A microphysiological system (MPS) is recently emerging as a promising alternative to the classical preclinical models, especially animal testing. A key factor for the construction of MPS is to provide a biomimetic three-dimensional (3D) cellular microenvironment. However, it still remains a challenge to introduce extracellular matrix (ECM)-like
biomaterials such as
hydrogels and nanofibers in a precise and spatiotemporal manner. Herein, we report a strategy to fabricate a MPS combining both electrospun nanofibers and
hydrogels. The in situ formation of microsized
hydrogel (
microgel) array in MPS is realized by patterning electrospun
poly(l-lactic acid) (PLLA)/Ca2+ nanofibers via a
solvent-loaded
agarose stamp and injecting an
alginate solution to trigger the quick ionic cross-linking between
alginate and Ca2+ released from patterned nanofibers. The one-on-one integration of electrospun nanofibers and
microgels not only provides a 3D cellular microenvironment in designated regions in MPS but also improves the stability of these microenvironments under dynamic culture. In addition, due to the biocompatible properties of an ionic cross-linking reaction, patterned cell array can be achieved simultaneously during the
microgel formation process. A
breast cancer model is then built in MPS by coculturing human
breast cancer cells and human fibroblasts in
microgel array, and its application in drug (
cisplatin) testing is evaluated. Our data prove that MPS-MA offers a more precise platform for drug testing to evaluate the drug concentration, duration time, cancer microenvironment, etc, mainly due to its successful construction of the biomimetic 3D cellular microenvironment.