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Hydrogels are ideal materials for mimicking and engineering soft tissue. Hyaluronic acid is a linear polysaccharide native to the human extracellular matrix. In this study, we first develop and characterize two hydrogel compositions built from oxidized HA and gelatin with and without alginate-di-aldehyde (ADA) crosslinked by ionic and enzymatic agents with potential applications in soft tissue engineering and tissue mimicking structures. The stability under incubation conditions was improved by adjusting crosslinking times. Through large-strain mechanical measurements, the hydrogels' properties were compared to human brain tissue and the samples containing ADA revealed similar mechanical properties to the native tissue specimens in cyclic compression-tension.

3D printing for tissue engineering requires biomaterials with mechanical and biological properties suitable for both tissue regeneration and the printing process. A filament made of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) combined with 45S5 Bioglass (BG) was used to print 3D scaffolds by fused deposition modeling (FDM). Chemical treatment of BG particles with chlorotrimethylsilane (CTMS) improved the ductility of the extruded filaments and allowed excellent printability. Controlling the printing parameter infill density (I%), from 20 to 90%, scaffolds were obtained with interconnected pores and channel sizes in the 100–800 µm range and exhibiting tensile modulus from 0.25 to 1.36 GPa. PHBV + BG scaffolds and PHBV scaffolds coated with CTMS treated BG particles, as a model of a rough and biologically active coating, showed no cytotoxic effects, and cells preferred the scaffolds containing BG in terms of cell spreading. Mechanical and biological properties of the scaffolds were similar to those of the extracellular matrix (ECM) of trabecular bone.

During bioprinting, cells are suspended in a viscous bioink and extruded under pressure through small diameter printing needles. The combination of high pressure and small needle diameter exposes cells to considerable shear stress, which can lead to cell damage and death. Approaches to monitor and control shear stress-induced cell damage are currently not well established. To visualize the effects of printing-induced shear stress on plasma membrane integrity, we add FM 1-43 to the bioink, a styryl dye that becomes fluorescent when bound to lipid membranes, such as the cellular plasma membrane. Upon plasma membrane disruption, the dye enters the cell and also stains intracellular membranes. Extrusion of alginate-suspended NIH/3T3 cells through a 200 µm printing needle led to an increased FM 1-43 incorporation at high pressure, demonstrating that typical shear stresses during bioprinting can transiently damage the plasma membrane. Cell imaging in a microfluidic channel confirmed that FM 1-43 incorporation is caused by cell strain. Notably, high printing pressure also impaired cell survival in bioprinting experiments. Using cell types of different stiffnesses, we find that shear stress-induced cell strain, FM 1-43 incorporation and cell death were reduced in stiffer compared to softer cell types and demonstrate that cell damage and death correlate with shear stress-induced cell deformation. Importantly, supplementation of the suspension medium with physiological concentrations of CaCl2 greatly reduced shear stress-induced cell damage and death but not cell deformation. As the sudden influx of calcium ions is known to induce rapid cellular vesicle exocytosis and subsequent actin polymerization in the cell cortex, we hypothesize that calcium supplementation facilitates the rapid resealing of plasma membrane damage sites. We recommend that bioinks should be routinely supplemented with physiological concentrations of calcium ions to reduce shear stress-induced cell damage and death during extrusion bioprinting.

Hydrogels that allow for the successful long-term in vitro culture of cell-biomaterial systems to enable the maturation of tissue engineering constructs are highly relevant in regenerative medicine. Naturally derived polysaccharide-based hydrogels promise to be one material group with enough versatility and chemical functionalization capability to tackle the challenges associated with long-term cell culture. We report a marine derived oxidized alginate, alginate dialdehyde (ADA), and gelatin (GEL) system (ADA-GEL), which is cross-linked via ionic (Ca2+) and enzymatic (microbial transglutaminase, mTG) interaction to form dually cross-linked hydrogels. The cross-linking approach allowed us to tailor the stiffness of the hydrogels in a wide range (from 30 days) degradation kinetics. The cytocompatibility of mTG cross-linked ADA-GEL was assessed using NIH-3T3 fibroblasts and ATDC-5 mouse teratocarcinoma cells. Both cell types showed highly increased cellular attachment on mTG cross-linked ADA-GEL in comparison to Ca2+ cross-linked hydrogels. In addition, ATDC-5 cells showed a higher proliferation on mTG cross-linked ADA-GEL hydrogels in comparison to tissue culture polystyrene control substrates. Further, the attachment of human umbilical vein endothelial cells (HUVEC) on ADA-GEL (+) mTG was confirmed, proving the suitability of mTG+Ca2+ cross-linked ADA-GEL for several cell types. Summarizing, a promising platform to control the properties of ADA-GEL hydrogels is presented, with the potential to be applied in long-term cell culture investigations such as cartilage, bone, and blood-vessel engineering, as well as for biofabrication.

