A molecular-engineered rotaxane overcomes longstanding biofluid-challenges and enables optical tryptophan detection in human serum

Abstract Despite excelling in simple solvent mixtures, almost all known supramolecular chemosensors cannot be applied in real biofluids due to their adverse interactions with salts, proteins, and other biomolecules. Instead of following the established strategy of searching for alternative synthetic binders with improved affinity and selectivity parameters, we herein report a molecular engineering approach that specifically addresses this bio¬fluid challenge. The developed dual-macrocycle rotaxane is the first supramolecular system that can sense the biomarker tryptophan in biofluids at physiological relevant concentrations, even in protein- and lipid-containing blood serum. Moreover, this chemosensor is used for emission-based high-throughput screening in a microplate format, in label-free enzymatic reaction monitoring, and in chirality sensing through induced circular dichroism. Printed sensor chips with surface-immobilized microarrays of this rotaxane were used for fluorescence microscopy imaging of tryptophan. Our chemosensor achieves a long-awaited applicability in complex biomedia and will foster future applications of supramolecular sensors for molecular diagnostics.