The "How" and "Where" Behind the Functionalization of Graphene Oxide by Thiol-ene "Click" Chemistry.

Graphene oxide (GO) is a 2D nanomaterial with unique chemistry due to the combination of sp2 hybridization and oxygen functional groups (OFGs) even in single layer. OFGs play a fundamental role in the chemical functionalization of GO to produce GO-based materials for diverse applications. However, traditional strategies that employ epoxides, alcohols, and carboxylic acids suffer from low control and undesirable side reactions, including by-product formation and GO reduction. Thiol-ene "click" reaction offers a promising and versatile chemical approach for the alkene functionalization (-C=C-) of GO, providing orthogonality, stereoselectivity, regioselectivity, and high yields while reducing by-products. This review examines the chemical functionalization of GO via thiol-ene "click" reactions, providing insights into the underlying reaction mechanisms, including the role of radical or base catalysts in triggering the reaction. We discuss the "how" and "where" the reaction takes place on GO, the strategies to avoid unwanted side reactions, such as GO reduction and by-product formation. We anticipate that multi-functionalization of GO via the alkene groups will enhance GO physicochemical properties while preserving its intrinsic chemistry.

Dynamics of Endothelial Engagement and Filopodia Formation in Complex 3D Microscaffolds.

The understanding of endothelium-extracellular matrix interactions during the initiation of new blood vessels is of great medical importance; however, the mechanobiological principles governing endothelial protrusive behaviours in 3D microtopographies remain imperfectly understood. In blood capillaries submitted to angiogenic factors (such as vascular endothelial growth factor, VEGF), endothelial cells can transiently transdifferentiate in filopodia-rich cells, named tip cells, from which angiogenesis processes are locally initiated. This protrusive state based on filopodia dynamics contrasts with the lamellipodia-based endothelial cell migration on 2D substrates. Using two-photon polymerization, we generated 3D microstructures triggering endothelial phenotypes evocative of tip cell behaviour. Hexagonal lattices on pillars ("open"), but not "closed" hexagonal lattices, induced engagement from the endothelial monolayer with the generation of numerous filopodia. The development of image analysis tools for filopodia tracking allowed to probe the influence of the microtopography (pore size, regular vs. elongated structures, role of the pillars) on orientations, engagement and filopodia dynamics, and to identify MLCK (myosin light-chain kinase) as a key player for filopodia-based protrusive mode. Importantly, these events occurred independently of VEGF treatment, suggesting that the observed phenotype was induced through microtopography. These microstructures are proposed as a model research tool for understanding endothelial cell behaviour in 3D fibrillary networks.

A New Transcutaneous Method for Breast Cancer Detection with Dogs.

We developed a new transcutaneous method for breast cancer detection with dogs: 2 dogs were trained to sniff skin secretion samples on compresses that had been worn overnight by women on their breast, and to recognize a breast cancer sample among 4 samples. During the test, the dogs recognized 90.3% of skin secretion breast cancer samples. This proof-of-concept study opens new avenues for the development of a reliable cancer diagnostic tool integrating olfactory abilities of dogs.

Functional analysis of Escherichia coli Yad fimbriae reveals their potential role in environmental persistence.

Initial adhesion of bacterial cells to surfaces or host tissues is a key step in colonisation and biofilm formation processes, and is mediated by cell surface appendages. It was previously demonstrated that Escherichia coli K-12 possesses an arsenal of silenced chaperone-usher fimbriae that were functional when constitutively expressed. Among them, production of prevalent Yad fimbriae induces adhesion to abiotic surfaces. Functional characterisation of Yad fimbriae were undertook, and YadN was identified as the most abundant and potential major pilin, and YadC as the potential tip-protein of Yad fimbriae. It was showed that Yad production participates to binding of E. coli K-12 to human eukaryotic cells (Caco-2) and inhibits macrophage phagocytosis, but also enhances E. coli K-12 binding to xylose, a major component of the plant cell wall, through its tip-lectin YadC. Consistently, it was demonstrated that Yad production provides E. coli with a competitive advantage in colonising corn seed rhizospheres. The latter phenotype is correlated with induction of Yad expression at temperatures below 37°C, and under anaerobic conditions, through a complex regulatory network. Taken together, these results suggest that Yad fimbriae are versatile adhesins that beyond potential capacities to modulate host-pathogen interactions might contribute to E. coli environmental persistence.

Poly(ε-caprolactone)-block-polysarcosine by Ring-Opening Polymerization of Sarcosine N-Thiocarboxyanhydride: Synthesis and Thermoresponsive Self-Assembly.

