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Sucrose and glycerol have gained attention as additives for hydrogels, owing to their capacity to exert considerable influence over the physicochemical, mechanical, and biological characteristics of these materials. Herein, these effects on agarose hydrogels (AHs) are explored. A series of AHs are synthesized using sucrose (30% and 300% w/v) and glycerol as additives. The storage modulus (10.0–13.7 kPa) and hydrophilicity of the hydrogels (contact angle < 50°) do not vary significantly with sucrose or glycerol addition. However, sucrose enhances the hydration capacity of the hydrogels by up to 170%, whereas glycerol reduces it. Interestingly, sucrose and glycerol individually do not have bacteriostatic effects against Staphylococcus epidermidis, but their combination significantly (p ≤ 0.001) inhibits the growth of both S. epidermidis and Pseudomonas aeruginosa by 63% and 29%, respectively, in comparison to native agarose. Cytotoxicity testing on NIH/3T3 murine fibroblasts reveals that sucrose increases cell viability up to 98%, while glycerol reduces it below 60%. Overall, these hydrogels hold promise for antibacterial biomedical applications as wound dressing materials and surface coatings for medical devices and can also be used to formulate bioinks for 3D bioprinting. [ABSTRACT FROM AUTHOR]

In 2007, polydopamine (PDA) films were shown to be formed spontaneously on the surface of all known classes of materials by simply dipping those substrates in an aerated dopamine solution at pH = 8.5 in the presence of Tris(hydroxymethyl) amino methane buffer. This universal deposition method has raised a burst of interest in surface science, owing not only to the universality of this water based one pot deposition method but also to the ease of secondary modifications. Since then, PDA films and particles are shown to have applications in energy conversion, water remediation systems, and last but not least in bioscience. The deposition of PDA films from aerated dopamine solutions is however a slow and inefficient process at ambient temperature with most of the formed material being lost as a precipitate. This incited to explore the possibility to get PDA and related films based on other catecholamines, using other oxidants than dissolved oxygen and other deposition methods. Those alternatives to get PDA and related films are reviewed and compared in this paper. It will appear that many more investigations are required to get better insights in the relationships between the preparation method of PDA and the properties of the obtained coatings. [ABSTRACT FROM AUTHOR]

