Zinc Oxide Nano-Spicules on Polylactic Acid for Super-Hydrophilic and Bactericidal Surfaces

Abstract

The artificial construction of nature-mimic inorganic-organic heterostructures is an emerging technological interest for protective surface applications. Mimicking the spikiness of sea urchin spicules for their protective function, here, the synthesis of zinc oxide (ZnO) nanometer-scale spicules grown from micrometer-scale polylactic acid (PLA) beads and fibers as super-hydrophilic and bactericidal surfaces is reported. The thermodynamic mechanism behind the interfacial assembly of pre-entrapped ZnO nanoparticles right at the PLA-water interfaces above the glass transition temperature of PLA, allowing for the follow-up growth of nano-spicules on the PLA templates is uncovered. This sea urchin-like topography of ZnO nano-spicules induces super-hydrophilicity while generating reactive oxygen species as well as allowing the stabbing action of nano-spicules. All of the above help enhance the bactericidal activity against both gram-positive and gram-negative bacteria in an unprecedentedly effective way. The findings conceptualize a new strategy to spontaneously assemble nanoparticles at the polymer-liquid interfaces, enabling various heterostructures with topography-induced functions.