Electropolymerizable Thiophene-Oligonucleotides for Electrode Functionalization

Inserting complex biomolecules such as oligonucleotides during the synthesis of polymers remains an important challenge in the development of functionalized materials. In order to engineer such a biofunctionalized interface, a single-step method for the covalent immobilization of oligonucleotides (ONs) based on novel electropolymerizable lipid thiophene-oligonucleotide (L-ThON) conjugates was employed. Here, we report a new thiophene phosphoramidite building block for the synthesis of modified L-ThONs. The biofunctionalized material was obtained by direct electropolymerization of L-ThONs in the presence of 2,2'-bithiophene (BTh) to obtain a copolymer film on indium tin oxide electrodes. In situ electroconductance measurements and microstructural studies showed that the L-ThON was incorporated in the BTh copolymer backbone. Furthermore, the covalently immobilized L-ThON sequence showed selectivity in subsequent hybridization processes with a complementary target, demonstrating that L-ThONs can directly be used for manufacturing materials via an electropolymerization strategy. These results indicate that L-ThONs are promising candidates for the development of stable ON-based bioelectrochemical platforms.

Hydrogel Matrix-Grafted Impedimetric Aptasensors for the Detection of Diclofenac

Driven by the growing concern about the release of untreated emerging pollutants and the need for determining small amounts of these pollutants present in the environment, novel biosensors dedicated to molecular recognition are developed. We have designed biosensors using a novel class of grafted polymers, surface-attached hydrogel thin films, on conductive transducers as a biocompatible matrix for biomolecule immobilization. We showed that they can be dedicated to the molecular recognition of diclofenac (DCL). The immobilization of the aptamer onto surface-attached hydrogel thin films by covalent attachment provides a biodegradable shelter, providing the aptamer with excellent environments to preserve its active and functional structure while allowing the detection of DCL. The grafting of the aptamer is obtained using the formation of amide bonds via the activation of carboxylic acid groups of the poly(acrylic acid) hydrogel thin film. For improved sensitivity and higher stability of the sensor, a high density of the immobilized aptamer is enabled. The aptamer-modified electrode was then incubated with DCL solutions at different concentrations. The performances of the aptasensor were investigated by electrochemical impedance spectroscopy. The change in charge-transfer resistance was found to be linear with DCL concentration in the 30 pM to 1 μM range. The detection limit was calculated to be 0.02 nM. The improvement of the limit of detection can be mainly attributed to the three-dimensional environment of the hydrogel matrix which improves the grafting density of the aptamer and the affinity of the aptamer to DCL.