Surface topography-dependent calcium-phosphate coating of 3D-printed PCL scaffolds: enhanced osteogenic activity by MC3T3-E1 pre-osteoblasts

IntroductionPoly(ԑ-caprolactone) (PCL; FDA approved) scaffold is often used in bone tissue engineering because of its high stiffness and long degradation time. Since PCL is not bioactive, surface coating of PCL scaffold with calcium phosphate (CaP) is commonly used to render the surface bioactive. ObjectivesWe aimed to test the effect of biomimetic CaP coating on NaOH-etched 3D-printed PCL scaffolds on osteogenic activity of MC3T3-E1 pre-osteoblasts. MethodsPCL scaffolds were fabricated using an extrusion-based 3D-bioprinter. Scaffolds were etched by 3 M NaOH for 24 or 72 h to create topography on the surface. Biomimetic CaP coating was done through alternate dipping of etched PCL scaffolds in 200 mM CaCl2 and K2HPO4.3H2O aqueous solutions. Scanning electron microscopy (SEM) was used to study the surface topography. The elemental composition of the surface was studied by energy dispersive spectroscopy (EDS). MC3T3-E1 pre-osteoblasts were cultured for 14 days on PCL scaffolds with or without CaP-coating. Alkaline phosphatase (ALP) activity was measured and normalized to protein content after 14 days of culture using p-nitrophenol liberated enzymatically from p-nitrophenyl phosphate. ResultsSEM showed that NaOH etching changed the scaffold surface topography from smooth to a honeycomb-like pattern with small (24 h NaOH-etched) and large (72 h NaOH-tched) pores. EDS showed that after CaP coating, percent Ca and P atoms on the surface of 24 h NaOH-etched scaffold was 2.5-fold higher than on 72 h-etched scaffold. Cells showed increased ALP activity by 3.4-fold on 24 h NaOH-etched CaP-coated scaffold and 1.5-fold on 72 h NaOH-etched CaP-coated scaffold compared to the scaffold without CaP coating. ConclusionOur results suggest that a honeycomb-like surface topography enhances biomimetic CaP coating on 3D-printed PCL scaffolds and therefore, enhances osteogenic activity of pre-osteoblasts which might have implications for bone tissue engineering

Keywords:

Poly (ɛ-caprolactone) , Surface topography , Calcium-phosphate coating , Osteogenic activity