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

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.