Chiral, pH responsive hydrogels constructed by N-Acryloyl-alanine and PEGDA/α-CD inclusion complex: preparation and chiral release ability

Chiral, pH-responsive hydrogels are constructed by poly(ethylene glycol) diacrylate/ α -cyclodextrin (PEGDA/ α -CD) inclusion complex and L- N -acryloyl-alanine or D- N -acryloyl-alanine (L-NAA or D-NAA) by an effective free radical polymerization approach. PEGDA containing two C=C end groups was used simultaneously to introduce α -CD units in the resulting hydrogels and to serve as a cross-linking agent, by which forming the designed hydrogels in quantitative yield. Hydrophilic α -CD moieties acted as pore-forming agent, while the L(D)-NAA-based polymer chains bearing –COOH groups enabled the hydrogels to display remarkable swelling–deswelling behavior in response to pH variation. The chiral NAA monomer-derived polymer chains rendered the hydrogels with intriguing optical activity, according to circular dichroism spectra. Scanning electron microscopy revealed the uniformly porous microstructures of hydrogels. More remarkably, the L-NAA-based hydrogels preferentially adsorbed trans -4-hydroxy- d -proline and preferentially released trans -4-hydroxy- l -proline, while D-NAA-based hydrogels provided opposite results. The hydrogels also demonstrated remarkable enantioselective release ability towards chiral drug ibuprofen. Copyright © 2015 John Wiley & Sons, Ltd.