Recyclable DNA-Derived Polymeric Sensor: Ultrasensitive Detection of Hg(II) Ions Modulated by Morphological Changes

Going beyond organic solvent as the solubilizer for small-molecular organic probes motivates exploration of water-soluble polymeric sensors. In this respect, dye-derived thermal-responsive polymeric sensors are an attractive direction, but for its practical application, it is limited by sensor recycling because only irreversible change in the structure of the recognition unit for many sensors can trigger the appearance of the detection signal. Here, we established the oligonucleotide-derived thermal-responsive polymeric sensor, TBC-P1, which overcame this fundamental limitation. The TBC-P1 sensor was based on reversible binding between oligonucleotides and Hg²⁺ ions, and easy sensor separation via tuning temperature, achieving the Hg²⁺ detection in a cost-effective and green manner. The TBC-P1 sensor displayed specific and rapid sensing properties toward Hg²⁺ ions in pure aqueous media via turn-off fluorescence emission, with a limit of detection as low as 0.65 nM (much lower than the presently reported dye-derived polymeric sensors). This high detection sensitivity was further enhanced (with LOD = 0.17 nM) via warming to yield spherical micelles, in which the oligonucleotide-containing thermoresponsive PNIPAM block forming a hydrophobic core amplified the fluorescence signals. Treating the Hg²⁺-trapped micelles with cysteine (Cys) led to competition-induced release of these combined Hg²⁺ ions and then thermally precipitating and recycling polymeric sensor TBC-P1. This oligonucleotide-derived thermalresponsive polymeric sensor will open a universal avenue for sensor recycling, which will achieve the goal of reducing cost and improving detection sensitivity of sensors.