Biofunctional coatings for 3D-printed bone scaffolds: A comparative study on polydopamine-assisted bioactive ceramic coatings

Polycaprolactone (PCL) is one of the most intensively studied biomaterials for three-dimensional (3D) printing in bone tissue engineering. However, without modification, it lacks bioactivity and osteogenic properties to function as a bone scaffold alone. Here, a facile single-step co -deposition to graft three different bioactive ceramics onto the surface of PCL scaffolds using polydopamine (PDA) is studied. The specific objective of this study was to conduct a comparative study on PDA-assisted bioactive ceramic coatings on 3D-printed PCL scaffolds, including conventional nanohydroxyapatite (nHA), industrial-grade 45S5 Bioglass® (BG), and synthesized mesoporous bioactive glass nanoparticles (MBGN), with a special interest in the application of MBGN for its applicability and expandability. First, PDA-assisted bioactive ceramic-coated PCL scaffolds were validated by observing and characterizing the microstructure, morphology, and chemistry. Thermogravimetric analysis (TGA), topographical characterization, and uniaxial compression tests were performed to understand the effect of the PDA-assisted bioactive ceramic coatings on PCL scaffolds. An acellular bioactivity study was conducted using simulated body fluid (SBF), where the PDA-nHA/PCL and PDA-45S5 BG/PCL scaffolds were comparably superior in biomineralization ability. In vitro cell studies using osteoblast-like MG-63 cells allowed a general understanding of osteogenic properties, including cell adhesion, viability, differentiation, and proliferation, compared to PDA/PCL scaffolds without grafted bioactive ceramics. Osteogenic properties such as cell adhesion, viability, and differentiation were not distinctively different from those of PDA/PCL scaffolds, but PDA-MBGN/PCL scaffolds showed improved cell proliferation. Overall, the PDA-assisted bioactive ceramic coating enables convenient biofunctional surface modification of 3D-printed PCL scaffolds with potential for applicability, scalability, and expandability.