Despite ongoing efforts and technology development, the contamination of medical device surfaces by disease-causing microbes remains problematic. Two approaches to producing antimicrobial surfaces are using antimicrobial materials and applying physical topography such as nanopatterns. In this work, we describe the use of physical topography on a soft hydrogel to control microbial growth. We demonstrate this approach by using chitosan hydrogel films with nanopillars having periodicities ranging from 300 to 500 nm. The flat hydrophilic chitosan films exhibit antimicrobial activity against the pathogenic bacteria Pseudomonas aeruginosa and filamentous fungi Fusarium oxysporum . The addition of nanopillars to the hydrogel surface further reduces the growth of P. aeruginosa and F. oxysporum up to ∼52 and ∼99%, respectively. Multiple modes of antimicrobial action appear to act synergistically to inhibit microbial growth on the nanopillar hydrogels. We verified that the strongly bactericidal and fungicidal nanopillared material retains biocompatibility to human epithelial cells with the MTT assay. The nanopillared material is a promising candidate for applications that require a biocompatible and antimicrobial film. The study demonstrates that taking advantage of multiple modes of antimicrobial action can effectively inhibit pathogenic microbial growth.
Natural load-bearing mammalian tissues, such as cartilage and ligaments, contain ∼70% water yet can be mechanically stiff and strong due to the highly templated structures within. Here, we present a bioinspired approach to significantly stiffen and strengthen biopolymer hydrogels and films through the combination of nanoscale architecture and templated microstructure. Imprinted submicrometer pillar arrays absorb energy and deflect cracks. The produced chitosan hydrogels show nanofiber chains aligned by nanopillar topography, subsequently templating the microstructure throughout the film. These templated nanopillar chitosan hydrogels mechanically outperform unstructured flat hydrogels, with increases in the moduli of ∼160%, up to ∼20 MPa, and work at break of ∼450%, up to 8.5 MJ m −3 . Furthermore, the strength at break increases by ∼350%, up to ∼37 MPa, and it is one of the strongest hydrogels yet reported. The nanopillar templating strategy is generalizable to other biopolymers capable of forming oriented domains and strong interactions. Overall, this process yields hydrogel films that demonstrate mechanical performance comparable to that of other stiff, strong hydrogels and natural tissues.
the ToxR/TcpP/toxT protein-DNA complex important in early pathogenesis. In addition to elucidating the regulatory pathway of V. cholerae, the impact of this work will be to further provide a general model for outermembrane-bound transcription control in bacteria and nuclear-membranebound transcription in eukaryotic cells.
In nature, structural biopolymers are highly organized to allow for the development of complex tissues within a living entity, including the human body. To match the properties found in these fibrous structural tissues, synthetic biomimetic hydrogels must have an optimal combination of stiffness, strength, and toughness; though an ideal combination remains challenging to achieve. Here, we report a general strategy to design stiff, strong, and tough hydrogels by confining biopolymers with a balance of rigid and weak domains into nanopillar topography. The confinement within nanopillars templates the fiber assembly process throughout the bulk of the film. Compared to a flat control, the application of the nanopillar topography increases the bulk stiffness ~ 160% to 20 MPa, strength ~ 350% to 36 MPa, and toughness ~ 450% to 8,500 kJ m− 3. This simple templating strategy is suitable for a vast range of hydrogels, opening up the potential applications for a diverse array of materials.
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