2020, Apsite, Indra, Constante, Gissela, Dulle, Martin, Vogt, Lena, Caspari, Anja, Boccaccini, Aldo R., Synytska, Alla, Salehi, Sahar, Ionov, Leonid

In this paper, we describe the application of the 4D biofabrication approach for the fabrication of artificial nerve graft. Bilayer scaffolds consisting of uniaxially aligned polycaprolactone-poly(glycerol sebacate) (PCL-PGS) and randomly aligned methacrylated hyaluronic acid (HA-MA) fibers were fabricated using electrospinning and further used for the culture of PC-12 neuron cells. Tubular structures form instantly after immersion of fibrous bilayer in an aqueous buffer and the diameter of obtained tubes can be controlled by changing bilayer parameters such as the thickness of each layer, overall bilayer thickness, and medium counterion concentration. Designed scaffolds showed a self-folded scroll-like structure with high stability after four weeks of real-time degradation. The significance of this research is in the fabrication of tuneable tubular nerve guide conduits that can simplify the current existing clinical treatment of neural injuries. © 2020 The Author(s). Published by IOP Publishing Ltd.

2004, Atiq, Shabbar, Rawlings, Rees D., Boccaccini, Aldo R.

Α study of the ballistic impact resistance of a commercial wired glass has been undertaken using a gas gun capable of velocities up to 400 m s-1. The projectile was a steel ball and impact energies up to 7.32 J were used. The extent of the impact damage was assessed by the mass of ejected material, the area of the Hertzian cone left by the impact and residual strength. Crack morphologies similar to those reported in monolithic glasses were observed, namely ring, cone and radial cracks. The impact energy dependencies of the mass of ejected material and cone area were similar showing a rapid increase at energies above about 4.35 J. In contrast, the residual strength remained at 20 % or less of the as received wired glass irrespective of impact energy. This was attributed to the wire mesh remaining intact for the ballistic impact conditions investigated.

2015, Zaloga, Jan, Janko, Christina, Agarwal, Rohit, Nowak, Johannes, Müller, Robert, Boccaccini, Aldo R., Lee, Geoffrey, Odenbach, Stefan, Lyer, Stefan, Alexiou, Christoph

Superparamagnetic iron oxide nanoparticles (SPIONs) have attracted increasing attention in many biomedical fields. In magnetic drug targeting SPIONs are injected into a tumour supplying artery and accumulated inside the tumour with a magnet. The effectiveness of this therapy is thus dependent on magnetic properties, stability and biocompatibility of the particles. A good knowledge of the effect of storage conditions on those parameters is of utmost importance for the translation of the therapy concept into the clinic and for reproducibility in preclinical studies. Here, core shell SPIONs with a hybrid coating consisting of lauric acid and albumin were stored at different temperatures from 4 to 45 °C over twelve weeks and periodically tested for their physicochemical properties over time. Surprisingly, even at the highest storage temperature we did not observe denaturation of the protein or colloidal instability. However, the saturation magnetisation decreased by maximally 28.8% with clear correlation to time and storage temperature. Furthermore, the biocompatibility was clearly affected, as cellular uptake of the SPIONs into human T-lymphoma cells was crucially dependent on the storage conditions. Taken together, the results show that the particle properties undergo significant changes over time depending on the way they are stored.

1996, West, Grant, Taplin, David M. R., Boccaccini, Aldo R., Plucknett, Kevin, Lewis, Mike H.

The mechanical behaviour of three continuous Silicon carbide fibre-reinforced glass-ceramic matrix composites has been investigated at room and high temperatures. Commercially available composites with magnesium aluminosilicate, calcium aluminosilicate and barium magnesium aluminosilicate glass-ceramic matrices were considered. The materials were tested in the as-received and aged (heat-treated in a n oxidizing environment) condition. Four-point bend static tests and fiexural creep, fatigue and creep-fatigue tests were carried out a s well as a small quantity of tensile tests of aged composites. The experimental results have highlighted the importance of the carbon-rich layer at the fibre/matrix interface for obtaining "graceful" failures. At temperatures of 700 to 800 °C oxidative degradation of the interface results in significant strength reduction and a transition to brittle fracture mode. By rapid heat treatment of the materials at 1100°C for 1 h it is possible to seal the fibre ends by forming a silica "plug" which prevents oxygen ingress, retaining the carbon-rich interphase and composite behaviour. The results of the creep and creep-fatigue tests indicate low-cycle loading has a strong influence on the life of components at high temperatures.

2020, Polley, Christian, Distler, Thomas, Detsch, Rainer, Lund, Henrik, Springer, Armin, Boccaccini, Aldo R., Seitz, Hermann

The prevalence of large bone defects is still a major problem in surgical clinics. It is, thus, not a surprise that bone-related research, especially in the field of bone tissue engineering, is a major issue in medical research. Researchers worldwide are searching for the missing link in engineering bone graft materials that mimic bones, and foster osteogenesis and bone remodeling. One approach is the combination of additive manufacturing technology with smart and additionally electrically active biomaterials. In this study, we performed a three-dimensional (3D) printing process to fabricate piezoelectric, porous barium titanate (BaTiO3) and hydroxyapatite (HA) composite scaffolds. The printed scaffolds indicate good cytocompatibility and cell attachment as well as bone mimicking piezoelectric properties with a piezoelectric constant of 3 pC/N. This work represents a promising first approach to creating an implant material with improved bone regenerating potential, in combination with an interconnected porous network and a microporosity, known to enhance bone growth and vascularization.

