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.

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.

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.

Pulsed Electric Fields Induce Extracellular Matrix Remodeling through Matrix Metalloproteinases Activation and Decreased Collagen Production.

Impairment of extracellular matrix remodeling is observed in the tumor microenvironment or fibrosis and results in excessive collagen production and/or decreased degradation by matrix metalloproteinases (MMPs). Thanks to their local application and transient effects, physical stimuli appear as attractive tools to remodel the extracellular matrix. We assessed the potential of pulsed electric field technology, classically applied to drug delivery, to induce collagen remodeling at the tissue scale. A sophisticated in vitro tissue-engineered human dermal substitute was used to show that microsecond and millisecond pulsed electric fields induced (i) a rapid modulation (4 hours after electrostimulation) of mRNA genes composing the matrisome, particularly a downregulation of procollagens and extracellular matrix maturation enzymes such as transglutaminase 2 and lysyl oxidase like; (ii) a transient decrease in procollagens production and hydroxyproline tissue content within a week after electrostimulation; (iii) a long-lasting ROS-dependent overactivation of matrix metalloproteinases for at least 48 hours; and (iv) a downregulation of TGFß1. These observations underpin that pulsed electric fields, a technology already approved for clinical use combined with anticancer agents, are particularly promising to provide local and effective treatment of abnormal extracellular matrix.

Cold helium plasma jet does not stimulate collagen remodeling in a 3D human dermal substitute.

Cold Atmospheric Plasma (CAP) is an emerging physical approach displaying encouraging antitumor and wound healing effects both in vitro and in vivo. In this study, we assessed the potential of direct CAP to remodel skin collagens using an original tissue-engineered human dermal substitute model rich in endogenous extracellular matrix (ECM) covered with 600 µl of culture medium and treated with CAP for 30 and 120 s. Our results indicated that Reactive Oxygen and Nitrogen Species (RONS) such as H2O2, NO3- and NO2- were produced in the medium during treatment. It appeared that in the CAP-treated dermal substitutes 1) cell viability was not altered, 2) pro-collagen I secretion was not modified over 48 h of culture after treatment, 3) global activity of matrix metalloproteinases MMPs was not modulated over 48 h after treatment, and 4) no change in hydroxyproline content was observed over 5 days after treatment. In order to confirm the efficiency of our device, we showed that the plasma-activated culture medium induced cell apoptosis and growth delay using a 3D human tumor spheroid model. In conclusion, no effect of direct CAP treatment was monitored on dermal ECM production and degradation, indicating that CAP does not stimulate collagen remodeling at the tissue scale.

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].

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.

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.

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.

Author Correction: Effect of trans(NO, OH)-[RuFT(Cl)(OH)NO](PF6) ruthenium nitrosyl complex on methicillin-resistant Staphylococcus epidermidis.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Amphiphilic polymers based on polyoxazoline as relevant nanovectors for photodynamic therapy.

An amphiphilic polymer (CmPOX) based on poly(2-methyl-2-oxazoline) linked to a hydrophobic part composed of an aliphatic chain ending with a photo-active coumarin group has been synthesized. It exhibits the ability of forming small polymeric self-assemblies, typically of ca. 10 nm in size, which were characterized by TEM, cryo-TEM and DLS. The nanocarriers were further formulated to yield photo-crosslinked systems by dimerization of coumarin units of coumarin-functionalized poly(methyl methacrylate) (CmPMMA) and CmPOX. The formed vectors were used to encapsulate Pheophorbide a, a known photosensitizer for photodynamic therapy. Cytotoxicity as well as phototoxicity experiments performed in vitro on human tumor cells revealed the great potential of these nanovectors for photodynamic therapy.

Effect of trans(NO, OH)-[RuFT(Cl)(OH)NO](PF6) ruthenium nitrosyl complex on methicillin-resistant Staphylococcus epidermidis.

