Bioactive zinc-doped sol-gel coating modulates protein adsorption patterns and in vitro cell responses

Zinc is an essential element with an important role in stimulating the osteogenesis and mineralization and suppressing osteoclast differentiation. In this study, new bioactive ZnCl2-doped sol-gel materials were designed to be applied as coatings onto titanium. The biomaterials were physicochemically characterized and the cellular responses evaluated in vitro using MC3T3-E1 osteoblasts and RAW264.7 macrophages. The effect of Zn on the adsorption of human serum proteins onto the material surface was evaluated through nLC-MS/MS. The incorporation of Zn did not affect the crosslinking of the sol-gel network. A controlled Zn2+ release was obtained, reaching values below 10 ppm after 21 days. The materials were no cytotoxic and lead to increased gene expression of ALP, TGF-beta, and RUNX2 in the osteoblasts. In macrophages, an increase of IL-1 beta, TGF-beta, and IL-4 gene expression was accompanied by a reduced TNF-alpha liberation. Proteomic results showed changes in the adsorption patterns of proteins associated with immunological, coagulative, and regenerative functions, in a Zn dose-dependent manner. The variations in protein adsorption might lead to the downregulation of the NF-kappa B pathway, thus explain the observed biological effects of Zn incorporation into biomaterials. Overall, these coatings demonstrated their potential to promote bone tissue regeneration.

Automated summary

The study designed new bioactive ZnCl2-doped sol-gel materials that showed positive effects on osteoblasts and macrophages. The incorporation of zinc led to increased gene expression in osteoblasts and changes in gene expression in macrophages, as well as alterations in protein adsorption patterns in a zinc dose-dependent manner. These findings suggest the potential of zinc-doped coatings to promote bone tissue regeneration.