Changes in the volume phase transition temperature of hydrogels for detection of the DNA hybridization process

A simple biosensing platform which involves the application of thermoresponsive hydrogels (p(NIPA-co-AA)) for detection of target DNA sequences is presented. For this aim the hydrogel based on N-isopropylacrylamide grafted with carboxyl groups was modified with H₂N-ssDNA via the amide bond. The detection of target DNA sequences was achieved successfully by monitoring the volume phase transition temperature (VPTT). It was found that the dependence between the VPTT and the concentration of the target complementary DNA is linear in the concentration range from 10^-12 to 10^-6 M. The proposed DNA detection method is characterized by high sensitivity and good reproducibility. The detection limit obtained (∼1 pM) is a substantial improvement over DNA biosensor labelling with tags, because the detection is based on a physical parameter (VPTT). Circular dichroism (CD) and inductively coupled plasma mass spectrometry with laser ablation (LA-ICP-MS) proved that the hybridization process took place in the hydrogel matrix without any restrictions.