Optically Coupled PtOEP and DPA Molecules Encapsulated into PLGA-Nanoparticles for Cancer Bioimaging

Triplet-triplet annihilation upconversion (TTA-UC) nanoparticles (NPs) have emerged as imaging probes and therapeutic probes in recent years due to their excellent optical properties. In contrast to lanthanide ion-doped inorganic materials, highly efficient TTA-UC can be generated by low excitation power density, which makes it suitable for clinical applications. In the present study, we used biodegradable poly(lactic-co-glycolic acid) (PLGA)-NPs as a delivery vehicle for TTA-UC based on the heavy metal porphyrin Platinum(II) octaethylporphyrin (PtOEP) and the polycyclic aromatic hydrocarbon 9,10-diphenylanthracene (DPA) as a photosensitizer/emitter pair. TTA-UC-PLGA-NPs were successfully synthesized according to an oil-in-water emulsion and solvent evaporation method. After physicochemical characterization, UC-efficacy of TTA-UC-PLGA-NPs was assessed in vitro and ex vivo. TTA-UC could be detected in the tumour area 96 h after in vivo administration of TTA-UC-PLGA-NPs, confirming the integrity and suitability of PLGA-NPs as a TTA-UC in vivo delivery system. Thus, this study provides proof-of-concept that the advantageous properties of PLGA can be combined with the unique optical properties of TTA-UC for the development of advanced nanocarriers for simultaneous in vivo molecular imaging and drug delivery.

Supramolecular block copolymers incorporating chiral and achiral chromophores for the bottom-up assembly of nanomaterials

The coordination of the chiral metalloporphyrin ([5,10,15,20-[4-([Formula: see text]-2-[Formula: see text]-octadecylamidoethyloxiphenyl]porphyrin] zinc (II)) and an achiral homologue to an amphiphilic block copolymer of poly(styrene-[Formula: see text]-4-vinyl pyridine) (PS-[Formula: see text]-P4VP) have been studied in solution and as cast material. The resulting chiral dye-polymer hybrid material has been accomplished via axial coordination between the zinc (II) metal ion in the core of the porphyrin ring and the pyridyl units of the block-copolymer in a non-coordinative solvent. The supramolecular organization and possible chirality transfer to the hybrid material have been studied in solution by UV-visible absorption spectroscopy, fluorescence spectroscopy, Nuclear Magnetic Resonance and Circular Dichroism. The morphology of the chiral and achiral doped polymers has been studied in solid state by Transmission Electron Microscopy and Atomic Force Microscopy. We show that the nanostructures formed depend greatly upon the nature of the side-chains on the porphyrins, where a chiral group leads to a very homogeneous phase-separated material, perhaps indicating that chiral side groups are useful for the preparation of this type of supramolecular hybrid.

Imidazoporphyrins as supramolecular tectons: synthesis and self-assembly of zinc 2-(4-pyridyl)-1H-imidazo[4,5-b]porphyrinate

First evidence of self-assembling of imidazoporphyrins is revealed with the example of zinc(ii) 5,10,15,20-tetramesityl-2-(4-pyridyl)-1H-imidazo[4,5-b]porphyrin in the solid state and in solution.

Bottom-Up Hierarchical Self-Assembly of Chiral Porphyrins through Coordination and Hydrogen Bonds

A series of chiral synthetic compounds is reported that shows intricate but specific hierarchical assembly because of varying positions of coordination and hydrogen bonds. The evolution of the aggregates (followed by absorption spectroscopy and temperature-dependent circular dichroism studies in solution) reveal the influence of the proportion of stereogenic centers in the side groups connected to the chromophore ring in their optical activity and the important role of pyridyl groups in the self-assembly of these chiral macrocycles. The optical activity spans 2 orders of magnitude depending on composition and constitution. Two of the aggregates show very high optical activity even though the isolated chromophores barely give a circular dichroism signal. Molecular modeling of the aggregates, starting from the pyridine-zinc(II) porphyrin interaction and working up, and calculation of the circular dichroism signal confirm the origin of this optical activity as the chiral supramolecular organization of the molecules. The aggregates show a broad absorption range, between approximately 390 and 475 nm for the transitions associated with the Soret region alone, that spans wavelengths far more than the isolated chromophore. The supramolecular assemblies of the metalloporphyrins in solution were deposited onto highly oriented pyrolitic graphite in order to study their hierarchy in assembly by atomic force microscopy. Zero and one-dimensional aggregates were observed, and a clear dependence on deposition temperature was shown, indicating that the hierarchical assembly took place largely in solution. Moreover, scanning electron microscopy images of porphyrins and metalloporphyrins precipitated under out-of-equilibrium conditions showed the dependence of the number and position of chiral amide groups in the formation of a fibrillar nanomaterial. The combination of coordination and hydrogen bonding in the complicated assembly of these molecules-where there is a clear hierarchy for zinc(II)-pyridyl interaction followed by hydrogen-bonding between amide groups, and then van der Waals interactions-paves the way for the preparation of molecular materials with multiple chromophore environments.

Metal-metalloporphyrin frameworks: a resurging class of functional materials

This review presents comprehensively recent progress in metal-metalloporphyrin frameworks (MMPFs) with an emphasis on versatile functionalities. Following a brief introduction of basic concepts and the potential virtues of MMPFs, we give a snapshot of the historical perspective of MMPFs since 1991. We then summarize four effective strategies implemented frequently to construct prototypal MMPFs. MMPFs represent a resurging class of promising functional materials, highlighted with diverse applications including guest-molecule adsorption and separation, catalysis, nano-thin films and light-harvesting.

Aggregation of asphaltene model compounds using a porphyrin tethered to a carboxylic acid

Two model compounds are used in NMR spectroscopic studies to probe aggregation toward unraveling the mysteries of intermolecular interactions in asphaltenes, which are the heaviest portions of petroleum.

Molecular tectonics based nanopatterning of interfaces with 2D metal–organic frameworks (MOFs)

The nanostructuring of the graphite surface with 2DMOF, based on a combination of an acentric porphyrin tecton and a CoCl₂metallatecton, was achieved at the solid–liquid interface and characterized by scanning tunnelling microscopy.