Polymer-Ceramic Composite Scaffolds: The Effect of Hydroxyapatite and β-tri-Calcium Phosphate

Abstract

The design of bioactive scaffolds with improved mechanical and biological properties is an important topic of research. This paper investigates the use of polymer-ceramic composite scaffolds for bone tissue engineering. Different ceramic materials (hydroxyapatite (HA) and β-tri-calcium phosphate (TCP)) were mixed with poly-ε-caprolactone (PCL). Scaffolds with different material compositions were produced using an extrusion-based additive manufacturing system. The produced scaffolds were physically and chemically assessed, considering mechanical, wettability, scanning electron microscopy and thermal gravimetric tests. Cell viability, attachment and proliferation tests were performed using human adipose derived stem cells (hADSCs). Results show that scaffolds containing HA present better biological properties and TCP scaffolds present improved mechanical properties. It was also possible to observe that the addition of ceramic particles had no effect on the wettability of the scaffolds.

Keywords: 3D printing; hydroxyapatite; scaffold; tri-calcium phosphate.

Figure 1

SEM (Scanning electron microscopy) images of (A) a poly-ε-caprolactone (PCL) scaffold top view and zoom-in view of filament; (B) a PCL scaffold cross section view; (C) a PCL/ hydroxyapatite (HA) 20 wt % scaffold top view and zoom-in view of filament; (D) a PCL/HA 20 wt % scaffold cross section view and zoom-in view of cut surface; (E) a PCL/ β-tri-calcium phosphate (TCP) 20 wt % scaffold top view and zoom-in view of filament; (F) a PCL/TCP 20 wt % scaffold cross section view and zoom-in view of cut surface.

Figure 2

Thermal Gravimetric Analysis (TGA) curves (a) and derivative thermogravimetric (DTG) curves (b) for all scaffolds.

Figure 3

Water drop on a PCL scaffold filament at 0 s (left) and 20 s (right).

Figure 4

Contact angles obtained for all processed scaffolds at 0 s and 20 s, respectively.

Figure 5

The compressive modulus of different materials. * Statistical evidence ($p<0.05$) using one-way analysis of variance (ANOVA) with Tukey test.

Figure 6

Live (green) and dead (red) cells on PCL, PCL/HA 10 wt %, PCL/HA 20 wt %, PCL/TCP 10 wt %, and PCL/TCP 20 wt % at day 1 (A–E, respectively, 20× magnification) and day 14 (F–J, respectively, 10× magnification).

Figure 7

Cell viability (%) for all scaffolds at day 1.

Figure 8

Fluorescence intensity for all different scaffolds at day 1, day 7, and day 14. ${}^{*}p<0.05$ and ${}^{**}p<0.01$ using one-way analysis of variance (ANOVA) with Tukey test.

Figure 9

SEM images of PCL/HA 20 wt % surface (A) without cells (printed scaffold) and (B) with cells after 14 days (cell cultured scaffold).

Figure 10

SEM images of cell attachment (A–E) and cell bridging (F–J) on the PCL, PCL/HA 10 wt %, PCL/HA 20 wt %, PCL/TCP 10 wt %, and PCL/TCP 20 wt % scaffolds, respectively.

Figure 11

Cross section of (A) a PCL scaffold and (B) a PCL/HA scaffold after 14 days of cell culture.

Figure 12

0/90° lay-down pattern and design characteristics.