2001, Boccaccini, Aldo R., Gevorkian, Gevork

The self-lubricating wear behaviour of a C-fibre reinforced borosilicate glass matrix composite in vacuum was investigated by using a rotating pump experimental facility. The vanes were made of the composite material and the stator of the pump was of cast iron. Glass composite wear was accompanied by material transfer onto the stator surface. The formation of isle-type and continuous graphitic films on the counter-body surface was observed. The continuous film provided adequate lubrication during friction, leading to a relatively low wear rate of the composite for the conditions investigated.

2021, Distler, Thomas, Polley, Christian, Shi, Fukun, Schneidereit, Dominik, Ashton, Mark D., Friedrich, Oliver, Kolb, Jürgen F., Hardy, John G., Detsch, Rainer, Seitz, Hermann, Boccaccini, Aldo R.

Electroactive hydrogels can be used to influence cell response and maturation by electrical stimulation. However, hydrogel formulations which are 3D printable, electroactive, cytocompatible, and allow cell adhesion, remain a challenge in the design of such stimuli-responsive biomaterials for tissue engineering. Here, a combination of pyrrole with a high gelatin-content oxidized alginate-gelatin (ADA-GEL) hydrogel is reported, offering 3D-printability of hydrogel precursors to prepare cytocompatible and electrically conductive hydrogel scaffolds. By oxidation of pyrrole, electroactive polypyrrole:polystyrenesulfonate (PPy:PSS) is synthesized inside the ADA-GEL matrix. The hydrogels are assessed regarding their electrical/mechanical properties, 3D-printability, and cytocompatibility. It is possible to prepare open-porous scaffolds via bioplotting which are electrically conductive and have a higher cell seeding efficiency in scaffold depth in comparison to flat 2D hydrogels, which is confirmed via multiphoton fluorescence microscopy. The formation of an interpenetrating polypyrrole matrix in the hydrogel matrix increases the conductivity and stiffness of the hydrogels, maintaining the capacity of the gels to promote cell adhesion and proliferation. The results demonstrate that a 3D-printable ADA-GEL can be rendered conductive (ADA-GEL-PPy:PSS), and that such hydrogel formulations have promise for cell therapies, in vitro cell culture, and electrical-stimulation assisted tissue engineering. © 2021 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH

1994, Boccaccini, Aldo R., Ondracek, Gerhard, Syhre, Claudia

The reinforcement of a borosihcate glass with Hastelloy X short fibres is discussed. A fabrication process consisting of wet mixing of the glass powder and the metallic fibres and hot pressing of the mixtures was developed. Composites containing 15 vol.% fibres homogeneously distributed in a near fully dense glass matrix were obtained. Both Young's modulus and fracture strength increased with increasing volume fraction of fibres. The experimental values for the Young's modulus are in agreement with theoretical predictions. No fibre pull-out during fracture was detected and there is a good interfacial bond. By means of a rule-of-mixture calculation for the fracture energy, a five-fold increase in fracture toughness for composites containing 15 vol.% fibres can be predicted.

1999, Boccaccini, Aldo R., Pfeiffer, Kerstin

Improving the thermal shock resistance of sintered glasses is an important task to broaden their technical and structural applications. In this study, the incorporation of second phase particles with low Young's modulus (E) into glass matrices to form composite materials is shown to be a convenient approach to increase their thermal shock resistance. Novel aluminosilicate glass matrix composites containing aluminium titanate (Al₂TiO₅) particles were fabricated by powder technology and pressureless sintering. By incorporating up to 30 vol.% of aluminium titanate particles a nearly fourfold increase of the thermal shock resistance was achieved. This was determined by measuring the critical temperature difference necessary to cause superficial cracks in cylindrical samples subjected to water-quench tests. The experimental results are shown to confirm qualitatively the theoretical prediction of the model of Hasselman et al. for the thermal shock resistance of low-E'/high-E composites.

2002, Rozenstrauha, Ineta, Cimdins, Rudolfs, Berzina, Liga, Bajare, Diana, Bossert, Jörg, Boccaccini, Aldo R.

Powder technology and sintering were used to fabricate glass-ceramic matrix composites from Latvian industrial wastes and alumina platelets reinforcement. The optimization of the sintering behaviour of glass-ceramic compositions containing clay and alumina platelets was carried out. Highly crystalline and dense products (> 90 % theoretical density) were fabricated by sintering at temperatures in the range 1040 to 1060 °C, depending on composition. Addition of waste glass to influence the sintering temperature and sintering interval was also investigated. Composites showed higher fracture strength (up to 97 MPa) and hardness than unreinforced glass-ceramics. The "best" composition in terms of density and mechanical properties contained 20 wt% alumina platelets. The matrix exhibited a microstructure composed mainly of elongated crystals of pyroxene type in a residual glassy matrix. These composites are candidates for applications as building materials, such as floor and wall tiles, and for manufacturing machine elements and parts.