Effects of Nanoparticle Exposure on the Growth of Retinal Pigment Epithelial Cells

Abstract

 

Purpose

 

Various kind of intentionally created metal and metal oxide nanoparticles have been widely used in medicine, engineering, electronics, agriculture and allied sciences. However, their toxicity to the ocular tissue is still not clear. In the present study we used three different kinds of nanoparticles i.e. gold, titanium dioxide (TiO₂), and organosilica. Their toxic effects in retinal pigment epithelial cell line ARPE 19 were determined in vitro.

 

Methods

 

Nanoparticles of Au, TiO₂ and organosilica were synthesized according to Wu et al., 2010, Katoch et al., 2012, and Irmukhametova et al. 2011 respectively. NPs were characterized by UV-VIS, Size distribution and Zeta potential by DLS, and morphological analysis by TEM (Table 1). To evaluate biocompatibility on retinal pigmented epithelial cells (ARPE-19) we used thiazolyl blue (MTT) assay. A standard growth curve was established for ARPE-19 cells and mathematical models based on the Gompertz function and the Ontogenetic General Model set by West et. al., 2001. These values were fed into the mathematical models to solve for the treatment effect and whether it is apoptotic or inhibitory to the cell cycle.

 

Results

 

Both the Gompertz and Ontogenetic General Model curves created show the ability to accurately fit the data (R2 of 0.9773 and 0.9645 respectively) and can reproduce established constants of human tissue growth (Fig. 1). With treatment added into the model we are able to represent and predict, through the variations in concentration, what effects the “pollutants” have on the cell cycle. The MTT assay shows an LC₅₀ for TiO₂ particles around 350 ppm while for gold particles the lethal dose is below 1 ppm, and for the organosilica particles the LC50 exceeds 1000 ppm. MTT assay is not compatible with gold nanoparticle exposure at the concentrations we have run, due to nanoparticle absorbance of yellow light.

 

Conclusions

 

Nanoparticles were successfully synthesized on the basis of previously established protocols. Of the three NPs evaluated on ARPE19 cells, the order of toxicity was highest in Au followed by TiO₂ and lastly organosilica NPs. Root cause of maximum toxicity by Au NPs is may be due to positive surface charge and its oxidation state of +3.

 

 

Table 1: Nanoparticle characterization

 

 

Figure 1: Ontogenetic General Model curve for ARPE 19 cells fit to experimental data. Showing equation and R2 fit.

 

Keywords: 620 ocular irritancy/toxicity testing • 607 nanotechnology