To determine and compare the cytotoxic effects on porcine corneal epithelial cells of commercially available multipurpose solutions (MPS) using fluorescein staining and flow cytometry (FCM).
Effects of exposure time of 10 s to 10 min of MPS containing polyquaternium-1 (MPS-A), polyaminopropyl biguanide (MPS-B), and polyhexanide (MPS-C), on porcine corneal epithelial cells were determined. Cell viability and membrane integrity were assessed by Annexin V-FITC/7-AAD staining and FCM. In further trials, whole corneas were immersed in MPS and control (buffered saline), and corneal fluorescein staining assessed before FCM analysis.
Significantly higher percentages of 7-AAD-stained cells (early necrosis) were observed at all exposure times for MPS-A than for other solutions and control (p < 0.05). Exposure time in MPS-A and 7-AAD-stained cell proportions showed significant correlation (r = 0.9957; p < 0.0001). Significantly more cells dual-stained with Annexin V-FITC/7-AAD (late necrosis) after 5 min MPS-A exposure (11.8 ± 1.1%), compared with 1.2 ± 0.9% (MPS-B), 0.9 ± 0.5% (MPS-C), and 1.8 ± 0.2% (control). However, only 10 min exposure resulted in significant increases in fluorescein grades (p < 0.001), with median grade 0.75 for MPS-A, and 0.50 for the other MPS.
MPS exposure, especially MPS-A, affected the viability and integrity of porcine corneal epithelial cells. Furthermore, our results confirmed that fluorescein staining correlates poorly with cytotoxicity
. As fluorescein staining lacks sensitivity to determine cytotoxic effects of ophthalmic solutions, more objective and sensitive assessment methods such as differential staining and FCM should be developed.