Fig. 1. (A) Decrease in the catalytic activity of anionic enzymes through reversible PIC formation with PEGylated polyamines, and the subsequent partial recovery of activity through competitive interaction with secreted molecules. (B) A PIC sensor array for markerless and noninvasive identification of cell types and lineages. The culture supernatants collected from cells with varying seeding densities were diluted for normalization, followed by the addition of PICs to generate activity patterns reflecting the secretomic signatures for given cell types or lineages. The patterns were then interpreted using a chemometric method.