Ultrafine calcium-titania-polyester dry powder coatings promote human mesenchymal cell attachment and biomineralization
Surface and Coatings Technology
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An electrostatic ultrafine dry powder coating technique was developed, which utilizes nanoparticles to prevent agglomeration. When polyester resin, TiO2 (25%), nano-TiO2 (0.5%), filler, flow, degassing and curing agents were combined in a high-shear mixer, then sprayed (20kV) onto metal sheets and cured (200°C), biocompatible polymeric powder coatings (PPC) were created. This study's objective was to determine if these surface coatings could be successfully augmented with calcium-rich functional additives. Thus, formulations were enriched with CaO (1, 3 and 5%) and Ca3(PO4)2 (5%, CaP), and their coatings characterized. Particle size analysis of the powders confirmed their ultrafine dimensions. Volume diameters for 50% (D 0.5) were under 30μm, and 90% (D 0.9) under 50μm. Energy dispersive X-ray (EDX) analysis confirmed integration with minimal modification to the PPC base. Carbon (61-67%), oxygen (15-25%) and titanium (9-15%) dominated all surfaces, whereas calcium (0.5-1.0%) and phosphorus (0.3%) were only detected in the CaO and CaP enriched coatings respectively. Elemental mapping showed calcium clusters that were smaller but more abundant with more CaO (PPC+3%CaO, PPC+5%CaO), and colocalized to phosphorus in the PPC+5%CaP. Contact angle measurements indicated hydrophilic coatings (62-81°) and significantly (P<0.05) increased surface wetting with CaO. Optical microscopy showed human mesenchymal cell (HEPM, ATCC CRL-1486) attachment and spreading on all coatings within 24h, and increasing confluence with CaO incorporation. Alizarin Red-S staining detected the biomineralization of cultures on all coatings that increased with CaO and time. Ultimately, the PPC+5%CaO had the most cells and biomineralization. This ultrafine dry powder coating technology can create biocompatible surfaces from polyester resins and TiO2, which can be readily augmented with functional additives such as calcium, to titrate optimal cellular responses. © 2014 Elsevier B.V.