Potential neurotoxicity of titanium implants: Prospective, in-vivo and in-vitro study.

Titanium dioxide (TiO2) is a frequently used biomaterial, particularly in orthopedic and dental implants, and it is considered an inert and benign compound. This has resulted in toxicological scrutiny for TiO2 in the past decade, with numerus studies showing potential pathologic downstream effects. Herein we describe case report of a 77-year-old male with subacute CNS dysfunction, secondary to breakdown of a titanium-based carotid stent and leading to blood levels 1000 times higher (3 ppm) than the reported normal. We prospectively collected tissues adjacent to orthopedic implants and found a positive correlation between titanium concentration and time of implant in the body (r = 0.67, p < 0.02). Rats bearing titanium implants or intravascularly treated with TiO2 nanoparticles (TiNP) exhibited memory impairments. A human blood-brain barrier (BBB) in-vitro model exposed to TiNP showed paracellular leakiness, which was corroborated in-vivo with the decrease of key BBB transcripts in isolated blood vessels from hippocampi harvested from TiNP-treated mice. Titanium particles rapidly internalized into brain-like endothelial cells via caveolae-mediated endocytosis and macropinocytosis and induced pro-inflammatory reaction with increased expression of pro-inflammatory genes and proteins. Immune reaction was mediated partially by IL-1R and IL-6. In summary, we show that high levels of titanium accumulate in humans adjacent to orthopedic implants, and our in-vivo and in-vitro studies suggest it may be neurotoxic.

Effects of compost application on soil vulnerability to heavy metal pollution.

Soil vulnerability to heavy metal pollution is low in soils exhibiting an ability to strongly adsorb heavy metals on their geochemical fractions. Organic matter (OM) is among other components of soils, one of the most effective sorbing fractions. Compost addition is often used for soil remediation thereby enriching the soil with OM. However, compost is often enriched with heavy metals and thereby may induce adverse effects on the soil and plants growing in them. Compost-derived dissolved organic matter (DOM) can mobilize heavy metals. The balance between two contrasting effects of compost-mobilization and immobilization of heavy metals-was studied under the conditions of adsorption-desorption batch experiment. Metal adsorption to different geochemical fractions of soil treated with compost was examined by a combined batch-adsorption experiment and a sequential extraction procedure. Compost-derived DOM mobilized Cu at low loading levels, whereas adsorption of Cd and Pb was not decreased by DOM application. Compost was found to be a source of an important reducible oxides fraction (RO-sorbing and fixation fraction) and also of the OM geochemical fractions that most commonly immobilizes heavy metals. The Langmuir and Freundlich models employed in our study exhibited a good fit for most of data the experimental data obtained on bulk samples. Adsorption of the metals on operationally defined geochemical fractions was described by a linear function in several experimental instances.