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    3D printed biodegradable polyurethaneurea elastomer recapitulates skeletal muscle structure and function
    (American Chemical Society (ACS), 2021) Gokyer, Seyda; Berber, Emine; Vrana, Engin; Orhan, Kaan; Abou Monsef, Yanad; Guvener, Orcun; Zinnuroglu, Murat; Oto, Cagdas; Huri, Pinar Yilgor; Department of Chemistry; Department of Chemistry; Yılgör, Emel; Yılgör, İskender; Researcher; Faculty Member; Department of Chemistry; College of Sciences; College of Sciences; N/A; 24181
    Effective skeletal muscle tissue engineering relies on control over the scaffold architecture for providing muscle cells with the required directionality, together with a mechanical property match with the surrounding tissue. Although recent advances in 3D printing fulfill the first requirement, the available synthetic polymers either are too rigid or show unfavorable surface and degradation profiles for the latter. In addition, natural polymers that are generally used as hydrogels lack the required mechanical stability to withstand the forces exerted during muscle contraction. Therefore, one of the most important challenges in the 3D printing of soft and elastic tissues such as skeletal muscle is the limitation of the availability of elastic, durable, and biodegradable biomaterials. Herein, we have synthesized novel, biocompatible and biodegradable, elastomeric, segmented polyurethane and polyurethaneurea (TPU) copolymers which are amenable for 3D printing and show high elasticity, low modulus, controlled biodegradability, and improved wettability, compared to conventional polycaprolactone (PCL) and PCL-based TPUs. The degradation profile of the 3D printed TPU scaffold was in line with the potential tissue integration and scaffold replacement process. Even though TPU attracts macrophages in 2D configuration, its 3D printed form showed limited activated macrophage adhesion and induced muscle-like structure formation by C2C12 mouse myoblasts in vitro, while resulting in a significant increase in muscle regeneration in vivo in a tibialis anterior defect in a rat model. Effective muscle regeneration was confirmed with immunohistochemical assessment as well as evaluation of electrical activity produced by regenerated muscle by EMG analysis and its force generation via a custom-made force transducer. Micro-CT evaluation also revealed production of more muscle-like structures in the case of implantation of cell-laden 3D printed scaffolds. These results demonstrate that matching the tissue properties for a given application via use of tailor-made polymers can substantially contribute to the regenerative outcomes of 3D printed tissue engineering scaffolds.
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    Liposomes under shear: structure, dynamics, and drug delivery applications
    (Wiley-VCH, 2023) Department of Chemical and Biological Engineering; N/A; Şenses, Erkan; Karaz, Selcan; Faculty Member; Master Student; Department of Chemical and Biological Engineering; College of Engineering; Graduate School of Sciences and Engineering; 280298; N/A
    The targeted delivery to specific locations while not causing damage to healthy tissues efficiently remains a challenge in drug delivery systems. Through addressing this issue, stimuli-responsive materials have been under investigation. As one of the fundamental forces associated with blood flow, shear stress is taken as an advantage to design shear-sensitive drug carriers. Although blood flow is modeled as laminar flow under normal conditions, in case of constrictions caused by endothelial shear stress, cardiovascular diseases, or angiogenesis due to tumor formation, local shear stress can dramatically increase. To date, shear-sensitive materials have been investigated under two main categories: shear-disaggregated and shear-deformed nanoparticles based on their structural mechanism after exposure to high-shear stress. Among them, liposomes are promising materials with their soft and deformable structure, high biocompatibility, controlled-release properties, and sensitivity to shear stress. Herein, in this review, the effects of shear stress on liposomes in terms of their structural changes, flow regimes, rheological properties, and drug delivery applications are discussed. It is believed that this work provides a basis for designing more effective drug delivery systems considering the complexity of the human body.