Xylan-Porphyrin Hydrogels as Light-Triggered Gram-Positive Antibacterial Agents.

In the present work, we report on the synthesis of light-triggered antibacterial hydrogels, based on xylan chains covalently bound to meso-tetra(4-carboxyphenyl)porphyrin (TCPP). Not only does TCPP act as a photosensitizer efficient against Gram-positive bacteria, but it also serves as a cross-linking gelator, enabling the simple and easy building of xylan conjugate hydrogels. The hydrogels were characterized by infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), along with swelling and rheological tests. The antimicrobial activity of the hydrogels was tested under visible light irradiation against two Gram-positive bacterial strains, Staphylococcus aureus and Bacillus cereus. The preliminary results showed an interesting activity on these bacteria, indicating that these hydrogels could be of great potential in the treatment of skin bacterial infections with this species by photodynamic antimicrobial chemotherapy (PACT).

Synthesis and Investigation of Flavanone Derivatives as Potential New Anti-Inflammatory Agents.

Flavonoids are polyphenols with broad known pharmacological properties. A series of 2,3-dihydroflavanone derivatives were thus synthesized and investigated for their anti-inflammatory activities. The target flavanones were prepared through cyclization of 2'-hydroxychalcone derivatives, the later obtained by Claisen-Schmidt condensation. Since nitric oxide (NO) represents an important inflammatory mediator, the effects of various flavanones on the NO production in the LPS-induced RAW 264.7 macrophage were assessed in vitro using the Griess test. The most active compounds were flavanone (4G), 2'-carboxy-5,7-dimethoxy-flavanone (4F), 4'-bromo-5,7-dimethoxy-flavanone (4D), and 2'-carboxyflavanone (4J), with IC50 values of 0.603, 0.906, 1.030, and 1.830 µg/mL, respectively. In comparison, pinocembrin achieved an IC50 value of 203.60 µg/mL. Thus, the derivatives synthesized in this work had a higher NO inhibition capacity compared to pinocembrin, demonstrating the importance of pharmacomodulation to improve the biological potential of natural molecules. SARs suggested that the use of a carboxyl-group in the meta-position of the B-ring increases biological activity, whereas compounds carrying halogen substituents in the para-position were less active. The addition of methoxy-groups in the meta-position of the A-ring somewhat decreased the activity. This study successfully identified new bioactive flavanones as promising candidates for the development of new anti-inflammatory agents.

Biosorption of nickel ions Ni2+ by natural and modified Pinus caribaea Morelet sawdust.

The potential of Pinus caribaea Morelet sawdust for the removal of nickel ions (Ni2+) and other metallic trace ions (Co2+, Cr3+, Mn2+) from aqueous solutions was investigated under batch conditions. Several parameters such as size of particles, contact time, pH, initial metal and biomass concentrations, desorption conditions and reusability were evaluated on natural biomass. Biosorption was fast, effective (73%) and biomaterial can be reused after five cycles. To enhance the removal capacity of nickel, pine sawdust was modified by acidic and oxidative treatments. Cellulosic residues from sawdust sequential extraction showed great biosorption capacity (96%). In the presence of a metal mixture, oxidized sawdust had better selectivity for Cr3+ ions than for Ni2+ . Pinus caribaea biomass could be an environmental, inexpensive and renewable material for the depollution of water laden with metallic trace elements.

Design and synthesis of zinc protoporphyrin IX-adamantane/cyclodextrin/cellulose nanocrystals complexes for anticancer photodynamic therapy.

Two protoporphyrin IX (PpIX) adamantane derivatives were synthesized and then metallated with zinc. The Zn-PpIX derivatives, exhibiting a high singlet oxygen quantum yield, were tested for their photodynamic activity against the HT-29 cell line. In order to enhance their water-solubility and their cellular bioavailability, these photosensitizers were encapsulated into the hydrophobic cavity of cyclodextrins (CD) previously attached to cellulose nanocrystals (CNCs) via electrostatic interactions. Under illumination, the encapsulated adamantanyl-porphyrins exerted an enhanced in vitro cytotoxicity, as compared with the corresponding free photosensitizers.

