Dissolving microneedles based on ZnO nanoparticles and an ionic liquid as synergistic antibacterial agents

The use of nanomaterials to replace antibiotics has developed rapidly in the past decade, among which zinc oxide nanoparticles (ZnO NPs) have been proven to exhibit antibacterial properties and low toxicity in the treatment of microbial infections, and have been applied in antibacterial agent preparation. However, one of the problems of ZnO NPs is that these particles do not disperse well in some media, which reduces their antibacterial effects. Ionic liquids (ILs) are a class of low melting point salts containing organic cations and organic/inorganic anions; they have good biocompatibility and can not only enhance the dispersion of ZnO NPs but also have antibacterial properties. Microneedles (MNs) are an emerging transdermal drug delivery platform, which can effectively establish a transport channel in the epidermis and deliver the drug to a predetermined depth without causing pain, skin damage or overstimulation. Dissolving microneedles (DMNs) have developed rapidly because of several advantages. In this study, it is verified that ZnO NPs dispersed in the imidazolidinyl IL exhibit excellent and enhanced antibacterial effects compared with single ZnO NPs and a single IL. Therefore, ZnO NPs/IL dispersion showed good antibacterial activity. Then, ZnO NPs/IL dispersions with synergistic antibacterial properties were used as antibacterial agents to prepare DMNs. In vitro antibacterial results showed that DMNs also had good antibacterial properties. Furthermore, DMNs were applied to treat wound infection. Antibacterial DMNs were inserted into the infected wound and then dissolved and released, resulting in microbial death and acceleration of wound healing.