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This work demonstrated the successful application of N-halamine technology for wound dressings rendered antimicrobial by facile and inexpensive processes. Four N-halamine compounds, which possess different functional groups and chemistry, were synthesized. The N-halamine compounds, which contained oxidative chlorine, the source of antimicrobial activity, were impregnated into or coated onto standard non-antimicrobial wound dressings. N-halamine-employed wound dressings inactivated about 6 to 7 logs of Staphylococcus aureus and Pseudomonas aeruginosa bacteria in brief periods of contact time. Moreover, the N-halamine-modified wound dressings showed superior antimicrobial efficacies when compared to commercially available silver wound dressings. Zone of inhibition tests revealed that there was no significant leaching of the oxidative chlorine from the materials, and inactivation of bacteria occurred by direct contact. Shelf life stability tests showed that the dressings were stable to loss of oxidative chlorine when they were stored for 6 months in dark environmental conditions. They also remained stable under florescent lighting for up to 2 months of storage. They could be stored in opaque packaging to improve their shelf life stabilities. In vitro skin irritation testing was performed using a three-dimensional human reconstructed tissue model (EpiDerm™). No potential skin irritation was observed. In vitro cytocompatibility was also evaluated. These results indicate that N-halamine wound dressings potentially can be employed to prevent infections, while at the same time improving the healing process by eliminating undesired bacterial growth.

Reducing biofouling while increasing lubricity of inserted medical catheters is highly desirable to improve their comfort, safety, and long-term use. We report here a simple method to create thin (∼30 μm) conformal lubricating hydrogel coatings on catheters. The key to this method is a three-step process including shape-forming, gradient cross-linking, and swell-peeling (we label this method as SGS). First, we took advantage of the fast gelation of agar to form a hydrogel layer conformal to catheters; then, we performed a surface-bound UV cross-linking of acrylamide mixed in agar in open air, purposely allowing gradual oxygen inhibition of free radicals to generate a gradient of cross-linking density across the hydrogel layer; and finally, we caused the hydrogel to swell to let the non-cross-linked/loosely attached hydrogel fall off, leaving behind a surface-bound, thin, and mostly uniform hydrogel coating. This method also allowed easy incorporation of different polymerizable monomers to obtain multifunctionality. For example, incorporating an antifouling, zwitterionic moiety sulfobetaine in the hydrogel reduced both in vitro protein adsorption and in vivo foreign-body response in mice. The addition of a biocidal N-halamine monomer to the hydrogel coating deactivated both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) O157:H7 within 30 min of contact and reduced biofilm formation by 90% compared to those of uncoated commercial catheters when challenged with S. aureus for 3 days. The lubricating, antibiofouling hydrogel coating may bring clinical benefits in the use of urinary and venous catheters as well as other types of medical devices.

A TPU elastomer was modified with N-halamine polymers as a novel food contact surface material with rechargeable antimicrobial activity.