A new antibacterial nano-system based on hematoporphyrin-carboxymethyl chitosan conjugate for enhanced photostability and photodynamic activity.

To promote bactericidal activity, improve photostability and safety, novel antibacterial nanoparticle system based on photodynamic action (PDA) was prepared here through conjugation of photosensitizer hematoporphyrin (HP) onto carboxymethyl chitosan (CMCS) via amide linkage and followed by ultrasonic treatment. The system was stable in PBS (pH 7.4) and could effectively inhibit the photodegradation of conjugated HP because of aggregation-caused quenching effect. ROS produced by the conjugated HP under light exposure could change the structure of nanoparticles by oxidizing the CMCS skeleton and thereby significantly promote the photodynamic activity of HP and its photodynamic activity after 6 h was higher than that of HP·2HCl under the same conditions. Antibacterial experiments showed that CMCS-HP nanoparticles had excellent photodynamic antibacterial activity, and the bacterial inhibition rates after 60 min of light exposure were greater than 97%. Safety evaluation exhibited that the nanoparticles were safe to mammalian cells, showing great potential for antibacterial therapy.

Aggregation-Dependent Photoreactive Hemicyanine Assembly as a Photobactericide.

Organic materials that show substantial reactivity under visible light have received considerable attention due to their wide applications in chemical and biological systems. Hemicyanine pigments possess a strong intramolecular donor-acceptor structure and thereby display intense absorption in the visible spectral region. However, most excitons are consumed via the twisted intramolecular charge-transfer (TICT) process, making hemicyanines generally inert to light. Herein, we describe the development of an amphiphilic hemicyanine dye whose aggregation could be easily regulated using salt or counterions. More importantly, its intrinsic photoreactivity was successfully induced by steric restriction and cofacial arrangement within the H-aggregate, thus creating an effective photobactericide. This strategy could be extended to the development of photocatalysts for photosynthesis and a photosensitizer for photodynamic therapy.

A photocleavable surfactant for top-down proteomics.

We report the identification of a photocleavable anionic surfactant, 4-hexylphenylazosulfonate (Azo), which can be rapidly degraded by ultraviolet irradiation, for top-down proteomics. Azo can effectively solubilize proteins with performance comparable to that of sodium dodecyl sulfate (SDS) and is compatible with mass spectrometry. Azo-aided top-down proteomics enables the solubilization of membrane proteins for comprehensive characterization of post-translational modifications. Moreover, Azo is simple to synthesize and can be used as a general SDS replacement in SDS-polyacrylamide gel electrophoresis.

Cationic Photopolymerized Polydiacetylenic (PDA) Micelles for siRNA Delivery.

Polymerized micelles obtained by photopolymerization of diacetylenic surfactants and which are forming polydiacetylenic systems (PDAs) have recently gained interest as stabilized monodisperse systems showing potential for the delivery of hydrophobic drugs as well as of larger biomolecules such as nucleic acids. Introduction of pH-sensitive histidine groups at the surface of the micellar PDA systems allows for efficient delivery of siRNA resulting in specific gene silencing through RNA interference. Here, we describe the detailed experimental procedure for the reproducible preparation of these photopolymerized PDA micelles. We provide physicochemical characterization of these nanomaterials by dynamic light scattering, transmission electron microscopy, and diffusion ordered spectroscopy. Moreover, we describe standardized biological tests to evaluate the silencing efficiency by the use of a cell line constitutively expressing the luciferase reporter gene.

A photo-controlled hyaluronan-based drug delivery nanosystem for cancer therapy.

In this paper, a novel photo-controlled drug-loaded nanomicelles were self-assembled by the amphiphile of hyaluronan-o-nitrobenzyl-stearyl chain (HA-NB-SC) with doxorubicin (DOX) encapsulated within the hydrophobic core. DOX-loaded HA-NB-SC nanomicelles are ∼139 nm in diameter. CD44-overexpressed HeLa cells can easily take up HA-NB-SC micelles through recognition of HA moiety. DOX-loaded HA-NB-SC nanomicelles could be disassembled upon UV light (365 nm) and consequently, release DOX at desired pathological sites. Furtherly, nitrosobenzaldehyde derivative, photo-induced products of HA-NB-SC and DOX could inhibit the proliferation of HeLa cells together. This strategy may shed some light on delivery of hydrophobic anti-cancer drugs in a controlled manner.

Photoinduced Intermolecular Electron Transfer Mediated by the Colloidal Tyrosyl Bolaamphiphile Assembly.