Xylan-Based Cross-Linked Hydrogel for Photodynamic Antimicrobial Chemotherapy.

Photodynamic antimicrobial chemotherapy or PACT has been shown to be a promising antibacterial treatment that could overcome the challenge of multidrug-resistant bacteria. However, the use of most existing photosensitizers has been severely hampered by their significant self-quenching effect, poor water solubility, lack of selectivity against bacterial cells, and possible damage to the surrounding tissues. The use of hydrogels may overcome some of these limitations. We herein report a simple strategy to synthesize a cross-linked hydrogel from beech xylan. The hydrogel showed a high swelling ratio, up to 62, an interconnected porous structure, and good mechanical integrity, and 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetraiodide (TMPyP) was chosen as a model of hydrophilic photosensitizer (PS) and was encapsulated inside the xylan-based hydrogel. TMPyP-loaded hydrogel prolonged release of PS up to 24 h with a cumulative amount that could reach 100%. TMPyP-loaded hydrogel showed a photocytotoxic effect against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus strains, and Bacillus cereus, while no cytotoxicity was observed in the dark.

The mannose 6-phosphate receptor targeted with porphyrin-based periodic mesoporous organosilica nanoparticles for rhabdomyosarcoma theranostics.

Porphyrin-based periodic mesoporous organosilica nanoparticles (PMO) synthesized from a large functional octatriethoxysilylated porphyrin precursor and allowing two-photon excitation photodynamic therapy (TPE-PDT) and NIR imaging were synthesized. These PMO were grafted with polyethylene glycol (PEG) moieties and an analogue of mannose 6-phosphate functionalized at the anomeric position (AMFA). AMFAs are known to efficiently target mannose 6-phosphate receptors (M6PRs) which are over-expressed in various cancers. Here, we demonstrated for the first time that M6PRs were over-expressed in rhabdomyosarcoma (RMS) cells and could be efficiently targeted with PMO-AMFA allowing TPE imaging and TPE-PDT of RMS cells. The comparison with healthy myoblasts demonstrated an absence of biological effects, suggesting a cancer cell specificity in the biomedical action observed.

Antibacterial activity of the lichens Usnea Florida and Flavoparmelia caperata (Parmeliaceae).

Acetone extracts of the two common epiphytes lichens Usnea florida and Flavoparmelia caperata have been evaluated for their antimicrobial activities against Staphylococcus aureus, Candida albicans and Aspergillus brasiliensis. The dibenzofuran derivative (+)-usnic acid (1) was the main metabolite in these two species. Thamnolic (5), evernic (6), physodic (7) and 3-hydroxyphysodic acids (8) were isolated from U. florida, as well as 5,7-dihydroxy-6-methylphtalide (2) which was newly identified in this Genus. Protocetraric (3) and caperatic acids (4) and ergosterol peroxide (9) are usually biosynthezised by F. caperata. Antibacterial activity was determined for the four main compounds against Staphylococcus aureus using bioautography and broth dilution method. Minimal inhibitory concentrations of usnic acid, caperatic acid and protocetraric acid were comprised between 7.25 and 12.5 µg/mL.

Photodynamic Therapy Activity of New Porphyrin-Xylan-Coated Silica Nanoparticles in Human Colorectal Cancer.

