A General Methodology for Testing Nanomaterial Toxicology — Cytotoxicity and Genotoxicity of the Exfoliated Silicate Platelets from the Natural Clays
Date Issued
2009
Date
2009
Author(s)
Li, Pei-Ru
Abstract
Recent advances in nanotechnology may largely impact science advance and industrial progresses. However, the creation of new material might also affect the society and environmental pollutions due to their unknown properties. Safety issues and the detailed understandings on the newly developed materials ought to be the concerns and responsibilities of the scientists. In this thesis, the toxicity concerns on the nanometer-sized silicate platelets (NSP) that were developed in our research group are addressed. The NSP material is first time prepared from the exfoliation of the natural clays which is commonly considered as a benign silicate mineral. However, the NSP material is unique and unknown to the environment, with the exfoliated structure of individual platelets rather than in an isomerism form but lamellar platelet alignment. Especially the layered silicates are totally delaminated into highly surfaced silicates in thin platelet forms. Its toxicity is academically interesting because their difference in high aspect ratio and geometric shape. Furthermore, the NSP possessing ionic charges on the surface of silicate plates with average geometric dimension of ca. 80 × 80 × 1 nm3 has demonstrated its potential antimicrobial behavior. With these reasons in mind, this study has centered on the chemistry of NSP interacting with the incubated CHO cells and the physical examination of their interacting morphologies by scanning electron microscope. The genotoxic effect of NSP was examined by using three different test systems: the Comet assay test in Chinese Hamster Qvary (CHO) cells in vitro, micronucleus (MN) assay in vivo and the Salmonella gene mutation assay (Ames test) in strain TA98, TA100, TA102, TA1535 and TA1537. It is importantly noted that the results from the Comet assay showed none of DNA damage after 24 h of incubation with 1000 μg/mL of NSP concentration. The MN test indicated no significant micronucleus induction by NSP in the CHO cells at any concentrations tested. With five different strains of Salmonella typhimurium, there are none of mutation found when exposing with NSP. No mutagenic effect was observed in three different genetic toxicity test systems. The cytotoxicity was assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) release, and shown a low cytotoxicity effect on Hs68 cells. The CHO cells below a concentration of 1000 μg/mL at 12 h incubation and dose dependent cytotoxicity effect at 24 h incubation and LDH assay also showed low damage on Hs68 cells and CHO cells below a concentration of 1000 μg/mL at 24 h incubation. Investigation on potential acute oral toxicity in rats showed that the median lethal dose (LD50) of NSP by oral treatment was greater than 5,700 mg/kg for both male and female Sprague-Dawley (SD) rats. These results have implicated that NSP is a promising new silicate materials for using as a labeling reagent and carries for biomedical applications.
Subjects
nanoscale silicate platelets
cytotoxicity
genotoxicity
nanomaterials
acute oral toxicity
Type
thesis
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