A Water Soluble Macromolecular Nanobox Having Porphyrinic Walls as a Large Host for Giant Guests

Cyclic tetra{5,15-di-[p(x-methoxypolyethyleneoxy)-phenyl]-10,20-[p-oxyphenyl] methylen porphyrin}, cy-[O-(H2-PTPEG2)-O-CH2-]4, a water soluble macromolecule consisting of four porphyrin units [each with two longx-methoxypolye-thyleneoxy (PEG) branches bound on its peripheral positions]linked by means of four methylenoxy bridges, was prepared by an interfacial etherification reaction. Structural and spectro-scopic characterization of cy-[O-(H2-PTPEG2)-O-CH2-]4and of itscobalt-derivative {cy-[O-(Co-PTPEG2)-O-CH2-]4} was performed by means of MALDI-TOF mass spectrometry, NMR, UV–vis, and circular dichroism spectroscopy. The data obtained fromthe cy-[O-(Co-PTPEG2)-O-CH2-]4/Gramicidin-S mixture showed that some evident spectral changes were compatible with theformation of a supramolecular structure between the porphyr-inic nanobox and the Gramicidin S (a polypeptide having a relevant pharmacological importance). These preliminary datahighlight how cy-[O-(H2-PTPEG2)-O-CH2-]4 and/or its metalled derivatives, for their both chemical composition and structuralarrangement, have promising properties for applications as a drug carrier in aqueous media.