Alina Grünewald

Increase in VEGF secretion from human fibroblast cells by bioactive glass S53P4 to stimulate angiogenesis in bone

Bioactive glasses (BAGs) are being investigated for the repair and reconstruction of bone defects, as they exhibit osteoconductive and osteostimulatory potential. However, successful bone regeneration requires also the neovascularization of the construct which is, among other factors, guided by vascular endothelial growth factor (VEGF). In this study, BAG S53P4 (53% SiO2 , 23% Na2 O, 20% CaO, 4% P2 O5 ) is investigated in relation to VEGF-release and response of fibroblast cells. Human CD-18CO fibroblasts were cultivated in contact with different granules of different sizes (0.5-0.8 mm, 1.0-2.0 mm, and 2.0-3.15 mm) and at different concentrations (0-1 wt/vol % of BAG) for 72 h. The analysis of morphology revealed no toxic effect for all granule sizes and concentrations. Compared with the reference, lactate dehydrogenase-activity of CCD-18CO cells increased in contact with BAG samples. The VEGF release from CCD-18CO fibroblasts cultured on different granule sizes and at different concentrations after 72 h of incubation was quantified. It was found that particles of 0.5-0.8 mm and 1.0-2.0 mm in size enhanced VEGF release, whereas BAG particle sizes of 2.0-3.15 mm led to inhibition of VEGF release. The results are relevant to understand the influence of the particle size and concentration of BAG S53P4 on VEGF expression and neovascularization.

Antibacterial 45S5 Bioglass®-based scaffolds reinforced with genipin cross-linked gelatin for bone tissue engineering

45S5 Bioglass® (BG) scaffolds with high porosity (>90%) were coated with genipin cross-linked gelatin (GCG) and further incorporated with poly(p-xylyleneguanidine) hydrochloride (PPXG). The obtained GCG coated scaffolds maintained the high porosity and well interconnected pore structure. A 26-fold higher compressive strength was provided to 45S5 BG scaffolds by GCG coating, which slightly retarded but did not inhibit the in vitro bioactivity of 45S5 BG scaffolds in SBF. Moreover, the scaffolds were made antibacterial against both Gram-positive and Gram-negative bacteria by using polyguanidine, i.e. PPXG, in this study. Osteoblast-like cells (MG-63) were seeded onto PPXG and GCG coated scaffolds. PPXG was biocompatible with MG-63 cells at a low concentration (10 μg mL-1). MG-63 cells were shown to attach and spread on both uncoated and GCG coated scaffolds, and the mitochondrial activity measurement indicated that GCG coating had no negative influence on the cell proliferation behavior of MG-63 cells. The developed novel antibacterial bioactive 45S5 BG-based composite scaffolds with improved mechanical properties are promising candidates for bone tissue engineering.

45S5 bioactive glass-based scaffolds coated with cellulose nanowhiskers for bone tissue engineering

Highly porous 45S5 bioactive glass-based scaffolds prepared by foam replication method were coated with cellulose nanowhiskers by dip coating method. The obtained cellulose nanowhisker-coated scaffolds retained the high porosity and interconnected pore structure. The cellulose coating improved the mechanical properties of the scaffolds and did not hinder their bioactivity in simulated body fluid. In vitro biocompatibility assessment was carried out by qualitative evaluation of the morphology of osteoblast-like cells (MG-63) seeded onto the scaffolds. The cells were shown to attach and spread on both uncoated scaffolds and cellulose nanowhisker-coated scaffolds, thus cellulose nanowhisker coating seems to have no negative influence on the behavior of MG-63 cells. The obtained bioactive and biocompatible composite scaffolds represent promising candidates for bone tissue engineering applications.

Pulse electrodeposition and characterization of non-continuous, multi-element-doped hydroxyapatite bioceramic coatings

Multi-element-modified bioactive hydroxyapatite (mHAp) coatings were developed onto commercial titanium alloy material (Ti6Al4V) in clusters. The coatings were prepared by applying pulse current deposition technique. The pure HAp layer was doped and co-deposited with Ag+, Zn2+, Mg2+, and Sr2+ ions. Potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) were performed in simulated body fluid (SBF) using three-electrode open cell over a long time period to assess the corrosion properties of bioceramic coatings. The biocompatible characteristics of layers were investigated by seeding osteoblast-like MG-63 cells onto the samples’ surface. The morphology and structure of coatings were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) while cross-sectional analyses were carried out by focused ion beam (FIB). The elemental composition of coatings was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The biocompatible measurements revealed enhanced bioactivity of modified HAp compared to uncoated implant materials and pure HAp bioceramic coating. The corrosion tests confirmed that the coatings were biodegradable.

Influence of dissolution products of a novel Ca-enriched silicate bioactive glass-ceramic on VEGF release from bone marrow stromal cells

Abstract This study evaluated the influence of ionic dissolution products of a novel Ca-enriched silicate bioactive glass compared to commercial available hydroxyapaptite samples (Endobonr) on cell activity and vascular endothelial growth factor (VEGF) release in vitro. Bone marrow stromal cells (ST-2) were cultivated with the supernatant of granules of different sizes and at different concentrations (0-1 wt/vol % of granules) for 48 h. In addition to in vitro studies, Ca-ion release from all as cell morphology observation revealed no cytotoxic effect of the released products from all tested materials. It was found that supernatants from granules in concentrations of 1 wt/vol %enhanced the VEGF release from ST2 cells, which is important as a marker of the vascularisation ability of the glass during the bone healing process.