Abstract
Aptamer–polyelectrolyte microcapsules are prepared for potential use as triggered delivery vehicles and microreactors. The hollow microcapsules are prepared from the sulforhodamine B aptamer and the polyelectrolytes poly(allylamine hydrochloride) and poly(sodium 4‐styrene‐sulfonate), using layer‐by‐layer (LbL) film deposition templated on a sacrificial CaCO~3~ spherical core. Scanning electron microscopy and confocal microscopy confirm the formation of spherical CaCO~3~ cores and LbL‐aptamer microcapsules. Colocalization studies with fluorescently‐tagged aptamer and sulforhodamine B verify the ability of the aptamer to recognize its cognate target in the presence of the K^+^ ions that are required for its characteristic G‐quadruplex formation. Fluorescence recovery after photobleaching studies confirms a significant difference in the permeability of the aptamer–polyelectrolyte microcapsules for the sulforhodamine B dye target compared to control microcapsules prepared with a random oligonucleotide. These results suggest that aptamer‐based ‘smart’ responsive films and microcapsules could be applied to problems of catalysis and controlled release.