Effect of sterilization processes on alginate/gelatin inks for three-dimensional printing

Sterilization is a crucial step in the process of developing bioinks for tissue engineering applications. In this work, alginate/gelatin inks were subjected to three sterilization methods: ultraviolet (UV) radiation, filtration (FILT), and autoclaving (AUTO). In addition, to simulate the sterilization effect in a real environment, inks were formulated in two different media, specifically, Dulbecco's Modified Eagle's Medium (DMEM) and phosphate-buffered saline (PBS). First, rheological tests were performed to evaluate the flow properties of the inks, and we observed that UV samples showed shear thinning behavior, which was favorable for three-dimensional (3D) printing. Furthermore, the 3D-printed constructs developed with UV inks showed better shape and size fidelity than those obtained with FILT and AUTO. In order to relate this behavior to the material structure, Fourier transform infrared (FTIR) analysis was carried out and the predominant conformation in protein was determined by deconvolution of the amide I band, which confirmed that the prevalence of a-helix structure was greater for UV samples. This work highlights the relevance of sterilization processes, which are essential for biomedical applications, in the research field of bioinks.