The process of evaluating the efficacy and toxicity of drugs is important in the production of new drugs to treat diseases. Testing in humans is the most accurate method, but there are technical and ethical limitations. To overcome these limitations, various models have been developed in which responses to various external stimuli can be observed to help guide future trials. In particular, three-dimensional (3D) cell culture has a great advantage in simulating the physical and biological functions of tissues in the human body. This article reviews the biomaterials currently used to improve cellular functions in 3D culture and the contributions of 3D culture to cancer research, stem cell culture and drug and toxicity screening.

We report a biocompatible and in situ cross-linkable hydrogel derived from hyaluronic acid via a bioorthogonal reaction and confirm the clinical potential of our hydrogel through in vivo cartilage regeneration. Gelation is attributed to copper-free click reactions between an azide and dibenzyl cyclooctyne. HA-PEG4-DBCO was synthesized and cross-linked via 4-arm PEG azide. The effects of the ratio of HA-PEG4-DBCO to 4-arm PEG azide on the gelation time, microstructure, surface morphology, equilibrium swelling, and compressive modulus were examined. The potential of a hydrogel as an injectable scaffold was demonstrated by the encapsulation of chondrocytes within the hydrogel matrix in vitro and in vivo. The results demonstrated that the hydrogel supported cell survival, and the cells regenerated cartilaginous tissue. In addition, these characteristics provide potential opportunities for the use of injectable hydrogels in tissue engineering applications.

Three-dimensional (3D) cell culture systems have promising applications compared with conventional two-dimensional cell culture systems. Herein, we report a facile method for the formation of 3D spheroids using novel thermo-reversible polysaccharide-based hydrogels. A series of thermo-reversible hydrogels consisting of N-acyl glycol chitosans (NAGCs) are synthesized through a simple N-acylation reaction, and the degree of acylation is finely tuned to obtain adequate thermo-reversible properties and gel stability. Among the NAGCs, N-hexanoyl glycol chitosan is the most thermo-sensitive and is highly effective for forming multi-cellular spheroids when used to coat the surfaces of cell culture dishes. Cell spheroids are effectively formed at various cell concentrations, and their spheroid shape and cellular functions are well maintained for longer times. The hydrogel culture system is also useful for co-cultures that mimic a biological microenvironment. Our thermo-reversible hydrogels may offer a convenient method for the development of in vitro 3D cell culture systems to provide enhanced performance in tissue regeneration, organ-on-chips, drug screening research and other biomedical applications.

Metabolic labeling techniques are powerful tools for cell labeling, tracking and proteomic analysis. However, at present, the effects of the metabolic labeling agents on cell metabolism and physiology are not known. To address this question, in this study, we analyzed the effects of cells treated with Ac4ManNAz through microarray analysis and analyses of membrane channel activity, individual bio-physiological properties, and glycolytic flux. According to the results, treatment with 50 μM Ac4ManNAz led to the reduction of major cellular functions, including energy generation capacity, cellular infiltration ability and channel activity. Interestingly, 10 μM Ac4ManNAz showed the least effect on cellular systems and had a sufficient labeling efficiency for cell labeling, tracking and proteomic analysis. Based on our results, we suggest 10 μM as the optimum concentration of Ac4ManNAz for in vivo cell labeling and tracking. Additionally, we expect that our approach could be used for cell-based therapy for monitoring the efficacy of molecule delivery and the fate of recipient cells.