Chirality transfer from a 3D macro shape to the molecular level by controlling asymmetric secondary flows

Homochirality is a fundamental feature of living systems, and its origin is still an unsolved mystery. Previous investigations showed that external physical forces can bias a spontaneous symmetry breaking process towards deterministic enantioselection. But can the macroscopic shape of a reactor play a role in chiral symmetry breaking processes? Here we show an example of chirality transfer from the chiral shape of a 3D helical channel to the chirality of supramolecular aggregates, with the handedness of the helical channel dictating the direction of enantioselection in the assembly of an achiral molecule. By combining numerical simulations of fluid flow and mass transport with experimental data, we demonstrated that the chiral information is transferred top-down thanks to the interplay between the hydrodynamics of asymmetric secondary flows and the precise spatiotemporal control of reagent concentration fronts. This result shows the possibility of controlling enantioselectively molecular processes at the nanometer scale by modulating the geometry and the operating conditions of fluidic reactors.

External physical forces can bias a spontaneous symmetry breaking process but whether the shape of a reactor plays a role in chiral symmetry breaking processes is an open question. Here, the authors demonstrate chirality transfer from the chiral shape of a 3D helical channel to chiral supramolecular aggregates whereby the handedness of the helical channel dictates the direction of enantioselection.

Unsymmetrical, monocarboxyalkyl meso-arylporphyrins in the photokilling of breast cancer cells using permethyl-β-cyclodextrin as sequestrant and cell uptake modulator

In the search for photosensitizers with chemical handles to facilitate their integration into complex drug delivery nanosystems, new, unsymmetrically substituted, water insoluble meso-tetraphenylporphyrin and meso-tetra(m-hydroxyphenyl)porphyrin derivatives bearing one carboxyalkyl side chain were synthesized. Permethyl-β-cyclodextrin (pMβCD) was their ideal monomerizing host and highly efficient shuttle to transfer them into water. New assembly modes of the extremely stable (K_binding > 10¹² M^-2) 2:1 complexes were identified. The complexes are photostable and do not disassemble in FBS-containing cell culture media for 24 h. Incubation of breast cancer MCF-7 cells with the complexes results in intense intracellular fluorescence, strongly enhanced in the endoplasmic reticulum (ER), high photokilling efficiency (~90%) and low dark toxicity. pMβCD stands out as a very capable molecular isolator of mono-carboxyalkyl-arylporphyrins that increases uptake and modulates their localization in the cells. The most efficient porphyrins are envisaged as suitable photosensitizers that can be linked to biocompatible drug carriers for photo- and chemo-therapy applications.

Lewis acid induced spectral changes of sterically hindered and unhindered meso-tetra(aryl)porphyrins: fluorescence emission spectra

Fluorescence spectra of a series of electron-rich and electron-deficient meso-tetra(aryl)porphyrins and their molecular complexes with DDQ, TCNE and BF₃ were investigated and compared. In spite of the great resemblance between the absorption spectra of the molecular complexes, large differences were observed between their emission spectra.

Modelling haemoproteins: porphyrins and cyclodextrins as sources of inspiration

The association of hydrophobic cavities with porphyrin derivatives has been used to mimic haemoprotein structures. The most employed cavity in this field is β-cyclodextrin (β-CD), and scaffolds combining β-CDs and porphyrins are expected to inspire the combination of porphyrins and cucurbiturils in the near future. Aside from providing water solubility to various porphyrinic structures, the β-CD framework can also modulate and control the reactivity of the metal core of the porphyrin. After a general introduction of the challenges faced in the field of haemoprotein models and the binding behavior of β-CDs, this article will discuss covalent and non-covalent association of porphyrins with β-CDs. In each approach, the role of the CD differs according to the relative position of the concave CD host, either directly controlling the binding and transformation of a substrate on the metalloporphyrin or playing a dual role of controlling the water solubility and selecting the axial ligand of the metal core. The discussion will be of interest to the cucurbituril community as well as to the cavitand community, as the information provided should be useful for the design of haemoprotein mimics using cucurbiturils.

