Tissue engineering utilizes 3D printing and bioink to grow human cells on scaffolds, creating replacements for damaged tissues like skin, cartilage, and even organs. A team of researchers led by Professor Insup Noh from Seoul National University of Science and Technology, Republic of Korea, has developed a bioink using nanocellulose derived from Kombucha SCOBY (Symbiotic Culture of Bacteria and Yeast) as the scaffold material. The biomaterial offers a sustainable alternative to conventional options, and it can be loaded onto a hand-held 'Biowork' biopen, also developed by the same team. The digital biopen allows the precise application of bioink to damaged defected areas, such as irregular cartilage and large skin wounds, paving the way for more personalized and effective in vivo tissue repair, eliminating the need for in vitro tissue engineering processes.
This paper was made available online on 28 October 2024 and subsequently published in Volume 282, Part 3, of the International Journal of Biological Macromolecules on 1 December 2024.
"Our prefabricated nanocellulose hydrogel network from symbiotic culture of bacteria and yeast has the potential to be used as a platform bioink for in vivo tissue engineering by loading all types of biomolecules and drugs and direct bioprinting," says Prof. Noh.
Kombucha SCOBY is a symbiotic culture of bacteria and yeast used to ferment green tea. The microorganisms produce cellulose, which is biodegradable and compatible with cells. However, the nanocellulose derived from Kombucha SCOBY has an entangled structure, which requires modification for 3D bioprinting. This involves adjusting its rheological properties (how it flows) and mechanical properties to improve extrusion and maintain structural integrity after printing.
The researchers accomplished this by partially hydrolyzing nanocellulose with acetic acid, breaking glucose bonds and disentangling the network for its bioprintablity. However, this treatment lacked control of its properties, leading to a reduction of its structural strength. The team reinforced the nanocellulose with chitosan (positively charged) and kaolin (negatively charged) nanoparticles. These chitosan and kaolin particles interact with cellulose through electrostatic forces, forming a stable hydrogel suitable for 3D bioprinting.
The bioink was prepared by mixing the ingredients, including live cells, within a biopen. Digitally controlled, two counter-rotating screws within the biopen uniformly mixed the ingredients, creating a homogeneous bioink that could be directly applied through a needle onto damaged tissue. When attached to a 3D bioprinter, the biopen enabled the creation of multilayer, self-standing structures with high resolution, such as bifurcated tubes and pyramids exceeding 1 cm in height. The biopen was also used for direct in situ layer-by-layer printing of irregularly shaped defects. Using it, the researchers accurately filled 3D-printed cranium and femoral head molds with designed defects.
The bioink and digital biopen combination offers a cost-effective solution for treating large areas and irregularly shaped wounds without any in vitro tissue regeneration process, particularly in emergency and first-aid situations. "This technology allows for a quick and easy one-step process where the drug and hydrogel are mixed and immediately applied on-site to injured areas of different shapes," says Prof. Noh.
