Microfluidic systems including a housing configured to receive a cartridge. Three-dimensional scaffolds, devices, and systems comprising such scaffolds that mimic the in vivo structure, physical properties, and protein composition of extracellular matrix surrounding pancreatic islet cells and adipocytes, with use for, e.g., in vitro drug screening and/or toxicity assays, disease modeling, and therapeutic applications. The cartridge including a plurality of wells for receiving one or more biological cells. The microfluidic systems include a structure with channels for introducing a medium into the housing and through channels the cartridge. Microfluidic systems including a housing configured to receive a cartridge, the housing including channels for loading one or more biological cells within wells of the cartridge.