Mechanical Properties of the Composite Material consisting of β-TCP and Alginate-Di-Aldehyde-Gelatin Hydrogel and Its Degradation Behavior

Abstract

This work aimed to determine the influence of two hydrogels (alginate, alginate-di-aldehyde (ADA)/gelatin) on the mechanical strength of microporous ceramics, which have been loaded with these hydrogels. For this purpose, the compressive strength was determined using a Zwick Z005 universal testing machine. In addition, the degradation behavior according to ISO EN 10993-14 in TRIS buffer pH 5.0 and pH 7.4 over 60 days was determined, and its effects on the compressive strength were investigated. The loading was carried out by means of a flow-chamber. The weight of the samples (manufacturer: Robert Mathys Foundation (RMS) and Curasan) in TRIS solutions pH 5 and pH 7 increased within 4 h (mean 48 ± 32 mg) and then remained constant over the experimental period of 60 days. The determination surface roughness showed a decrease in the value for the ceramics incubated in TRIS compared to the untreated ceramics. In addition, an increase in protein concentration in solution was determined for ADA gelatin-loaded ceramics. The macroporous Curasan ceramic exhibited a maximum failure load of 29 ± 9.0 N, whereas the value for the microporous RMS ceramic was 931 ± 223 N. Filling the RMS ceramic with ADA gelatin increased the maximum failure load to 1114 ± 300 N. The Curasan ceramics were too fragile for loading. The maximum failure load decreased for the RMS ceramics to 686.55 ± 170 N by incubation in TRIS pH 7.4 and 651 ± 287 N at pH 5.0.

Keywords: ADA-gelatin gels; degradation behavior; fracture strength; mechanical properties; β-TCP.

Figure 1

ESEM images of (a): Robert Mathys Foundation (RMS) and (b): Curasan β-TCP Ceramics; ESEM images of RMS Ceramics in TRIS buffer: (c): pH 5.0; (d): pH 7.4; Curasan Ceramics in TRIS buffer: (e): pH 7.4; (f): pH 5.0; Images were taken with an FEI Quanta 250 FEG and (e,f) FEI Scios, acceleration voltage 10 kV, HFW of 46.6 µm.

Figure 2

Dispersive X-ray spectroscopy (EDX) spectra of (a): RMS ceramics; (b): Curasan Ceramics; XRD pattern of (c): RMS ceramics; (d): Curasan ceramics; (e): XRD pattern RMS, Curasan with reference lines for β-TCP; EDX measurements carried out at Philips XL 30 FEG ESEM with EDX unit, 12 kV acceleration voltage and 300 s lifetime counting period; XRD measurements with Bruker D8 Advance, (measurement conditions: 40 kV/40 mA, 1°2 theta/min, step size 0.02°2 theta).

Figure 2

Dispersive X-ray spectroscopy (EDX) spectra of (a): RMS ceramics; (b): Curasan Ceramics; XRD pattern of (c): RMS ceramics; (d): Curasan ceramics; (e): XRD pattern RMS, Curasan with reference lines for β-TCP; EDX measurements carried out at Philips XL 30 FEG ESEM with EDX unit, 12 kV acceleration voltage and 300 s lifetime counting period; XRD measurements with Bruker D8 Advance, (measurement conditions: 40 kV/40 mA, 1°2 theta/min, step size 0.02°2 theta).

Figure 3

Pore size distribution (a): RMS ceramics and (b): Curasan ceramics.

Figure 4

3D laser scanning microscopy images of the surface of (a): RMS and (b): Curasan Ceramics, Inner surface after incubation in TRIS buffer pH 7.4 for 60d (c): RMS and (d): Curasan ceramics; white bar represents 10 µm, Images taken with KEYENCE VK-X210.

Figure 4

3D laser scanning microscopy images of the surface of (a): RMS and (b): Curasan Ceramics, Inner surface after incubation in TRIS buffer pH 7.4 for 60d (c): RMS and (d): Curasan ceramics; white bar represents 10 µm, Images taken with KEYENCE VK-X210.

Figure 5

Micro-computed tomography (µCT) reconstruction of the different β-TCP ceramics: (a): RMS and (b): Curasan; µCT reconstruction of the porosity (c): RMS and (d): Curasan, the pores are displayed in false colors, the brighter, the larger the pores, the white bar corresponds to 1 mm, the colored bar goes from 0 (dark blue) to 0.316 mm (orange).

Figure 5

Micro-computed tomography (µCT) reconstruction of the different β-TCP ceramics: (a): RMS and (b): Curasan; µCT reconstruction of the porosity (c): RMS and (d): Curasan, the pores are displayed in false colors, the brighter, the larger the pores, the white bar corresponds to 1 mm, the colored bar goes from 0 (dark blue) to 0.316 mm (orange).

Figure 6

Weight development over the duration of the experiment; (a): incubation in TRIS pH 5.0, (b): incubation in TRIS pH 7.4; CG…control group = empty RMS; ALG…RMS + Alginate; ADA/gelatin … RMS + ADA/gelatin; CUR … empty Curasan.

Figure 7

Overview of protein release out of the alginate–alginate-di-aldehyde (ADA-gelatin) hydrogel; (a): pH 5.0; (b) pH 7.4.

Figure 8

Maximum tolerated force for the different samples; (a): Comparison Curasan vs. RMS; (b): Control Group after incubation in different buffers for 30 (SBF) or 60 days; (c): Alginate loaded RMS ceramics after incubation in the different buffers for 30 (SBF) or 60 days; (d): ADA/GEL loaded RMS ceramics after incubation in the different buffers for 30 (SBF) or 60 days; the measurements was performed on ZWICK/Roell Z005 Universal Testing machine; * significant difference with p < 0.05.

Figure 8

Maximum tolerated force for the different samples; (a): Comparison Curasan vs. RMS; (b): Control Group after incubation in different buffers for 30 (SBF) or 60 days; (c): Alginate loaded RMS ceramics after incubation in the different buffers for 30 (SBF) or 60 days; (d): ADA/GEL loaded RMS ceramics after incubation in the different buffers for 30 (SBF) or 60 days; the measurements was performed on ZWICK/Roell Z005 Universal Testing machine; * significant difference with p < 0.05.