Antibiotic resistance is becoming a global scourge with 700,000 deaths each year and could cause up to 10 million deaths by 2050. As an example, Staphylococcus epidermidis has emerged as a causative agent of infections often associated with implanted medical devices. S. epidermidis can form biofilms, which contribute to its pathogenicity when present in intravascular devices. These staphylococci, embedded in the biofilm matrix, are resistant to methicillin, which had long been the recommended therapy and which has nowadays been replaced by less toxic and more stable therapeutic agents. Moreover, current reports indicate that 75 to 90% of Staphylococcus epidermidis isolates from nosocomial infections are methicillin-resistant strains. The challenge of successfully combating antibiotics resistance in biofilms requires the use of compounds with a controlled mode of action that can act in combination with antibiotics. Ruthenium nitrosyl complexes are potential systems for NO release triggered by light. The influence of trans(NO, OH)-[RuFT(Cl)(OH)NO](PF6) on Staphylococcus epidermidis resistant to methicillin is described. The results show a 50% decrease in cell viability in bacteria treated with low concentrations of NO. When combined with methicillin, this low dose of NO dramatically decreases bacterial resistance and makes bacteria 100-fold more sensitive to methicillin.

Elucidation of in vitro cellular steps induced by antitumor treatment with plasma-activated medium.

Numerous studies have reported cold atmospheric plasma cytotoxic activities in various cancer cell lines, either by direct exposure to non-thermal plasma or indirectly by activating a medium (plasma-activated medium, PAM) prior to cell treatment. We suggested the use of in vitro 3D tumor model spheroids to determine the potential of PAM for cancer therapy at the tissue scale, especially in human tumor tissue. This work aimed to better understand the effect of PAM on human colorectal tumor spheroids by describing the in vitro-induced-cell death kinetics and associated mechanisms to further improve its therapeutic potential. Tumor spheroid growth was delayed depending on contact time with PAM. Medium osmolarity was increased by activation with low temperature Helium plasma jet but it did not fully explain the observed growth delay. PAM impaired tumor cell viability through intracellular ATP depletion, leading within hours to both cell apoptosis and necrosis as well as mitochondrial oxidative stress. When successive treatments were spaced over time, cumulative effects on the growth delay of spheroids were observed. Taken together, these results demonstrated that plasma-activated liquids may represent a novel and efficient therapeutic method for the treatment of tumors, especially when successive treatments are applied.

Effects of Plasma Activated Medium on Head and Neck FaDu Cancerous Cells: Comparison of 3D and 2D Response.

OBJECTIVE: The aim of this work is to investigate the inhibitory effect of Plasma Activated Medium (PAM) on Head and Neck cancerous cells (FaDu). The response of FaDu cells in monolayer cultures and Multi Cellular Tumor Spheroids (MCTS) after treatment with different PAMs will be compared. BACKGROUND: Head and Neck squamous cell carcinoma is a widespread cancer that responds poorly to anticancer treatments such as chemotherapy and radiotherapy. Nowadays there is a growing interest in cold plasmas and their applications in cancer therapy. METHODS: A homemade helium plasma jet is used to produce PAM. The effects of PAM and hydrogen peroxide H2O2 on FaDu 2D cells cultures and MCTS were characterized by evaluating the cell viability with PrestoBlue test and by measuring the size of MCTS. RESULTS: One treatment with PAM induce cell detachment from MCTS since the first day in a PAM exposure dependent manner. This is due to the presence of H2O2 in PAM. However, a rapid spheroids regrowth is observed attributed to a resistance of FaDu cells to H2O2. After multiple treatments of MCTS with PAM we obtained an inhibition of cell growth. MCTS are brought out when comparing PAM effect on 2D versus MCTS. Inversely, PAM induces cell death in the case of 2D cell culture. CONCLUSION: PAM may be considered as a potentially efficient agent in the therapy of head and neck cancer. We also point out that MCTS is a more valuable model than 2D cell culture for the evaluation of the anti-cancer activity of PAM.

Analysis of reactive oxygen and nitrogen species generated in three liquid media by low temperature helium plasma jet.