Biocompatible amphiphilic block copolymers composed of polysarcosine (PSar) and poly(ε-caprolactone) (PCL) were synthesized using ring-opening polymerization of sarcosine N-thiocarboxyanhydride initiated by oxyamine-ended PCL and characterized by NMR, SEC, and DSC. Self-assembling of two triblock copolymers PSar8-b-PCL28-b-PSar8 (CS7) and PSar16-b-PCL40-b-PSar16 (CS10) in dilute solution was studied in detail toward polymersome formation using thin-film hydration and nanoprecipitation techniques. A few giant vesicles were obtained by thin-film hydration from both copolymers and visualized by confocal laser scanning microscope. Unilamellar sheets and nanofibers (with 8-10 nm thickness or diameter) were obtained by nanoprecipitation at room temperature and observed by Cryo-TEM. These lamellae and fibrous structures were transformed into worm-like cylinders and spheres (D∼30-100 nm) after heating to 65 °C (>Tm,PCL). Heating CS10 suspensions to 90 °C led eventually to multilamellar polymersomes (D∼100-500 nm). Mechanism II, where micelles expand to vesicles through water diffusion and hydrophilic core forming, was proposed for polymersome formation. A cell viability test confirmed the self-assemblies were not cytotoxic.

Preventing biofilm formation and associated occlusion by biomimetic glycocalyxlike polymer in central venous catheters.

The use of catheters and other implanted devices is constantly increasing in modern medicine. Although catheters improve patients' healthcare, the hydrophobic nature of their surface material promotes protein adsorption and cell adhesion. Catheters are therefore prone to complications, such as colonization by bacterial and fungal biofilms, associated infections, and thrombosis. Here we describe the in vivo efficacy of biologically inspired glycocalyxlike antiadhesive coatings to inhibit Staphylococcus aureus and Pseudomonas aeruginosa colonization on commercial totally implantable venous access ports (TIVAPs) in a clinically relevant rat model of biofilm infection. Although noncoated TIVAPs implanted in rats were heavily colonized by the 2 biofilm-forming pathogens with a high percentage of occlusion, coating TIVAPs reduced their initial adherence and subsequently led to 4-log reduction in biofilm formation and reduced occlusion. Our antiadhesive approach is a simple and generalizable strategy that could be used to minimize clinical complications associated with the use of implantable medical devices.

Efficient One-Step Passivation of Polyurethane Using Transurethanization.

The uncontrolled accumulation of biological materials on the surface of medical devices through protein adsorption or cell adhesion causes adverse biological reactions in the living host system, leading to complications. In this study, poly(ethylene glycol) (PEG) is successfully grafted onto polyurethane (PU) surfaces by using a new strategy through a simple and efficient transurethanization reaction. The PEG hydroxyl group is deprotonated and then reacted with the PU surface to provide antiadhesive hydrophilic surfaces in a single step. Surface analysis techniques proved the grafting to be efficient and the formation of a hydrophilic polymeric layer at the surface of PU. Biological assays showed that the surface modification induced lower protein adsorption, cell, platelet, and bacterial adhesion than untreated surfaces, showing a potential for biomedical applications.

Characterization of end-of-life LED lamps: Evaluation of reuse, repair and recycling potential.

The characterization of wastes constituted by LED lamps at the end of their lives is currently a concern of researchers and environmental managers not only because of the large volume will be generated by such wastes, but also to identify appropriate strategies for their reuse as well as their recyclability. This research describes the different steps involved in the characterization of LED lamps at the end of their lives such as, testing the functionality of the whole lamps, as well as modules and the LED components of the non-functional lamps. The results revealed that about 30.8 % of the wasted LED lamps are still working and could be reused in the social and solidarity economy or remarketed if economically viable. On the other hand, functionality test of the non-functional lamps showed that 56.5 % of the LED modules and 75% of the LED chips are still functional. Our investigations revealed that, repairing the non-functional lamps or reusing their functional components is challenging and therefore, their recycling is highly recommended.

Recycling Polyurethanes through Transcarbamoylation.

In this paper, we describe a new strategy to recycle polyurethanes (PUs) using base-catalyzed transcarbamoylation. PUs were depolymerized qualitatively in the presence of MeOH (methanol)/tetrahydrofuran as a solvent and tert-butoxide as a base catalyst. The resulting depolymerized mixture constituted by O-dimethylcarbamates and polyols can either be used as the starting material to synthesize new PUs with the transcarbamoylation approach or be purified to recover polyols and diisocyanates. The versatility and easy scaling-up of the experimental procedures and high depolymerization outcomes of the presented method make this strategy very attractive for PU recycling.

Light-Gated Nano-Porous Capsules from Stereoisomer-Directed Self-Assemblies.