Stimuli-triggered reversible switching mechanism between H- and J-type supramolecular assemblies of cationic porphyrins adsorbed on tungsten(VI) oxide surface

Supramolecular organic dye–inorganic semiconductor nanocrystal assemblies are potentially useful in a broad range of technologies and applications, including photovoltaic systems, but the molecular basis of the adsorption of dye molecules onto the semiconductor surfaces remains poorly understood. Herein, we investigated the pH-dependent adsorption and conformational change of two cationic porphyrin stereoisomers [5,10-diphenyl-15,20-di([Formula: see text]-methyl-4-pyridyl)porphyrin (cis-DMPyP) and 5,15-diphenyl-10,20-di([Formula: see text]-methyl-4-pyridyl)porphyrin (trans-DMPyP)] on the tungsten(VI) oxide (WO[Formula: see text] colloid nanoparticle in aqueous media by means of UV-vis absorption spectroscopy. In accordance with the combination of a modified Langmuir adsorption model and Kasha’s exciton coupling model, the molecular orientation and stacking arrangement of DMPyP derivatives on the WO[Formula: see text] colloid surface are discussed in detail. In the trans-DMPyP/WO[Formula: see text] aqueous system, trans-DMPyP molecules adopted flat-on orientation with respect to the WO[Formula: see text] colloid surface and eventually formed head-to-tail [Formula: see text]-dimers regardless of pH conditions. cis-DMPyP molecules in the acidic system also lay flat-on and mainly formed [Formula: see text]-dimers on the WO[Formula: see text] colloid surface, whereas ones in the neutral system exhibited a dominant edge-on orientation and had a higher tendency to form face-to-face [Formula: see text]-dimers. Additionally, we have also convincingly demonstrated the pH-triggered switchable [Formula: see text]-stacking geometry of cis-DMPyP molecules from [Formula: see text]- to [Formula: see text]-dimer and vice versa on the WO[Formula: see text] colloid surface. Such findings will undoubtedly provide a pertinent guideline for the rational design of stimuli-responsive organic-inorganic materials.

A novel porphyrinic photosensitizer based on the molecular complex of meso-tetraphenylporphyrin with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone: higher photocatalytic activity, photooxidative stability and solubility in non-chlorinated solvents

The 1 : 2 molecular complex ofmeso-tetraphenylporphyrin with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) has been used as a promising photosensitizer for the aerobic oxidation of olefins in different chlorinated and non-chlorinated solvents.

Light-harvesting nanorods based on pheophorbide-appending cellulose

In contrast to the success in artificial DNA- and peptide-based nanostructures, the ability of polysaccharides to self-assemble into one-, two-, and three-dimensional nanostructures are limited. Here, we describe a strategy for designing and fabricating nanorods using a regioselectively functionalized cellulose derivative at the air-water interface in a stepwise manner. A semisynthetic chlorophyll derivative, pyro-pheophorbide a, was partially introduced into the C-6 position of the cellulose backbone for the design of materials with specific optical properties. Remarkably, controlled formation of cellulose nanorods can be achieved, producing light-harvesting nanorods that display a larger bathochromic shift than their solution counterparts. The results presented here demonstrate that the self-assembly of functionalized polysaccharides on surfaces could lead the nanostructures mimicking the naturally occurring chloroplasts.

NEW PORPHYRIN ADDUCT OF FULLERENE-C60: A PROMISING NANOTOOL FOR MEDICINAL USE IN THE HEART MUSCLE HYPOXIA CASES

This is a first case ever reported on the fullerene-based low toxic nanocationite particles (porphyrin adducts of cyclohexl fullerene- C60) designed for targeted delivery of the paramagnetic magnesium stable isotope to the heart muscle providing a sharp clinical effect close to about 80% recovery of the tissue hypoxia symptoms in less than 24 h after a single injection (0.03–0.1 LD50). A whole principle of this therapy is novel:25Mg2+-magnetic isotope effect selectively stimulates the ATP over-production in the oxygen-depleted cell due to25Mg2+released by nanoparticles. Being membranotropic cationites, these "smart nanoparticles" release the over-activating paramagnetic cations only in response to the metabolic acidic shift. The resulting positive changes in the heart cell energy metabolism may help to prevent and/or treat the local myocardial hypoxic disorders and, hence, to protect the heart muscle from a serious damage in a vast variety of the hypoxia-caused clinical situations including both Doxorubicin and 1-methylnicotineamide cardiotoxic side effects. Both pharmacokinetics and pharmacodynamics of the drug proposed makes it suitable for safe and efficient administration in either single or multi-injection (acute or chronic) therapeutic schemes.