Hydrogels are key components in several biomedical research areas such as drug delivery, tissue engineering, and biofabrication. Here, a novel ABA-type triblock copolymer comprising poly(2-methyl-2-oxazoline) as the hydrophilic A blocks and poly(2-phenethyl-2-oxazoline) as the aromatic and hydrophobic B block is introduced. Above the critical micelle concentration, the polymer self-assembles into small spherical polymer micelles with a hydrodynamic radius of approx 8-8.5 nm. Interestingly, this specific combination of hydrophilic and hydrophobic aromatic moieties leads to rapid thermoresponsive inverse gelation at polymer concentrations above a critical gelation concentration (20 wt %) into a macroporous hydrogel of densely packed micelles. This hydrogel exhibited pronounced viscoelastic solid-like properties, as well as extensive shear-thinning, rapid structure recovery, and good strain resistance properties. Excellent 3D-printability of the hydrogel at lower temperature opens a wide range of different applications, for example, in the field of biofabrication. In preliminary bioprinting experiments using NIH 3T3 cells, excellent cell viabilities of more than 95% were achieved. The particularly interesting feature of this novel material is that it can be used as a printing support in hybrid bioink systems and sacrificial bioink due to rapid dissolution at physiological conditions.

Hydrogels are key components in bioink formulations to ensure printability and stability in biofabrication. In this study, a well-known Diels-Alder two-step post-polymerization modification approach is introduced into thermogelling diblock copolymers, comprising poly(2-methyl-2-oxazoline) and thermoresponsive poly(2-n-propyl-2-oxazine). The diblock copolymers are partially hydrolyzed and subsequently modified by acid/amine coupling with furan and maleimide moieties. While the thermogelling and shear-thinning properties allow excellent printability, trigger-less cell-friendly Diels-Alder click-chemistry yields long-term shape-fidelity. The introduced platform enables easy incorporation of cell-binding moieties (RGD-peptide) for cellular interaction. The hydrogel is functionalized with RGD-peptides using thiol-maleimide chemistry and cell proliferation as well as morphology of fibroblasts seeded on top of the hydrogels confirm the cell adhesion facilitated by the peptides. Finally, bioink formulations are tested for biocompatibility by incorporating fibroblasts homogenously inside the polymer solution pre-printing. After the printing and crosslinking process good cytocompatibility is confirmed. The established bioink system combines a two-step approach by physical precursor gelation followed by an additional chemical stabilization, offering a broad versatility for further biomechanical adaptation or bioresponsive peptide modification.

Bu çalışmanın amacı hedef grupta organ bağışı ve nakli konusunda bilgi düzeyinin artırılması, yanlış ya da eksik bilgilerin giderilmesi ve bu konuda farkındalığı artırmak için yapılan eğitimin etkinliğinin incelenmesidir. Bu araştırma organ bağışı ve nakli eğitiminin etkinliğini saptamayı amaçlayan müdahale tipinde epidemiyolojik bir çalışmadır. Bu çalışma 2016 yılında Kasım-Aralık aylarında ve 2017 yılı Nisan ayında Çanakkale Belediyesi’ne ait Barbaros, Troia ve Esenler Sosyal Yaşam Merkezleri’nde yürütüldü. Sosyal yaşam evlerinde günlük aktivitelere katılan bireylerden çalışmaya katılmaya gönüllü olanlar çalışmaya dâhil edildi. Katılımcılara organ bağışı ve nakli konusunda eğitim verildi. Bu çalışmada katılımcılar (n=55) ön test, son test ve tekrar test uygulanarak değerlendirildi. Çalışma grubunun tamamı kadındı. ‘Beyin ölümü gerçekleşen biri tekrar hayata dönebilir mi?’ sorusuna ön testte katılımcıların %55,8’i, son testte ve tekrar testte %84,6’sı hayır cevabı verdi. Bu fark istatistiksel olarak anlamlıydı (p=0.0001). Katılımcıların ön testte %38,5’i, son testte %59,6’sı ve tekrar testte %55,8’i organ bağışında bulunmayı düşündüğünü belirtti ve bu fark istatistiksel olarak anlamlıydı (p=0.004). Çalışmamızın sonuçları, eğitim öncesi bilgi ve tutum durumlarının eğitim sonrasında iyileştirilebilmesine rağmen 3 ay sonra yapılan tekrar testte bilgi ve tutum durumlarında gerileme olduğunu göstermektedir. Bireylerin tekrarlayıcı eğitimler ve bilgilendirme toplantıları ile bu konudaki duyarlılıklarının artırılması gerekmektedir.Anahtar Kelimeler: Organ bağışı, beyin ölümü, eğitim etkinliği, ÇanakkaleAbstract:The aim of this study is investigate the efficacy of training given to increase the knowledge levels about organ donation and transplantation in the target group, to correct mistaken or deficient information and to increase awareness of this topic. This research aiming to identify the efficacy of organ donation and transplantation training is an interventional-type epidemiological study. This study was completed in November-December of 2016 and April of 2017 in the Barbaros, Troia and Esenler Social Life Centers belonging to Canakkale Municipality. Individuals in daily activities in the social life centers who volunteered to participate were included in the study. Participants were given training on organ donation and transplantation. Participants (n=52) were assessed pre-test, post-test and repeat test in the present study. The whole study group were women. The rate giving the answer no to the question “Can someone who is brain dead return to life?” was 55.8% on the pre-test, while it was 84.6% on the post-test and repeat test and this difference was statistically significant(p=0.0001). Of participants, 38.5% stated they would consider organ donation on the pre-test, 59.6% said they would on the post-test and 55.8% said they would on the repeat test and this difference was statistically significant(p=0.004). The result of our study is that though knowledge and attitude levels before training were improved after training, repeated test completed 3 months later showed regressions in knowledge and attitude levels. Repeated training and information meetings are required to increase the sensitivity of the individual about this topic.

