3D-printed PEEK/Na-alginate scaffolds coated with Ag-Sr doped hydroxyapatite for dental tissue engineering: A detailed in vitro analysis

Objectives: The aim of this study was to develop a novel dental bone implant that could enhance bioactivity and provide strength to native dental bones. Such 3D-printed PEEK/Na-ALG scaffolds coated with bioactive Ag-Sr-HA, via electrospray to achieve synergistic effects. Methods: Detailed in vitro characterizations including the rheological properties, i.e., flowability and printability of the PEEK/Na-ALG blend, was investigated with experiments performed in triplicate (n = 3). The fabricated scaffolds were 3D printed by direct ink write (DIW). The morphology and chemical interactions of the scaffolds was studied by scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR). The mechanical properties were investigated through compression and micro-tensile test following ISO 604/B/5 and ASTM D638 type IV standards, respectively (n = 3). The biocompatibility of the scaffolds with osteoblasts and human dental pulp stems (hDPSCs) was assessed via WST-8 assay with 5 specimens (n = 5) for cell viability with both the cell lines. Alkaline phosphatase (ALP) activity of coated scaffolds was quantified using ELISA kit and 5 specimens were examined (n = 5). One-way analysis of variance (ANOVA) (Tukey method) was performed on the experimental values, and the statistical differences were examined for cell viability and ALP release studies. Results: SEM images revealed a homogeneous layer fidelity and pore size of ∼580 ± 20 µm. Energy dispersive x-ray spectroscopy (EDS), which confirmed successful deposition of Ag-Sr-HA. FTIR analysis confirmed successful photo-polymerization and presence of Ag-Sr-HA on 3D-printed PEEK/Na-ALG scaffold. The coated scaffolds exhibited tensile strength of 0.089 GPa and Young's modulus of 1.91 GPa. Moreover, coated scaffolds exhibited an initial burst release of Ag⁺ and Sr²⁺ ions which provided inhibition zone of 11 mm, 13 mm and 15 mm against Escherichia coli, Staphylococcus aureus, and Streptococcus mutans, respectively. The release of Sr²⁺ upregulated osteoblasts and hDPSCs viability (108 % and 103.5 %, respectively), and ALP activity. Significance: The novel Ag-Sr-HA coated 3D-printed PEEK/Na-ALG is expected to enhance the mechanical and biological activity particularly in dental tissue engineering.