Structural colors, originating from the physical interaction of light with intrinsic periodic nanostructures, have attracted much interest. It has been widely studied and used in tissue engineering, cell behavior, drug screening and other biological processes. In cytological studies, the interaction between cells and materials has been a hot topic, such as adsorption, growth, proliferation and differentiation. Therefore, the development of a detection platform based on structure color materials, will play an important role in the study of the interactions between cell and material. Unlike some others, the cellular detection platforms based on structural color materials do not require fluorescent staining, therefore avoiding the occurrence of cell death or fluorescence quenching. The encoding strategy of structure color materials was highly efficient, stable, and undisturbed. It can realize real-time detection of cellular physiological processes without cells damage. Herein, we focused on this goal and developed organ-on-chips based on the structural color hydrogels, and explored their applications in drug screening, evaluation and others biological analysis. The detail works are as follow:
(1) The photonic crystal templates, such as photonic crystal films, photonic crystal fibers and photonic crystal beads were fabricated by self-assembly of silica nanoparticles. The inverse structural color materials were fabricated by replicating photonic crystal templates.
(2) The self-healing structural color hydrogels were prepared by constructing them with a composite nanostructure. This nanostructure was composed of a methacrylated gelatin (GelMA) hydrogel inverse opal scaffold and a filler of glutaraldehyde cross-linked BSA hydrogel. A series of unprecedented structural color materials, such as 1D linear structures, 2D patterns, and 3D counterfeit-prevention objects and photonic path structures, could be created by assembling and healing the elements of the composite hydrogel. We have demonstrated their different applications, such as counterfeit prevention, integrated optics, and biomedical engineering.
(3) We have developed novel structural-color hydrogels that have autonomic regulation capability by assembling engineered cardiomyocyte tissues on soft inverse-opal GelMA hydrogel films. Taking advantage of the surface microgroove structure of structural colors films, the assembled cardiomyocytes with guided cellular orientation were achieved. These features make our self-healing structural color hydrogels highly promising for in vitro culture of high-activity cardiomyocytes.
(4) Based on these biohybrid structural-color hydrogels, an unprecedented heart-on-a-chip device has been developed for biological research and drug (isoproterenol) screening. In this heart-on-a-chip platform, the cardiomyocytes contractile force and beating frequency were monitored.
(5) A novel GelMA hydrogel-encapsulated core-shell PhC barcode particles were developed. It was used for high-activity organ cells (HepG2, HCT-116 and NIH-3T3) cultured.
(6) On the basis of these core-shell PhC barcode particles, HepG2, HCT-116, and NIH-3T3 were cocultured into liver and tumor cell spheroids to test the cytotoxic effect of TF. The system appeared to reproduce the hepatic function of synthesizing P450 enzymes, which could convert the noncytotoxic TF to cytotoxic 5-FU and reveal its cytotoxicity.