Protective effects of a magnesium magnetic isotope (Mg25)-exchanging nanoparticle (25MgPMC16 ) on mitochondrial functional disorders in esmolol-induced cardiac arrest in rats

In cardiac surgery, agents are needed to produce temporary cardiac arrest (cardioplegia). One of these agents is esmolol (ESM) which is a short-acting selective beta-1 adrenergic receptor antagonist and its overdose causes diastolic ventricular arrest. The (25) MgPMC(16) (porphyrin adducts of cyclohexil fullerene-C60) is known as a nanoparticle which has a cardioprotective effect when the heart is subjected to stressful conditions. In this study, we aimed to confirm the deleterious effects of ESM overdose on cardiac mitochondria and identify any protective effects of (25) MgPMC(16) in male Wistar rats. Esmolol 100 mg kg(-1) (LD50 = 71 mg kg(-1) ) was injected intravenously (i.v.) into tail vein to induce cardiac arrest. This dose was obtained from an ESM dose-response curve which induces at least 80% arrest in rats. (25) MgPMC(16) at three different doses (45, 90 and 224 mg kg(-1) ) was injected i.v. as pretreatment, eight hours before ESM injection. (25) MgCl(2) or (24) MgPMC(16) were used as controls. Following cardiac arrest, the heart was removed and the mitochondria extracted. Mitochondrial viability and the adenosine 5'-diphosphate sodium salt hydrate/Adenosine 5'-triphosphate disodium salt hydrate (ADP/ATP) ratio were measured as biomarkers of mitochondrial function. Results indicate that (25) MgPMC(16) caused a significant increase in mitochondrial viability and decrease in ADP/ATP ratio. No significant changes were seen with (24) MgPMC(16) or (25) MgCl(2) . It is concluded that cardiac arrest induced by ESM overdose leads to a significant decrease in mitochondrial viability and their ATP levels, whereas pretreatment by (25) MgPMC(16) can protect mitochondria by increasing ATP level through liberation of Mg into cells and the improvement of hypoxia.

Protective effect of magnesium-25 carrying porphyrin-fullerene nanoparticles on degeneration of dorsal root ganglion neurons and motor function in experimental diabetic neuropathy

Diabetic neuropathy (DN) is the most common peripheral neuropathy and long-term complication of diabetes. In view of the pathological basis for the treatment of DN, it is important to prevent nerve degeneration. Most of the current treatment strategies are symptomatic therapies. In this study, we evaluated the effectiveness of magnesium-25, carrying porphyrin-fullerene nanoparticles, on diabetes-induced neuropathy. Previous studies have suggested that dorsal root ganglion (DRG) neurons comprise a specific target and may be responsible for the known complications of DN. Experimental DN was induced by intraperitoneal injection of streptozotocin (STZ) (45 mg/kg). Different forms of magnesium including (25)Mg-PMC16, (24)Mg-PMC16 and MgCl(2) were administered intravenously in equal dose (0.5 LD(50)) at 48-hr intervals before STZ injection. Peripheral nerves were studied after 2 months of diabetes in groups using qualitative approaches, morphometric analysis of DRG neurons and motor function tests. We showed that STZ-induced DN caused morphological abnormalities in DRG neurons comprising changes in area, diameter and number of A and B cells as well as motor dysfunction in DN. Moreover, our findings indicated that administration of (25)Mg-PMC16 as a magnetic form of Mg improved morphological abnormalities and motor dysfunctions significantly, whereas other forms of Mg were ineffective.

Fullerene-based low toxic nanocationite particles (porphyrin adducts of cyclohexyl fullerene-C(60)) to treat hypoxia-induced mitochondrial dysfunction in mammalian heart muscle

BACKGROUND

This is the first report on the targeted delivery of fullerene-based low toxic nanocationite particles (porphyrin adducts of cyclohexyl fullerene-C(60)) to treat hypoxia-induced mitochondrial dysfunction in mammalian heart muscle.