Structuring pores into stable membrane and controlling their opening is extremely useful for applications that require nanopores as channels for material exchange and transportation. In this work, nanoporous vesicles with aggregation-induced emission (AIE) properties were developed from the amphiphilic polymer PEG550-TPE-Chol, in which the hydrophobic part is composed of a tetraphenylethene (TPE) group and a cholesterol moiety and the hydrophilic block is a poly(ethylene glycol) (PEG, Mn = 550 Da). Two stereoisomers, trans-PEG550-TPE-Chol and cis-PEG550-TPE-Chol, were successfully synthesized. These thermally stable stereoisomers showed distinct self-assembly behavior in water: trans-PEG550-TPE-Chol formed classical vesicles, while cis-PEG550-TPE-Chol self-assembled into cylindrical micelles. Interestingly, trans/cis mixtures of PEG550-TPE-Chol (trans/cis = 60/40), either naturally synthesized without isomers' separation during the synthesis or intentionally mixed using trans- and cis-isomers, constructed perforated vesicles with nanopores. Moreover, under the illumination of high intensity UV light (365 nm, 15 mW/cm2), the classical vesicles of trans-PEG550-TPE-Chol were perforated by its cis counterparts generated from the trans-cis photoisomerization, while the cylindrical micelles of cis-PEG550-TPE-Chol interweaved to form meshes and nanoporous membranes due to the trans-isomers produced by cis-trans photoisomerization. All of these assemblies in water emitted bright cyan fluorescence under UV light, while their constituent molecules were not fluorescent when solubilized in organic solvent. The AIE fluorescent normal vesicles and nanoporous vesicles may find potential applications in biotechnology as light-gated delivery vehicles and capsules with nanochannels for material exchange.

Using ion channel-forming peptides to quantify protein-ligand interactions.

This paper proposes a method for sensing affinity interactions by triggering disruption of self-assembly of ion channel-forming peptides in planar lipid bilayers. It shows that the binding of a derivative of alamethicin carrying a covalently attached sulfonamide ligand to carbonic anhydrase II (CA II) resulted in the inhibition of ion channel conductance through the bilayer. We propose that the binding of the bulky CA II protein (MW approximately 30 kD) to the ion channel-forming peptides (MW approximately 2.5 kD) either reduced the tendency of these peptides to self-assemble into a pore or extracted them from the bilayer altogether. In both outcomes, the interactions between the protein and the ligand lead to a disruption of self-assembled pores. Addition of a competitive inhibitor, 4-carboxybenzenesulfonamide, to the solution released CA II from the alamethicin-sulfonamide conjugate and restored the current flow across the bilayer by allowing reassembly of the ion channels in the bilayer. Time-averaged recordings of the current over discrete time intervals made it possible to quantify this monovalent ligand binding interaction. This method gave a dissociation constant of approximately 2 microM for the binding of CA II to alamethicin-sulfonamide in the bilayer recording chamber: this value is consistent with a value obtained independently with CA II and a related sulfonamide derivative by isothermal titration calorimetry.

A new, simple approach to confer permanent antimicrobial properties to hydroxylated surfaces by surface functionalization.

A new, simple method to obtain ultrathin polycationic monolayers on hydroxylated surfaces is described which uses a bifunctional copolymer comprising a reactive part (trimethoxysilane) and positive charges (quaternary ammonium salts) to confer antimicrobial properties.

Microtopographies control the development of basal protrusions in epithelial sheets.

Cells are able to develop various types of membrane protrusions that modulate their adhesive, migratory, or functional properties. However, their ability to form basal protrusions, particularly in the context of epithelial sheets, is not widely characterized. The authors built hexagonal lattices to probe systematically the microtopography-induced formation of epithelial cell protrusions. Lattices of hexagons of various sizes (from 1.5 to 19 µm) and 5-10 µm height were generated by two-photon photopolymerization in NOA61 or poly(ethylene glycol) diacrylate derivatives. The authors found that cells generated numerous, extensive, and deep basal protrusions for hexagons inferior to cell size (3-10 µm) while maintaining a continuous epithelial layer above structures. They characterized the kinetics of protrusion formation depending on scaffold geometry and size. The reported formation of extensive protrusions in 3D microtopography could be beneficial to develop new biomaterials with increased adhesive properties or to improve tissue engineering.

Structural and immunological characterisation of heteroclitic peptide analogues corresponding to the 600-612 region of the HIV envelope gp41 glycoprotein.

