Dna/π-conjugated polymer supramolecular structures: insights into the self-assembly

Water-soluble -conjugated polymers (CPs) are good candidates for developing aqueous optical biosensing systems, because their optical response are very sensitive to their conformation and supramolecular assembly.1 Recently, the design of cationic polythiophenes (CPT)2 has attracted much interest, as they represent a versatile, central class of -conjugated polymers, and bind to DNA through electrostatic interactions. For instance, the complexes formed by DNA and CPT have been exploited for the identification of proteins and for the determination of very low DNA concentrations. The detection of Single-Nucleotide Polymorphism (SNP) and the identification of neurodegenerative diseases, based on the capability of CP-based biosensors to report DNA-DNA hybridization, are other promising applications of these optical biosensors.3 However, the hybridization and self-assembly mechanisms in these DNA-CPT supramolecular structures are still lacking.
In this frame, we present our recent studies on the design and self-assembly of a series of cationic polythiophenes in interaction with various types of DNA sequences. By means of (chir)optical spectroscopy, we have studied the influence of the CPT cationic side groups, DNA sequence and topology (single-stranded vs. double-stranded), and composition, in order to establish the structure-properties relationships and give insights into the self-assembly mechanisms. Importantly, we have observed that DNA sequence-specific interactions are at play upon self-assembly with CPE, with induced circular dichroism signatures related to the right- or left-handed conformational chirality of polymer backbone within the supramolecular complexes.4 These results indicate the possibility of using these cationic polymers for designing hybrid structures with functional nucleic acids, such as G-quadruplexes, aptamers, etc. to evolve towards specific optical biosensors.