Three dimensional TiO2 scaffolds are receiving renewed attention for bone tissue engineering (TE) due to their biocompatibility and attractive mechanical properties. However the bioactivity of these scaffolds is comparatively lower than that of bioactive glass or hydroxyapatite (HA) scaffolds. One strategy to improve bioactivity is to functionalize the surface of the scaffolds using biomolecules. Alkaline phosphatase (ALP) was chosen in this study due to its important role in the bone mineralization process. The current study investigated the ALP functionalization of 3D titanium dioxide scaffolds using self-polymerization of dopamine. Robust titanium scaffolds (compressive strength∼2.7 ± 0.3 MPa) were produced via foam replica method. Enzyme grafting was performed by dip-coating in polydopamine/ALP solution. The presence of ALP was indirectly confirmed by contact angle measurements and enzymatic activity study. The influence of the enzyme on the bioactivity, e.g. hydroxyapatite formation on the scaffold surface, was measured in simulated body fluid (SBF). After 28 days in SBF, 5 mg ALP coated titania scaffolds exhibited increased hydroxyapatite formation. It was thus confirmed that ALP enhances the bioactivity of titania scaffolds, converting an inert bioceramic in an attractive bioactive system for bone TE.

This paper reports the characteristics of ferrochrome slag and its feasibility as aggregate in refractories aiming to substitute virgin refractory raw materials. Refractory castable specimens were formulated with ferrochrome slag as an aggregate and commercial calcium aluminate cement as a binder. Objective was to prepare refractory specimens with a maximum slag utilization but simultaneously to sustain good properties, comparable to those of virgin raw material refractory products. Mechanical and thermo-physical properties of the cured, dried and sintered specimens were characterized. Cold crushing strengths of best performing ferrochrome slag containing specimens were higher than 90 MPa and compressive strength values measured at 1200 °C were over 9 MPa. Thermal insulation properties were even better than those of commercial refractory reference, showing thermal conductivity values as low as λRT−1000 °C = 1.3 − 0.9 W/m K. The liquid phase formation above 1200 °C limits the ferrochrome slag use for refractory applications. Results suggest ferrochrome slag’s feasibility as an aggregate raw material for refractory materials up to temperatures of 1200 °C in air and up to temperatures of 700 °C in acidic gaseous atmosphere. Possible applications for this kind of novel refractory materials are, e.g., insulating secondary layers or bottom zones in metallurgical processes to substitute virgin refractories. A direct contact to molten metal must be avoided, but they are applicable as, e.g. floorings when exposed only to occasional melt droplets. Graphic Abstract

Three dimensional titanium dioxide (TiO 2 ) scaffolds are receiving attention for the reconstruction of damaged bone tissue. Although these scaffolds show sufficient mechanical properties, their bioactivity is significantly lower than that of bioactive glass scaffolds. Sol-gel derived mesoporous bioactive glasses exhibit high bioactivity in vitro and can also be loaded with drugs and growth factors due to their tunable pore size. Hence, the main aim of this work is to produce and characterize TiO 2 scaffolds coated with sol-gel derived mesoporous calcium silicate spheres (MCS) and to test their in vitro bioactivity and drug delivery properties. TiO 2 scaffolds were coated with different wt% of MCS using a simple dip coating method. The bioactivity of the MCS-coated TiO 2 scaffolds was tested in vitro in simulated body fluid (SBF). TiO 2 scaffolds coated with 2 wt% and 4 wt% MCS showed bioactivity after 1 week of immersion in SBF. The formation of hydroxyapatite (HA) was confirmed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). Ibuprofen drug loading and release rate were investigated in MCS and MCS coated TiO 2 scaffolds. A 3 weeks in vitro drug release test was performed and the amount of drug released by MCS was measured by UV-Vis spectroscopy. The MCS were successfully loaded with Ibuprofen, as model drug. Sustained drug release was measured, proving the applicability of MCS as drug delivery carriers. Thus, TiO 2 scaffolds with enhanced functionalities were produced exploiting MCS coating. K E Y W O R D Sbioactivity, drug release, ibuprofen, mesoporous calcium silica coatings, scaffold, titania