Assistant Professor University of Michigan Ann Arbor, Michigan, United States
Introduction:: Infections are a significant risk to patients who receive medical implants, and can often lead to implant failure, tissue necrosis, and even amputation. So far, although various surface modification approaches have been proposed for prevention and treatment of microbial biofilms on indwelling medical devices, most are too expensive/complicated to fabricate, unscalable, or limited in durability for clinical use. Here we present a new bottom-up design for fabricating scalable and durable nano-patterned coatings with dynamic topography for long-term antibacterial effects.
Materials and Methods:: Briefly, we first generate a conformal MXene multilayer coating via the LbL assembly method on a biaxially-oriented polystyrene substrate, and the as-prepared MXene coating is shrunk by thermal annealing to form a crumpled structure due to the shrinkage of the polystyrene substrate. Subsequently, the crumpled MXene coating is transferred onto a flexible PDMS substrate by spin-coating PDMS directly on the crumpled MXene coating followed by the removal of the polystyrene substrate. The morphological features of the crumpled MXene coating are characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The antibacterial effects of the coatings are evaluated by fluorescence microscopy and SEM. We further implement surface deformation by mechanically stretching the MXene coatings to detach the debris of dead bacterial cells, and then examine the antifouling effects by fluorescence microscopy.
Results, Conclusions, and Discussions:: We show that MXene layer-by-layer (LbL) self-assembled coatings—with finely tunable crumpled structures with nanometer resolution and excellent mechanical durability—can be successfully fabricated on stretchable poly(dimethylsiloxane) (PDMS). The crumpled MXene coating with sharp-edged peaks shows potent antibacterial effects against Staphylococcus aureus and Escherichia coli. In addition, we find that on-demand dynamic deformation of the crumpled coating can remove ≥99% of adhered bacterial cells for both species, resulting in a clean surface with restored functionality. This approach offers improved practicality, scalability, and antibacterial durability over previous methods, and its flexibility may lend itself to many types of biomaterials and implantable devices.