Chemistry

Acid-Driven Delivery

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Science  11 Sep 2009:
Vol. 325, Issue 5946, pp. 1320-1321
DOI: 10.1126/science.325_1320d

Rotaxane molecules consist of a macrocycle that can move along a linear threader. This movement can be constrained by creating docking sites along the threader, and the strength of these docking interactions in some cases can be controlled by pH. One concept for exploiting these molecular states is to create mechanized nanoparticles for pH-dependent release of trapped molecules. Angelos et al. prepared mesoporous silica nanoparticles using a template to create pores. The pore surfaces were derivatized with amine groups, which hold the threaders. On addition of large cucurbit[6]uril macrocycles and dye molecules to a particle dispersion near neutral pH, the macrocycles migrate to the particle surface and trap the dye in the pores. Raising or lowering the pH displaces the macrocycles and releases the dye, much like opening a valve. Unlike previous examples that only released the macrocycles at high pH, this system would operate at conditions useful for drug delivery—blood is near neutral pH, whereas lysosomal compartments are acidic.

J. Am. Chem. Soc. 131, 10.1021/ja9010157 (2009).

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