Mesoporous Titania Coatings with carboxylated Pores for Complexation and slow Delivery of Strontium for osteogenic Induction

Abstract The release of bioactive Strontium ions (Sr2+) from titanium implants has a positive impact on osseointegration. It is however challenging to achieve a slow Sr2+ release over weeks until tissue regeneration. A hybrid mesoporous titania film (MTF) displaying carboxylic moieties in pore walls has been developed here for encapsulation and slow delivery of Sr2+. Mesoporous films are prepared by Evaporation Induced Self-Assembly. Vinylmethoxysilanes are co-condensed during film assembly and vinyl groups of silanes are reacted with mercaptosuccinic acid resulting in pores displaying carboxylic groups. Modified MTFs are loaded with Sr2+, which is retained both as non-complexed ion in the pores and complexed to the carboxylic acid groups. The complexation of Sr2+ to the carboxylic groups is proven by X-ray Photoelectron Spectroscopy and Infrared Spectroscopy. Inductively Coupled Plasma Mass Spectrometry shows that the non-complexed Sr2+ is released from the pores in approximately one day while complexed Sr2+ is released slowly over one week. The released Sr2+ has a positive effect on MC3T3-E1 pre-osteoblastic cell proliferation and the Alkaline Phosphatase test shows that at 15 days of culture in osteogenic medium the differentiation is enhanced due to the slow release of Sr2+ complexed to carboxylates.