Additive manufacturing of antibacterial PLA-ZnO nanocomposites: Benefits, limitations and open challenges

Polymeric biomaterials such as polylactic acid (PLA) play a prominent role in the advancement of biomedical additive manufacturing (AM). PLA offers indeed a very advantageous combination of thermo-mechanical properties and functional attributes, as it is biobased, biodegradable, biocompatible and easy to print. However, PLA can be damaged by common sterilization methods and is sensitive to most chemical disinfectants, and this may impair its widespread usage. One of the most promising ways to overcome this shortcoming is to provide PLA with embedded antibacterial activity by the addition of appropriate fillers such as zinc oxide (ZnO) nanoparticles. After a detailed introduction to the basic properties of PLA and ZnO nanoparticles, the present review analyzes the main variables that govern the antibacterial activity of PLA-ZnO nanocomposites. Current applications and related manufacturing processes are also presented to showcase the importance of having embedded antibacterial functions in demanding applications such as food packaging and wound dressing. Emphasis is then placed on the emerging literature of the AM of PLA-ZnO nanocomposites, with a focus on fused filament fabrication (also known as fused deposition modeling). Existing gaps and hurdles related to the development and 3D printing of such composites is critically discussed. It is envisioned that a deeper understanding of the processability, thermo-mechanical behavior, biocompatibility and antibacterial efficacy of additively manufactured PLA-ZnO nanocomposites will foster their adoption in the biomedical field and, ultimately, in all circumstances where it is crucial to limit infection transmission.