Characteristics of sintered calcium deficient hydroxyapatite scaffolds produced by 3D printing

This study investigates the parametric quality and reliability of 3D-printed scaffolds using a composite filament comprising a thermoplastic polymer and hydroxyapatite in 1:1 wt ratio. Employing a fused filament fabrication printer, we verified the 3D printing strategy, sintering temperature range, and preparation of hydroxyapatite scaffolds. To complete the study, in vitro cytotoxicity tests using animal and human cell models were conducted. The calcium-deficient hydroxyapatite (Ca/P ∼ 1.54) used in preparation of filament exhibited after sintering differences in crystalochemical phases in different rations, comparing to stoichiometric hydroxyapatite (Ca/P ≅ 1.67). The FFF process successfully produced scaffold macropores suitable for tissue vascularization (∼380 µm or smaller). Optimal sintering temperature for cell proliferation was identified at 1300 °C, especially effective for used investigated calcium-deficient hydroxyapatite. Cytotoxicity assessment with murine and human fibroblastic cells demonstrated differing behaviour, emphasizing the need for careful material property modifications for practical scaffold utilization.