Surface-Anchored Metal–Organic Framework–Cotton Material for Tunable Antibacterial Copper Delivery

In the present study, a new copper metal-organic framework (MOF)–cotton material was strategically fabricated to exploit its antibacterial properties for postsynthetic modification (PSM) to introduce a free amine to tune the physicochemical properties of the material. A modified methodology for carboxymethylation of natural cotton was utilized to enhance the number of nucleation sites for the MOF growth. Subsequently, MOF Cu 3 (NH 2 BTC) 2 was synthesized into a homogenous surface-supported film via a layer-by-layer dip-coating process. The resultant materials contained uniformly distributed 1 μm × 1 μm octahedral MOF crystals around each carboxymethylated fiber. Importantly, the accessible free amine of the MOF ligand allowed for the PSM of the MOF–cotton surface with valeric anhydride, yielding 23.5 ± 2.2% modified. The Cu 2+ ion-releasing performance of the materials was probed under biological conditions per submersion in complex media at 37 °C. Indeed, PSM induces a change in the copper flux of the material over the first 6 h. The materials continue to slowly release Cu 2+ ions beyond 24 h tested at a flux of 0.22 ± 0.003 μmol·cm –2 ·h –1 with the unmodified MOF–cotton and at 0.25 ± 0.004 μmol·cm –2 ·h –1 with the modified MOF–cotton. The antibacterial activity of the material was explored using Escherichia coli by testing the planktonic and attached bacteria under a variety of conditions. MOF–cotton materials elicit antibacterial effects, yielding a 4-log reduction or greater, after 24 h of exposure. Additionally, the MOF–cotton materials inhibit the attachment of bacteria, under both dry and wet conditions. A material of this type would be ideal for clothing, bandages, and other textile applications. As such, this work serves as a precedence toward developing uniform, tunable MOF–composite textile materials that can kill bacteria and prevent the attachment of bacteria to the surface.