The conformational and immunological properties of different analogues corresponding to the 600-612 disulfide loop of the human immunodeficiency virus (HIV) gp41 glycoprotein envelope were studied. Fourteen analogues were designed and synthesised; namely, a series of seven analogues in which the disulfide bond was replaced by a lactam bridge and a series of seven analogues in which one residue of each analogue at a time, was replaced by its corresponding homologised alpha-amino acid (beta(3)-amino acid). In the case of the lactam analogues, the influence of the two possible CO-NH and NH-CO orientations of the lactam bridge as well as the size of the lactam ring was explored. The analogues were tested in ELISA with monoclonal antibodies raised against the 600-612 cyclic parent peptide as well as with sera from HIV-1 infected patients. A structural analysis of the parent and analogue peptides was carried out in dimethyl sulfoxide (DMSO-d(6)) using two-dimensional NMR techniques and molecular dynamics simulations. Comparison of the own conformation of the cyclic analogues with their either strong or weak reactivity with the antibodies reveals structural features that may be correlated with the antibody reactivity. Thus, a close structural similarity, particularly a characteristic orientation of the side-chains of residues Lys606, Leu607 and Ile608 in the loop, was found in certain beta(3)-analogues that were better recognised than the parent peptide by anti-peptide mouse monoclonal antibodies and patients' antibodies.

A facile and versatile approach to design self-assembled monolayers on glass using thiol-ene chemistry.

This work describes an integrated approach for designing on demand Self-Assembled Monolayers (SAMs) on silicon oxides and particularly glass substrates for cell biology applications. Starting from commercially available compounds, the strategy relies on thiol-ene reaction and provides high quality SAMs exhibiting adhesive and anti-adhesive patterns.

Root canal hydrophobization by dentinal silanization: improvement of silicon-based endodontic treatment tightness.

A new strategy to improve silicon-based endodontic treatment tightness by dentine hydrophobization is presented in this work: root dentine was silanized to obtain a hydrophobic dentine-sealer interface that limits fluid penetration. This strategy was based on the grafting of aliphatic carbon chains on the dentine through a silanization with the silane end groups [octadecyltrichlorosilane (OTS) and octadecyltriethoxysilane]. Dentine surface was previously pretreated, applying ethylenediaminetetraacetic acid and sodium hypochlorite, to expose hydroxyl groups of collagen for the silane grafting. Collagen fibers exposure after pretreatment was visible with scanning electron microscopy, and Fourier transform infrared (FTIR) spectroscopy showed their correct exposition for the silanization (amide I and II, with 1630, 1580, and 1538 cm⁻¹ peaks corresponding to the vibration of C=O and C--N bonds). The grafting of aliphatic carbon chains was confirmed by FTIR (peaks at 2952 and 2923 cm⁻¹ corresponding to the stretching of C--H bonds) and by the increasing of the water contact angle. The most efficient hydrophobization was obtained with OTS in ethyl acetate, with a water contact angle turning from 51° to 109°. Gas and liquid permeability tests showed an increased seal tightness after silanization: the mean gas and water flows dropped from 2.02 × 10⁻8 to 1.62 × 10⁻8 mol s⁻¹ and from 10.8 × 10⁻³ to 5.4 × 10⁻³ µL min⁻¹, respectively. These results show clear evidences to turn hydrophilic dentine surface into a hydrophobic surface that may improve endodontic sealing.

Chemical treatment of the intra-canal dentin surface: a new approach to modify dentin hydrophobicity.

OBJECTIVE: This study evaluated the hydrophobicity of dentin surfaces that were modified through chemical silanization with octadecyltrichlorosilane (OTS). MATERIAL AND METHODS: An in vitro experimental study was performed using 40 human permanent incisors that were divided into the following two groups: non-silanized and silanized. The specimens were pretreated and chemically modified with OTS. After the chemical modification, the dentin hydrophobicity was examined using a water contact angle measurement (WCA). The effectiveness of the modification of hydrophobicity was verified by the fluid permeability test (FPT). RESULTS AND CONCLUSIONS: Statistically significant differences were found in the values of WCA and FPT between the two groups. After silanization, the hydrophobic intraradicular dentin surface exhibited in vitro properties that limit fluid penetration into the sealed root canal. This chemical treatment is a new approach for improving the sealing of the root canal system.

Optimizing the formation of biocompatible gold nanorods for cancer research: functionalization, stabilization and purification.

We have investigated the most efficient way of preparing biocompatible gold nanorods (GNR) used as tool for cancer imaging and therapy. The surface of cetyltrimethylammonium bromide-stabilized gold nanorods (GNR-CTAB) was functionalized with various thio-polyethylene glycols of the general formula HS-PEGmX (m=356-10,000; X=-OMe, -NH(2)). The influence of several parameters such as PEG chain length, reaction conditions and purification method on long-term stability, morphology and optical properties of the produced GNR-S-PEGmX was studied, demonstrating the existence of a threshold HS-PEGmX chain length (with molecular weight m≥2000) for efficient steric stabilization of GNR. Several purification techniques were compared: dialysis, centrifugation and a rarely used technique in this field, size exclusion chromatography. While a very weak efficiency of dialysis was evidenced, both centrifugation and size exclusion chromatography were found to provide pure GNRs, though the latter method yielded nanoparticles with a significantly higher stability. Finally, the long-term stability of the produced GNRs was investigated in various media: water, PBS buffer and serum.