In order to identify aqueous species formed in Plasma activated media (PAM), quantitative investigations of reactive oxygen and nitrogen species (ROS, RNS) were performed and compared to Milli-Q water and culture media without and with Fetal Calf Serum. Electron paramagnetic resonance, fluorometric and colorimetric analysis were used to identify and quantify free radicals generated by helium plasma jet in these liquids. Results clearly show the formation of ROS such as hydroxyl radical, superoxide anion radical and singlet oxygen in order of the micromolar range of concentrations. Nitric oxide, hydrogen peroxide and nitrite-nitrate anions (in range of several hundred micromolars) are the major species observed in PAM. The composition of the medium has a major impact on the pH of the solution during plasma treatment, on the stability of the different RONS that are produced and on their reactivity with biomolecules. To emphasize the interactions of plasma with a complex medium, amino acid degradation by means of mass spectrometry was also investigated using methionine, tyrosine, tryptophan and arginine. All of these components such as long lifetime RONS and oxidized biological compounds may contribute to the cytotoxic effect of PAM. This study provides mechanistic insights into the mechanisms involved in cell death after treatment with PAM.

Testosterone Prevents Cutaneous Ischemia and Necrosis in Males Through Complementary Estrogenic and Androgenic Actions.

OBJECTIVE: Chronic nonhealing wounds are a substantial medical concern and are associated with morbidity and mortality; thus, new treatment strategies are required. The first step toward personalized/precision medicine in this field is probably in taking sex differences into account. Impaired wound healing is augmented by ischemia, and we previously demonstrated that 17ß-estradiol exerts a major preventive effect against ischemia-induced skin flap necrosis in female mice. However, the equivalent effects of testosterone in male mice have not yet been reported. We then investigated the role of steroid hormones in male mice using a skin flap ischemia model. APPROACH AND RESULTS: Castrated male mice developed skin necrosis after ischemia, whereas intact or castrated males treated with testosterone were equally protected. Testosterone can (1) activate the estrogen receptor after its aromatization into 17ß-estradiol or (2) be reduced into dihydrotestosterone, a nonaromatizable androgen that activates the androgen receptor. We found that dihydrotestosterone protected castrated wild-type mice by promoting skin revascularization, probably through a direct action on resistance arteries, as evidenced using a complementary model of flow-mediated outward remodeling. 17ß-estradiol treatment of castrated male mice also strongly protected them from ischemic necrosis through the activation of estrogen receptor-α by increasing skin revascularization and skin survival. Remarkably, 17ß-estradiol improved skin survival with a greater efficiency than dihydrotestosterone. CONCLUSIONS: Testosterone provides males with a strong protection against cutaneous necrosis and acts through both its estrogenic and androgenic derivatives, which have complementary effects on skin survival and revascularization.

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.

trans- and cis-(Cl,Cl)-[RuII(FT)Cl2(NO)](PF6): promising candidates for NO release in the NIR region.

cis- and trans-(Cl,Cl)-[RuII(FT)Cl2(NO)](PF6) complexes show efficient NO photodelivery upon two-photon excitation in the NIR region. Moreover, cytotoxicity and phototoxicity studies provide evidence that these complexes are promising candidates as photoactivatable molecular tools for resection of malignancies.

Degradation of tyrosine and tryptophan residues of peptides by type I photosensitized oxidation.

Pterin derivatives are involved in various biological functions, including enzymatic processes that take place in human skin. Unconjugated oxidized pterins are efficient photosensitizers under UV-A irradiation and accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder. These compounds are able to photoinduce the oxidation of the peptide α-melanocyte-stimulating hormone (α-MSH), which stimulates the production and release of melanin by melanocytes in skin and hair. In the present work we have used two peptides in which the amino acid sequence of α-MSH was mutated to specifically investigate the reactivity of tryptophan (Trp) and tyrosine residues (Tyr). The parent compound of oxidized pterins (Ptr) was used as a model photosensitizer in aqueous solution at pH5.5 and was exposed to UV-A radiation, a wavelength range where the peptides do not absorb. Trp residue yields N-formylkynurenine and hydroxytryptophan as oxidized products, whereas the Tyr undergoes dimerization and incorporation of oxygen atoms. In both cases, the first step of the mechanism involves an electron transfer from the amino acid to the photosensitizer triplet excited state, Ptr is not consumed and hydrogen peroxide (H2O2) is released. The role of singlet oxygen produced by energy transfer from 3Ptr⁎ to dissolved O2 was negligible or minor. Other amino acid residues, such as histidine, might be also affected.

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.