One of the main problems encountered in cancer pathologies is the lack of proper in vitro systems resembling the architecture of tumoral tissues. Since 2D surfaces do not represent the morpho-mechanical characteristics of malignant milieus, 3D systems are rapidly gaining interest in the field of Biomaterials for Cancer Research. In this work, we used a new kind of hydrogel-based scaffold constituted by crosslinked alginate di-aldehyde (ADA) and gelatin (GEL) to mimic the tumoral milieu in vitro by biofabrication. For this purpose, flat 2D films and 3D bioprinted scaffolds were crosslinked with solutions of calcium, barium, and combinations of the two. These structures were analyzed in terms of their chemical and mechanical properties, as well as their biological compatibility in the presence of the tumoral cell line HCT116 (colorectal cancer). Our results indicate that ADA-GEL, crosslinked with these divalent ions, can perform effectively as an artificial cancer model, matching the mechanical properties of colorectal tumors, as well as enabling cell growth in confinement. Furthermore, the use of different combinations of divalent ions allowed the tailoring of the mechanical properties of the material. The cell-loaded ADA-GEL constructs are not significantly affected by the type of crosslinking ion. The best outcome was achieved when 3D printed structures were produced with an ADA concentration of 2.5 (w/v)% and crosslinked with barium, showing remarkable results in terms of printability and mechanical properties. With this composition and barium as the crosslinking ion, a stiffness of 44.97 kPa was achieved, compared with calcium crosslinked samples, where it was only possible to achieve an elastic modulus of 21.55 kPa. This work demonstrates that ADA-GEL-based matrices are a very interesting option to perform as tumor-like scaffolds, which could be used to improve current methods of drug testing as well as for personalized medicine.

Many different biofabrication approaches as well as a variety of bioinks have been developed by researchers working in the field of tissue engineering. A main challenge for bioinks often remains the difficulty to achieve shape fidelity after printing. In order to overcome this issue, a homogeneous pre-crosslinking technique, which is universally applicable to all alginate-based materials, was developed. In this study, the Young’s Modulus after post-crosslinking of selected hydrogels, as well as the chemical characterization of alginate in terms of M/G ratio and molecular weight, were determined. With our technique it was possible to markedly enhance the printability of a 2% (w/v) alginate solution, without using a higher polymer content, fillers or support structures. 3D porous scaffolds with a height of around 5 mm were printed. Furthermore, the rheological behavior of different pre-crosslinking degrees was studied. Shear forces on cells as well as the flow profile of the bioink inside the printing nozzle during the process were estimated. A high cell viability of printed NIH/3T3 cells embedded in the novel bioink of more than 85% over a time period of two weeks could be observed.

The main objective of this research was to investigate the oxidative destruction of free cyanide with hydrogen peroxide and copper-impregnated pumice as a heterogeneous catalyst. Original or copper-impregnated pumices added alone were not effective adsorbents of negatively charged cyanide ions due to incompatible surface interactions. Peroxide and original pumices added together were also ineffective in removing cyanide. However, for all of the three natural pumices tested with various particle size fractions, the use of copper-impregnated pumices and peroxide together significantly enhanced both the initial rate and extent of cyanide removal. Although copper-impregnated specific surface area was the major factor affecting the rate and extent of cyanide destruction for a particular pumice source with similar surface chemistries, the type of surface chemistry (i.e., specific functional groups) within different pumice sources also appears to be a very important factor. Lower rates and extents of cyanide removals were observed at pH 11 compared to pH 8 probably because of the negative impacts of alkaline conditions in terms of scavenging peroxide and forming more negatively charged pumice surfaces. Both the initial rate and ultimate extent of cyanide removals were generally higher at a temperature of 20 degrees C compared with those found at 10 degrees C. The use of copper-impregnated pumice as a light, cheap, readily available, natural, and porous heterogeneous catalyst either in completely mixed/suspended or fixed-bed reactor configurations may be an effective treatment technology for cyanide removal from solution. This new approach may minimize downstream metal removal problems experienced in conventional cyanide oxidation technologies.