Photo of 3D-Printed Ear.
A 3D-printed ear: Empa researcher Michael Hausmann uses nanocellulose as the basis for novel implants. (Credit: Empa)

Researchers have discovered that cellulose nanocrystals in a viscous state can easily be shaped together with other biopolymers into complex three-dimensional structures using a 3D printer. Once cross-linked, the structures remain stable despite their soft mechanical properties. The objective is to incorporate both human cells and therapeutics into the base structure to produce biomedical implants. They have already printed an ear entirely made of cellulose nanocrystals and a biopolymer.

They are currently investigating the characteristics of the nanocellulose composite hydrogels in order to further optimize their stability as well as the printing process. They have used x-ray analysis to determine how cellulose is distributed and organized within the printed structures.

A new project is looking into how chondrocytes (cartilage cells) can be integrated into the scaffold to yield artificial cartilage tissue. As soon as the colonization of the hydrogel with cells is established, nanocellulose based composites in the shape of an ear could serve as an implant for children with an inherited auricular malformation as for instance, in microtia, where the external ears are only incompletely developed. A reconstruction of the auricle can esthetically and medically correct the malformation; otherwise the hearing ability can be severely impaired. In the further course of the project, cellulose nanocrystals containing hydrogels will also be used for the replacement of articular cartilage (e.g., knee) in cases of joint wear due to, for example, chronic arthritis.

Once the artificial tissue has been implanted in the body, the biodegradable polymer material is expected to degrade over time. The cellulose itself is not degradable in the body, but biocompatible. However, it is not only its biocompatibility that makes nanocellulose the perfect material for implant scaffolds. Moreover, nanocellulose allows the incorporation of various functions by chemical modifications into the viscous hydrogel. Thus, the structure, the mechanical properties and the interactions of the nanocellulose with its environment can be specifically tailored to the desired end product.