Synthesis and Self-Assembly of UV-Cross-Linkable Amphiphilic Polyoxazoline Block Copolymers: Importance of Multitechnique Characterization.

In the nanomedicine field, there is a need to widen the availability of nanovectors to compensate for the increasingly reported side effects of poly(ethene glycol). Nanovectors enabling cross-linking can further optimize drug delivery. Cross-linkable polyoxazolines are therefore relevant candidates to address these two points. Here we present the synthesis of coumarin-functionalized poly(2-alkyl-2-oxazoline) block copolymers, namely, poly(2-methyl-2-oxazoline)-block-poly(2-phenyl-2-oxazoline) and poly(2-methyl-2-oxazoline)-block-poly(2-butyl-2-oxazoline). The hydrophilic ratio and molecular weights were varied in order to obtain a range of possible behaviors. Their self-assembly after nanoprecipitation or film rehydration was examined. The resulting nano-objects were fully characterized by transmission electron microscopy (TEM), cryo-TEM, multiple-angle dynamic and static light scattering. In most cases, the formation of polymer micelles was observed, as well as, in some cases, aggregates, which made characterization more difficult. Cross-linking was performed under UV illumination in the presence of a coumarin-bearing cross-linker based on polymethacrylate derivatives. Addition of the photo-cross-linker and cross-linking resulted in better-defined objects with improved stability in most cases.

Quantitative Kinetic Modeling in Photoresponsive Supramolecular Chemistry: The Case of Water-Soluble Azobenzene/Cyclodextrin Complexes.

Hydrophilic host-guest complexes, consisting of water-soluble azobenzene and α-, ß-, or γ-cyclodextrins, have been proposed as a model to study supramolecular photoresponsive systems in aqueous environments through a full spectrometric approach combined with a simulation and data fitting methodology. Various essential and complementary spectroscopic techniques have been used: circular dichroism to determine whether the complex is formed or not, NMR for the stoichiometry elucidation, and UV-visible spectrophotometry to obtain the association equilibrium constant of each complex and the quantum yield for each photochemical process. A step-by-step fitting procedure is presented, which enables the determination of all thermodynamic and photokinetic parameters. A sequential methodology is applied to dissipate all uncertainties on the variability of the results and to develop a relevant and reliable protocol applicable to other types of complexes. The proposed procedure has thus been shown to be very robust and largely applicable to other photoresponsive host-guest systems.

Molecular-Scale Understanding of the Embrittlement in Polyethylene Ocean Debris.

The fate of plastic waste is a pressing issue since it forms a visible and long-lived reminder of the environmental impact of consumer habits. In this study, we examine the structural changes in the lamellar arrangements of semicrystalline polyethylene (PE) packaging waste with the aim of understanding the physical mechanisms of embrittlement in PE exposed to the marine environment. PE microplastics and macroplastics from identifiable PE packaging were collected in the Atlantic Ocean and compared to new PE boxes. Several experimental techniques interrogate the effects of environmental exposure on their bulk and surface properties. Size exclusion chromatography determines the molecular weight distribution of the PE polymer chains and differential scanning calorimetry gives the crystallinity. Small- and wide-angle X-ray scattering examines the packing of PE chains into semicrystalline lamellae. Longitudinal acoustic mode Raman spectroscopy provides a complementary measurement of the length of PE polymer chains extending through the crystalline lamellar domains. While there is a high degree of uncertainty in the time scale for the changes, the overall picture at the molecular scale is that although PE becomes more crystalline with environmental exposure, the lamellar order present in new packing boxes is disrupted by the weathering process. This process has important implications for embrittlement and subsequent degradation.

Microstructure Characterization of Oceanic Polyethylene Debris.