Photodynamic therapy (PDT) using porphyrins has been approved for treatment of several solid tumors due to the generation of cytotoxic reactive oxygen species (ROS). However, low physiological solubility and lack of selectivity towards tumor sites are the main limitations of their clinical use. Nanoparticles are able to spontaneously accumulate in solid tumors through an enhanced permeability and retention (EPR) effect due to leaky vasculature, poor lymphatic drainage, and increased vessel permeability. Herein, we proved the added value of nanoparticle vectorization on anticancer efficacy and tumor-targeting by 5-(4-hydroxyphenyl)-10,15,20-triphenylporphyrin (TPPOH). Using 80 nm silica nanoparticles (SNPs) coated with xylan-TPPOH conjugate (TPPOH-X), we first showed very significant phototoxic effects of TPPOH-X SNPs mediated by post-PDT ROS generation and stronger cell uptake in human colorectal cancer cell lines compared to free TPPOH. Additionally, we demonstrated apoptotic cell death induced by TPPOH-X SNPs-PDT and the interest of autophagy inhibition to increase anticancer efficacy. Finally, we highlighted in vivo, without toxicity, elevated anticancer efficacy of TPPOH-X SNPs through improvement of tumor-targeting compared to a free TPPOH protocol. Our work demonstrated for the first time the strong anticancer efficacy of TPPOH in vitro and in vivo and the merit of SNPs vectorization.

Advanced protocol to functionalize CaP bioceramic surface with peptide sequences and effect on murine pre-osteoblast cells proliferation.

To bring osteoinductive properties to calcium phosphate (CaP) bioceramics, a silicon-substituted hydroxyapatite was functionalized by integrin-adhesive cyclic-pentapeptides (c-(DfKRG)). A new two-step protocol was set up to immobilize peptides at low and controlled density on the ceramic surface and limit contamination by adsorbed molecules. To this aim, a spacer bearing c-(DfKRG)-S-PEG6-NHS molecule was synthesized and bonded to an organosilane previously covalently bonded to the ceramic surface. The functionalized ceramic was tested in vitro for MC3T3-E1 murine pre-osteoblasts. CaP ceramic surface retained good biological properties thanks to low density of bonded molecules preserving part of the bioactive CaP surface free of bioorganic molecules. The final SiHA-T-PEG6-S-c-(DfKRG) was shown to increase cell density and to improve proliferation. Furthermore, the use of a strong and stable covalent bond between inorganic and organic parts prevented early burst release of the peptide and increased the persistence of its bioactivity over time. So, this CaP ceramic associating c-(DfKRG) by covalent grafting could be considered as promising new biomaterials for bone tissue engineering.

Porphyrin-xylan-coated silica nanoparticles for anticancer photodynamic therapy.

Porphyrins are widely used in anticancer photodynamic therapy (PDT). However, low physiological solubility and lack of selectivity towards cancer cells are the main limitations of their clinical use. Nanoparticles are being intensively explored as photosensitizer carriers for PDT to overcome these limitations. The aims of this work are to synthesize core-shell hybrid nanoparticles formed by a silica core and xylan carrying a 5-(4-hydroxyphenyl)-10,15,20-triphenylporphyrin (TPPOH) shell, and evaluate their anticancer activity. To afford drug-controlled incorporation and enhance blood circulation, TPPOH was covalently linked to xylan. Different xylans with degrees of substitution in TPPOH ranging from 0.034 to 1.11, were obtained and characterized. Then, the xylan-TPPOH conjugate (PX) was used to coat the silica nanoparticles (PX SNPs). The obtained nano-objects were characterized and their therapeutic potential for photodynamic therapy evaluated against colorectal cancer cell lines. in vitro analysis showed that PX SNPs were 40-fold and 10-fold more effective against HCT116 cells and HT-29 cells respectively compared to free TPPOH.

Porphyrin-based bridged silsesquioxane nanoparticles for targeted two-photon photodynamic therapy of zebrafish xenografted with human tumor.

BACKGROUND: Bridged silsesquioxane nanoparticles (BSNs) recently described represent a new class of nanoparticles exhibiting versatile applications and particularly a strong potential for nanomedicine. AIMS: In this work, we describe the synthesis of BSNs from an octasilylated functional porphyrin precursor (PORBSNs) efficiently obtained through a click reaction. These innovative and very small-sized nanoparticles were functionalized with PEG and mannose (PORBSNs-mannose) in order to target breast tumors in vivo. METHODS AND RESULTS: The structure of these nanoparticles is constituted of porphyrins J aggregates that allow two-photon spatiotemporal excitation of the nanoparticles. The therapeutic potential of such photoactivable nanoparticles was first studied in vitro, in human breast cancer cells in culture and then in vivo on zebrafish embryos bearing human tumors. These animal models were intravenously injected with 5 nL of a solution containing PORBSNs-mannose. An hour and half after the injection of photoactivable and targeted nanoparticles, the tumor areas were excited for few seconds with a two-photon beam induced focused laser. We observed strong tumor size decrease, with the involvement of apoptosis pathway activation. CONCLUSION: We demonstrated the high targeting, imaging, and therapeutic potential of PORBSNs-mannose injected in the blood stream of zebrafish xenografted with human tumors.

