TY - JOUR A1 - Kowalewicz, Katharina A1 - Vorndran, Elke A1 - Feichtner, Franziska A1 - Waselau, Anja-Christina A1 - Brueckner, Manuel A1 - Meyer-Lindenberg, Andrea T1 - In-vivo degradation behavior and osseointegration of 3D powder-printed calcium magnesium phosphate cement scaffolds JF - Materials N2 - Calcium magnesium phosphate cements (CMPCs) are promising bone substitutes and experience great interest in research. Therefore, in-vivo degradation behavior, osseointegration and biocompatibility of three-dimensional (3D) powder-printed CMPC scaffolds were investigated in the present study. The materials Mg225 (Ca\(_{0.75}\)Mg\(_{2.25}\)(PO\(_4\))\(_2\)) and Mg225d (Mg225 treated with diammonium hydrogen phosphate (DAHP)) were implanted as cylindrical scaffolds (h = 5 mm, Ø = 3.8 mm) in both lateral femoral condyles in rabbits and compared with tricalcium phosphate (TCP). Treatment with DAHP results in the precipitation of struvite, thus reducing pore size and overall porosity and increasing pressure stability. Over 6 weeks, the scaffolds were evaluated clinically, radiologically, with Micro-Computed Tomography (µCT) and histological examinations. All scaffolds showed excellent biocompatibility. X-ray and in-vivo µCT examinations showed a volume decrease and increasing osseointegration over time. Structure loss and volume decrease were most evident in Mg225. Histologically, all scaffolds degraded centripetally and were completely traversed by new bone, in which the remaining scaffold material was embedded. While after 6 weeks, Mg225d and TCP were still visible as a network, only individual particles of Mg225 were present. Based on these results, Mg225 and Mg225d appear to be promising bone substitutes for various loading situations that should be investigated further. KW - farringtonite KW - stanfieldite KW - 3D powder printing KW - scaffold KW - biocompatibility KW - degradable bone substitutes KW - osseointegration KW - in-vivo Micro-Computed Tomography Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-228929 SN - 1996-1944 VL - 14 IS - 4 ER - TY - JOUR A1 - Krieter, Detlef H. A1 - Jeyaseelan, Jarline A1 - Rüth, Marieke A1 - Lemke, Horst-Dieter A1 - Wanner, Christoph A1 - Drechsler, Christiane T1 - Clinical hemocompatibility of double-filtration lipoprotein apheresis comparing polyethersulfone and ethylene-vinyl alcohol copolymer membranes JF - Artificial Organs N2 - Activation of the complement system and leukocytes by blood–membrane interactions may further promote arteriosclerosis typically present in patients on lipoprotein apheresis. As clinical data on the hemocompatibility of lipoprotein apheresis are scarce, a controlled clinical study comparing two different types of plasma separation and fractionation membranes used in double-filtration lipoprotein apheresis was urgently needed, as its outcome may influence clinical decision-making. In a prospective, randomized, crossover controlled trial, eight patients on double-filtration lipoprotein apheresis were subjected to one treatment with recent polyethersulfone (PES) plasma separation and fractionation membranes and one control treatment using a set of ethylene-vinyl alcohol copolymer (EVAL) membranes. White blood cell (WBC) and platelet (PC) counts, complement factor C5a and thrombin–antithrombin III (TAT) concentrations were determined in samples drawn at defined times from different sites of the extracorporeal blood and plasma circuit. With a nadir at 25 minutes, WBCs in EVAL decreased to 33.5 ± 10.7% of baseline compared with 63.8 ± 22.0% at 20 minutes in PES (P < .001). The maximum C5a levels in venous blood reentering the patients were measured at 30 minutes, being 30.0 ± 11.2 µg/L with EVAL and 12.3 ± 9.0 µg/L with PES (P < .05). The highest C5a concentrations were found in plasma after the plasma filters (EVAL 56.1 ± 22.0 µg/L at 15 minutes vs PES 23.3 ± 15.2 µg/L at 10 minutes; P < .001). PC did not significantly decrease over time with both membrane types, whereas TAT levels did not rise until the end of the treatment without differences between membranes. Regarding lipoprotein(a) and low-density lipoprotein (LDL) cholesterol removal, both membrane sets performed equally. Compared with EVAL, PES membranes cause less leukocyte and complement system activation, the classical parameters of hemocompatibility of extracorporeal treatment procedures, at identical treatment efficacy. Better hemocompatibility may avoid inflammation-promoting effects through blood–material interactions in patients requiring double-filtration lipoprotein apheresis. KW - lipoprotein(a) KW - biocompatibility KW - fractionation membranev KW - hypercholesterolemia KW - LDL cholesterol KW - lipoprotein apheresis Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-258307 VL - 45 IS - 9 ER - TY - JOUR A1 - Mechau, Jannik A1 - Frank, Andreas A1 - Bakirci, Ezgi A1 - Gumbel, Simon A1 - Jungst, Tomasz A1 - Giesa, Reiner A1 - Groll, Jürgen A1 - Dalton, Paul D. A1 - Schmidt, Hans‐Werner T1 - Hydrophilic (AB)\(_{n}\) Segmented Copolymers for Melt Extrusion‐Based Additive Manufacturing JF - Macromolecular Chemistry and Physics N2 - Several manufacturing technologies beneficially involve processing from the melt, including extrusion‐based printing, electrospinning, and electrohydrodynamic jetting. In this study, (AB)\(_{n}\) segmented copolymers are tailored for melt‐processing to form physically crosslinked hydrogels after swelling. The copolymers are composed of hydrophilic poly(ethylene glycol)‐based segments and hydrophobic bisurea segments, which form physical crosslinks via hydrogen bonds. The degree of polymerization was adjusted to match the melt viscosity to the different melt‐processing techniques. Using extrusion‐based printing, a width of approximately 260 µm is printed into 3D constructs, with excellent interlayer bonding at fiber junctions, due to hydrogen bonding between the layers. For melt electrospinning, much thinner fibers in the range of about 1–15 µm are obtained and produced in a typical nonwoven morphology. With melt electrowriting, fibers are deposited in a controlled way to well‐defined 3D constructs. In this case, multiple fiber layers fuse together enabling constructs with line width in the range of 70 to 160 µm. If exposed to water the printed constructs swell and form physically crosslinked hydrogels that slowly disintegrate, which is a feature for soluble inks within biofabrication strategies. In this context, cytotoxicity tests confirm the viability of cells and thus demonstrating biocompatibility of this class of copolymers. KW - 3D printing KW - (AB)\(_{n}\) segmented copolymers KW - biocompatibility KW - melt electrowriting Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224513 VL - 222 IS - 1 ER -