A Bimodal, Cationic, and Water-Soluble Calix[4]arene Conjugate: Design, Synthesis, Characterization, and Transfection of Red Fluorescent Protein Encoded Plasmid in Cancer Cells.

A new bimodal fluorescent cationic calix[4]arene (L) conjugate has been synthesized in multiple steps and well characterized by NMR and electrospray ionization-mass spectrometry (ESI-MS) techniques. L has been investigated for its DNA binding ability by various spectroscopy techniques like absorption, fluorescence, and circular dichroism (CD). The formation of L-DNA complex has been confirmed by the gel electrophoresis in the presence of incremental concentration of L. To visualize the packing of the plasmid (pBR322), detailed tapping mode atomic force microscopy study has been performed, which revealed blob-like structure of plasmid upon addition of the incremental amount of L. Concentration dependent transfection ability of L has been established in MCF-7 cells by confocal microscopy by carrying the red fluorescent protein (RFP) encoded plasmid pCMV-tdTomato-N1 to emit both intrinsic fluorescence of L as well as that from RFP. All this has been possible in the absence of any adjuvant phospholipids (DOPE) that are commonly used as helper. Further transfection efficiency of L has been compared with the commercially available lipofectamine (LTX) in two cancer cell lines, MCF 7 and SH-SY5Y, and found that the L is as efficient as that of LTX. Hence, L is an efficient and effective cargo to transport genetic material into the cells.