Three-Dimensional Calcium Alginate Hydrogel Assembly via TiOPc-Based Light-Induced Controllable Electrodeposition

Abstract

Artificial reconstruction of three-dimensional (3D) hydrogel microstructures would greatly contribute to tissue assembly in vitro, and has been widely applied in tissue engineering and drug screening. Recent technological advances in the assembly of functional hydrogel microstructures such as microfluidic, 3D bioprinting, and micromold-based 3D hydrogel fabrication methods have enabled the formation of 3D tissue constructs. However, they still lack flexibility and high efficiency, which restrict their application in 3D tissue constructs. Alternatively, we report a feasible method for the fabrication and reconstruction of customized 3D hydrogel blocks. Arbitrary hydrogel microstructures were fabricated in situ via flexible and rapid light-addressable electrodeposition. To demonstrate the versatility of this method, the higher-order assembly of 3D hydrogel blocks was investigated using a constant direct current (DC) voltage (6 V) applied between two electrodes for 20–120 s. In addition to the plane-based two-dimensional (2D) assembly, hierarchical structures—including multi-layer 3D hydrogel structures and vessel-shaped structures—could be assembled using the proposed method. Overall, we developed a platform that enables researchers to construct complex 3D hydrogel microstructures efficiently and simply, which has the potential to facilitate research on drug screening and 3D tissue constructs.

Light-addressable Electrodes for Dynamic and Flexible Addressing of Biological Systems and Electrochemical Reactions

“…Furthermore, by sequentially illuminating two different areas for 400 ms, a wide-range pH gradient could be achieved when applying in the first area a cathodic potential (−3 V, +∆pH) and in the second area an anodic potential (4 V, −∆pH) ( Figure 6c). This experimental setup with a DMD projector as the illumination source was also used with a glass/ITO/n-doped a-Si:H/undoped a-Si:H or glass/ITO/titanium dioxide phthalocyanine (TiOPc) structure to manipulate the pH values by photoelectrolysis for spatial deposition of calcium alginate [85,86] and chitosan [87,88]. For the a-Si:H structure, the pH change was monitored by a pH-sensitive fluoerescence dye (BCECF) diluted in DI water and an applied current density of 4 Am −2 .…”

“…Furthermore, fibroblasts were added to the solution and, under certain conditions, the cells had a viability of more than 90%. Deposition of calcium alginate was also performed on TiOPc [86]. Different geometries were patterned, ranging from connected calcium alginate blocks and stacked layers to vessel-shaped structures by sequential illumination of the electrode.…”

“…Polymer Polystyrene TiO 2 [110] Polyaniline WO 3 [111] Polyaniline TiO 2 [111] Polypyrrol TiO 2 [56,111,112,114,115,122] Polypyrrol n-Si [55,92] Polypyrrol ZnO [113] Others Calcium alginate gels a:Si [110] Calcium alginate gels TiOPc [85,86] Chitosan a:Si [87,88] Polyhistidine-tagged proteins TiO 2 [89] DNA oligonucleotids n-Si [119] DNA oligonucleotids a:Si [120]…”

On-Chip Construction of Multilayered Hydrogel Microtubes for Engineered Vascular-Like Microstructures

“…All these cells have defined positions and contribute to the gut endothelium in order for the complex structure to function properly [37]. A method to achieve multicellular 3D structures is becoming an important issue [38,39] and such technology would contribute significantly by revealing cell-cell interactions and functionalization factors [40]. Inside the multicellular environment, cell groups stimulate each other and form functional tissues [41,42].…”

Editorial for the Special Issue on Microdevices and Microsystems for Cell Manipulation

“…Cell culturing in three-dimensional (3D) scaffolds is expected to significantly impact the fields of drug-screening and tissue engineering. In the work of Liu et al electrodeposition was used to synthesize alginate hydrogel microstructures in arbitrary shapes, and the assembly of 3D hydrogel blocks was achieved [ 10 ]. This platform offers a way for researchers to synthesize complex 3D hydrogel structures for use in tissue engineering.…”