Evaluation and activity of new porphyrin-peptide cage-type conjugates for the photoinactivation of Mycobacterium abscessus

Mycobacterium abscessus is increasingly recognized as an emerging opportunistic pathogen causing severe lung diseases and cutaneous infections. However, treatment of M. abscessus infections remains particularly challenging, largely due to intrinsic resistance to a wide panel of antimicrobial agents. New therapeutic alternatives are urgently needed. Herein, we show that, upon limited irradiation with a blue-light source, newly developed porphyrin-peptide cage-type photosensitizers exert a strong bactericidal activity against smooth and rough variants of M. abscessus in planktonic cultures and in biofilms, at low concentrations. Atomic force microscopy unraveled important morphological alterations that include a wrinkled and irregular bacterial surface. The potential of these compounds for a photo-therapeutic use to treat M. abscessus skin infections requires further evaluations.IMPORTANCEMycobacterium abscessus causes persistent infections and is extremely difficult to eradicate. Despite intensive chemotherapy, treatment success rates remain very low. Thus, given the unsatisfactory performances of the current regimens, more effective therapeutic alternatives are needed. In this study, we evaluated the activity of newly described porphyrin-peptide cage-type conjugates in the context of photodynamic therapy. We show that upon light irradiation, these compounds were highly bactericidal against M. abscessus in vitro, thus qualifying these compounds for future studies dedicated to photo-therapeutic applications against M. abscessus skin infections.

Self-assembled porphyrin-peptide cages for photodynamic therapy

The development of photodynamic therapy requires access to smart photosensitizers which combine appropriate photophysical and biological properties. Interestingly, supramolecular and dynamic covalent chemistries have recently shown their ability to produce novel architectures and responsive systems through simple self-assembly approaches. Herein, we report the straightforward formation of porphyrin-peptide conjugates and cage compounds which feature on their surface chemical groups promoting cell uptake and specific organelle targeting. We show that they self-assemble, in aqueous media, into positively-charged nanoparticles which generate singlet oxygen upon green light irradiation, while also undergoing a chemically-controlled disassembly due to the presence of reversible covalent linkages. Finally, the biological evaluation in cells revealed that they act as effective photosensitizers and promote synergistic effects in combination with Doxorubicin.

Are tumour-associated carbonic anhydrases genuine therapeutic targets for photodynamic therapy?

INTRODUCTION

Photodynamic therapy (PDT) is a reactive oxygen species (ROS)-dependent treatment modality which has emerged as an alternative cancer therapy strategy. However, in solid tumors, the therapeutic efficacy of PDT is strongly reduced by hypoxia, a typical feature of many such tumors. The tumor-associated carbonic anhydrases IX (hCA IX) and XII (hCA XII), which are overexpressed under hypoxia are attractive, validated anticancer drug targets in solid tumors. Current challenges in therapeutic design of effective PDT systems aim to overcome the limitation of hypoxia by developing synergistic CA-targeted therapies combining photosensitizers and hCA IX/XII inhibitors.

AREA COVERED

In this review, the current literature on the use of hCA IX/XII inhibitors (CAi) for targeting photosensitizing chemical systems useful for PDT against hypoxic solid tumors is summarized, along with recent progress, challenges, and future prospects.

EXPERT OPINION

hCA IX/XII-focused photosensitizers have recently provided new generation of compounds of considerable potential. Proof of concept of in vivo efficacy studies suggested enhanced efficacy for CAi-PDT hybrid systems. Further research is needed to deepen our understanding of how hCA IX/hCA XII inhibition can enhance PDT and for obtaining more effective such derivatives.

Synthesis and Characterization of Tetraphenylethene AIEgen-Based Push-Pull Chromophores for Photothermal Applications: Could the Cycloaddition-Retroelectrocyclization Click Reaction Make Any Molecule Photothermally Active?

