Investigating the Influence of Architecture and Material Composition of 3D Printed Anatomical Design Scaffolds for Large Bone Defects

Abstract

There is a significant unmet clinical need to prevent amputations due to large bone loss injuries. We are addressing this problem by developing a novel, cost-effective osseointegrated prosthetic solution based on the use of modular pieces, bone bricks, made with biocompatible and biodegradable materials that fit together in a Lego-like way to form the prosthesis. This paper investigates the anatomical designed bone bricks with different architectures, pore size gradients, and material compositions. Polymer and polymer-composite 3D printed bone bricks are extensively morphological, mechanical, and biological characterized. Composite bone bricks were produced by mixing polycaprolactone (PCL) with different levels of hydroxyapatite (HA) and β-tri-calcium phosphate (TCP). Results allowed to establish a correlation between bone bricks architecture and material composition and bone bricks performance. Reinforced bone bricks showed improved mechanical and biological results. Best mechanical properties were obtained with PCL/TCP bone bricks with 38 double zig-zag filaments and 14 spiral-like pattern filaments, while the best biological results were obtained with PCL/HA bone bricks based on 25 double zig-zag filaments and 14 spiral-like pattern filaments.

Keywords: Biomanufacturing; Bone grafts; Hydroxyapatite; Polycaprolactone; Tissue engineering; β-Tri-calcium phosphate.

Figure 1

Bone bricks approach for large bone loss treatment.

Figure 2

Anthropometric based geometries and different path planning strategies considered to produce bone bricks with different porosities.

Figure 3

Scanning electron microscopy images of the top view of polycaprolactone bone bricks with different architectures (A) case 1 and (B) case 2.

Figure 4

Top and cross-section scanning electron microscopy images of bone bricks (case 2) for different material composition on (A), (B) polycaprolactone bone brick, (C), (D) hydroxyapatite/β-tri-calcium phosphate (HA/TCP) 10 wt%/10 wt% bone brick, (E), (F) HA 20 wt%, and (G), (H) TCP 20 wt% bone brick.

Figure 5

Compressive modulus as a function of bone brick architecture and material composition. *Statistical evidence (P < 0.05) analyzed by one-way analysis of variance and Tukey post-test.

Figure 6

Average fluorescence intensity as a function of bone bricks architecture and material composition for different days after cell seeding. *Statistical evidence (P < 0.05) analyzed by one-way analysis of variance and Tukey post-test.

Figure 7

Top and cross-section scanning electron microscopy images of cells spreading in bone bricks (case 3) with different material compositions (A), (B) polycaprolactone, (C), (D) 10/10 wt% hydroxyapatite/β-tri-calcium phosphate (HA/TCP), (E), (F) 20 wt% HA, and (G), (H) 20 wt% TCP.

Figure 8

Scanning electron microscopy images of cells attachment and spreading on (A) polycaprolactone bone brick (case 1), (B) 10 wt%/10 wt% hydroxyapatite/β-tri-calcium phosphate (HA/TCP) bone brick (case 2), (C) 20 wt% HA bone brick (case 2), (D) 20 wt% HA bone brick (case 3), (E) 20 wt% TCP bone brick (case 3), and (F) 20 wt% TCP bone brick (case 4).