Heterocomponent ternary supramolecular complexes of porphyrins: A review

Porphyrins are prominent host molecules which are widely used due to their structural characteristics and directional interaction sites. This review summarizes non-covalently bound ternary complexes of porphyrins, constructed from at least three non-identical species. Progress in supramolecular chemistry allows the creation of complex molecular machinery tools, such as rotors, motors and switches from relatively simple structures in a single self-assembly step. In the current review, we highlight the collection of sophisticated molecular ensembles including sandwich-type complexes, cages, capsules, tweezers, rotaxanes, and supramolecular architectures mediating oxygen-binding and oxidation reactions. These diverse structures have high potential to be applied in sensing, production of new smart materials as well as in medical science.

Porphyrinoid-Cyclodextrin Assemblies in Biomedical Research: An Update

Porphyrinoids, well-known cofactors in fundamental processes of life, have stimulated interest as synthetic models of natural systems and integral components of photodynamic therapy, but their utilization is compromised by self-aggregation in aqueous media. The capacity of cyclodextrins to include hydrophobic molecules in their cavity provides porphyrinoids with a protective environment against oxidation and the ability to disperse efficiently in biological fluids. Moreover, engineered cyclodextrin-porphyrinoid assemblies enhance the photodynamic abilities of porphyrinoids, can carry chemotherapeutics for synergistic modalities, and can be enriched with functions including cell recognition, tissue penetration, and imaging. This Perspective includes synthetic porphyrinoid-cyclodextrin models of proteins participating in fundamental processes, such as enzymatic catalysis, respiration, and electron transfer. In addition, since porphyrinoid-cyclodextrin systems comprise third generation photosensitizers, recent developments for their utilization in photomedicine, that is, multimodal therapy for cancer (e.g., PDT, PTT) and antimicrobial treatment, and eventually in biocompatible therapeutic or diagnostic platforms for next-generation nanomedicine and theranostics are discussed.

Detection and Removal of Endogenous Carbon Monoxide by Selective and Cell-Permeable Hemoprotein Model Complexes

Carbon monoxide (CO) is produced in mammalian cells during heme metabolism and serves as an important signaling messenger. Here we report the bioactive properties of selective CO scavengers, hemoCD1 and its derivative R8-hemoCD1, which have the ability to detect and remove endogenous CO in cells. HemoCD1 is a supramolecular hemoprotein-model complex composed of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphinatoiron(II) and a per-O-methylated β-cyclodextrin dimer having an pyridine linker. We demonstrate that hemoCD1 can be used effectively to quantify endogenous CO in cell lysates by a simple spectrophotometric method. The hemoCD1 assay detected ca. 260 pmol of CO in 10⁶ hepatocytes, which was well-correlated with the amount of intracellular bilirubin, the final breakdown product of heme metabolism. We then covalently attached an octaarginine peptide to a maleimide-appended hemoCD1 to synthesize R8-hemoCD1, a cell-permeable CO scavenger. Indeed, R8-hemoCD1 was taken up by intact cells and captured intracellular CO with high efficiency. Moreover, we revealed that removal of endogenous CO by R8-hemoCD1 in cultured macrophages led to a significant increase (ca. 2.5-fold) in reactive oxygen species production and exacerbation of inflammation after challenge with lipopolysaccharide. Thus, R8-hemoCD1 represents a powerful expedient for exploring specific and still unidentified biological functions of CO in cells.

Supramolecular intracellular delivery of an anionic porphyrin by octaarginine-conjugated per-O-methyl-β-cyclodextrin

A convenient and efficient method for intracellular delivery of a water-soluble anionic porphyrin has been developed by utilizing its supramolecular interaction with per-O-methyl-β-cyclodextrin bearing an octaarginine chain as a cell-penetrating peptide.