Plastic pollution has become a worldwide concern. It was demonstrated that plastic breaks down to nanoscale particles in the environment, forming so-called nanoplastics. It is important to understand their ecological impact, but their structure is not elucidated. In this original work, we characterize the microstructure of oceanic polyethylene debris and compare it to the nonweathered objects. Cross sections are analyzed by several emergent mapping techniques. We highlight deep modifications of the debris within a layer a few hundred micrometers thick. The most intense modifications are macromolecule oxidation and a considerable decrease in the molecular weight. The adsorption of organic pollutants and trace metals is also confined to this outer layer. Fragmentation of the oxidized layer of the plastic debris is the most likely source of nanoplastics. Consequently the nanoplastic chemical nature differs greatly from plastics.

Self-assembled polymeric vectors mixtures: characterization of the polymorphism and existence of synergistic effects in photodynamic therapy.

The objective of this work was to assess the relation between the purity of polymeric self-assemblies vectors solution and their photodynamic therapeutic efficiency. For this, several amphiphilic block copolymers of poly(ethyleneoxide-b-ε-caprolactone) have been used to form self-assemblies with different morphologies (micelles, worm-like micelles or vesicles). In a first step, controlled mixtures of preformed micelles and vesicles have been characterized both by dynamic light scattering and asymmetrical flow field flow fractionation (AsFlFFF). For this, a custom-made program, STORMS, was developed to analyze DLS data in a thorough manner by providing a large set of fitting parameters. This showed that DLS only sensed the larger vesicles when the micelles/vesicles ratio was 80/20 w/w. On the other hand, AsFlFFF allowed clear detection of the presence of micelles when this same ratio was as low as 10/90. Subsequently, the photodynamic therapy efficiency of various controlled mixtures was assessed using multicellular spheroids when a photosensitizer, pheophorbide a, was encapsulated in the polymer self-assemblies. Some mixtures were shown to be as efficient as monomorphous systems. In some cases, mixtures were found to exhibit a higher PDT efficiency compared to the individual nano-objects, revealing a synergistic effect for the efficient delivery of the photosensitizer. Polymorphous vectors can therefore be superior in therapeutic applications.

Drug Release by Direct Jump from Poly(ethylene-glycol-b-ε-caprolactone) Nano-Vector to Cell Membrane.

Drug delivery by nanovectors involves numerous processes, one of the most important being its release from the carrier. This point still remains unclear. The current work focuses on this point using poly(ethyleneglycol-b-ε-caprolactone) micelles containing either pheophorbide-a (Pheo-a) as a fluorescent probe and a phototoxic agent or fluorescent copolymers. This study showed that the cellular uptake and the phototoxicity of loaded Pheo-a are ten times higher than those of the free drug and revealed a very low cellular penetration of the fluorescence-labeled micelles. Neither loaded nor free Pheo-a displayed the same cellular localization as the labeled micelles. These results imply that the drug entered the cells without its carrier and probably without a disruption, as suggested by their stability in cell culture medium. These data allowed us to propose that Pheo-a directly migrates from the micelle to the cell without disruption of the vector. This mechanism will be discussed.

Room-Temperature, Strain-Tunable Orientation of Magnetization in a Hybrid Ferromagnetic Co Nanorod-Liquid Crystalline Elastomer Nanocomposite.

Hybrid nanocomposites based on magnetic nanoparticles dispersed in liquid crystalline elastomers are fascinating emerging materials. Their expected strong magneto-elastic coupling may open new applications as actuators, magnetic switches, and for reversible storage of magnetic information. We report here the synthesis of a novel hybrid ferromagnetic liquid crystalline elastomer. In this material, highly anisotropic Co nanorods are aligned through a cross-linking process performed in the presence of an external magnetic field. We obtain a highly anisotropic magnetic material which exhibits remarkable magneto-elastic coupling. The nanorod alignment can be switched at will at room temperature by weak mechanical stress, leading to a change of more than 50 % of the remnant magnetization ratio and of the coercive field.

Polymeric micelles encapsulating photosensitizer: structure/photodynamic therapy efficiency relation.

