Systematic Study of Protein Detection Mechanism of Self-Assembling 19F NMR/MRI Nanoprobes toward Rational Design and Improved Sensitivity
journal contributionposted on 03.08.2011, 00:00 by Yousuke Takaoka, Keishi Kiminami, Keigo Mizusawa, Kazuya Matsuo, Michiko Narazaki, Tetsuya Matsuda, Itaru Hamachi
19F NMR/MRI probe is expected to be a powerful tool for selective sensing of biologically active agents owing to its high sensitivity and no background signals in live bodies. We have recently reported a unique supramolecular strategy for specific protein detection using a protein ligand-tethered self-assembling 19F probe. This method is based on a recognition-driven disassembly of the nanoprobes, which induced a clear turn-on signal of 19F NMR/MRI. In the present study, we conducted a systematic investigation of the relationship between structure and properties of the probe to elucidate the mechanism of this turn-on 19F NMR sensing in detail. Newly synthesized 19F probes showed three distinct behaviors in response to the target protein: off/on, always-on, and always-off modes. We clearly demonstrated that these differences in protein response could be explained by differences in the stability of the probe aggregates and that “moderate stability” of the aggregates produced an ideal turn-on response in protein detection. We also successfully controlled the aggregate stability by changing the hydrophobicity/hydrophilicity balance of the probes. The detailed understanding of the detection mechanism allowed us to rationally design a turn-on 19F NMR probe with improved sensitivity, giving a higher image intensity for the target protein in 19F MRI.