Functionalization of phosphocalcic bioceramics for bone repair applications.

This work is devoted to the processing of bone morphogenetic protein (BMP-2) functionalized silicate substituted hydroxyapatite (SiHA) ceramic spheres. The motivation behind it is to develop injectable hydrogel/bioceramic composites for bone reconstruction applications. SiHA microspheres were shaped by spray drying and thoroughly characterized. The silicate substitution was used to provide preferred chemical sites at the ceramic surface for the covalent immobilization of BMP-2. In order to control the density and the release of the immobilized BMP-2, its grafting was performed via ethoxysilanes and polyethylene glycols. A method based on Kaiser's test was used to quantify the free amino groups of grafted organosilanes available at the ceramic surface for BMP-2 immobilization. The SiHA surface modification was investigated by means of X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy and thermogravimetry coupled with mass spectrometry. The BMP-2 bioactivity was assessed, in vitro, by measuring the luciferase expression of a stably transfected C3H10 cell line (C3H10-BRE/Luc cells). The results provided evidence that the BMP-2 grafted onto SiHA spheres remained bioactive.

Antibacterial activity of a photosensitive hybrid cellulose fabric.

We report the preparation of a cellulose fabric bearing derivative protoporphyrin IX units covalently attached to the cellulose backbone of a fabric. Ce(IV) redox system radical polymerization was used to polymerize methacrylic acid (MAA) onto a cotton material and to obtain cotton-g-polyMAA. Attachment of the photosensitizer, a protoporphyrin IX (PpIX) amino derivative, on cotton-g-polyMAA was realized successfully by a classical peptidic covalent link. The modified surfaces were characterized by ATR-FTIR, DRUV, TGA, and SEM methods. Under visible light irradiation, protoporphyrinic cotton showed antibacterial activity against Staphyloccoccus aureus. This concept is very promising in the field of bacterial decontamination (sterile area, hospital equipment, etc.).

Delivery of tanshinone IIA and α-mangostin from gold/PEI/cyclodextrin nanoparticle platform designed for prostate cancer chemotherapy.

A new anti-cancer drug delivery system, based on gold nanoparticles, has been designed for hydrophobic active compounds. The system is a conjugate of gold/polyethyleneimine (AuNPs/PEI) nanoparticles and sulphated ß-cyclodextrin (CD). Anionic cyclodextrin was attached to the positively charged AuNPs/PEI nanoparticles by ionic bonds. Tanshinone IIA and α-mangostin were extracted, purified and encapsulated into the AuNPs/PEI/CD nanoparticles. In vitro preliminary cell viability assays against prostate cancer cell lines PC-3 and DU145 showed that encapsulation resulted in increased cytotoxicity.

Development of curcumin-cyclodextrin/cellulose nanocrystals complexes: New anticancer drug delivery systems.

The synthesis of curcumin-cyclodextrin/cellulose nanocrystals (CNCx) nano complexes was performed. CNCx were functionalized by ionic association with cationic ß-cyclodextrin (CD) and CD/CNCx complexes were used to encapsulate curcumin. Preliminary in vitro results showed that the resulting curcumin-CD/CNCx complexes exerted antiproliferative effect on colorectal and prostatic cancer cell lines, with IC50s lower than that of curcumin alone.

Porphyrin-functionalized mesoporous organosilica nanoparticles for two-photon imaging of cancer cells and drug delivery.