Various polymeric micelles were formed from amphiphilic block copolymers, namely, poly(ethyleneoxide-b-ε-caprolactone), poly(ethyleneoxide-b-d,l-lactide), and poly(ethyleneoxide-b-styrene). The micelles were characterized by static and dynamic light scattering, electron microscopy, and asymmetrical flow field-flow fractionation. They all displayed a similar size close to 20 nm. The influence of the chemical structure of the block copolymers on the stability upon dilution of the polymeric micelles was investigated to assess their relevance as carriers for nanomedicine. In the same manner, the stability upon aging was assessed by FRET experiments under various experimental conditions (alone or in the presence of blood proteins). In all cases, a good stability over 48 h for all systems was encountered, with PDLLA copolymer-based systems being the first to release their load slowly. The cytotoxicity and photocytotoxicity of the carriers were examined with or without their load. Lastly, the photodynamic activity was assessed in the presence of pheophorbide a as photosensitizer on 2D and 3D tumor cell culture models, which revealed activity differences between the 2D and 3D systems.

Asymmetrical flow field-flow fractionation with multi-angle light scattering and quasi-elastic light scattering for characterization of polymersomes: comparison with classical techniques.

Polymersomes formed from amphiphilic block copolymers, such as poly(ethyleneoxide-b-ε-caprolactone) (PEO-b-PCL) or poly(ethyleneoxide-b-methylmethacrylate), were characterized by asymmetrical flow field-flow fractionation coupled with quasi-elastic light scattering (QELS), multi-angle light scattering (MALS), and refractive index detection, leading to the determination of their size, shape, and molecular weight. The method was cross-examined with more classical ones, like batch dynamic and static light scattering, electron microscopy, and atomic force microscopy. The results show good complementarities between all the techniques; asymmetrical flow field-flow fractionation being the most pertinent one when the sample exhibits several different types of population.

Coumarin-poly(2-oxazoline)s as synergetic and protein-undetected nanovectors for photodynamic therapy.

Because of the difficult challenges of nanopharmaceutics, the development of a variety of nanovectors is still highly desired. Photodynamic therapy, which uses a photosensitizer to locally produce reactive oxygen species to kill the undesired cells, is a typical example for which encapsulation has been shown to be beneficial. The present work describes the use of coumarin-functionalized polymeric nanovectors based on the self-assembly of amphiphilic poly(2-oxazoline)s. Encapsulation of pheophorbide a, a known PDT photosensitizer, is shown to lead to an increased efficiency compared to the un-encapsulated version. Interestingly, the presence of coumarin both enhances the desired photocytotoxicity and enables the crosslinking of the vectors. Various nanovectors are examined, differing by their size, shape and hydrophilicity. Their behaviour in PDT protocols on HCT-116 cells monolayers is described, the influence of their crosslinking commented. Furthermore, the formation of a protein corona is assessed.

Secured Nanosynthesis-Deposition Aerosol Process for Composite Thin Films Incorporating Highly Dispersed Nanoparticles.

Application of nanocomposites in daily life requires not only small nanoparticles (NPs) well dispersed in a matrix, but also a manufacturing process that is mindful of the operator and the environment. Avoiding any exposure to NPs is one such way, and direct liquid reaction-injection (DLRI) aims to fulfill this need. DLRI is based on the controlled in situ synthesis of NPs from the decomposition of suitable organometallic precursors in conditions that are compatible with a pulsed injection mode of an aerosol into a downstream process. Coupled with low-pressure plasma, DLRI produces nanocomposite with homogeneously well-dispersed small nanoparticles that in the particular case of ZnO-DLC nanocomposite exhibit unique properties. DLRI favorably compares with the direct liquid injection of ex situ formed NPs. The exothermic hydrolysis reaction of the organometallic precursor at the droplet-gas interface leads to the injection of small and highly dispersed NPs and, consequently, the deposition of fine and controlled distribution in the nanocomposite. The scope of DLRI nanosynthesis has been extended to several metal oxides such as zinc, tin, tungsten, and copper to generalize the concept. Hence, DLRI is an attractive method to synthesize, inject, and deposit nanoparticles and meets the prevention and atom economy requirements of green chemistry.

