Spatially Defined Cell-Secreted Protein Detection Using Granular Hydrogels: μGeLISA.

Intercellular communication through secreted proteins is necessary in essential processes such as embryo and limb development, disease progression, and immune responses. There exist many techniques to study bulk solution protein concentrations, but there is a limited set of tools to study the concentrations of cell-secreted proteins in situ within diverse cell platforms while retaining spatial information. In this study, we have developed a microgel system that is able to quantitatively measure the cell-secreted protein concentration within defined three-dimensional culture configurations with single-cell spatial resolution, called μGeLISA (microgel-linked immunosorbent assay). This system, which is based on the surface modification of polyethylene glycol microgels, was able to detect interleukin 6 (IL-6) concentrations of 2.21-21.86 ng/mL. Microgels were also able to detect cell spheroid-secreted IL-6 and distinguish between low- and high-secreting single cells. The system was also adapted to measure the concentration of cell-secreted matrix metalloproteinase-2 (MMP-2). μGeLISA represents a highly versatile system with a straightforward fabrication process that can be adapted toward the detection of secreted proteins within a diverse range of cell culture configurations.