Flow field-flow fractionation and multi-angle light scattering as a powerful tool for the characterization and stability evaluation of drug-loaded metal-organic framework nanoparticles.

Asymmetric flow field-flow fractionation (AF4) coupled with UV-Vis spectroscopy, multi-angle light scattering (MALS) and refractive index (RI) detection has been applied for the characterization of MIL-100(Fe) nanoMOFs (metal-organic frameworks) loaded with nucleoside reverse transcriptase inhibitor (NRTI) drugs for the first time. Empty nanoMOFs and nanoMOFs loaded with azidothymidine derivatives with three different degrees of phosphorylation were examined: azidothymidine (AZT, native drug), azidothymidine monophosphate (AZT-MP), and azidothymidine triphosphate (AZT-TP). The particle size distribution and the stability of the nanoparticles when interacting with drugs have been determined in a time frame of 24 h.

Efficient "green" encapsulation of a highly hydrophilic anticancer drug in metal-organic framework nanoparticles.

Metal-organic frameworks (MOFs) are coordination polymers of interest for biomedical applications. Of particular importance, nanoparticles made of iron(III) trimesate (MIL-100, MIL standing for Material Institut Lavoisier) (nanoMOFs) can be conveniently synthesised under mild and green conditions. They were shown to be biodegradable, biocompatible and efficient to encapsulate a variety of active molecules.

Scope and limitations of the TEMPO/EPR method for singlet oxygen detection: the misleading role of electron transfer.

For many biological and biomedical studies, it is essential to detect the production of (1)O2 and quantify its production yield. Among the available methods, detection of the characteristic 1270-nm phosphorescence of singlet oxygen by time-resolved near-infrared (TRNIR) emission constitutes the most direct and unambiguous approach. An alternative indirect method is electron paramagnetic resonance (EPR) in combination with a singlet oxygen probe.

Host-guest interactions in Fe(III)-trimesate MOF nanoparticles loaded with doxorubicin.

Doxorubicin (DOX) entrapment in porous Fe(III)-trimesate metal organic frameworks (MIL-100(Fe)) nanoparticles was investigated in neutral Tris buffer via UV-vis absorption, circular dichroism (CD), and fluorescence. The binding constants and the absolute spectra of the DOX-MIL-100(Fe) complexes were determined via absorption and fluorescence titrations. A binding model where DOX associates as monomer to the dehydrated Fe3O (OH)(H2O)2 [(C6H3)(CO2)3]2 structural unit in 1:1 stoichiometry, with apparent association constant of (1.

Two-photon fluorescence imaging and bimodal phototherapy of epidermal cancer cells with biocompatible self-assembled polymer nanoparticles.

We have developed herein an engineered polymer-based nanoplatform showing the convergence of two-photon fluorescence imaging and bimodal phototherapeutic activity in a single nanostructure. It was achieved through the appropriate choice of three different components: a β-cyclodextrin-based polymer acting as a suitable carrier, a zinc phthalocyanine emitting red fluorescence simultaneously as being a singlet oxygen ((1)O2) photosensitizer, and a tailored nitroaniline derivative, functioning as a nitric oxide (NO) photodonor. The self-assembly of these components results in photoactivable nanoparticles, approximately 35 nm in diameter, coencapsulating a multifunctional cargo, which can be delivered to carcinoma cells.

Supramolecular photochemistry of drugs in biomolecular environments.

In this tutorial review we illustrate how the interaction of photoactive drugs/potential drugs with proteins or DNA in supramolecular complexes can determine the course of the reactions initiated by the drug absorbed photons, evidencing the mechanistic differences with respect to the solution conditions. We focus on photoprocesses, independent of oxygen, that lead to chemical modification of the biomolecules, with formation of new covalent bonds or cleavage of existing bonds. Representative systems are mainly selected from the literature of the last decade.

Impact of phosphorylation on the encapsulation of nucleoside analogues within porous iron(iii) metal-organic framework MIL-100(Fe) nanoparticles.

