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Using Spheroids to build 3D Bioprinted Tumor Microenvironment

Ref [138] [139] [131] [137] [135] (Contd...)

Size consistent • Long fusion time Large quantity of spheroids preparation is time consuming Non-uniform • Weak spheroids Turnstile allows the deposition of spheroid one at a time vascularization Mechanical damage to the integrity of Fixed spacing between needles High resolution positioning (~10% spheroid size) High density micro-tissue • High cell viability ~11%with respect to the spheroid size --position accu

Feature • spheroids • • structure • Improved • • spheroids • • High cost • • • •

Spheroid size/ spheroidization time (ST)/ fusion time (FT) Size: 300/500 μm ST: 1-2 h FT: 5-7 d Size: thyroid, 388.2 μm±45.3; Allantoide, 493.6 μm±114.3 ST: 18-24 h Size: 500 µm ST: 48 h FT: 3 weeks Size: 5000 cells/200 µm 10000 cells/400 µm ST: 96h FT: 4d 80-800 µm (~30 s/spheroid) ST: 24h

Cell type (density) Chinese Hamster Ovary cell, Human umbilical vein smooth muscle cells, Human skin fibroblasts, porcine aortic smooth muscle cells Individual thyroid explants and allantoides iPSC-derived human neural progenitor cells (40,000 cells/well), U118 human glioma cells (10,000 cells/well) Human MSCs, Human cardiac fibroblasts Human iPSC-CM 3T3, mouse mammary carcinoma line 4T1, HUVECs/MSCs, HDF, electrocy

Materials Agarose as temporary support Collagen N.A. HA modified with either adamantane (Ad) or β-cyclodextrin (CD) Fibrin

Spheroid generation method Pellet centrifugation Hanging drop 96-well U-bottom plates Ultra-low attachment 96-well round-bottom plates U-bottom 96-well microplate

Target tissue Vascular Thyroid gland Glioblastoma Post-myocardial infarction (MI) scarring /

Table 1. (Continued) Printing strategy Extrusion-based printing (capillary micropipette) Multifunctional Fabion 3D bioprinter with the turnstile system Scaffold-free bioprinter/ Regenova/kenzan method Aspiration-assisted bioprinting Aspiration-assisted bioprinting

12 International Journal of Bioprinting (2021)–Volume 7, Issue 4