Epoxy resin-based ultrafine dry powder coatings for implants

Ultrafine dry powder coating technology creates biocompatible polymeric coatings for implants. Nanoparticles (nTiO(2)) modify flow to prevent agglomeration and create homogenous coatings. Since polyester-based coatings require the potentially harmful 1,3,5-triglycidyl isocyanurate (TGIC) curing agent, this study's objective was to develop alternative TGIC-free formulations. Epoxy and epoxy/polyester (1:1) hybrid mixtures were enriched with CaO (5% w/w) and nTiO(2) (0.5% w/w), as functional additives and flow modifiers, respectively. Epoxy-TiO2 and Hybrid-TiO2 mixtures were prepared with micron-sized TiO2 (25% w/w) to enhance biocompatibility. Polymer chips and additives were combined in a high-shear mixer and passed through a sieve (35 mu m) to yield ultrafine particles that were sprayed (20kV) onto metal sheets and cured (200 degrees C). Particle size analyses showed that all formulations were ultrafine (D 0.5<35 mu m), and epoxy/polyester/TiO2 mixtures were the smallest (D 0.5=16.34 mu m). Angles of repose, avalanche and resting indicated reduced flowability when epoxy was enriched with TiO2 and/or polyester, although all formulae were highly flowable. Elemental mapping of coatings showed a predominance of carbon (C) and oxygen (O) from resin polymer, and elevated titanium (Ti) in the TiO2 enriched surfaces. However, calcium (Ca) clusters were higher on the epoxy/polyester Hybrid coatings. Optical microscopy showed human mesenchymal cells (ATCC CRL-1486) attached and spread out, and Alizarin Red staining showed mineral deposits in 2-4 week cultures, particularly on epoxy/polyester/TiO2 Hybrid surfaces. These epoxy resin-based formulations were effective TGIC-free substitutes for ultrafine dry powder coatings on implants. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43960.