Encapsulation of azidothymidine (AZT) or its phosphorylated derivatives (AZT-MP and AZT-TP) has been performed using nanoparticles of the porous crystalline iron(iii) trimesate metal-organic framework MIL-100(Fe). The number of phosphate groups per nucleoside analogue has a high impact on the drug loading capacity, and their interaction with the Lewis acid sites from the nanoMOFs is also discussed through a combination of techniques such as UV-vis absorption, circular dichroism, isothermal titration calorimetry, HPLC and molecular simulations. Finally, the effect of the differences in terms of host-guest interactions is discussed through the release in physiological buffers of AZT, AZT-MP and AZT-TP.

Citric acid-γ-cyclodextrin crosslinked oligomers as carriers for doxorubicin delivery.

Two citric acid crosslinked γ-cyclodextrin oligomers (pγ-CyD) with a MW of 21-33 kDa and 10-15 γ-CyD units per molecule were prepared by following green chemistry methods and were fully characterized. The non-covalent association of doxorubicin (DOX) with these macromolecules was investigated in neutral aqueous medium by means of circular dichroism (CD), UV-vis absorption and fluorescence. Global analysis of multiwavelength spectroscopic CD and fluorescence titration data, taking into account the DOX monomer-dimer equilibrium, evidenced the formation of 1 : 1 and 1 : 2 pγ-CyD unit-DOX complexes.

A fluorine 1,2-migration via aryl cation/radical/radical anion/radical sequence.

Irradiation of a 7-piperazino-8-fluoroquinolone causes formal 1,2-fluorine migration, piperazine loss and reduction, or nucleophile addition in 8. Product study, laser flash photolysis, and computational modeling support F(-) detachment to yield a triplet 8-quinolyl cation that either inserts intramolecularly or is trapped by Cl(-), Br(-). However, iodide and pyrrole reduce it to the radical that continues the 'redox tour' (aryl cation→ radical→ radical anion→ radical and then again radical or radical anion) leading to the rearranged products.

Water-soluble naphthalene diimides as singlet oxygen sensitizers.

Bromo- and/or alkylamino-substituted and hydrosoluble naphthalene diimides (NDIs) were synthesized to study their multimodal photophysical and photochemical properties. Bromine-containing NDIs (i.e.

Towards an improved anti-HIV activity of NRTI via metal-organic frameworks nanoparticles.

Nanoscale mesoporous iron carboxylates metal-organic frameworks (nanoMOFs) have recently emerged as promising platforms for drug delivery, showing biodegradability, biocompatibility and important loading capability of challenging highly water-soluble drugs such as azidothymidine tryphosphate (AZT-TP). In this study, nanoMOFs made of iron trimesate (MIL-100) were able to act as efficient molecular sponges, quickly adsorbing up to 24 wt% AZT-TP with entrapment efficiencies close to 100%, without perturbation of the supramolecular crystalline organization. These data are in agreement with molecular modelling predictions, indicating maximal loadings of 33 wt% and preferential location of the drug in the large cages.

Unravelling molecular mechanisms in the fluorescence spectra of doxorubicin in aqueous solution by femtosecond fluorescence spectroscopy.

Doxorubicin (DOX) is a potent anti-tumoral agent widely used for cancer therapy. Despite numerous studies, the fluorescence properties of DOX, usually exploited for the characterization of the interaction with biological media, have until now led to controversial interpretations, mainly due to self-association of the drug in aqueous solution. We present here the first femtosecond study of DOX based on measurements with the fluorescence up-conversion technique in combination with time-correlated single photon counting using the same laser source.

Pyrazinoporphyrazines with externally appended pyridine rings. 13. Structure, UV-visible spectral features, and noncovalent interaction with DNA of a positively charged binuclear (Zn(II)/Pt(II)) macrocycle with multimodal anticancer potentialities.

