When molecular probes meet self-assembly: an enhanced quenching effect.

We demonstrate that the incorporation of one or two amino acids of phenylalanine (F) or 4-fluoro phenylalanine ((f)F) will greatly lower the background fluorescence intensities of conventional quenched probes with quenchers. This enhanced quenching effect was due to the synergetic effect of the aggregation caused quenching and the presence of a quencher. Such strategy will not greatly affect the enzyme recognition properties to the probes. We also demonstrated that our self-assembled nanoprobe with the enhanced quenching effect showed a better performance in cells for the detection of cell apoptosis than the unassembled probes. Our study demonstrates that using molecular self-assembly can optimize and improve the performance of molecular probes and it provides a simple but very useful strategy to boost the signal-to-noise ratios of fluorescence probes.

Disulfide bond reduction-triggered molecular hydrogels of folic acid-Taxol conjugates.

Molecular hydrogels of therapeutic agents are a novel kind of self-delivery system that can sustain release of drugs or pro-drugs. We have previously developed a molecular hydrogelator of folic acid (FA)-Taxol conjugate triggered by phosphatase. In this paper, we report a novel molecular hydrogelator system of FA-Taxol conjugates with improved synthetic strategy. The hydrogels are formed by the reduction of disulfide bond by glutathione (GSH). These hydrogels could sustain release of Taxol through ester bond hydrolysis. Compared with intravenous (i.v.) injection of clinically used Taxol® with four times the dosage, our hydrogel could inhibit tumor growth more efficiently by a single dose of intra-tumor (i.t.) administration. These observations suggested the big potential of this novel gelation system of Taxol for cancer therapy.