Preparation of a new nanobiosensor for the determination of some biogenic polyamines and investigation of their interaction with DNA.

Biogenic polyamines are small organic polycations involving in a variety of biological processes. They form high affinity complexes with DNA. Here, we have followed two different novel approaches, either fabrication of an electrochemical nanobiosensor for determination of three of the most important biogenic polyamines; spermine (SPM), spermidine (SPD) and putrescine (PUT), or electrochemical investigation of their interaction with DNA. Strong binding of polyamines to DNA makes the DNA a suitable recognition element for construction of a sensitive biosensor. The fabricated biosensor responded to SPM, SPD and PUT over an extended dynamic range of 0.04-100 µM, 0.01-24 µM, and 0.08-100 µM respectively, with low detection limits of a few nM. We also studied the interaction of polyamines with three different DNA sequences with base composition of 100% AT, 80% AT and 100% GC in the presence of [Ru(NH3)6]3(+) as a redox probe. The highest kb values were obtained in the interaction of polyamines with 80% AT (mixed) DNA sequence. The kb values were 5.24 × 10(5), 4.17 × 10(5) and 1.46 × 10(5)M(-1) for SPM, SPD and PUT, respectively, which correlated well with their increasing number of amino groups. In addition, competition study showed the impotence of SPD to replace with histone H1 in histone H1-DNA complex, which indicates the more potent interaction of histone H1 with DNA. In this proof-of-principle study, we have proposed an approach for simple, cost-effective, miniaturizable, and direct-readout detection of polyamines, as well as the understanding of the modes of interaction between polyamines and DNA.