No abstract

The perpetual health and safety concerns caused by bacterial adhesion on surfaces demand the development of next-generation antibacterial materials. Inspired by bactericidal surfaces on cicada wings with protrusive nanostructures, which induce mechanical rupture of adhered bacterial membranes without antibacterial, chemical treatments, analogous structures have been fabricated on various synthetic materials to achieve such mechanical bactericidal efficacy. Herein, we developed a series of protrusive nanopillars on hard silicon (Si) substrates and soft poly­(ethylene glycol) diacrylate (PEGDA) thin films by colloidal lithography. We first investigated the correlation of interpillar distance and bactericidal efficacy against a model Gram-negative bacterium, Escherichia coli, using Si surfaces with different nanopillar number densities. We demonstrated that the bactericidal efficacy increased with decreasing nanopillar number density, which occurred when the average interpillar distance was smaller than the cell size. The bactericidal efficacy decreases when the average interpillar distance becomes larger than the comparable size of bacteria. We then designed PEGDA thin films with optimized bactericidal nanopillar density to improve their antibacterial and antireflective performance. The results indicate that the surface nanostructure plays a critical role in dictating antibacterial performance, regardless of the material type. This work provides insight into the understanding of physical interactions between nanostructured surfaces and bacterial cells as well as practical solutions for the development of antibacterial polymer surfaces for the application of optical lenses or screen displays to prevent public pathogenic infections.

Vesicles made from functionally folded, globular proteins that perform specific biological activities, such as catalysis, sensing, or therapeutics, show potential applications as artificial cells, microbioreactors, or protein drug delivery vehicles. The mechanical properties of vesicle membranes, including the elastic modulus and hardness, play a critical role in dictating the stability and shape transformation of the vesicles under external stimuli triggers. Herein, we have developed a strategy to tune the mechanical properties and integrity of globular protein vesicle (GPV) membranes of which building molecules are recombinant fusion protein complexes: a mCherry fused with an acidic leucine zipper (mCherry-Z E ) and a basic leucine zipper fused with an elastin-like polypeptide (Z R -ELP). To control the mechanical properties of GPVs, we introduced a nonstandard amino acid (paraazidophenylalanine (pAzF)) into the ELP domains (ELP-X), which enabled the creation of crosslinked vesicles under ultraviolet (UV) irradiation. Crosslinked GPVs made from mCherry-Z E /Z R -ELP-X complexes presented higher stability than noncrosslinked GPVs under hypotonic osmotic stress. The degree of swelling of GPVs increased as less crosslinking was achieved in the vesicle membranes, which resulted in the disassembly of GPVs into membraneless coacervates. Nanoindentation by atomic force microscopy (AFM) confirmed that the stiffness and Young's elastic modulus of GPVs increase as the blending molar ratio of Z R -ELP-X to Z R -ELP increases to make vesicles. The results obtained in this study suggest a rational design to make GPVs with tunable mechanical properties for target applications by simply varying the blending ratio of Z R -ELP and Z R -ELP-X in the vesicle selfassembly.

No abstract