The self-assembly of tyrosyl bolaamphiphiles is exploited to create a colloidal protein-like host matrix, upon which sacrificial electron-donor molecules associate to create a photosystem II (PSII) mimetic electron-relay system. This system harnesses the tyrosine phenol groups abundant on the surface of the assemblies to mediate photoinduced intermolecular electron transfer. Compared with the l-tyrosine molecules, the tyrosyl bolaamphiphile assembly facilitates electron transfer from the sacrificial electron donor to the oxidized photosensitizer. The enhanced electron relay is likely to be driven by the host function of the assembly associated with the sacrificial electron donor and by the suppression of the oxidative cross-linking of phenoxyl radicals. The tyrosyl bolaamphiphile assembly is advantageous in the construction of a PSII mimetic system with a protein-like nature and displaying biochemical functions.

Pure white light emission and charge transfer in organogels of symmetrical and unsymmetrical π-chromophoric oligo-p-(phenyleneethynylene) bola-amphiphiles.

Two novel bola-amphiphilic oligo-p-(phenyleneethynylene) (OPE) dicarboxylates have been synthesized having non-polar and mixed-polar side chains. This led to gelation in both with vesicular morphology. Upon in situ loading of a suitable dye and redox-active molecule, pure white light emitting and charge transfer (CT)-gels, respectively, were realized.

Photosensitive Peptidomimetic for Light-Controlled, Reversible DNA Compaction.

Light-induced DNA compaction as part of nonviral gene delivery was investigated intensively in the past years, although the bridging between the artificial light switchable compacting agents and biocompatible light insensitive compacting agents was not achieved until now. In this paper, we report on light-induced compaction and decompaction of DNA molecules in the presence of a new type of agent, a multivalent cationic peptidomimetic molecule containing a photosensitive Azo-group as a branch (Azo-PM). Azo-PM is synthesized using a solid-phase procedure during which an azobenzene unit is attached as a side chain to an oligo(amidoamine) backbone. We show that within a certain range of concentrations and under illumination with light of appropriate wavelengths, these cationic molecules induce reversible DNA compaction/decompaction by photoisomerization of the incorporated azobenzene unit between a hydrophobic trans- and a hydrophilic cis-conformation, as characterized by dynamic light scattering and AFM measurements. In contrast to other molecular species used for invasive DNA compaction, such as widely used azobenzene containing cationic surfactant (Azo-TAB, C4-Azo-OCX-TMAB), the presented peptidomimetic agent appears to lead to different complexation/compaction mechanisms. An investigation of Azo-PM in close proximity to a DNA segment by means of a molecular dynamics simulation sustains a picture in which Azo-PM acts as a multivalent counterion, with its rather large cationic oligo(amidoamine) backbone dominating the interaction with the double helix, fine-tuned or assisted by the presence and isomerization state of the Azo-moiety. However, due to its peptidomimetic backbone, Azo-PM should be far less toxic than photosensitive surfactants and might represent a starting point for a conscious design of photoswitchable, biocompatible vectors for gene delivery.

Photopolymerized micelles of diacetylene amphiphile: physical characterization and cell delivery properties.

A series of polydiacetylene (PDA) - based micelles were prepared from diacetylenic surfactant bearing polyethylene glycol, by increasing UV-irradiation times. These polymeric lipid micelles were analyzed by physicochemical methods, electron microscopy and NMR analysis. Cellular delivery of fluorescent dye suggests that adjusting the polymerization state is vital to reach the full in vitro potential of PDA-based delivery systems.

Degradation of the commercial surfactant nonylphenol ethoxylate by advanced oxidation processes.

Four different oxidation process, namely direct photolysis (DP) and three advanced oxidation processes (heterogeneous photocatalysis - HP, eletrochemical oxidation - EO and photo-assisted electrochemical oxidation - PEO) were applied in the treatment of wastewater containing nonylphenol ethoxylate (NPnEO). The objective of this work was to determine which treatment would be the best option in terms of degradation of NPnEO without the subsequent generation of toxic compounds. In order to investigate the degradation of the surfactant, the processes were compared in terms of UV/Vis spectrum, mineralization (total organic carbon), reaction kinetics, energy efficiency and phytotoxicity. A solution containing NPnEO was prepared as a surrogate of the degreasing wastewater, was used in the processes. The results showed that the photo-assisted processes degrade the surfactant, producing biodegradable intermediates in the reaction. On the other hand, the electrochemical process influences the mineralization of the surfactant. The process of PEO carried out with a 250W lamp and a current density of 10mA/cm(2) showed the best results in terms of degradation, mineralization, reaction kinetics and energy consumption, in addition to not presenting phytotoxicity. Based on this information, this process can be a viable alternative for treating wastewater containing NPnEO, avoiding the contamination of water resources.

Synthesis and characterization of amphiphilic photocleavable polymers based on dextran and substituted-ɛ-caprolactone.