Three new tetraphenylethene (TPE) push-pull chromophores exhibiting strong intramolecular charge transfer (ICT) are described. They were obtained via [2 + 2] cycloaddition-retroelectrocyclization (CA-RE) click reactions on an electron-rich alkyne-tetrafunctionalized TPE (TPE-alkyne) using both 1,1,2,2-tetracyanoethene (TCNE), 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F₄-TCNQ) as electron-deficient alkenes. Only the starting TPE-alkyne displayed significant AIE behavior, whereas for TPE-TCNE, a faint effect was observed, and for TPE-TCNQ and TPE-F₄-TCNQ, no fluorescence was observed in any conditions. The main ICT bands that dominate the UV-Visible absorption spectra underwent a pronounced red-shift beyond the near-infrared (NIR) region for TPE-F₄-TCNQ. Based on TD-DFT calculations, it was shown that the ICT character shown by the compounds exclusively originated from the clicked moieties independently of the nature of the central molecular platform. Photothermal (PT) studies conducted on both TPE-TCNQ and TPE-F4-TCNQ in the solid state revealed excellent properties, especially for TPE-F4-TCNQ. These results indicated that CA-RE reaction of TCNQ or F₄-TCNQ with donor-substituted are promising candidates for PT applications.

D-Mannose-appended 5,15-diazaporphyrin for photodynamic therapy

5,15-Diazaporphyrin appended with D-mannose moieties was prepared through Suzuki-Miyaura cross-coupling reaction and S_N2 alkylation. The resultant diazaporphyrin was hydrophilic enough to exhibit sufficient solubility in aqueous media. Because of the photosensitizing ability of diazaporphyrins, the in vitro activity of the D-mannose-appended diazaporphyrin in photodynamic therapy (PDT) was investigated. The specific internalization of the functionalized diazaporphyrin into human breast adenocarcinoma (MDA-MB-231) cells through mannose receptors was confirmed by confocal microscopy imaging. We also demonstrated the strong PDT activity of the functionalized diazaporphyrin at a nanomolar level with short light irradiation time.

Electronic, steric and catalytic properties of N-heterocyclic carbene rhodium(I) complexes linked to (metallo)porphyrins

Electronic and steric properties of NHC ligands functionalized with porphyrins were investigated. When porphyrins are used as NHC-wingtips, nickel(II) in the macrocyle significantly improves the catalytic activity of the neighbouring...

Bio-based porphyrins pyropheophorbide a and its Zn-complex as performing visible-light photosensitizers for free-radical photopolymerization

A chlorophyll a derivative, namely pyropheophorbide a (Pyro), and the corresponding zinc (II) complex (Zn-Pyro) were used for the first time as performing visible-light photosensitizers (PS) for free-radical photopolymerization (FRP)...

Synthesis, Characterization, and Encapsulation Properties of Rigid and Flexible Porphyrin Cages Assembled from N-Heterocyclic Carbene-Metal Bonds

Four porphyrins equipped with imidazolium rings on the para positions of their meso aryl groups were prepared and used as tetrakis(N-heterocyclic carbene) (NHC) precursors for the synthesis of porphyrin cages assembled from eight NHC-M bonds (M = Ag⁺ or Au⁺). The conformation of the obtained porphyrin cages in solution and their encapsulation properties strongly depend on the structure of the spacer -(CH₂)_n- (n = 0 or 1) between meso aryl groups and peripheral NHC ligands. In the absence of methylene groups (n = 0), porphyrin cages are rather rigid and the short porphyrin-porphyrin distance prevents the encapsulation of guest molecules like 1,4-diazabicyclo[2.2.2]octane (DABCO). By contrast, the presence of methylene functions (n = 1) between meso aryl groups and peripheral NHCs offers additional flexibility to the system, allowing the inner space between the two porphyrins to expand enough to encapsulate guest molecules like water molecules or DABCO. The peripheral NHC-wingtip groups also play a significant role in the encapsulation properties of the porphyrin cages.

