Sulfanilamide-conjugated polyurethane coating with enzymatically-switchable antimicrobial capability for leather finishing

Microbial deterioration of polyurethane (PU) leather coating continues to represent a significant challenge in maintaining the durability and hygiene of leather products. In the present study, model biocide sulfanilamide (SA) was covalently conjugated into PU backbone as chain extender, yielding a novel PU with enzymatically-switchable antimicrobial capability as leather-finishing material. The anticipated structure of the conjugate was evidenced by ultraviolet spectroscopy, high-performance liquid chromatography, Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy and differential scanning calorimetry, respectively. In the presence of urease, a representative hydrolase derived from one microbial species prevalent on leather coating, such SA-conjugated PU coating was found to release free SA by urease-catalyzed cleavage of urea linkages. These regenerated SA molecules still exhibited bacteriostatic efficiency as pristine ones, against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Micrococcus luteus. When incubated without urease however, the coating displayed such substantially high resistance against hydrolysis that it maintained structural integrity throughout the incubation period. Furthermore, cell culture assay revealed that the SA-conjugated PU coating supported attachment and proliferation of normal human dermal fibroblasts, indicating a dermis-friendly feature. According to these results, the enzymatically-responsive PU designed in this study has great potential as an ideal leather-finishing material, which is capable of providing efficient protection against microbial deterioration while minimizing undesirable side effects associated with biocide abuse.

► Sulfanilamide (SA) was conjugated into polyurethane for antimicrobial coating.
► In response to urease, the coating released SA that remained antimicrobial.
► The coating was dermis-friendly as functional leather-finishing material.