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Nicole Nghiem, David A Ammar, Mark Petrash, Jeffrey Olson; Ocular Biocompatibility of Nitinol. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1542.
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© ARVO (1962-2015); The Authors (2016-present)
There is limited research assessing the biocompatibility of nitinol (a nickel-titanium alloy) in ocular tissues. This study aims to evaluate the safety of a minimally invasive nitinol suture developed for use in ocular surgeries by examining its effects on the viability and proliferation of human retinal and corneal cells in vitro.
Cultures of human retinal pigment epithelium (ARPE-19) and human corneal endothelium (HCN E6/E7) were used. First, to establish the levels at which nickel is toxic to these ocular cells, different concentrations of nickel chloride were added to confluent cells and incubated for 3 days. Cell viability was then measured with MTT assay against a control of cells unexposed to nickel. Second, to test for leaching effects, media exposed to nitinol wire for 1, 3 and 8 weeks was incubated with both cell lines for 2 days and cell viability was measured with MTT assay. Media that was incubated for 8 weeks but not exposed to nitinol was used as a control. Third, in order to assess cell growth in the presence of nitinol, cells were seeded onto culture plates containing nitinol wire and examined after growing to confluency. The two-sample t-test was used for statistical analysis.
When exposed to various concentrations of nickel chloride, there was a statistically significant decrease in cell viability for ARPE-19 cells at 2.5 mM (p=0.01) and for HCN E6/E7 cells at 0.5 mM (p=0.002). The leaching experiments showed no statistically significant decrease in cell viability with exposure to media incubated with nitinol for 1, 3 and 8 weeks for ARPE-19 cells (p = 0.33, 0.68, 0.54 respectively) or for HCN E6/E7 cells (p = 0.48, 0.37, 0.68 respectively). Cell growth experiments demonstrated that the cells were able to grow to confluency in the presence of the nitinol.
The results are promising in establishing the safety of nitinol sutures for use in the eye. Nitinol showed minimal leaching effects and did not appear to affect cell proliferation. Further experimentation is required to examine the long-term effects of nitinol exposure and to determine the absolute level of nickel that may be released from the nitinol wire.
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