Bioactive Inorganic Scaffolds

Contact:
Prof. Dr. rer. nat. Uwe Gbureck
Telephone +49(0)931 201-73550
uwe.gbureck@uni-wuerzburg.de

Main strategies followed at FMZ to improve the typical brittle fracture behavior of bioceramics and cements are the integration of reinforcing fibers or by using a “dual-setting” approach. The latter is based on a simultaneous formation of a second hydrogel matrix within the cement to overcome the typical brittle behavior of the cement.  Here, reactive monomer systems are dissolved in the cement liquid and rapidly polymerized during setting by internal or external stimuli. This forms a hydrogel matrix with embedded cement particles, which are subsequently converted into the setting product to form interpenetrating hydrogel-cement composites. The advantages of this approach compared to simply adding dissolved polymers are the possibility of a higher polymer loading of the cement (and hence a large strength and toughness increase) as well as practically unchanged viscosity of the fresh cement paste. This concept was applied to a couple of different polymers such as Poly-hydroxyethylmethacrylate (poly-HEMA), silk fibroin or isocyanate functionalized star-PEGs leading to a strong reduction of cement brittleness and hence improved fracture behavior.

Cement powders are also used for rapid-prototyping by 3D printing techniques for the construction of individualized geometries with a high lateral resolution (Figure left) and precisely defined macropores for blood vessel ingrowth (Figure right). The advantage of using cements for 3D printing is a processing regime at low temperature, which allows the fabrication of hydrated, secondary phosphates such as brushite (CaHPO₄ ·2H₂O) or struvite (MgNH₄PO₄ ·6H₂O), which are more soluble than commonly used hydroxyapatite or tricalcium phosphate ceramics. In addition, the use of multi-colour printers allows the local deposition of bioactives in the 3D scaffolds during printing for a spatial control of tissue response and drug release kinetics.

The biocompatibility especially of non-degradable implant materials arises from its surface. Electrochemically assisted deposition is used to equip metallic surfaces with low-crystalline calcium and magnesium phosphate coatings. One aim of these studies is the development of novel multi-phase coatings with incorporated ions, which combine bactericidal and bioactive properties and hence can decrease the risk of inflammation after surgery and support the subsequent in-growth of the medical implant. Another strategy for increasing the lifetime of orthopedic implants is the deposition of hard coatings by physical vapor deposition (PVD). Here, refractory metal (Ti, Zr, Ta) oxides and nitrides are used, which can be further modified by silver ions for antimicrobial properties.