The electrodeposition of derivatives of phenol or of other polyphenols by means of cyclic voltammetry or other electrochemical methods offers the opportunity to eliminate rather hazardous molecules from solution and to coat conductive surfaces with robust, conformal and chemically reactive films. Herein electrodeposition of resveratrol, a natural polyphenol of wines, is investigated on amorphous carbon electrodes and compared to the well known electrodeposition of resorcinol from which it derives with the aim to understand the role of basic constituents in the electrochemistry of complex polyphenols. It is shown that the presence of 4-vinylphenol group on resorcinol to yield resveratrol does not hinder the electrode passivation under cyclic voltammetry but at the contrary that the oxidation of resveratrol occurs at lower potentials than the oxidation of resorcinol. The electron transfer coefficient on amorphous carbon is also evaluated and it is shown that resveratrol based coatings, contrarily to resorcinol ones, display an interesting antioxidant activity. All the obtained films were conformal and hydrophilic. [Display omitted] • Electrodeposition of conformal films from resveratrol. • Antioxidant films. • Faster electron transfer to carbon than with resorcinol. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • One pot film deposition using cyclic voltametry. • Deposition using catechols, catecholamines and aminomalononitrile. • Constant potential deposition is also possible. • Impermeable films to redox probes. • Possible applications as biomaterials and protection against corrosion. Abstract The possibility to functionalize almost all kinds of interfaces with catecholamines, catechols or aminomalonitrile to produce conformal films which can be subsequently functionalized with metal nanoparticles or organic molecules, revolutionized surface science in the last few years. However, when performed from solution using appropriate oxidants (in the case of catecholamines and catechols) or the appropriate pH range (in the case of aminomalonitrile), the film deposition is accompanied with precipitation of insoluble precipitates in solution implying a considerable lost of active molecules. This drawback can be circumvented on conductive substrates by performing deposition by cyclic voltammetry or by constant deposition methods. This short review aims to describe the state of the art in such deposition methods, to highlight common features of the obtained coatings and to give some perspectives to improve their properties, notably in terms of electronic conductivity. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Polyelectrolyte multilayer (PEM) films display either a linear or an exponential increase of their thickness with increasing the number of polycation/polyanion deposition cycles. Each of these growth regimes is further associated with a specific mode of internal PEM charge compensation: either intrinsic in the case of linearly growing films, or extrinsic for exponentially growing films with incorporation of small ions from the neighbouring electrolyte solution. In this report, we investigate by electrochemistry the charge compensation mechanism operational for poly(diallyldimethyl ammonium chloride)-poly(acrylic acid sodium salt) (PDAMAC-PAA) n films recently found to be out-of-equilibrium immediately after the deposition process despite of their exponential growth mode. It is found here that these films are defined by a negative Donnan potential drop (ca. −160 mV), thus evidencing an extrinsic charge compensation process, and most importantly, by a remarkably slow kinetics for loading of hexacyanoferrate anions, a very unusual property for PEMs with exponential growth. Depending on the film thickness, the diffusion coefficient of the redox probe in the film is found to be of the order of 10−13 − 10−15 cm2 s−1, i.e. about 8 to 10 orders of magnitude less than that typically measured in aqueous solution. This results in a steady state filling of e.g. a 2.8 µm thick PEM film with the redox probe that is achieved after more than 40 h, a feature in line with the typical 4 to 5 days relaxation timescale of the film structure previously determined by atomic force microscopy and Raman micro-spectroscopy analyses. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Hypothesis The layer-by-layer deposition of films including polyoxometalates (POMs) results in a very interesting range of applications in various fields such as electrochemical devices and as photochromic coatings. However, the fundamental knowledge of the parameters responsible for tuning the properties of the film (i.e. relation between the structure and composition of the POM and the properties of the final film) is still lacking. Experiments The current work establishes the relationship between the film thickness, the quantity of POM incorporated in each layer and the electrochemical response of the (PAH-POM) x coatings, where PAH is poly(allylamine hydrochloride). Findings The results presented in this work show that the film thickness, composition and electrochemical activity scale proportionally with the number of W atoms in a series of heteropolytungstates ranging from 5 to 48 (P 2 W 5 , PW 12 , P 2 V 3 W 15 , P 2 W 18 , P 5 W 30 , P 8 W 48). The obtained results allow us to establish a method to predict the behavior as well as the properties of the film based on the nature of the POM used. [ABSTRACT FROM AUTHOR]

Versatile coatings based on the polymerization of aminomalonitrile (AMN) start to attract attention in the field of surface science owing to their biocompatibility and also in relation to the use of a precursor molecule being considered as a fundamental building block in prebiotic chemistry. As other emerging versatile coating methods, the polymerization of AMN produces not only coatings on almost all kinds of known materials but also the deposition of a useless precipitate in solution when AMN is dissolved at pH = 8.5. To circonvent this drawback, at least on conductive substrates, it is shown that AMN coatings can be obtained in a scan rate dependant manner on amorphous carbon electrodes by means of cyclic voltammetry at pH = 6.0 in conditions where AMN is stable in solution. The composition of the electrodeposited AMN coatings is compared with that of the solution processed coatings by means of X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Coatings obtained from the oxidation of catecholamines, most often dopamine, allow not only to coat the surface of all classes of known materials (metals, oxides, polymers, liquid/liquid and liquid/air interfaces) with a conformal and robust film but also to easily post-functionalize such coatings with metal nanoparticles and enzymes using the intrinsic redox and quinone functionalities of the coating. Hence polydopamine (PDA) based coatings offer huge perspectives for the immobilization of catalysts. This review provides a summary of the first successful research efforts in this domain and provides some first proofs of concept that PDA may act as a catalyst by itself for aldolations, formation of carbonates from CO 2 and epoxides and for hydrolysis reactions without addition of further enzymes or metal nanoparticles. [ABSTRACT FROM AUTHOR]