In this study, we synthesized photocleavable amphiphilic block copolymers containing photodegradable linkers, 5-hydroxy-2-nitrobenzyl alcohol, as junction points between hydrophilic dextran (or maltodextrin) and hydrophobic poly(4-substituted-ɛ-caprolactone) chains, by using a combination of ring-opening polymerization and nucleophilic substitution reactions. When the polymer solutions were exposed to ultraviolet (UV) irradiation, major structural and morphological changes were observed in the particles. The copolymers were biodegradable and biocompatible, and they can self-assemble into spherical photoresponsive micelles. Fluorescence emission measurements indicated the release of Nile red, a hydrophobic dye, encapsulated by the Dex-ONB-PXCL micelles, in response to irradiation caused by the disruption of the micelles. Light-triggered bursts were observed for indomethacin (IMC)-loaded Dex-ONB-PXCL micelles during the first 5 h. The nanoparticles were associated with nonsignificant toxicity at concentrations of less than 100 µg mL(-1). The confocal microscopy and flow cytometry results showed that the uptake of DOX-loaded micelles by HeLa cells was slightly less than that of free DOX, and it was predominantly retained in the cytoplasm.

Treatment of solutions containing nonylphenol ethoxylate by photoelectrooxidation.

In this work the photoelectrooxidation (PEO) was applied in the treatment of a solution containing nonylphenol ethoxylate surfactant (NP4EO). The use of different lamps (125 and 250 W), current density (5 and 10 mA cm(-2)) and treatment time (0, 60, 120, 180 and 240 min) were investigated. The samples were characterized by UV/Vis, total organic carbon (TOC), gas chromatography associated to mass spectroscopy (GC/MS) and ecotoxicity. The reaction kinetics were calculated and the light flux and pH were measured. The results of analysis by UV/Vis show that there is degradation of nonylphenol ethoxylated in the treatment time of 240 min for all configurations, and the configurations that used a 250 W lamp and a current density of 10 mA cm(-2) obtained better results, with a reduction of 83% in TOC, indicating a high mineralization of the surfactant. It was further found in the GC/MS that the configurations that used the 125 W lamp promoted a smaller incident light flux on the solution, and, regardless of the applied current density, it was generated the reaction intermediate nonylphenol, more toxic than the parent compound. The opposite can be observed when a 250 W lamp was used, which produced a higher incident light flux. Based on the degradation products detected, a simplified mechanism for degradation of nonylphenol ethoxylate was proposed. Although a treatment time of 240 min with photoelectrooxidation with different configurations was not effective in the complete mineralization of the compound, a promising process was developed with the treatment using a lamp of 250 W and a current density of 10 mA cm(-2), which generated a solution with less toxicity than the original one.

Sonication-induced formation of size-controlled self-assemblies of amphiphilic Janus-type polymers as optical tumor-imaging agents.

In this study, amphiphilic Janus-type polymers were synthesized via ring-opening metathesis polymerization (ROMP), multiple vicinal diol formation, and grafting of poly(ethylene glycol) monomethyl ether (mPEG). These amphiphilic polymers formed self-assemblies, which were a mixture of micelles and multimicellar aggregates, in water. By choosing suitable Janus-type polymers and irradiating an aqueous solution of polymers using a sonicator, either small micelles or large multimicellar aggregates were obtained selectively. Hydrophobic substituents controlled the aggregation-disaggregation behavior, leading to the formation of metastable self-assemblies by sonication. The formation of self-assemblies with a uniform size was affected by ultrasonic frequency, rather than power. In vivo optical tumor imaging revealed that the large-size multimicellar aggregates persisting for a long time in blood circulation slowly accumulated in tumor tissues. In contrast, the tumor site was rapidly, clearly visualized using the small-size micelles.

Photo responsive monoolein cubic phase containing coumarin-Tween 20 conjugates.

Photo-responsive monoolein (MO) cubic phase was developed by incorporating coumarin-Tween 20 conjugate in the cubic phase. 7-chlorocarbonylmethoxycoumarin was obtained from 7-hydroxycoumarin through three-step reactions with the yield of 19.8% and it was conjugated to the head group of Tween 20. The molar ratio of the coumarin derivative/Tween 20 in the conjugate was about 1/1 on ¹H NMR spectrum. The cubic phase was prepared by melting the mixture of MO/conjugate (100/0.88, w/w) and hydrating the molten mixture with 5(6)-carboxyfluorescein (CF) solution. UV irradiation (254 nm and/or 365 nm) for 3 h resulted in 1.27% to 2.69% reduction in the double bond of MO but the cubic phase was stable in terms of its integrity under the UV irradiation. The release of CF from coumarin-Tween 20 conjugate-incorporated cubic phase was somewhat suppressed by being subjected to the UV irradiation. The head groups of coumarin-Tween 20 conjugate will be cross-linked so the diffusion in the water channel will be suppressed.

UVB irradiation changes genotoxic potential of nonylphenolpolyethoxylates--remarkable generation of γ-H2AX with degradation of chemical structure.

