Targeted drug delivery: nanospheres with nanoclaps
In order for the drug to enter the affected organ without damaging healthy tissues, a delivery system is needed that would ensure strictly selective release of the drug in the target organ. One of the successful examples of such nanosystems are porous nanospheres made of silicon oxide. The pores of nanospheres can be filled with drugs and closed with tiny controlled valves, but all nanoclaps created so far have worked only in organic solvents.
Scientists at the University of California, working under the guidance of Dr. Fraser Stoddart and Jeffrey I. Zink, have developed nanoclaps that function in aqueous media, including in conditions corresponding to the composition of biological fluids, which makes it possible to use them as part of nanoparticles designed for the delivery and release of medicinal drugs in the right place at the right time.
To create such nanoclaps, the authors used supramolecular structures known as pseudorotaxanes (the figure shows a schematic representation of one of the many variants of pseudorotaxanes).
The surface of porous silicon oxide nanospheres was coated with molecules that play the role of "axes", and volumetric curved cucurbituril molecules were attached to them in a neutral or acidic medium. These structures blocked the pores, preventing the release of the substance filling them, i.e. closed the valves.
With an increase in the pH of the medium (shifting towards an alkaline reaction), the interaction between the two components of the nanoclaps weakened, and the pores opened, releasing a luminescent substance imitating the drug.
The final goal of the work is to select the molecular details of the individual components of the system, which will allow to regulate the operation of the valve in conditions of minor differences in the acidity levels of normal and diseased tissues and selectively release the drug in pathologically altered cells.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily
12.03.2008