One of the exciting future directions in the 3D printing field is the development of innovative personalized smart constructions for bio-applications, including drug delivery, namely high-throughput drug screening and customized topical/oral administration of pharmaceuticals, as well as tissue engineering. In this context, hydrogels have emerged as a promising material that, when combined with extrusion 3D printing, allow the creation of soft-material structures with defined spatial locations, that can be printed at room temperature and customized by tuning the geometric design and/or the formulation components. Thus, the efficacy and quality of such vehicles is dependent on formulation, design, and printing process parameters. However, hydrogel inks are often designed and characterized using different methods and this lack of uniformity impairs. Characterization techniques are usually arbitrary and differ among research groups, challenging the inference of possible conclusions on hydrogel behaviour and potential applications. Therefore, to properly analyse the potential of a particular hydrogel ink formulation, we review, for the first time, the most frequently employed characterization procedures, from rheological approaches to printing parameters and settings, and discuss their relevance, limitations and drawbacks, and highlight future perspectives. Overall, to accelerate the development of high-quality 3D constructs, comprehensive characterization protocols for both pre-printing and printing assays should be adopted. Furthermore, their transversal adoption could serve as a boost in terms of quality requirements and regulatory aspects.

The advances on the development of novel materials capable to enhance the shelf life of food products may contribute to reduce the current worldwide food waste problem. Zinc oxide nanoparticles (ZnO NPs) are considered GRAS (Generally Recognized as Safe) by the Food and Drug Administration (FDA) and due to their good antimicrobial properties are suitable to be applied as active compounds in food packaging. ZnO NPs were synthesized to be tested in active bionanocomposites through an eco-friendlier route using apple peel wastes. This work aimed to develop bionanocomposites based on chitosan and incorporated with ZnO NPs to characterize its bioactivity via in vitro and in situ studies, using fresh poultry meat as the food matrix. Overall, bio-based biodegradable films presented good antimicrobial activity, being the intrinsic antimicrobial properties of chitosan enhanced by the ZnO NPs added on the system. When used as primary packaging of the meat, the samples protected with the films presented a decrease on the deterioration speed, which was represented by the preservation of the initial reddish color of the meat and reduction on the oxidation process and microbiological growth. The nanoparticles enhanced especially the antioxidant properties of the films and proved to be potential food preservatives agents to be used in active food packaging.

Biodegradable metals have been extensively studied due to their potential use as temporary biomedical devices, on non-load bearing applications. These types of implants are requested to function for the healing period, and should degrade after the tissue heals. A balance between mechanical properties requested at the initial stage of implantation and the degradation rate is required. The use of temporary biodegradable implants avoids a second surgery for the removal of the device, which brings high benefits to the patients and avoids high societal costs. Among the biodegradable metals, iron as a biodegradable metal has increased attention over the last few years, especially with the incorporation of additive manufacturing processes to obtain tailored geometries of porous structures, which give rise to higher corrosion rates. Withal by mimic natural bone hierarchical porosity, the mechanical properties of obtained structures tend to equalize that of human bone. This review article presents some of the most important works in the field of iron and porous iron. Fabrication techniques for porous iron are tackled, including conventional and new methods highlighting the unparalleled opportunities given by additive manufacturing. A comparison among the several methods is taken. The effects of the design and the alloying elements on the mechanical properties are also revised. Iron alloys with antibacterial properties are analyzed, as well as the biodegradation behavior and biocompatibility of iron. Although is necessary for further in vivo research, iron is presenting satisfactory results for upcoming biomedical applications, as orthopaedic temporary scaffolds and coronary stents.