The structural heterogeneity, critical therapeutic applications, and associated clinical risks of glycosaminoglycans (GAGs) necessitate rigorous quality control. However, discriminating between different GAGs remains challenging due to their structural complexity and the limited sensitivity of current sensor array-based methods. In this study, four complexes consisting of sodium 4-(pyren-1-yl) butane-1-sulfonate (PBSS) and functionalized polyethylenimine (PEI)─PEI–PBSS5, PEI–PBSS10, PEI–PBSS15,