Purpose: The aim was to determine the cytotoxic effects of three multipurpose solutions (MPS) on human corneal epithelial cells (HCEC) and to assess the metabolic rates of recovering cells at different levels of cell membrane damage.
Method: The effects of one to 15 minutes exposure to multipurpose solutions containing polyquaternium-1 (MPS-A), polyaminopropyl biguanide (MPS-B) and polyhexanide (MPS-C) on HCEC were determined. Recovery rates at different levels of cell membrane damage were assessed after re-culture for two hours at 37°C. Cell viability and membrane integrity were assessed using Annexin V-FITC/7-AAD staining and flow cytometry. Effects of concentrations of 10 to 40 per cent multipurpose solutions on the metabolic rate of recovering HCEC were assessed using a Vybrant MTT cell proliferation assay kit.
Results: The highest percentage of late necrotic cells resulted after exposure to MPS-A compared with other solutions and the control (p < 0.001). The percentages of early necrotic cells after 10 and 15 minutes of soaking in MPS-B were significantly higher than the control and other multipurpose solutions (p < 0.001). Although MPS-C exposure also resulted in statistically significant higher percentages of early necrotic cells than the control (p < 0.005), these differences were small. No recovery was noted when HCEC treated with multipurpose solutions were re-cultured, with numbers of dead cells in MPS-B-treated cultures increasing fourfold. The MTT assay showed significant dose-response decreases of 500 nm absorbance for all MPS-treated cells. In 40 per cent MPS-A-treated HCEC, lack of activity indicated the cells were non-viable.
Conclusions: Multipurpose solutions induced varying levels of irreversible tissue sensitivity reactions, with MPS-A showing the greatest effects. The solutions damaged cell integrity and reduced metabolic rates suggesting delayed healing ability. The formulations of multipurpose solutions need to balance antimicrobial effectiveness with low cytotoxicity, which might not be currently possible to achieve. In light of our results, we suggest that contact lens wearers should be advised to rinse the soaked lenses with saline before lens insertion.