Aptamer-functionalized smart photonic hydrogels: application for the detection of thrombin in human serum

Smart photonic hydrogels based on two-dimensional photonic crystals (2DPC) provide a promising sensing platform for constructing novel chemical and biological sensors due to their facile optical signal readout and highly sensitive responsivity toward target analytes. Aptamers, as recognition elements with high selectivity and affinity, are extensively used to construct a variety of sensors. Herein, we developed two partially base complementary aptamer-functionalized 2DPC hydrogels as aptasensors for the detection of thrombin (TB) in human serum. The photonic hydrogel aptasensors swelled upon exposure to TB solution, leading to an increase in the particle spacing of the 2DPCs. The particle spacing changes were acquired by simply measuring the diameters of the Debye ring diffracted by the 2DPCs without the requirement of sophisticated instruments. The aptasensor swelling resulted from the decrease in the hydrogel cross-linking density induced by the specific binding between one of the aptamers and TB and the increase in hydrogel mixing free energy induced by the introduction of TB. The particle spacing increase of the optimized aptasensor was linear over the TB concentration range of 1–500 nM, and the limit of detection was 0.64 nM. The constructed 2DPC hydrogel aptasensor was used to detect TB in human serum and achieved recoveries of 95.74–104.21% and a relative standard deviation of 2.52–6.58%, showing the practicability and accuracy of the sensor. The aptamer-actuated 2DPC hydrogel biosensor provides a new strategy for designing other target molecule-sensitive aptasensors, showing great potential for development into home kits.