Cell growth underpinned by sepiolite

Abstract

This paper reports the role of clay minerals, sepiolites, on the proliferation behaviour of human cancer cells. It reports as well on the proliferation of U251 (central nervous system, glioblastoma) and SKLU-1 (lung adenocarcinoma) cells by sepiolite bearing different extent of isomorphic substitution (IS), either because of the inclusion of Al3+, Fe3+.2+, or Ti4+ in Si structural sites (IS at the tetrahedral sheet, T) or that of Ni2+ in Mg structural sites (IS at the octahedral sheet, O). Studied sepiolites were originally from Ampandrandara, Madagascar; Cerro del Almodóvar, Spain; Deiva Forest, Italy; Eskidir, Turkey; Peguera, Falcondo Plant, Dominican Republic; Sepetciköyü, Turkey; Shimien, China; and Vallecas, Spain. Furthermore, obtained results for sepiolites were compared against those for clays (bentonites). Diffractograms showed characteristic patterns for sepiolite, with no evidence of significant accumulation of secondary phases. XRF data confirmed the incorporation of Al, Fe and, Ti; and Ni, consistent with IS at T and O. The effect of sepiolite on cellular proliferation was determined using the SRB protocol. All sepiolites induced inhibition or increment on the proliferation response of U251 or SKLU cells, depending on the sepiolite; however no correlation between proliferation against composition or microporosity properties became evident. Most notably, sepiolite from Sepetciköyü, Turkey, owning the highest microporosity (evidenced by surface area σs) of the sepiolite series, 343m2g−1, exerted the highest proliferation response for U251 and SKLU-1 cells, namely, 100% inhibition and 22.8±12.1% increase, respectively. Sepiolites from Ampandrandara, Sepetciköyü, and Deiva Forest, owing very low contents of Al (Al2O3≤0.2%) and variable σs yielded the highest inhibition in U251 cells proliferation, best accounted for by growth was limited by specific-adsorption mechanisms in which structural changes associated to Al-for-Si IS at T favoured the adsorption of metabolic growth components [epidermal growth factor receptor (EGFR)], thereby inhibiting the development of primary glioblastomas. On the other hand, increments (%) in SKLU-1 cells proliferation did not correlate with microporosity (measured σs values), yet two data clusters were identified, higher and lower data values, i.e., 22.8≤% increment≤39% (σs=83, 220, or 343m2g−1) and 6.9≤% increment≤14.2% (96≤σs≤266). The second group was composed by Ampandrandara, Sepetciköyü, and Deiva Forest, generating surface sites that catalyze the overexpression of activin A. So, the growth behaviour for both U251 and SKLU-1 cells was affected by Al at Tvia Al-for-Si IS if proceeded to a small degree. In all, however, the overall chemical composition lacked to serve as predictor for growth. Structural considerations supported the idea that controlled cell growth by sepiolite was not limited by the retention of small solutes at inner surfaces. Finally, whether variations in microporosity exerted changes in the cell proliferation behaviour was strongly dependent if the phyllosilicate was a clay mineral (sepiolite) or a clay (bentonite).