Mesoporous silica adsorbents modified with amino polycarboxylate ligands – functional characteristics, health and environmental effects

: A series of hybrid adsorbents were produced by surface modification 30 with amino polycarboxylate ligands of industrially available microparticles (MP) of 31 Kromasil® mesoporous nanostructured silica beads, bearing grafted amino propyl 32 ligands. Produced materials, bearing covalently bonded functions as EDTA and 33 TTHA, original Kromasil®, bearing amino propyl ligands, and bare particles, obtained 34 by thermal treatment of Kromasil® in air, were characterized by SEM-EDS, AFM, 35 FTIR, TGA and gas sorption techniques. Adsorption kinetics and capacity of surface- 36 modified particles to adsorb Rare Earth Elements (REE), crucial for extraction in 37 recycling processes, were evaluated under dynamic conditions, revealing specificity 38 matching the ligand nature and the size of REE cations. A detailed comparison with 39 earlier reported adsorbents for REE extraction was presented. The cytotoxicity was 40 assessed using four different types of healthy cells, human skeletal muscles derived 41 cells (SKMDC), fibroblast cells, macrophage cells (RAW264.7), and human umbilical 42 vein endothelial cells (HUVECs), indicating lower toxicity of ligand-free MP than MP 43 bearing amino poly-carboxylate functions. Internalization of the MP inside the cells 44 and release of nitric oxide were observed. In addition, zebrafish embryos were 45 exposed to high concentrations of MP and did not show any pronounced toxicity. 46


INTRODUCTION
Silica has been listed as "generally recognized as safe" by the FDA. 30 For that 92 reason, silica-based nano-or micro-particles became an attractive tool for industrial, 93 environmental and medical applications. The toxicological behavior of nano-or 94 micro-particles was not limited only to the chemical composition but also extended to 95 their sizes, surface charges and shapes. 31-36 Therefore, considerable attention 96 should be paid to studying the impact of silica-based particles on health and 97 environment. 33 Toxicological behavior of new materials was investigated on four healthy cell lines.

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They were selected with respect to the most probable ways of exposure and 116 retention in the body. These particles, expected to be used in recycling of REE 117 materials or in water purification, would potentially be able to escape into 118 wastewaters with most probable exposure scenario being the uptake via 119 gastrointestinal tract. The cell lines were thus represented by macrophage cells as 120 the most common cells of the immune system, fibroblast cells as the most common 121 cells of the connective tissue, HUVECs as model for blood vessel cells, and by 122 skeletal muscle-derived cells to evaluate the potential retention effects.

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In addition, cellular uptake and nitric oxide release were described. Moreover, in vivo 124 toxicity study was conducted using zebrafish embryos as a predictive model for 125 assessing the nano-and micro-material toxicity. 37       For this process, an automatic sorption analyzer ASAP 2020 (Micromeritics, USA) 189 was used. The samples were degassed at 120 °C during 10 h before measurements.

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The analysis report was generated automatically using Micromeritics software (for    Cells were washed three times with their culture medium then exposed to Z-stack 242 imaging using Zeiss LSM780 confocal fluorescence microscopy, 10x objective.

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Several images were taken along the Z-direction to know whether MP were present 244 inside the cell or not. Images were treated with imageJ program.

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In vivo toxicity in zebrafish embryos. Wild-type AB zebrafish strain was purchased    For experimental details, please, see Figure FS14. where the LC50 values could not be detected under these conditions (>500 µg mL -1 ).

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The LC50 values for all MP were decreased by days (Fig. 4E), which suggested

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The internalization of the MP inside the cells was tested as shown in Fig. 6.

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To study the toxicological behavior of these MP on the endothelial cell function,  Nano-or micro-particles will discard in the aquatic system in the form of wastewater 564 or effluents. 60,61 Therefore, their environmental impact must be addressed. In vivo 565 toxicity of MP was evaluated in zebrafish embryos. Gastrula stage embryos were

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In case of Kromasil grafted with TTHA, exposing the embryos to 125 mg L -1 showed 576 low toxicity with no changes in motility, morphology and hatching rate in compared to 577 control. In contrast, at 500 mg L -1 , 85% of mortality was observed at 24 hpf embryos, 578 which reached to 90% after 96 hpf.   Note: S BETthe Brunauer-Emmet-Teller (BET) surface area; V porestotal pore volume; D pores 828 -BJH average pore diameter. 829 The curves of pore-size distribution by volume were obtained using the Barret-Joyner- and obtained pore-size distribution (Fig. Y), all synthesized materials belong to mesoporous 836 materials with diameter in the range from 6 -15 nm. 837