Periodic Mesoporous Ionosilica Nanoparticles for Green Light Photodynamic Therapy and Photochemical Internalization of siRNA

We report periodic mesoporous ionosilica nanoparticles (PMINPs) as versatile nano-objects for imaging, photodynamic therapy (PDT), and efficient adsorption and delivery of small interfering RNA (siRNA) into breast cancer cells. In order to endow these nanoparticles with PDT and siRNA photochemical internalization (PCI) properties, a porphyrin derivative was integrated into the ionosilica framework. For this purpose, we synthesized PMINPs via hydrolysis-cocondensation procedures from oligosilylated ammonium and porphyrin precursors. The formation of these nano-objects was proved by transmission electron microscopy. The formed nanoparticles were then thoroughly characterized via solid-state NMR, nitrogen sorption, dynamic light scattering, and UV-vis and fluorescence spectroscopies. Our results indicate the formation of highly porous nanorods with a length of 108 ± 9 nm and a width of 54 ± 4 nm. A significant PDT effect of type I mechanism (95 ± 2.8% of cell death) was observed upon green light irradiation in nanoparticle-treated breast cancer cells, while the blue light irradiation caused a significant phototoxic effect in non-treated cells. Furthermore, PMINPs formed stable complexes with siRNA (up to 24 h), which were efficiently internalized into the cells after 4 h of incubation mostly with the energy-dependent endocytosis process. The PCI effect was obvious with green light irradiation and successfully led to 83 ± 1.1% silencing of the luciferase gene in luciferase-expressing breast cancer cells, while no gene silencing effect was observed with blue light irradiation. The present work highlights the high potential of porphyrin-doped PMINPs as multifunctional nanocarriers for nucleic acids, such as siRNA, with a triple ability to perform imaging, PDT, and PCI.

Synthesis, characterization and use of a POSS-arylamine based push–pull octamer

This article reports on the synthesis and first use of a POSS-arylamine based push–pull octamer as molecular donor in organic solar cells.

Binding Mode Multiplicity and Multiscale Chirality in the Supramolecular Assembly of DNA and a π-Conjugated Polymer

Water-soluble π-conjugated polymers are increasingly considered for DNA biosensing. However, the conformational rearrangement, supramolecular organization and dynamics upon interaction with DNA have been overlooked, which prevents the rational design of such detection tools. To elucidate the binding of a cationic polythiophene (CPT) to DNA with atomistic resolution, we performed molecular simulations of their supramolecular assembly. Comparison of replicated simulations show a multiplicity of CPT binding geometries that contribute to the wrapping of CPT around DNA. The different binding geometries are stabilized by both electrostatic interactions between CPT lateral cations and DNA phosphodiesters and van der Waals interactions between the CPT backbone and the DNA grooves. Simulated circular dichroism (CD) spectra show that the induced CD signal stems from a conserved geometrical feature across the replicated simulations, i. e. the presence of segments of syn configurations between thiophene units along the CPT chain. At the macromolecular scale, we inspected the different shapes related to the CPT binding modes around the DNA through symmetry metrics. Altogether, molecular dynamics (MD) simulations, model Hamiltonian calculations of the CD spectra, and symmetry indices provide insights into the origin of induced chirality from the atomic to the macromolecular scale. Our multidisciplinary approach points out the hierarchical aspect of CPT chiral organization induced by DNA.

Polythiophenes with Cationic Phosphonium Groups as Vectors for Imaging, siRNA Delivery, and Photodynamic Therapy

In this work, we exploit the versatile function of cationic phosphonium-conjugated polythiophenes to develop multifunctional platforms for imaging and combined therapy (siRNA delivery and photodynamic therapy). The photophysical properties (absorption, emission and light-induced generation of singlet oxygen) of these cationic polythiophenes were found to be sensitive to molecular weight. Upon light irradiation, low molecular weight cationic polythiophenes were able to light-sensitize surrounding oxygen into reactive oxygen species (ROS) while the highest were not due to its aggregation in aqueous media. These polymers are also fluorescent, allowing one to visualize their intracellular location through confocal microscopy. The most promising polymers were then used as vectors for siRNA delivery. Due to their cationic and amphipathic features, these polymers were found to effectively self-assemble with siRNA targeting the luciferase gene and deliver it in MDA-MB-231 cancer cells expressing luciferase, leading to 30-50% of the gene-silencing effect. In parallel, the photodynamic therapy (PDT) activity of these cationic polymers was restored after siRNA delivery, demonstrating their potential for combined PDT and gene therapy.

