Abstract
Purpose:
This study evaluated the effects of polyhexamethylene biguanide (PHMB) contact lens multi-purpose (MPS) solution on cell cytotoxicity, metabolic activity, membrane integrity, and biocompatibility.
Methods:
Five MPS were used - MPS-1: polyhexamethylene biguanide (PHMB) + poloxamer (PLX), MPS-2: PHMB + PLX, MPS-3: PHMB + poloxamine (PLA), MPS-4: PHMB + polyquaternium (PQ1) + PLA, and MPS-5: PHMB + PLX. In vitro biocompatibility was assessed according to ISO 10993. MPS effect on colony formation rate was evaluated in V79 Chinese Hamster Lung Fibroblast for 7 days. MPS were evaluated at 1.25%, 2.5%, 5% and 10% as diluted in cultured medium. Cytotoxicity and metabolic activity were determined using alamarBlue dye. Corneal epithelial barrier function was assessed by Zonula Occludens (ZO-1) immunohistochemistry (IHC) and trans-epithelial electrical resistance (TEER) in Simian virus transformed human corneal epithelial cell line (SV40 HCEC).
Results:
MPS-1 formulation was comparable to MPS-2 at 1.25% and 2.5% and MPS-3, MPS-4, and MPS-5 at 5% and 10% in cell cytotoxicity. Treatment with 1ppm PHMB alone did not induce a statistically significant inhibition on V79 colony formation (n=3, p>0.05). MPS-1 at 50% and 75% was comparable to MPS-2, MPS-3, MPS-4, and better than MPS-5 at 100% in corneal barrier integrity as evaluated by ZO-1 IHC. Exposure to MPS-1 for 120 mins at 50% concentration was superior to MPS-3, MPS-4, and MPS-5 and similar to MPS-2 on maintaining SV40 HCEC viability as assessed by alamarBlue. TEER of SV40 HCEC showed that exposure to MPS-1 for 120 mins at 50% concentration was better than MPS-3 but equal to MPS-2, MPS-4, and MPS-5. MPS-1 for 120 mins at 75% concentration was similar to MPS-5 and superior to MPS-3 and MPS-4 to maintain corneal cell membrane integrity (n=3-4, p<0.05).
Conclusions:
PHMB effects on in vitro cell cytotoxicity are best demonstrated by correlating results from multiple assays. Results of membrane integrity assays (ZO-1 IHC and TEER) showed the greatest differences among PHMB-formulated MPS solutions, followed by metabolic activity (alamarBlue) and colony forming assays. These in vitro results demonstrated that MPS-1 (PHMB + PLX) to be better than or equal to MPS-3, MPS-4, and MPS-5 in maintaining corneal barrier integrity and cell viability.
Keywords: 482 cornea: epithelium •
477 contact lens •
446 cell adhesions/cell junctions