Multifunctional Porous Microshuttles as Scaffolding Components and Carriers of Bioactive Factors in Self‐Assembled Microtissues

Co-assembly of cells and microsized, extracellular matrix (ECM)-mimicking biomaterials, for example, in the form of microparticles, is a promising strategy for generating 3D microtissues. Additionally, microparticles, especially the porous ones, are known for their role as microcarriers in delivery systems, owing to their high specific surface area. Therefore, this work proposes the use of multifunctional, bioactive compound-loaded porous microparticles, or microshuttles, that can simultaneously fulfill the roles of ECM-mimicking scaffolding components and delivery vehicles in self-assembled microtissues. This work presents a one-step emulsification method, followed by a chemical etching step, for generating a library of porous poly(lactic-co-glycolic acid) (PLGA) microparticles with tunable pore sizes. The microparticles undergo cell-guided assembly when co-seeded with human mesenchymal stromal cells (HMSCs) in microwells, forming hybrid cell-biomaterial microtissues. Additionally, the microparticles can be versatile microcarriers of various bone repair-related factors, including bone morphogenetic protein 2 (BMP-2), nanohydroxyapatite (nHA), and human umbilical vein endothelial cells (HUVECs). The results indicate enhanced expression of osteogenic genes and proteins in hybrid microtissues containing BMP-2- and nHA-loaded PLGA microparticles, and improved endothelial network formation in hybrid microtissues containing HUVEC-loaded PLGA microparticles, as compared to HMSC-only microtissues. These findings highlight the potential of the porous PLGA microshuttles in engineering potentially osteogenic, self-assembled microtissues.