Molecular complexes and main-chain organometallic polymers based on Janus bis(carbenes) fused to metalloporphyrins

Janus bis(N-heterocyclic carbenes) composed of a porphyrin core with two N-heterocyclic carbene (NHC) heads fused to opposite pyrroles were used as bridging ligands for the preparation of metal complexes. We first focused our attention on the synthesis of gold(i) chloride complexes [(NHC)AuCl] and investigated the substitution of the chloride ligand by acetylides to obtain the corresponding [(NHC)AuC[triple bond, length as m-dash]CR] complexes. Polyacetylides were then used to obtain molecular multiporphyrinic systems with porphyrins fused to only one NHC ligand, while main-chain organometallic polymers (MCOPs) were obtained when using Janus porphyrin bis(NHCs). Interestingly, MCOPs incorporating zinc(ii) porphyrins proved to be efficient as heterogeneous photocatalysts for the generation of singlet oxygen upon visible light irradiation.

Design of metalloporphyrins fused to imidazolium rings for binding DNA G-quadruplexes

Synthesis and characterization of nickel(II) meso-tetraarylporphyrins fused to imidazolium rings across [Formula: see text],[Formula: see text]-pyrrolic positions and X-ray structure of the porphyrin where two opposed pyrrole units are fused to an imidazolium ring are presented. The interactions between these mono-, bis-, tris- and tetrakis(imidazolium) porphyrins with human telomeric DNA G-quadruplexes (G4) were investigated using UV-vis absorption spectroscopy, Circular Dichroism (CD) spectroscopy and Fluorescence Resonance Energy Transfer (FRET) melting assay. Possible binding modes between cationic porphyrins and a selected G4 sequence (d[AG3(T2AG[Formula: see text]]), and relative stabilities of porphyrin/G4 complexes are discussed. Excepting porphyrins fused to one imidazolium ring, the other derivatives interact with G4 structures and their stabilization strongly depends on the porphyrin structure (number and localization of the imidazolium rings).

Synthesis, characterization and modeling of self-assembled porphyrin nanorods

Porphyrin nanorods were prepared by ion-association between free-base meso 5,10,15,20-tetrakis-(4-[Formula: see text]-methylpyridinium)porphyrin cations and tetraphenylborate anions. The nanorods have variable lengths (up to a few micrometers long) and diameters ([Formula: see text]50–500 nm). Their structure at the molecular level was elucidated by combining multinuclear solid state NMR spectroscopy, synchrotron X-ray powder diffraction and DFT calculations.

In Depth Analysis of Photovoltaic Performance of Chlorophyll Derivative-Based "All Solid-State" Dye-Sensitized Solar Cells

Chlorophyll a derivatives were integrated in "all solid-state" dye sensitized solar cells (DSSCs) with a mesoporous TiO2 electrode and 2',2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene as the hole-transport material. Despite modest power conversion efficiencies (PCEs) between 0.26% and 0.55% achieved for these chlorin dyes, a systematic investigation was carried out in order to elucidate their main limitations. To provide a comprehensive understanding of the parameters (structure, nature of the anchoring group, adsorption …) and their relationship with the PCEs, density functional theory (DFT) calculations, optical and photovoltaic studies and electron paramagnetic resonance analysis exploiting the 4-carboxy-TEMPO spin probe were combined. The recombination kinetics, the frontier molecular orbitals of these DSSCs and the adsorption efficiency onto the TiO2 surface were found to be the key parameters that govern their photovoltaic response.

Antiferromagnetic coupling in copper(II)porphyrin dimers linked by copper(II) or palladium(II) ion

The synthesis of porphyrin dimers linked by metal ions is described and the X-ray structure of two new dimers is presented. As previously shown for diamagnetic metal ions, strong electronic interactions between the individual subunits were observed. Antiferromagnetic coupling between copper(II)porphyrins linked by palladium(II) or copper(II) ions was studied by EPR and SQUID measurements. For the palladium(II)-linked dimer, the very small antiferromagnetic coupling was estimated by EPR measurements ([Formula: see text] <-1 cm[Formula: see text]. For the trinuclear-copper(II)-linked dimer, a large antiferromagnetic coupling between the copper(II) ions was measured. In this trinuclear compound, the linking copper(II) ion is used as a relay to increase the interaction between the two copper(II)porphyrins.

