Abstract
The reduction in size of Zinc oxide (ZnO) and Silicon dioxide (SiO2) particles from micron to nano scale offers unique physical characteristics on one hand while making them cytotoxic on other hand. The present study was aimed at comparing cytotoxic effects of ZnO and SiO2 nanoparticles with their micron size and secondary aim was to compare responses of these particles to two different cell types, namely, human lung epithelial cells (L-132) and human monocytes (THP-1). The L-132 and THP-1 cells were exposed to nano and micron size of ZnO and SiO2 particles with different concentrations (5–500 μg/mL) for 24 h, and cytotoxicity was analyzed by MTT assay, live-dead staining, and TC-50 was calculated. ZnO and SiO2 particles showed concentration-dependent cytotoxicity in both cell lines. In size-dependent study, ZnO particles exhibited nearly equal toxicity profile in L-132 cells while in THP-1 cells nano ZnO showed more toxicity than its micron size. The SiO2 particles showed more toxicity in their nano size than micron size in both cell lines. Human monocytes, THP-1 cells, were more sensitive towards the toxicity of both particles than human lung cells, L-132. The results highlight the difference of cytotoxicity between particle sizes and differential sensitivity of cells towards the particles of same composition. In conclusion, ZnO and SiO2 particles exhibited concentration-dependent toxicity, which was more in their nano size than micron counterpart. However, the toxic response varies depending on type of cell exposed due to differential sensitivity.
Highlights
Rapid advances in the field of nanotechnology led to creation of nano-sized particles with very different chemical and physical properties as compared to particles in their bulk form [1]
Dulbecco’s modified eagle’s medium (DMEM), Roswell park memorial institute (RPMI) medium, penicillinstreptomycin-neomycin solution, fetal bovine serum (FBS), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), dimethyl sulfoxide (DMSO) and Zinc oxide nanopowder < 100 nm, Zinc oxide < 5 μm, Silicon dioxide nanopowder < 10–20 nm, and Silicon dioxide ∼0.5–10 μm were purchased from Sigma-Aldrich
transmission electron microscopy (TEM) analysis showed that the particles were nearly spherical and cubical in shape (Figure 1)
Summary
Rapid advances in the field of nanotechnology led to creation of nano-sized particles with very different chemical and physical properties as compared to particles in their bulk form [1]. Studies on size-dependent toxicity between micro- and nano-scale particles [23,24,25,26,27,28] showed that toxicity of NP is more compared to larger particles and affirmed the hypothesis that NPs in general are more potent in causing damage. All these evidences suggested that NPs of the same or different size exhibited varied toxic response but the studies with reference to their micron size are lacking. Human monocytes (THP1) were chosen due to their role in clearing foreign particles [32]
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