We investigated with spectroscopic techniques the noncovalent interaction of a bimetallic water-soluble (Zn(II)/Pt(II)) porphyrazine hexacation, [(PtCl(2))(CH(3))(6)LZn](6+), and its octacationic analogue [(CH(3))(8)LZn](8+), lacking the cis-platin-like functionality, with a 21-mer double strand (ds) 5'-d[GGG(TTAGGG)(3)]-3'/3'-d[CCC(AATCCC)(3)]-5', as model for B-DNA. Both hexacation and octacation tend to aggregate in water. The structure as well as the ground and excited-state electronic properties of the Zn(II)/Pt(II) hexacation [(PtCl(2))(CH(3))(6)LZn](6+) in water solution were investigated using density functional theory (DFT) and time-dependent DFT (TDDFT) methods.

β-Cyclodextrin polymer nanoparticles as carriers for doxorubicin and artemisinin: a spectroscopic and photophysical study.

The association of doxorubicin (DOX) and artemisinin (ART) to a β-CyD-epichlorohydrin crosslinked polymer (pβ-CyD), organized in nanoparticles of ca. 15 nm size, was investigated in neutral aqueous medium by circular dichroism (CD), UV-vis absorption and fluorescence. The stability constants and the absolute CD spectra of the drug complexes were determined by global analysis of multiwavelength data from spectroscopic titrations.

Combination of spectroscopic and computational methods to get an understanding of supramolecular chemistry of drugs: from simple host systems to biomolecules.

Circular dichroism (CD) spectra of non-covalent ligand : biomolecule couples contain information on the equilibrium geometries of the associated structures that can be retrieved upon comparison of the sign and intensity of the experimental CD bands with the quantum mechanically calculated rotational strengths of low energy supramolecular complexes, obtained from molecular modelling methods. For both chiral and achiral ligands this approach proved useful to reach a structure based rationale of ground and excited state properties of the non-covalent ligand : protein associates. In this Perspective we illustrate the potential of this method focusing on the main achievements of our recent spectroscopic, conformational and photochemical studies on drug-albumin complexes and collocate it in the frame of current methodologies of molecular modelling and spectroscopic investigation of ligand : biomolecule binding.

Change in conformation with reduction of alpha-helix content causes loss of neutrophil binding activity in fully cytotoxic Shiga toxin 1.

Shiga toxins (Stx) play an important role in the pathogenesis of hemolytic uremic syndrome, a life-threatening renal sequela of human intestinal infection caused by specific Escherichia coli strains. Stx target a restricted subset of human endothelial cells that possess the globotriaosylceramide receptor, like that in renal glomeruli. The toxins, composed of five B chains and a single enzymatic A chain, by removing adenines from ribosomes and DNA, trigger apoptosis and the production of pro-inflammatory cytokines in target cells.

Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings. 9. Novel heterobimetallic macrocycles and related hydrosoluble hexacations as potentially active photo/chemotherapeutic anticancer agents.

New homo- and heterobimetallic porphyrazine complexes of general formula [(M'Cl(2))LM] (L = tetrakis-2,3-[5,6-di-(2-pyridyl)pyrazino]porphyrazinato dianion), with M = Zn(II), Mg(II)(H(2)O), or Pd(II) in the central cavity and one M'Cl(2) unit (M' = Pd(II), Pt(II)) peripherally coordinated at the pyridine N atoms of one of the dipyridinopyrazine fragments, were prepared and characterized by elemental analyses and IR/UV-visible spectroscopy. Related water-soluble salt-like species, carrying the hexacations [(PtCl(2))(CH(3))(6)LM](6+) (neutralized by I(-) ions), were also prepared and similarly characterized. Retention of clathrated water molecules is a common feature of all the compounds.

Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings. 10. A water-soluble bimetallic (Zn(II)/Pt(II)) porphyrazine hexacation as potential plurimodal agent for cancer therapy: exploring the behavior as ligand of telomeric DNA G-quadruplex structures.

