Bis-cyanostilbene bolaamphiphile conjugated with di-phosphonate functionality: Synthesis, self-assembly and live cell imaging

Abstract

The supramolecular self-assembly of a water-soluble (((((1Z,1′Z)-1,4-phenylenebis(2-cyanoethene-2,1-diyl))bis(4,1-phenylene))bis(oxy))bis(propane-3,1-diyl))bis (phosphonic acid) (coded as: OPVPDA) bolaamphiphile was studied in various pH (1–12). The UV–Vis, fluorescence and dynamic light scattering (DLS) spectroscopy was employed to study the mode of aggregation in solution. Scanning electron microscopy (SEM) elucidates the nanostructure of the self-assembled OPVPDA. It can be clearly seen, in acidic pH, phosphonate functional group of OPVPDA are protonated results in cubic microstructures, while increase pH to 4 produces amorphous structure. At pH 6, OPVPDA assembled into microstructure which was more asymmetric resulting in microsheets tens of microns in length. However, at environmental pH (7.0) fur ball like superstructures produces. Interestingly, at basic pH 9, these elongated features ∼100 of microns in length ∼10 of microns in width and microns in thickness formed. At pH 11, where OPVPDA phosphonate groups are fully neutralised, thus, general feature changes to rhombic crystal structure tens of microns in all dimensions. This self-assembly phenomenon at different pH could offer for the of innovative biomaterials development. Moreover, the toxicity of tetraethyl (((((1Z,1′Z)-1,4-phenylenebis(2-cyanoethene-2,1-diyl))bis(4,1-phenylene))bis(oxy))bis(propane-3,1-diyl))bis (phosphonate) (OPVPDE) and OPVPDA, and cellular uptake studies employing confocal microscopy images proved OPVPDE material exhibited better biocompatibility as compared to OPVPDA.