METHODS

The magnetic isotope effect generated by the release of paramagnetic (25)Mg(2+) from these nanoparticles selectively stimulates the ATP overproduction in the oxygen-depleted cell.

RESULTS

Because nanoparticles are membranotropic cationites, they will only release the overactivating paramagnetic cations in response to hypoxia-induced acidic shift. The resulting changes in the heart cell energy metabolism result in approximately 80% recovery of the affected myocardium in <24 h after a single injection (0.03-0.1 LD(50)).

CONCLUSIONS

Pharmacokinetics and pharmacodynamics of the nanoparticles suggest their suitability for safe and efficient administration in either single or multi-injection (acute or chronic) therapeutic schemes for the prevention and treatment of clinical conditions involving myocardial hypoxia.

Tetrakis(4-pyridyl)porphyrin supramolecular complexes with cyclodextrins in aqueous solution

The formation of inclusion complexes of hydroxypropyl-beta-cyclodextrin, heptakis(2,6-di-O-methyl)-beta-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin with 5,10,15,20-tetrakis(4-pyridyl)porphyrin (TpyP) has been studied in aqueous buffer solution (phosphate buffer pH = 7 and I = 0.01 M) to give a structural and spectroscopic characterization of a new class of potential sensitizers for photodynamic therapy. The interaction was investigated by a combination of UV/Vis absorption, fluorescence anisotropy, time-resolved fluorescence and circular dichroism. The experimental results point to the presence of the pigment in water in a monomeric complexed form. The fluorescence anisotropy measurements suggest that TpyP forms 1:1 complexes with heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin and hydroxypropyl-beta-cyclodextrin, while 1:2 complexes are obtained with heptakis(2,6-di-O-methyl)-beta-cyclodextrin.

Tetra-2,3-pyrazinoporphyrazines with Externally Appended Pyridine Rings. 3. A New Highly Electron-Deficient Octacationic Macrocycle: Tetrakis-2,3-[5,6-di{2-(N-methyl)pyridiniumyl}pyrazino]porphyrazine, [(2-Mepy)8TPyzPzH2]8+

A new octacationic macrocycle, tetrakis-2,3-[5,6-di{2-(N-methyl)pyridiniumyl}pyrazino]porphyrazine, was obtained in its hydrated form as the water-soluble iodide salt. This compound, abbreviated as [(2-Mepy)(8)TPyzPzH(2)](I(8)).8H(2)O (2-Mepy = 2(N-methyl)pyridiniumyl moiety), was obtained by demetalation of the corresponding Mg(II) complex, [(2-Mepy)(8)TPyzPzMg(H(2)O)](I(8)).5H(2)O, which in turn was prepared from its corresponding neutral hydrated species tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato(monoaquo)magnesium(II), [Py(8)TPyzPzMg(H(2)O)].4H(2)O, by reaction with CH(3)I in N,N-dimethylformamide. The quaternization reactions by using CH(3)I or methyl p-toluenesulfonate were also conducted on the monomeric precursor 2,3-dicyano-5,6-di(2-pyridyl)-1,4-pyrazine, [(CN)(2)Py(2)Pyz], with formation of the monoquaternized ion [(CN)(2)Py(2-Mepy)Pyz](+) neutralized by iodide and p-toluenesulfonate anions. Single-crystal X-ray work allowed elucidation of the structure of the two salt-like species. The diquaternized ion [(CN)(2)(2-Mepy)(2)Pyz](2+) could also be obtained as a p-toluenesulfonate salt, but attempts at direct macrocyclization of this dicationic species were unsuccessful. The iodide salt [(2-Mepy)(8)TPyzPzH(2)](I(8)).8H(2)O is water-soluble, with different solubilities depending on the range of pH explored. It was established that the macrocycle [(2-Mepy)(8)TPyzPzH(2)](8+) undergoes facile deprotonation and behaves as a strong acid. Aggregation phenomena are observed for both the octacation [(2-Mepy)(8)TPyzPzH(2)](8+) and its corresponding centrally deprotonated species [(2-Mepy)(8)TPyzPz](6+). Nevertheless, both cationic moieties exist in their monomeric form under specific experimental conditions. UV-visible monitored titrations with NaOH provide information about the type of protonation/deprotonation equilibria which are complicated by the occurrence of aggregation phenomena.