Single-component layer-by-layer weak polyelectrolyte films and capsules: Loading and release of functional molecules

Poly(carboxylic acid) hydrogel films and hollow capsules undergo reversible size changes in response to variations in pH and/or ionic strength. The films and capsules were obtained from hydrogenbonded poly-N-vinylpyrrolidone/poly(carboxylic acid) layer-by-layer films by chemical crosslinking of the polyacid, followed by pH-induced removal of poly-N-vinylpyrrolidone. Surface-attached hydrogel films present attractive matrices for reversible pH-stimulated loading and/or controlled release of large amounts of synthetic or natural macromolecules including proteins. By varying acidity of poly(carboxylic acids), the hydrogel swelling and the corresponding values of pH for encapsulation/release of functional molecules could be tuned in a wide range from pH 5 to 10. In addition, the capsules are capable of entrapping macromolecules by “locking” the capsule wall with an electrostatically associating polycation, followed by the release of the encapsulated macromolecules at high salt concentrations. The text was submitted by the authors in English.