Table 1.

Scaffolds/materials used in 3D printing of cardiac and microvascular structures

Materials	Scaffold types/approach	Properties	3D printing method	References
PCL	Hydrogel/nanofibers	Moderate mechanical strength. Biocompatible and degraded easily	Inkjet/extrusion	28, 31, 78
PCL-CNT	Nanofibers	High mechanical strength and electrical conductance	Extrusion/laser	78
PLGA	Hydrogel/nanofibers	Brittle and relatively hard. Not good for tissue remodeling. Biocompatible and biodegradable, immunogenic	Droplet	82, 207
Gelatin	Hydrogel/cell layers	Biocompatible, biodegradable, low cell adhesion and viability. Good printability, high cell viability and cross-linking agents. Low mechanical strength. Immunogenic	Extrusion/droplet	81, 102, 130, 131, 148
Chitosan	Spheroids/hydrogel/nanofibers	Biocompatible, biodegradable, immunogenic, high cell proliferation and cell remodeling, low mechanical strength, and antibacterial	Extrusion/laser	32, 50, 55, 86
Fibrin	Hydrogel/nanofibers/cell sheets	High cell adhesion and viability, quick gelation and low printability, biocompatibility, low mechanical strength, good cell migration, and vascularization	Extrusion	131, 134, 135, 144, 147, 208
Alginate	Hydrogel/microdroplet	Biocompatible, biodegradable, sustained release, adoptable mechanical strength with cell growth, rapid gelation, low cell adhesion, can be increased by surface modification with collagen type I	Extrusion/droplet	83, 127, 148
Hyaluronic acid Hyaluronic acid/gelatin	Hydrogel	Biocompatible, biodegradable, low mechanical strength, high cell proliferation and viability, high printability	Extrusion/inkjet	102
Decellularized extracellular matrix reinforced with PCL framework	Hydrogel	High cell viability, high cell adhesion, and maturation. Easily synchronized with grafted tissues, good printability, and mechanical strength. No immune reaction. Biocompatible	Extrusion/droplet	56, 57, 149, 150
Collagen	Hydrogel	High biocompatibility, biodegradable, high cell adhesion, and cell remodeling. Has high printability and acts as signal transducer and good in electromechanical coupling with host tissues	Extrusion/droplet	29, 76, 134
NIPAM	Hydrogel/nanofibers/cell sheets	Thermosensitive, sustained release, biocompatible, can be made biodegradable, low mechanical strength, can be modified easily with various functional groups	Laser	29, 35
Poly(ethylene glycol)	Hydrogel	Biocompatible, biodegradable, poor cell adhesion and proliferation, moderate mechanical strength, low printability, can be modified with various functional groups	Extrusion	83

Abbreviations: CNT, carbon nanotube; PCL, polycaprolactone; PLGA, poly(lactic-co-glycolic acid); NIPAM, N-isopropylacrylamide.