Association of poly(N-isopropylacrylamide) containing nucleobase multiple hydrogen bonding of adenine for DNA recognition

In this study we used the poly(N-isopropylacrylamide) (PNIPAAm) as a medium to generate PNIPAAm-adenine supramolecular complexes. A nucleobase-like hydrogen bonding (NLHB) between PNIPAAm and adenine was found that changed the morphology, crystalline structure, and temperature responsiveness of PNIPAAm microgels relatively to the adenine concentrations. With increasing the adenine concentration, the PNIPAAm-adenine supramolecular complexes gradually altered their morphologies from microgel particles to thin film structures and suppressed the thermodynamical coil-to-globule transition of PNIPAAm because of the NLHB existed between the PNIPAAm amide and ester groups and the adenine amide groups (CO⋯HN and NH⋯NR), verified by FTIR spectral analysis. NLHB was also diverse and extensive upon increasing the temperature; therefore, the thermoresponsive behavior of the complexes was altered with the NLBH intensity, evaluated by the inter-association equilibrium constant (Ka) above and below their LCST. Therefore, PNIPAAm can be as a medium to recognize adenine in various concentrations, which could potentially be applied in DNA recognition.

Highlights► Interaction between PNIPAAm and adenine is evaluated by FTIR for DNA recognition. ► Supramolecule by a nucleobase-like hydrogen bonding (NLHB) has been found firstly. ► The supramolecule generate specific surface properties and temp. responsiveness. ► Ka of the complexation is obtained to realize the formation of supramolecule.