Abstract
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 for 24 hours at 37 degrees C. Biofilms were quantified by determining the CFU (colony forming units) per lens. To determine the CFU/lens, each lens was gently rinsed with sterile distilled water, and placed into a microcentrifuge tube containing 1 ml phosphate buffered saline (PBS), and then vigorously vortexed three times for 1 min vortex 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 37 degrees C for 24 hours and the CFU were counted. For confocal laser scanning microscopy (CLSM), we used the S. aureus strain AH1333 which carries the gene that encodes the green fluorescent protein.
Results:
Colony forming unit assays showed total inhibition, representing over 6 logs of Staphylococcus aureus 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 in vitro.
Keywords: 477 contact lens •
422 antibiotics/antifungals/antiparasitics •
596 microscopy: confocal/tunneling