Synthesis, photophysical and electropolymerization properties of thiophene-substituted 2,3-diphenylbuta-1,3-dienes

Electropolymerizable diphenylbuta-1,3-diene derivatives with AIE or AEE properties were synthesized allowing low bandgap polymers to be obtained through electropolymerization processes.

A Cationic Tetraphenylethene as a Light-Up Supramolecular Probe for DNA G-Quadruplexes

Guanine-quadruplexes (G4s) are targets for anticancer therapeutics. In this context, human telomeric DNA (HT-DNA) that can fold into G4s sequences are of particular interest, and their stabilization with small molecules through a visualizable process has become a challenge. As a new type of ligand for HT-G4, we designed a tetraimidazolium tetraphenylethene (TPE-Im) as a water-soluble light-up G4 probe. We study its G4-binding properties with HT-DNA by UV-Visible absorption, circular dichroism and fluorescence spectroscopies, which provide insights into the interactions between TPE-Im and G4-DNA. Remarkably, TPE-Im shows a strong fluorescence enhancement and large shifts upon binding to G4, which is valuable for detecting G4s. The association constants for the TPE-Im/G4 complex were evaluated in different solution conditions via isothermal titration calorimetry (ITC), and its binding modes were explored by molecular modeling showing a groove-binding mechanism. The stabilization of G4 by TPE-Im has been assessed by Fluorescence Resonance Energy Transfer (FRET) melting assays, which show a strong stabilization (ΔT _1/2 around +20°C), together with a specificity toward G4 with respect to double-stranded DNA.

Diazachlorin and diazabacteriochlorin for one- and two-photon photodynamic therapy

Diazachlorin and diazabacteriochlorin have been prepared through reduction of diazaporphyrin and their in vitro and in vivo activity in photodynamic therapy has been investigated.

New Layered Polythiophene-Silica Composite Through the Self-Assembly and Polymerization of Thiophene-Based Silylated Molecular Precursors

A new layered hybrid polythiophene-silica material was obtained directly by hydrolysis and polycondensation (sol-gel) of a silylated-thiophene bifunctional precursor, and its subsequent oxidative polymerization by FeCl₃. This precursor was judiciously designed to guarantee its self-assembly and the formation of a lamellar polymer-silica structure, exploiting the cooperative effect between the hydrogen bonding interactions, originating from the ureido groups and the π-stacking interactions between the thiophene units. The lamellar structure of the polythiophene-silica composite was confirmed by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) analyses. The solid-state nuclear magnetic resonance (NMR), UV-Vis, and photoluminescence spectra unambiguously indicate the incorporation of polythiophene into the silica matrix. Our work demonstrates that using a polymerizable silylated-thiophene precursor is an efficient approach towards the formation of nanostructured conjugated polymer-based hybrid materials.

Peripherally Metalated Porphyrins with Applications in Catalysis, Molecular Electronics and Biomedicine

Porphyrins are conjugated, stable chromophores with a central core that binds a variety of metal ions and an easily functionalized peripheral framework. By combining the catalytic, electronic or cytotoxic properties of selected transition metal complexes with the binding and electronic properties of porphyrins, enhanced characteristics of the ensemble are generated. This review article focuses on porphyrins bearing one or more peripheral transition metal complexes and discusses their potential applications in catalysis or biomedicine. Modulation of the electronic properties and intramolecular communication through coordination bond linkages in bis-porphyrin scaffolds is also presented.

Cofacial porphyrin dimers assembled from N-heterocyclic carbene–metal bonds

Cofacial porphyrin dimers assembled from eight metal–carbene bonds were synthesized by using porphyrins with four imidazolium groups as precursors.

Mesoporous silica nanoparticles in recent photodynamic therapy applications

In this review, the use of mesoporous silica nanoparticles for photodynamic therapy (PDT) applications is described for the year 2017.

Mesoporous silicon nanoparticles for targeted two-photon theranostics of prostate cancer

Porous silicon nanoparticles grafted with a mannose-6-phosphate analogue were designed for targeting prostate cancer cells.

Expanding the light absorption of poly(3-hexylthiophene) by end-functionalization with π-extended porphyrins

Poly(3-hexylthiophene)s end-functionalized with π-extended porphyrins show a broad absorption profile up to 700 nm and a fibrillar microstructure tuned by the porphyrin molar ratio.

