A modular engineered tissue construct includes a plurality of fused self-assembled, scaffold-free, high-density cell aggregates. At least one cell aggregate includes a plurality of cells and a plurality of biocompatible and biodegradable nanoparticles and/or microparticles that are incorporated within the cell aggregates. The nanoparticles and/or microparticles acting as a bulking agent within the cell aggregate to increase the cell aggregate size and/or thickness and improve the mechanical properties of the cell aggregate as well as to deliver bioactive agents.