Abstract
Additive manufacturing (AM) has revolutionized the design of regenerative scaffolds for orthopaedic applications, enabling customizable geometric designs and material compositions that mimic bone. However, the available evidence is contradictory with respect to which geometric designs and material compositions are optimal. There is a lack of studies that systematically compare different pore sizes and geometries in conjunction with the presence or absence of calcium phosphates. We therefore evaluated the physicochemical and biological properties of additively manufactured scaffolds based on polylactic acid (PLA) in combination with hydroxyapatite (HA). HA was either incorporated in the polymeric matrix or introduced as a coating, yielding 15 and 2% wt., respectively. Pore sizes of the scaffolds varied between 200 and 450 μm and were shaped either triangularly or hexagonally. All scaffolds supported the adhesion, proliferation and differentiation of both primary mouse osteoblasts and osteosarcoma cells up to four weeks, with only small differences in the production of alkaline phosphatase (ALP) between cells grown on different pore geometries and material compositions. However, mineralization of the PLA scaffolds was substantially enhanced in the presence of HA, either embedded in the PLA matrix or as a coating at the surface level, and by larger hexagonal pores. In conclusion, customized HA/PLA composite porous scaffolds intended for the repair of critical size bone defects were obtained by a cost-effective AM method. Our findings indicate that the analysis of osteoblast adhesion and differentiation on experimental scaffolds alone is inconclusive without the assessment of mineralization, and the effects of geometry and composition on bone matrix deposition must be carefully considered in order to understand the regenerative potential of experimental scaffolds.
Highlights
Despite the inherent regenerative potential of bone, larger defects require exogenous support that enhances or guides osteogenesis
The emergence of additive manufacturing (AM) has enabled the development of new designs and geometries intended for use as artificial bone scaffolds, and the combination of high-resolution imaging implemented in computeraided design (CAD) and its translation into AM have demonstrated great potential [4,5,6]
Larger variations were observed for the composite PLA15HA samples in terms of crystallinity compared to pristine polylactic acid (PLA) and HAcoated PLAcHA
Summary
Despite the inherent regenerative potential of bone, larger defects require exogenous support that enhances or guides osteogenesis. The emergence of additive manufacturing (AM) has enabled the development of new designs and geometries intended for use as artificial bone scaffolds, and the combination of high-resolution imaging implemented in computeraided design (CAD) and its translation into AM have demonstrated great potential [4,5,6]. The combination of polymers with mineral phases, mainly calcium phosphates (CaP), is a common approach to engineer regenerative scaffolds [7,8,9]. The most common material used in FDM is polylactic acid (PLA), an aliphatic inexpensive biodegradable and biocompatible polyester that is already used in some commercially available medical devices such as meshes, suture anchors, screws and nails [10].
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