A rapidly magnetically assembled stem cell microtissue with "hamburger" architecture and enhanced vascularization...

Area of Science:

• Biomaterials Engineering
• Tissue Engineering
• Regenerative Medicine

Background:

• Scaffold-free microtissues are crucial for stem cell viability and function.
• Rapid construction and *in vivo* vascularization are key challenges in microtissue engineering.
• Endothelial cells are essential for blood vessel formation in engineered tissues.

Purpose of the Study:

• To develop a rapid method for constructing scaffold-free microtissues using magnetic nanoparticles (MNPs).
• To investigate the *in vivo* vascularization and self-assembly capabilities of MNP-labeled cells within complex microtissue architectures.
• To evaluate the potential of this technique for creating vascularized engineered tissues.

Main Methods:

• Safe and rapid magnetic labeling of cells using MNPs within 1 hour.
• Layer-by-layer assembly of ultrathick scaffold-free microtissues in 5-minute intervals.
• Fabrication of microtissues with sophisticated architectures, including 'hamburger' and trisection designs.

Main Results:

• Successfully assembled ultrathick, scaffold-free microtissues with complex architectures rapidly.
• *In vivo* transplantation demonstrated spontaneous vascular network formation by human umbilical vein endothelial cells (HUVECs).
• Connected HUVEC layers formed functional blood vessels that anastomosed with host vasculature, promoting stem cell survival.

Conclusions:

• Magnetic nanoparticle-based cell labeling and assembly offer a rapid and effective strategy for scaffold-free microtissue engineering.
• The 'hamburger' architecture facilitates enhanced vascularization and stem cell survival in engineered tissues.
• This approach holds significant promise for the future construction of functional vascularized tissues and organs.