In this report, a strategy for constructing three-dimensional (3D) cellular architectures comprising viable cells is presented. The strategy uses a redox-responsive hydrogel that degrades under mild reductive conditions, and a confluent monolayer of cells (i.e., cell sheet) cultured on the hydrogel surface peels off and self-folds to wrap other cells. As a proof-of-concept, the self-folding of fibroblast cell sheet was triggered by immersion in aqueous cysteine, and this folding process was controlled by the cysteine concentration. Such folding enabled the wrapping of human hepatocellular carcinoma (HepG2) spheroids, human umbilical vein endothelial cells and collagen beads, and this process improved cell viability, the secretion of metabolites and the proliferation rate of the HepG2 cells when compared with a two-dimensional culture under the same conditions. A key concept of this study is the ability to interact with other neighbouring cells, providing a new, simple and fast method to generate higher-order cellular aggregates wherein different types of cellular components are added. We designated the method of using a cell sheet to wrap another cellular aggregate the ‘cellular Furoshiki’. The simple self-wrapping Furoshiki technique provides an alternative approach to co-culture cells by microplate-based systems, especially for constructing heterogeneous 3D cellular microstructures.

Ulva lactuca is a green seaweed that has three times faster growth than other types of seaweed and high sulfate polysaccharide content that can be used for biological activities. Deep Eutectic Solvents (DES) emerged as an alternative to extracting ulvan due to its biodegradable, environmentally friendly, and harmless nature. This study aims to determine the type and concentration of DES that can produce the best ulvan extract characteristics based on yield, FTIR, and viscosity analysis as well as moisture and sulfate content tests. The stages of research carried out include preparation and characteristics of raw materials, DES synthesis, extraction, and further analysis and tests. Different types and concentrations of DES affect the results of the analysis. The test results showed the highest ulvan yield found in the 30% choline chloride-urea DES type treatment (KKU30), while the sulfate content and viscosity values were found in the 30% choline chloride-glycerol treatment (KKG30). The ulvan functional group in the 30% choline chloride-glycerol treatment (KKG30) showed absorption band results similar to HCl treatment.