Cellulose-based hydrogels were prepared by dissolving cellulose in aqueous sodium hydroxide (NaOH)/urea solutions and casting it into complex shapes by the use of sacrificial templates followed by thermal gelation of the solution. Both the gelling temperatures used (40–80 °C), as well as the method of heating by either induction in the form of a water bath and hot press or radiation by microwaves could be shown to have a significant effect on the compressive strength and modulus of the prepared hydrogels. Lower gelling temperatures and shorter heating times were found to result in stronger and stiffer gels. Both the effect of physical cross-linking via the introduction of additional non-dissolving cellulosic material, as well as chemical cross-linking by the introduction of epichlorohydrin (ECH), and a combination of both applied during the gelation process could be shown to affect both the mechanical properties and microstructure of the hydrogels. The added cellulose acts as a physical-cross-linking agent strengthening the hydrogen-bond network as well as a reinforcing phase improving the mechanical properties. However, chemical cross-linking of an unreinforced gel leads to unfavourable bonding and cellulose network formation, resulting in drastically increased pore sizes and reduced mechanical properties. In both cases, chemical cross-linking leads to larger internal pores.

In recent years, 3D printing has enabled the fabrication of complex designs, with low-cost customization and an ever-increasing range of materials. Yet, these abilities have also created an enormous challenge in optimizing a large number of process parameters, especially in the 3D printing of swellable, non-toxic, biocompatible and biodegradable materials, so-called bio-ink materials. In this work, a cellulose gel, made out of aqueous solutions of cellulose, sodium hydroxide and urea, was used to demonstrate the formation of a shear thinning bio-ink material necessary for an extrusion-based 3D printing. After analysing the shear thinning behaviour of the cellulose gel by rheometry a Design of Experiments (DoE) was applied to optimize the 3D bioprinter settings for printing the cellulose gel. The optimum print settings were then used to print a human ear shape, without a need for support material. The results clearly indicate that the found settings allow the printing of more complex parts with high-fidelity. This confirms the capability of the applied method to 3D print a newly developed bio-ink material.

Bio-separation is a crucial process in biotechnology and biochemical engineering for separating biological macromolecules, and the field has long relied on bead-based and expanded bed chromatography. Printed monolith adsorption (PMA) is a new alternative to which uses a 3D-printed monolithic structure containing self-supporting, ordered flow channels. PMA allows for direct purification of biological molecules from crude cell lysates and cell cultures, and like the other technologies, can functionalized to specifically target a molecule and enable affinity chromatography. Here we have combined PMA technology with an immobilized metal affinity ligand (iminodiacetic acid) to provide selectivity of binding to polyhistidine-tagged proteins during PMA chromatography. Two different PMA structures were created and tested for both static and dynamic protein-binding capacity. At comparative linear flow rates, the dynamic binding capacity of both columns was ≈3 mg/mL, while static capacity was shown to differentiate based on column voidage. We show that a polyhistidine-tagged protein can be directly purified from crude lysate with comparable results to the available commercial providers of IMAC, and with a substantially reduced purification time.