan-Ayisigi, Esra; Kazan, Aslihan; Guner, F. Seniha
    The effective treatment of critical-sized bone defects requires a coordinated interaction between osteogenesis and angiogenesis. Inspired by natural bone tissue, we developed a bilayer vascularized bone construct using extrusion-based dual 3D bioprinting. The construct consists of two layers: a bone-mimetic layer, which includes highly methacrylated gelatin (GelMAHIGH), hyaluronic acid, alginate, osteoblast cells, and bone morphogenetic protein-2 (BMP-2) loaded polylactic-co-glycolic acid (PLGA) nanoparticles; and a vessel-mimetic layer, composed of low methacrylated gelatin (GelMALOW), alginate, endothelial cells, and vascular endothelial growth factor (VEGF)-loaded PLGA nanoparticles. These layers were designed to form hierarchical microstructures that enable sustained release of growth factor (GF) thereby stimulating both osteogenic and angiogenic processes. The nanoparticles were synthesized using a microfluidic platform, achieving a narrow size distribution. The hydrogel bioinks were systematically optimized for printability, and it was found that incorporation of nanoparticles improved their mechanical properties, surface roughness, degradability, and GF release profiles. Notably, GF release followed zero-order kinetics, ensuring consistent delivery over time. The bilayer scaffolds demonstrated superior cell proliferation and spreading compared to single-layer scaffolds, and in vivo experiments showed enhanced repair of calvarial bone defects. These findings highlight the significant clinical potential of bilayer scaffolds with sequential GF delivery for treating critical-sized bone defects.
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    Optimization of culture conditions for the production and activity of recombinant xylanase from microalgal platform
    (Elsevier, 2023) Yildirim, Arzu; Ilhan-Ayisigi, Esra; Duzel, Ahmet; Mayfield, Stephen Patrick; Sargin, Sait
    Xylanases are enzymes responsible for the hydrolysis of the heteropolymer xylan. They have wide applications ranging from the bakery, animal husbandry, and textile to pulp and paper industry and biofuel productions. Recombinant xylanase production has been previously reported from different hosts such as bacteria and yeast. Microalgae offer a safe and cost-effective photosynthetic platform for producing recombinant proteins, including therapeutics and industrial enzymes. In this study, we optimized the production of recombinant xylanase expressed and secreted from the green alga, Chlamydomonas reinhardtii. The growth of the culture was optimized using response surface methodology (RSM) based on central composite design (CCD), with two numeric (culture incubation time and agitation rate) and one categoric (light intensity) factors. The optimum biomass concen-tration was obtained as 0.71 mg/mL from the CCD values. In addition, bubble column photobioreactors were set and compared for the culture growth, the protein concentration, and the enzyme activity under different light intensities and air flows. Increasing the aeration rate from 1 vvm to 2 vvm resulted in improved enzyme activity from 5330.5 U/g to 6277.7 U/g under 3500 lux illumination on the 3rd day of the culture. This study may lead to the further large-scale production of xylanase with high enzyme activity and reveal the advantage of the microalgae as a sustainable platform.