Toluidine blue-containing polymers exhibit potent bactericidal activity when irradiated with red laser light

Toluidine blue and toluidine blue-nanogold mixtures were incorporated into polyurethane and silicone polymers by a swell-encapsulation-shrink method using acetone-water mixtures. The surface and mechanical properties of the polymers were changed by the swell-shrink process especially the Young's modulus, but not by the introduction of toluidine blue or nanogold. The antibacterial properties of the various polymers were assessed under laser irradiation at 634 nm against Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). The toluidine blue-incorporated polymers showed kills of (>105 cfu/ml) for MRSA after just one minute of exposure. This is, to our knowledge, the most potent light-activated antimicrobial polymer combination reported to date.