Terahertz Spectroscopy Sheds Light on Real-Time Exchange Kinetics Occurring through Plasma Membrane during Photodynamic Therapy Treatment.

Methods to follow in real time complex processes occurring along living cell membranes such as cell permeabilization are rare. Here, the terahertz spectroscopy reveals early events in plasma membrane alteration generated during photodynamic therapy (PDT) protocol, events which are not observable in any other conventional biological techniques performed in parallel as comparison. Photodynamic process is examined in Madin-Darby canine kidney cells using Pheophorbide (Pheo) photosensitizer alone or alternatively encapsulated in poly(ethylene oxide)-block-poly(ε-caprolactone) micelles for drug delivery purpose. Terahertz spectroscopy (THz) reveals that plasma membrane permeabilization starts simultaneously with illumination and is stronger when photosensitizer is encapsulated. In parallel, the exchange of biological species is assessed. Over several hours, this conventional approach demonstrates significant differences between free and encapsulated Pheo, the latter leading to high penetration of propidium iodide, Na+ and Ca2+ ions, and a high level of leakage of K+ , ATP, and lactate dehydrogenase. THz spectroscopy provides, in a single measurement, the relative number of defects per membrane surface created after PDT, which is not achieved by any other method, providing early, sensitive real-time information. THz spectroscopy is therefore a promising technique and can be applied to any biological topic requiring the examination of short-term plasma membrane permeabilization.

Photoswitchable assembly of long-lived azobenzenes in water using visible light.

HYPOTHESIS: Switchable assemblies relevant for bio-applications may be accessed from water-soluble tetra-ortho-substituted azobenzenes that reversibly self-assemble and form complexes with ß-cyclodextrin under visible light. EXPERIMENTS: Two azobenzenes bearing either four fluorines or two chlorines and two fluorines in the ortho positions were synthesised with short poly(ethylene oxide) tails for water solubility. Photophysical properties were determined by UV-vis and 1H NMR spectroscopies, complexation with ß-cyclodextrin was assessed by 1H NMR spectroscopy, and self-assembly in water was investigated by static and dynamic light scattering. FINDINGS: Both molecules underwent trans-cis isomerization at 530 nm and cis-trans isomerization at 415 nm, with the cis forms exhibiting thermal half-lives > 300 days at room temperature. Both molecules formed inclusion complexes with ß-cyclodextrin in water, with cis-4F-AZO-PEO binding 3-fold stronger than trans, and 2Cl2F-AZO-PEO binding significantly weaker. Self-assembly of pure 2Cl2F-AZO-PEO in water showed an open association process regardless of configuration, while 4F-AZO-PEO showed an open association process for cis (Nagg increasing from 30 to 1000) but a closed association process for trans (Nagg stable at âˆ¼ 170). Aqueous solutions of 2Cl2F-AZO-PEO showed cloud points close to 45 °C, while the 4F-AZO-PEO isomers presented well-separated cloud points allowing reversible and all-visible transition between clear and turbid states at room temperature.

Hybrid polymeric micelles stabilized by gallium ions: Structural investigation.

The addition of gallium ions to a solution of a double-hydrophilic block copolymer, i.e. poly(ethylene oxide)-block-poly(acrylic acid), leads to the spontaneous formation of highly monodisperse micelles with a Hybrid PolyIon Complexes (HPICs) core. By combining several techniques, a precise description of the HPIC architecture was achieved. In particular and for the first time, NMR and anomalous small angle X-ray scattering (ASAXS) enable tracking of the inorganic ions in solution and highlighting the co-localization of the gallium and the poly(acrylic acid) blocks in a rigid structure at the core of the micelle. Such a core has a radius of ca 4.3 nm while the complete nano-object with its poly(ethylene oxide) shell has a total radius of ca 11 nm. The aggregation number was also estimated using the ASAXS results. This comprehensive structural characterization of the Ga HPICs corroborates the assumptions made for HPICs based on other inorganic ions and demonstrates the universality of the HPIC structure leading, for example, to new families of contrast agents in medical imaging.

