Microfluidic System for Spheroid Culture

Microfluidic systems were made of polydimethylsiloxane (PDMS). For the purpose of experimental flexibility, we constructed individual devices that had 5 linearly connected chambers, each containing 24 uniformly sized 125 nL cubic traps for spheroid formation (Fig. 2A). The dimension of each device is about 7.5 × 1 cm². The microfluidic device layout was designed using CATIA (Dassault Systemes, France), based on previously published design rules for spheroid culture chips to ensure proper oxygenation and nutrient supply^{31 (link)}. The mold was fabricated on poly-methyl methacrylate (PMMA) using micromachining. The device is made of two layers of PDMS: the bottom layer contains spheroid culture chambers with dimensions 500 × 500 × 500 µm³, and the top layer contains a straight channel covering all the culture chambers. Each device could be treated with a particular systemic agent, while each chamber could be treated with a particular RT dose (Fig. 2B).