Self-assembly and hybridization mechanisms of DNA with cationic polythiophene

The combination of DNA and π-conjugated polyelectrolytes (CPEs) represents a promising approach to develop DNA hybridization biosensors, with potential applications for instance in the detection of DNA lesions and single-nucleotide polymorphisms. Here we exploit the remarkable optical properties of a cationic poly[3-(6'-(trimethylphosphonium)hexyl)thiophene-2,5-diyl] (CPT) to decipher the self-assembly of DNA and CPT. The ssDNA/CPT complexes have chiroptical signatures in the CPT absorption region that are strongly dependent on the DNA sequence, which we relate to differences in supramolecular interactions between the thiophene monomers and the various nucleobases. By studying DNA-DNA hybridization and melting processes on preformed ssDNA/CPT complexes, we observe sequence-dependent mechanisms that can yield DNA-condensed aggregates. Heating-cooling cycles show that non-equilibrium mixtures can form, noticeably depending on the working sequence of the hybridization experiment. These results are of high importance for the use of π-conjugated polyelectrolytes in DNA hybridization biosensors and in polyplexes.

Ultrasmall NHC-coated gold nanoparticles obtained through solvent free thermolysis of organometallic Au(i) complexes

Ultrasmall gold nanoparticles (Au UNPs) represent a unique class of nanomaterials making them very attractive for certain applications. Herein, we developed an organometallic approach to the synthesis of Au UNPs stabilized with the C18H37-NHC ligand by the solvent free thermolysis of [RMIM][Au(C6F5)2] () or [Au(C6F5)(RNHC)] () (with R = C18H37-), by controlling the reactivity of pentafluorophenyl ligands as deprotonating or reductive elimination agents; Au UNPs can be achieved by solvent free thermolysis. Pentafluorophenyl Au(i) complexes and are synthesized from the corresponding ionic and neutral precursors. The presence of long alkyl chain imidazolium or carbene species in the complexes makes them to behave as isotropic liquids at moderate temperatures. The use of multinuclear NMR allows the description of the mechanism of formation of the UNPs as well as the surface state of the UNPs.

Binding modes of a core-extended metalloporphyrin to human telomeric DNA G-quadruplexes

A novel π-extended Ni^II-porphyrin shows a high selectivity towards human telomeric G-quadruplexes.

Reactivity of gold nanoparticles towards N-heterocyclic carbenes

The reaction of gold nanoparticles with benzimididazol-2-ylidene ligands leads to the formation of well-defined bis-carbene gold(i) complexes, as shown by characterization techniques such as powder XRD and solid state NMR.

Synthesis of TiO2-poly(3-hexylthiophene) hybrid particles through surface-initiated Kumada catalyst-transfer polycondensation

TiO2/conjugated polymers are promising materials in solar energy conversion where efficient photoinduced charge transfers are required. Here, a "grafting-from" approach for the synthesis of TiO2 nanoparticles supported with conjugated polymer brushes is presented. Poly(3-hexylthiophene) (P3HT), a benchmark material for organic electronics, was selectively grown from TiO2 nanoparticles by surface-initiated Kumada catalyst-transfer polycondensation. The grafting of the polymer onto the surface of the TiO2 nanoparticles by this method was demonstrated by (1)H and (13)C solid-state NMR, X-ray photoelectron spectrometry, thermogravimetric analysis, transmission electron microscopy, and UV-visible spectroscopy. Sedimentation tests in tetrahydrofuran revealed improved dispersion stability for the TiO2@P3HT hybrid material. Films were produced by solvent casting, and the quality of the dispersion of the modified TiO2 nanoparticles was evaluated by atomic force microscopy. The dispersion of the P3HT-coated TiO2 NPs in the P3HT matrix was found to be homogeneous, and the fibrillar structure of the P3HT matrix was maintained which is favorable for charge transport. Fluorescence quenching measurements on these hybrid materials in CHCl3 indicated improved photoinduced electron-transfer efficiency. All in all, better physicochemical properties for P3HT/TiO2 hybrid material were reached via the surface-initiated "grafted-from" approach compared to the "grafting-onto" approach.