Purpose
Biofilm formation on contact lenses has been cited as a possible cause of corneal infection and acute red eye. A contact lens that blocks biofilm formation should reduce the frequency of these clinically significant problems. Selenium compounds have the ability to catalyze the formation of superoxide radicals in the tear film, which are cytotoxic to bacteria. Thus, this study investigated the effectiveness of a covalent organo-selenium polymerized into a hydrogel, against bacterial biofilm formation.
Methods
Organo-selenium compounds were polymerized directly into a hydrogel. The inhibition of biofilm formation with the organo-selenium hydrogel was investigated by incubating organo-selenium hydrogels and selenium free hydrogel in a nutrient broth containing Staphylococcus aureus GFP and Pseudomonas aeruginosa GFP for 24 hours at 37oC. Biofilms were examined by the Confocal Laser Scanning Microscopy (CLSM) and quantified by determining the Colony Forming Unit (CFU) per lens. To determine the CFU/lens, each lens was gently rinsed twice with PBS and placed into a microcentrifuge tube containing 1 ml phosphate buffered saline (PBS), and then vigorously vortexed three times for 1 minute, to detach the cells. Suspended cells were serially diluted 10-fold in PBS and 10-μl aliquots of each dilution were spotted on LB agar plates. The plates were incubated at 37oC for 24 hours and the CFU were counted. For CLSM. we used the S. aureus and P. aeruginosa strains which carries the gene that encodes the green fluorescent protein. All the experiments were conducted at least in triplicate.
Results
Colony forming unit assays showed total inhibition, representing over 6 logs of Staphylococcus aureus and Pseudomonas aeruginosa killing on organo-selenium polymerized hydrogels. Confocal laser scanning microscopy confirmed these results.
Conclusions
The organo-selenium hydrogel polymer successfully blocked the formation of a bacterial biofilm on the polymer by Staphylococcus aureus and Pseudomonas aeruginosa in vitro.