Glucosylated steroid-porphyrins as new tools for nanotechnology applications

Abstract

Two glucosylated steroid-modified porphyrins, differing in the number and type of ring substitutions, were taken into consideration as versatile chiral elements with possible applications in different environments. Three distinctive features of the title compounds were investigated by optical spectroscopy methods: (i) the formation of chiral mesoscopic structures in solution; (ii) the formation of Langmuir–Blodgett films on hydrophilic substrates; (iii) the inclusion and localization in a liposome formulation. Specifically, the aggregation propensity of mono- and disubstituted porphyrin scaffolds was studied in DMSO–H₂O (40/60, v/v), where J-type aggregates were detected by the broadening and bathochromic shift of the Soret absorption band. Circular Dichroism (CD) experiments highlighted the occurrence of specific stereochemical interactions during the formation of such structures. The aggregation properties of the investigated compounds were further exploited in the formation of porphyrin multilayers through Langmuir–Blodgett deposition on hydrophilic quartz supports. The properties of the porphyrin films were characterized by pressure–area compression isotherms and optical (UV-Vis, CD, fluorescence) spectroscopy. Moreover, the interaction between the synthesized porphyrins and a membrane model represented by unilamellar 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) liposomes was investigated. In particular, the partition between the aqueous and lipid phases, and the location of the porphyrin derivatives in the lipid bilayer were studied by fluorescence methods. The reported results demonstrate the multitask versatility of the synthesized glucosylated steroid-porphyrins, exemplified by the formation of ordered structures in very different environments: chiral mesoscopic structures in solution, densely-packed films on inorganic supports, stable inclusion complexes in liposome formulations.