The behavior of a bimetallic water-soluble (Zn(II)/Pt(II)) porphyrazine hexacation as ligand of G-quadruplex (G4) structures adopted by a human telomeric DNA sequence has been examined with different spectroscopic techniques. In K(+) rich solution the hexacationic Zn(II) porphyrazine ligand bearing a peripheral cis-platin-like functionality changes the G-quadruplex conformational equilibrium of the human telomeric sequence 5'-d[AGGG(TTAGGG)(3)]-3' and drives it exclusively toward a very stable parallel G4 form in the complex with 2:1 stoichiometry. An increase of the melting temperature of more than 20 °C is observed in this complex compared to the G4 alone.

Complexes of the antitumoral drugs Doxorubicin and Sabarubicin with telomeric G-quadruplex in basket conformation: ground and excited state properties.

We studied the binding of two anthracycline drugs, Doxorubicin and Sabarubicin, to a model telomeric sequence 5'-d[GGG(TTAGGG)(3)]-3' (21-mer), assuming the basket G-quadruplex (G4) conformation in Na(+)-rich aqueous solution. We used an approach that combines spectroscopic and microcalorimetric techniques to obtain information about ground and excited state properties of the most stable complexes. Both drugs bind to the 21-mer in basket conformation and complexes of 1:1 and 2:1 drug : 21-mer stoichiometry coexist in solution.

A cationic Zn(II) porphyrazine induces a stable parallel G-quadruplex conformation in human telomeric DNA.

A water soluble Zn(II) porphyrazine drives the conformational equilibrium of the G-quadruplex of a human telomeric sequence exclusively towards a parallel conformation upon complexation.

Affinity of the anthracycline antitumor drugs Doxorubicin and Sabarubicin for human telomeric G-quadruplex structures.

Combining various techniques in solution we proved that Doxorubicin, also called Adriamycin, and Sabarubicin, also known as MEN 10755, bind to the human telomeric sequence, 5'-d[GGG(TTAGGG)(3)]-3' (21-mer), assuming a G-quadruplex structure in the presence of K(+). Complexes of drugs with the 21-mer in 1 : 1 and 2 : 1 stoichiometry coexist in solution. Association constants were obtained from titration experiments and confirmed by isothermal titration calorimetry.

Stereoselective interaction of ketoprofen enantiomers with β-cyclodextrin: ground state binding and photochemistry.

The chiral recognition ability of β-cyclodextrin (β-CyD) vs.S- and R-ketoprofen (KP) enantiomers has been studied by circular dichroism (CD), isothermal titration calorimetry (ITC) and NMR. The association constants of the 1 : 1 complexes obtained from CD and ITC titration experiments resulted to be the same for both enantiomers within the experimental uncertainty.

Fluoroquinolones as potential photochemotherapeutic agents: covalent addition to guanosine monophosphate.

The triplet aryl cation photochemically generated from fluoroquinolones bearing a fluoro atom at position 8 attacks guanosine monophosphate (k(r) > 10(9) M(-1)s(-1)) and forms covalent adducts. The reaction is a model for the implementation of oxygen-independent photochemotherapy.

Chiral recognition of 2-(3-benzoylphenyl)propionic acid (ketoprofen) by serum albumin: an investigation with microcalorimetry, circular dichroism and molecular modelling.

The interaction of enantiomeric ketoprofen (KP) with BSA and HSA was studied by isothermal titration calorimetry (ITC). Affinity constants and thermodynamic parameters for complexation in two main protein sites were determined. Affinity constants for both proteins are generally lower for S(+)- than for R(-)-KP.

Licochalcone A bound to bovine serum albumin: a spectroscopic, photophysical and structural study.

The interaction of Licochalcone A (LA) with bovine serum albumin (BSA) was studied by circular dichroism (CD), UV-Vis absorption, fluorescence and laser flash photolysis. The most stable 1 : 1 and 2 : 1 LA : BSA complexes were spectroscopically characterized. Two protein sites of similar affinity are involved in the LA association with both stoichiometries.