Hybrid giant lipid vesicles incorporating a PMMA-based copolymer.

BACKGROUND: In recent years, there has been a growing interest in the formation of copolymer-lipid hybrid self-assemblies, which allow combining and improving the main features of pure lipid-based and copolymer-based systems known for their potential applications in the biomedical field. As the most common method used to obtain giant vesicles is electroformation, most systems so far used low Tg polymers for their flexibility at room temperature. METHODS: Copolymers used in the hybrid vesicles have been synthesized by a modified version of the ATRP, namely the Activators ReGenerated by Electron Transfer ATRP and characterized by NMR and DSC. Giant hybrid vesicles have been obtained using electroformation and droplet transfer method. Confocal fluorescence microscopy was used to image the vesicles. RESULTS: Electroformation enabled to obtain hybrid vesicles in a narrow range of compositions (15 mol% was the maximum copolymer content). This range could be extended by the use of a droplet transfer method, which enabled obtaining hybrid vesicles incorporating a methacrylate-based polymer in a wide range of compositions. Proof of the hybrid composition was obtained by fluorescence microscopy using labeled lipids and copolymers. CONCLUSIONS: This work describes for the first time, to the best of our knowledge, the formation of giant hybrid polymer/lipid vesicles formed with such a content of a polymethylmethacrylate copolymer, the glass temperature of which is above room temperature. GENERAL SIGNIFICANCE: This work shows that polymer structures, more complex than the ones mostly employed, can be possibly included in giant hybrid vesicles by using the droplet transfer method. This will give easier access to functionalized and stimuli-responsive giant vesicles and to systems exhibiting a tunable permeability, these systems being relevant for biological and technological applications.

Heteroaggregates of Polystyrene Nanospheres and Organic Matter: Preparation, Characterization and Evaluation of Their Toxicity to Algae in Environmentally Relevant Conditions.

The environmental fate and behavior of nanoplastics (NPs) and their toxicity against aquatic organisms are under current investigation. In this work, relevant physicochemical characterizations were provided to analyze the ecotoxicological risk of NPs in the aquatic compartment. For this purpose, heteroaggregates of 50 nm polystyrene nanospheres and natural organic matter were prepared and characterized. The kinetic of aggregation was assimilated to a reaction-limited colloid aggregation mode and led to the formation of heteroaggregates in the range of 100-500 nm. Toxicities of these heteroaggregates and polystyrene nanospheres (50 and 350 nm) were assessed for a large range of concentrations using four benthic and one planktonic algal species, in regards to particle states in the media. Heteroaggregates and nanospheres were shown to be stable in the exposure media during the ecotoxity tests. The algal species exhibited very low sensitivity (growth and photosynthetic activity), with the noteworthy exception of the planktonic alga, whose growth increased by more than 150% with the heteroaggregates at 1 µg L-1. Despite the lack of a strong direct effect of the NPs, they may still impair the functioning of aquatic ecosystems by destabilizing the competitive interactions between species. Moreover, further work should assess the toxicity of NPs associated with other substances (adsorbed pollutants or additives) that could enhance the NP effects.

Vascular and extracellular matrix remodeling by physical approaches to improve drug delivery at the tumor site.

INTRODUCTION: Modern comprehensive studies of tumor microenvironment changes allowed scientists to develop new and more efficient strategies that will improve anticancer drug delivery on site. The tumor microenvironment, especially the dense extracellular matrix, has a recognized capability to hamper the penetration of conventional drugs. Development and co-applications of strategies aiming at remodeling the tumor microenvironment are highly demanded to improve drug delivery at the tumor site in a therapeutic prospect. AREAS COVERED: Increasing indications suggest that classical physical approaches such as exposure to ionizing radiations, hyperthermia or light irradiation, and emerging ones as sonoporation, electric field or cold plasma technology can be applied as standalone or associated strategies to remodel the tumor microenvironment. The impacts on vasculature and extracellular matrix remodeling of these physical approaches will be discussed with the goal to improve nanotherapeutics delivery at the tumor site. EXPERT OPINION: Physical approaches to modulate vascular properties and remodel the extracellular matrix are of particular interest to locally control and improve drug delivery and thus increase its therapeutic index. They are particularly powerful as adjuvant to nanomedicine delivery; the development of these technologies could have extremely widespread implications for cancer treatment.[Figure: see text].

