Bacterial cellulose (BC) nanofibers are promising building blocks for the development of sustainable materials with the potential to outperform conventional synthetic materials. BC, one of the purest forms of nanocellulose, is produced at the interface between the culture medium and air, where the aerobic bacteria have access to oxygen. Biocompatibility, biodegradability, high thermal stability, and mechanical strength are some of the unique properties that facilitate BC adoption in food, cosmetics, and biomedical applications including tissue regeneration, implants, wound dressing, burn treatment, and artificial blood vessels.

Bacterial cellulose biofabricated in the shape of an ear via superhydrophobized molding. (Credit: Luiz G. Greca)

In a study published in the journal Materials Horizons, researchers at Aalto University have developed a simple and customizable process that uses superhydrophobic interfaces to finely engineer the bacteria access to oxygen in three dimensions and in multiple length scales, resulting in hollow, seamless, nanocellulose-based predetermined objects.

According to the paper, “Biomass-based nanomaterials such as bacterial cellulose (BC) are one of the most promising building blocks for the development of sustainable materials with the potential to outperform their conventional, synthetic, counterparts. The formation of BC occurs at the air–water interface, which has been exploited to engineer materials with finely controlled microtopographical features or simple three-dimensional morphologies for a wide range of applications. However, a high degree of control over the 3D morphology of BC films across several length scales (micro to macro) has not yet been achieved.”

In the paper, the authors describe “a simple yet customizable process to finely engineer the morphology of BC in all (x, y, z) directions, enabling new advanced functionalities, by using hydrophobic particles and superhydrophobized surfaces. This results in hollow, seamless, cellulose-based objects of given shapes and with sizes from ca. 200 m to several centimeters.”

“We demonstrate some of the unique properties of the process and the resulting objects via postfabrication merging (biowelding), by in situ encapsulation of active cargo, and by multi-compartmentalization for near limitless combinations, thus extending current and new applications for example in advanced carbon materials or regenerative medicine.”

According to Orlando Rojas, a professor in the department of bioproducts and Biosystems at Aalto University, “The developed process is an easy and accessible platform for 3D biofabrication that we demonstrated for the synthesis of geometries with excellent fidelity. Fabrication of hollow and complex objects was made possible,” he says. “In teresting functions were enabled via multi-compartmentalization and encapsulation. For example, we tested in situ loading of functional particles or enzymes with metal organic frameworks, metal nanoparticles with plasmon adsorption, and capsule-in-capsule systems with thermal and chemical resistance.”

This facilitated biofabrication can be explored in new ways by the biomedical field through scaffolding of artificial organs. Advances in bioengineering, for instance by genome editing or co-culture of microorganisms, might also allow further progress toward the simplified formation of composite materials of highly controlled composition, properties, and functions.

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