Amphiphilic CuAAC dendrimers based on a Calix[4]arene core with a poly-amine periphery: synthesis, aggregation and CT DNA complexation

Abstract

Using a convergent approach and Cu-catalyzed azide–alkyne cycloaddition reaction (CuAAC), amphiphilic dendrimers of the 0-th and 1-st generation containing polar amino groups were obtained for the first time. According to the pyrene solubilization data, tetraalkyl-substituted calix[4]arenes possess the lowest critical aggregation concentration (CAC) values in the series (5–16 μM), while disubstituted ones possess values that are higher by 2 orders of magnitude (138–239 μM). The studied interaction with calf thymus DNA (CT DNA) and the established regularities in the studied samples as well as multiple compaction of DNA in the presence of dendrimers are demonstrated. Thus, when dendrimers were added to the CT DNA solution, the hydrodynamic size of nucleic acid in the binary system decreased significantly (750 → 200 nm) due to compaction, while the surface charge of aggregates remained positively charged. Using the fluorescence of two types of dyes (EthBr and DAPI) as well as a combination of CD and UV-visible spectrophotometry methods, the mechanism of dendrimer binding to CT DNA through a small groove was revealed. The influence of aminodendrimers on CT DNA was also investigated in CT DNA denaturation experiments, where the addition of polyamine slightly (1–2 degrees) increased the denaturation temperature.