Bioinks Functionalized with Natural Extracts for 3D Printing

Abstract

In the search of materials valid for direct ink writing (DIW) 3D printing and with special interest for the biomedical and pharmaceutical applications, the development of bioactive inks for DIW is of great interest. For that purpose, in this work bioactive waterborne polyurethane–urea inks were prepared by addition of natural extracts (logwood, chestnut, and alder buckthorn) and cellulose nanofibers (CNF). The rheological behavior of the inks proved to be strongly dependent on the extract type and content, and the addition route used. Inks prepared by ex-situ incorporation of the extracts showed a strong gel-like behavior, as did inks prepared with chestnut and alder buckthorn extracts, which, in turn, hindered a continuous flow during the printing process, resulting in 3D printed parts with poor shape fidelity. On the other hand, inks prepared in-situ and with logwood extract showed more facility to flow and higher homogeneity, which translated in better printability and better shape fidelity, further enhanced for CNF containing inks. 3D printed composites showed reinforced mechanical behavior, as well as in materials with enhanced antibacterial behavior. Overall, the possibility to successfully prepare bioactive inks valid for 3D printing was proven.