Rational design of block copolymer self-assemblies in photodynamic therapy.

Photodynamic therapy is a technique already used in ophthalmology or oncology. It is based on the local production of reactive oxygen species through an energy transfer from an excited photosensitizer to oxygen present in the biological tissue. This review first presents an update, mainly covering the last five years, regarding the block copolymers used as nanovectors for the delivery of the photosensitizer. In particular, we describe the chemical nature and structure of the block copolymers showing a very large range of existing systems, spanning from natural polymers such as proteins or polysaccharides to synthetic ones such as polyesters or polyacrylates. A second part focuses on important parameters for their design and the improvement of their efficiency. Finally, particular attention has been paid to the question of nanocarrier internalization and interaction with membranes (both biomimetic and cellular), and the importance of intracellular targeting has been addressed.

Electroporation does not affect human dermal fibroblast proliferation and migration properties directly but indirectly via the secretome.

Aesthetic wound healing is often experienced by patients after electrochemotherapy. We hypothesized that pulsed electric fields applied during electrochemotherapy (ECT) or gene electrotransfer (GET) protocols could stimulate proliferation and migration of human cutaneous cells, as described in protocols for electrostimulation of wound healing. We used videomicroscopy to monitor and quantify in real time primary human dermal fibroblast behavior when exposed in vitro to ECT and GET electric parameters, in terms of survival, proliferation and migration in a calibrated scratch wound assay. Distinct electric field intensities were applied to allow gradient in cell electropermeabilization while maintaining reversible permeabilization conditions, in order to mimic in vivo heterogeneous electric field distribution of complex tissues. Neither galvanotaxis nor statistical modification of fibroblast migration were observed in a calibrated scratch wound assay after application of ECT and GET parameters. The only effect on proliferation was observed under the strongest GET conditions, which drastically reduced the number of fibroblasts through induction of mitochondrial stress and apoptosis. Finally, we found that 24 h-conditioned cell culture medium by electrically stressed fibroblasts tended to increase the migration properties of cells that were not exposed to electric field. RT-qPCR array indicated that several growth factor transcripts were strongly modified after electroporation.

Role of Polymer Micelles in the Delivery of Photodynamic Therapy Agent to Liposomes and Cells.

The use of nanocarriers for hydrophobic photosensitizers, in the context of photodynamic therapy (PDT) to improve pharmacokinetics and bio-distribution, is well-established. However, the mechanisms at play in the internalization of nanocarriers are not well-elucidated, despite its importance in nanocarrier design. In this study, we focus on the mechanisms involved in copolymer poly(ethylene oxide)-block-poly(-caprolactone) PEO-PCL and poly(ethylene oxide)-block-poly styrene PEO-PS micelles - membrane interactions through complementary physico-chemical studies on biomimetic membranes, and biological experiments on two-dimensional (2D) and three-dimensional (3D) cell cultures. Förster Resonance Energy Transfer measurements on fluorescently-labelled lipid vesicles, and flow cytometry on two cancerous cell lines enabled the evaluation in the uptake of a photosensitizer, Pheophorbide a (Pheo), and copolymer chains towards model membranes, and cells, respectively. The effects of calibrated light illumination for PDT treatment on lipid vesicle membranes, i.e., leakage and formation of oxidized lipids, and cell viability, were assessed. No significant differences were observed between the ability of PEO-PCL and PEO-PS micelles in delivering Pheo to model membranes, but Pheo was found in higher concentrations in cells in the case of PEO-PCL. These higher Pheo concentrations did not correspond to better performances in PDT treatment. We demonstrated that there are subtle differences in PEO-PCL and PEO-PS micelles for the delivery of Pheo.