Inorganic-Organic Matrix and Cells Spray Deposition on Implant Surfaces

Objectives: The aim of this study was to introduce a spray method for polyelectrolytes, proteins and cells deposition on PEEK implant surfaces.
Methods: Consecutive spray deposition of PLL/PGA (poly-l-lysine/poly-glutamic acid), were used for polyelectrolyte multilayer (PEM) films build-up. Natural proteins: protein-1-CaP (calcium phosphate) and protein-2 are then sprayed on the PEM layers. Different types of physical treatments of PEM/protein coatings were performed. Consequently dental pulp stem cells (DPSCs) were sprayed on functionalized PEEK surfaces.
Roughness, thickness, elasticity, hydrophobicity and chemical changes of the layers were studied by Atomic Force Microscopy (AFM), contact angle measurements and Raman spectroscopy. Cell proliferation was evaluated at 1^st, 3^th and 8^th day after spraying. The degree of mineralization of the extracellular matrix on the PEEK surface at 21^st day was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and histological analysis.
Results: Films thickness, roughness and surface hydrophobicity change with increasing numbers of layers. Physical treatment by UV irradiation and dry-wet process affects the film thickness and the film elasticity, also increases the stiffness of the film. Protein-1-CaP and protein-2 coatings on PEM films increased the layer thickness (greater for protein-2) and influenced the hardness of the surface (higher for protein-1-CaP). Physical treatments and the protein absorption enhanced cell adhesion and cell proliferation. DPSCs osteogenic differentiation was improved by formation of mineralized extracellular matrix on PEEK surfaces.
Conclusions: In this work we established a spray deposition technic of PEMs, protein and pulp cells for PEEK implant functionalization.