The synthesis of a zinc porphyrin derivative possessing eight triethoxysilyl groups was performed through a CuAAC-click reaction. This porphyrin was covalently entrapped in ethenylene-bridged mesoporous organosilica nanoparticles which efficiently allowed performing doxorubicin delivery and two-photon imaging of breast cancer cells.

Uncommon chlorinated xanthone and other antibacterial compounds from the lichen Cladonia incrassata.

Bioassay-guided fractionation of an extract of the lichen Cladonia incrassata against Staphylococcus aureus led to a novel compound, 1,5-dihydroxy-2,4,6-trichloro-7-methylxanthone (1), along with six known compounds: (-)-usnic acid (2), didymic acid (3), condidymic acid (4), squamatic acid (5), thamnolic acid (6), and prasinic acid (7). Didymic, condidymic, and prasinic acids were isolated for the first time from C. incrassata. Didymic, condidymic, and (-)-usnic acids were active against S. aureus (a minimum inhibitory concentration of 7.5 µg/mL).

Partial structural characterization and antioxidant activity of a phenolic-xylan from Castanea sativa hardwood.

4-O-Methylglucuronoxylans (MGX) were isolated from chestnut wood sawdust using two different procedures: chlorite delignification followed by the classical alkaline extraction step, and an unusual green chemistry process of delignification using phthalocyanine/H2O2 followed by a simple extraction with hot water. Antioxidant properties of both MGX were evaluated against the stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) by electronic spin resonance (ESR). IC50 of water-extracted MGX was found to be less than 225 µg mL(-1), in contrast with alkali-extracted MGX for which no radical scavenging was observed. Characterization of extracts by colorimetric assay, GC, LC-MS and NMR spectroscopy provided some clues to understanding structure-function relationships of MGX in connection with their antioxidant activity.

Synthesis and photobiocidal properties of cationic porphyrin-grafted paper.

We report on the synthesis of cellulose paper bearing a cationic porphyrin, designed for antimicrobial applications. Tricationic porphyrin has been covalently grafted on paper, without previous chemical modification of the cellulosic support, using 1,3,5-triazine derivative as linker. The obtained porphyrin-grafted paper was characterized by infrared (ATR-FTIR), UV-visible and diffuse reflectance UV-vis (DRUV) spectroscopies to confirm the triazine linkage. Thermogravimetric analysis (TGA) was used to investigate thermal properties of grafted paper. Antimicrobial activity of porphyrin-cellulose material was tested under visible light irradiation against Staphylococcus aureus and Escherichia coli. The two bacterial strains deposited on the resulting photosensitizing filter paper are efficiently killed after illumination.

Reaction between the anesthetic agent propofol and the free radical DPPH in semiaqueous media: kinetics and characterization of the products.

The reaction of the free radical diphenylpicrylhydrazyl (DPPH ) with the anesthetic agent 2,6-diisopropylphenol (propofol, PPF) was investigated in buffered hydroalcoholic media. The kinetics was followed using a stopped-flow system. DPPH was reduced to the hydrazine analogue DPPH-H with a measured stoichiometry (DPPH /PPF) of 2. The main product of the reaction, 3,5,3',5'-tetraisopropyl-(4,4')-diphenoquinone (PPFDQ) was isolated by chromatography and its structure was fully characterized. The reaction mechanism was inferred from the stoichiometry, kinetics, and product identification. The first step, which primarily determines the kinetics, is the reaction of DPPH with PPF to produce DPPH-H and the PPF radical. The rate constant was found to be 31.8, 207, and 908 M(-1) s(-1) at pH 6.4, 7.4, and 8.4, respectively. The pH dependence is indicative of a higher reactivity of the phenolate form of PPF. Then, PPF radicals combine to form dipropofol, which is quickly oxidized to PPFDQ by the remaining DPPH . This reaction scheme is corroborated by numerical simulations of the kinetics. In the course of this study we also disclosed an unexpected effect, the photochemical degradation of PPFDQ. The need to compare antioxidants on a kinetics basis is again emphasized. In our hands, PPF presents a significantly weaker reactivity than Trolox.