Nonylphenolpolyethoxylates (NPEOs) are non-ionic surfactants widely used for industrial and household purposes. In actual environments, NPEOs can be biodegraded, but the products are reported to be more persistent and toxic than the parent compounds. NPEOs are also exposed to sunlight and degraded. Studies on the photodegradation of NPEOs have focused mainly on chemical changes after exposure to light. Toxic changes of photodegraded products correlating to the chemical changes are not completely understood. In this study, we examined the genotoxicity of UVB-irradiated NPEOs having ethylene oxide units 15 and 70 in a human breast adenocarcinoma cell line, MCF-7, based on the phosphorylation of histone H2AX (γ-H2AX), a sensitive marker for DNA damage. We clarified that UVB irradiation drastically changed the genotoxic potential of NPEOs: NPEO(15)'s ability to generate γ-H2AX was significantly reduced, whereas non-genotoxic NPEO(70) became able to generate γ-H2AX. Flow cytometric analysis showed that the γ-H2AX generated by UVB-irradiated NPEO(70)was produced independent of cell cycle phases. In addition, its production involved the activation of ATM or DNA-PK, a general signalling pathway in response to DNA double strand breaks. High-performance liquid chromatography analysis indicated that the formation of NPEO intermediates with a short side-chain like NPEO(15) was the cause of the γ-H2AX generation. This study suggests the importance of taking the genotoxicity of photodegraded intermediates into consideration when conducting risk assessments of environmental pollutants.

A novel approach for enhancing metal ion separation using acoustic nebulisation.

A novel technique for anionic surfactant assisted separation and preconcentration of metal cations was developed using ultrasound induced nebulization at MHz frequency. The ions of copper, zinc, cadmium, and calcium were used as model analytes. Analysis of the aerosol using flame atomic absorption spectrometry showed enrichment factors for the metal ions studied between 5 and 8, when dilute solutions containing sodium dodecylsulfate and the metal ions were nebulized. The mechanism of metal ion enrichment was explained based on surfactant adsorption and the droplet model for aerosol droplets. It was demonstrated that further increase in the enrichment factor could be achieved by increasing the ultrasound frequency, thus producing smaller droplets.

Light-regulated mRNA condensation by a photosensitive surfactant works as a series photoswitch of translation activity in the presence of small RNAs.

AzoTAB, a photosensitive azobenzene cationic surfactant, which phototriggers translation activity through light-regulated condensation of mRNA, is added to a translation solution containing several mRNAs, which can be selectively silenced by specific small RNAs. We find that gene silencing by small RNAs remains functional regardless of AzoTAB concentration and UV illumination. In the absence of UV, the translation of all genes present in the medium is partially to fully inhibited depending on AzoTAB concentration. In contrast, the application of a short UV stimulus (365 nm for 1.5 min) results in the selective photoactivation of genes that are not silenced by small RNA. These results show that light-regulated condensation by AzoTAB works as a sequence-independent series photoswitch added to parallel sequence-specific regulation by small RNAs.

Photoreversible fragmentation of a liquid interface for micro-droplet generation by light actuation.

We describe a method to induce by light a reversible switch from a continuous two-phase laminar flow to a droplet generating regime, in microfluidic devices with a usual water-in-oil flow focusing geometry. It consists in adding a photosensitive surfactant to the aqueous phase to modulate using light the interfacial energy between flowing liquids and the microfluidic substrate. We show that UV irradiation induces liquid fragmentation into monodisperse water microdroplets and that many cycles of reversible and rapid switches (<2 s) between continuous laminar flows and stable droplet regimes can be realized. By spatially controlling the application of the light stimulus, we also demonstrate the first spatially resolved remote induction of droplet generation.

Dynamics of counterion binding during acoustic nebulisation of surfactant solutions.

A metal ion (Cu(2+)) and a complex copper species, copper (II) bis-bipyridine, were used as alternate counterions in an aqueous surfactant solution of sodium dodecylbenzenesulfonate (SDBS) to investigate the dynamics of counterion interactions in an acoustic field. Sonoluminescence spectral studies showed that such counterions were able to replace sodium ions at the interface, even when the interface was rapidly oscillating under the acoustic field. Ultrasound induced nebulisation was then used to probe the interfacial profile of surfactant and bound counterions in a dynamic environment. At low bulk concentrations, the copper (II) bis-bipyridine cation was more effective at enhancing the loading of the dodecylbenzenesulfonate anion on the interface, due to its documented greater binding ability. However, at higher bulk concentrations, the movement of this cation is limited by its larger size and the smaller Cu(2+) cation is more effective in enhancing the loading of the dodecylbenzenesulfonate anion. The results show that under dynamic conditions, the surface concentrations are governed by mass transfer kinetics rather than equilibrium thermodynamics.