Structural tailoring of semiconducting tetrazine polymers based immobilizing matrix for superior electronic biosensing of carcinoembryonic antigen

Immobilizing matrix plays a crucial role in anchoring the receptors of target biomolecules and enhancing the sensing capability of biosensor. Howbeit, the immobilization platforms that induce stable molecular interactions with the receptors without the need for harsh reaction conditions (covalent bonding) are rare. Herein, we report the design, development and application of novel semiconducting one-dimensional (1D) tetrazine polymers (TTz, PhTTz, PhAlkTz) as immobilizing matrices for electronic biosensing of carcinoembryonic antigen (CEA), a cancer biomarker. The polymers are fully loaded with electron-deficient tetrazine units (nitrogen-rich), which develop strong hydrogen bonding (H-bonding) interactions and effectively immobilize the bioreceptor (anti-CEA). The sensor comprises reduced graphene oxide (rGO) as the base conducting layer and tetrazine polymers as immobilizing matrices for the CEA antibodies. The rGO/TTz/anti-CEA, rGO/PhTTz/anti-CEA, rGO/PhAlkTz/anti-CEA sensors exhibited 3.5 to 34.16 mu A, 2.2 to 34.89 mu A, 1.1 to 39.27 mu A responses, respectively, for 1 pg/ml to 200 ng/ml of CEA. The sensors' (TTz, PhTTz, and PhAlkTz) sensitivities, selectivities and stabilities are found to be better than that of previously reported partially tetrazine loaded polymer (PhPTz). The study discloses the presence of H-bonding in tetrazine units is highly critical for superior sensing. The concept of utilizing N-rich tetrazine units in the immobilizing platforms can be generalized to several other hetero-atom based systems and polymers. Thus, a wide variety of novel immobilizing substrates can be developed to realize superior sensing performance.