Novel nanocellulose hydrogel suitable for 3D printing

(Nanowerk News) Researchers in Finland have developed a nanocellulose-alginate hydrogel suitable for 3D printing. The composition of the hydrogel was optimized based on material characterization methods and 3D printing experiments.
The 3D-printable bioactivated nanocellulose-alginate hydrogel offers a platform for the development of 3D bioprinting, wearable sensors, and drug-releasing materials for wound healing.
In addition, the team studied the feasibility of computational fluid dynamics simulations for predicting dependencies between the printing parameters and the hydrogel behavior using separate models for the printer head and the deposition.
The hydrogel was biofunctionalized by covalent coupling of an enhanced avidin protein to the cellulose nanofibrils.
The team has published their findings in ACS Applied Materials & Interfaces ("3D-Printable Bioactivated Nanocellulose-Alginate Hydrogels").
Printed hydrogel structures before and after humidity tests
Printed hydrogel structures before the humidity tests (upper row) and after 4 days in the humidity chamber (lower row): (a) ATG50 noncross-linked, (b) ATG50 cross-linked, (c) ATG50 freeze-dried, and (d) TCNF reference. The yellow scale bars indicate 10 mm. (© ACS) (click on image to enlarge)
The authors benchmarked several biobased hydrogel compositions to be used as a printing paste for 3D printing. They found that a combination of alginate, cellulose nanofibrils, and glycerin enabled excellent printability and dimensional stability at room temperature.
They note that collapsing of the printing paste can be avoided by increasing the share of nonvolatile components and by using an effective strength additive such as cellulose nanofibrils (CNFs).
In addition, the print pattern can have a significant effect on the shape fidelity and stability.
According to the team's buffer tests, the 3D printing of porous structures reduced excess deformation of the objects, especially when the printed structure was cross-linked with CaCl2.
Voids within the structure provided room for swelling in moist and wet conditions. This can be a desired property in wound-healing applications, in which compressive forces may cause irritation and pain.
The core result of this work is that the described avidin-functionalized nanocellulose-alginate material provides a generic platform for the immobilization of bioactive components via biotin-avidin interaction.
Nevertheless, according to the scientists, more work is needed to improve the structural stability of the printed material, especially in wet or moist conditions and in prolonged use.
This could be achieved with other cross-linking methods or by using alternative polymeric reinforcing materials such as polyethylene glycol (PEG) or polypropylene glycol (PPG), which enable the formation of more-hydrophobic patterns when cured.
"Ultimately, 3D printing could provide the means for creating customized implant and wound-healing products with internal gradients of therapeutic agents and their gradual release," the authors conclude. "In addition, we envision potential use for the material in the development of wearable biosensors.
Michael Berger By – Michael is author of three books by the Royal Society of Chemistry:
Nano-Society: Pushing the Boundaries of Technology,
Nanotechnology: The Future is Tiny, and
Nanoengineering: The Skills and Tools Making Technology Invisible
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