Thick and robust free standing membranes were prepared by blending alginate modified with catechol groups and a mixture of two enzymes: glucose oxidase and peroxidase. The dried composite paste was crosslinked with sodium periodate, allowing to oxidize the catechol groups in quinones and to obtain thick free standing membranes. The enzymatic activity of those membranes was proportional to the mass of the used reactants, and hence to the membrane thickness, in the 100 μm range. This was possible owing to the microporous structure of the Alg-Cat@enzyme membrane. [ABSTRACT FROM AUTHOR]

Films based on catechols constitute a novel class of surface functionalization methods. Those films are produced by a complexation mechanism with metal cations. The deposition of films is accompagnied with the formation of colloids in solution. As an alternative, herein an electrochemical method is proposed and validated to produce films impermeable to hexacyanoferrate anions from pyrocatechol solutions at pH 5 and pH 7.4 in the absence of metallic cations. In such conditions the film deposition is slower from dopamine solutions in the same experimental conditions, most probably owing to the presence of a protonated ethylamine at pH = 5. Based on the pH influence of cyclic voltammetry curves, a possible mechanism for the formation of the pyrocatechol based film is proposed. This electrochemical deposition method even if it can be applied only on conductive substrates is surface specific with no apparent change in the pyrocatechol solution. Electrochemical impedance spectroscopy shows the formation of conformal and insulating films. [ABSTRACT FROM AUTHOR]

Understanding the molecular origin of the broadband optical absorption spectrum of eumelanin in solution remains a challenging task both from an experimental and a theoretical point of view. Eumelanin like materials can now be deposited on solid surfaces from dopamine solutions in oxidizing conditions allowing to easily functionalize the surface of almost all materials. The optical spectra of those “polydopamine” (PDA) films are close to the spectra of eumelanin but not identical. This article is a first attempt to quantify the optical absorption coefficient of PDA films which is made complicated by the uncertainty due to the need to know the density of this material. Using dissolved NaIO 4 as the oxidant, at 0.5, 1 or 10 mM, the film thickness versus time does superimpose with the absorbance versus time curves suggesting intrinsic film homogeneity and allowing to calculate the product of the extinction coefficient by the concentration of PDA in the film. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) are often used to functionalize surfaces with photochromic or electroactive compounds. Among the common deposition methods, besides the Langmuir-Blodgett deposition, the layer-by-layer (LBL) deposition method has become more and more popular due to its facility and versatility combined with the polyanionic character of POMs. The LBL deposition of POMs and oppositely charged nanoparticles is however poorly described in the literature. Using polydopamine nanoparticles (PDA) produced in the presence of poly(allylamine) and displaying a hydrodynamic diameter of 25 nm, we show that LBL films containing the large, cyclic P 8 W 48 polyanion and the PDA@PAH nanoparticles display reduction currents which are proportional to the number of deposition steps and hence to the film thickness. In addition the obtained films display not only the electrochemical properties of the POM but also that of PDA nanoparticles. Hence we demonstrate the feasibility to build up films based on particles only with the electrochemical behavior of each kind of particles being conserved. [ABSTRACT FROM AUTHOR]

Small cyclic polyphosphates, like sodium hexametaphosphates (HMP), behave as polyanions since they can be incorporated into aggregates with oppositely charged polycations or incorporated in to polyelectrolyte multilayer films. Their dilution heat in small electrolyte solutions, has however never been characterized. Isothermal titration calorimetry was used to determine the dilution enthalpy of HMP as a function of both the temperature and the NaCl concentration in the electrolyte solutions. A transition between exothermic and endothermic heats of dilution is found when the salt concentration is increased or when the temperature is decreased. A phenomenological model is developed to explain those results. It is based on an estimation of a translational entropy increase of the polyanion upon its dilution. The entropy changes due to counterion release are estimated to be negligible. [ABSTRACT FROM AUTHOR]

The formation of complexes (aggregates) between oppositely charged macromolecular species or between macromolecular species and multivalent ions is a fascinating fundamental research topic that allows one to understand fundamental processes in biology and in polymer science. In addition interpolyelectrolyte complexes hold by strong interactions and polyelectrolyte coacervates in which the stabilizing interactions are weaker find many applications in food and in colloidal science. The interactions between oppositely charged species are usually investigated as a function of intensive variables like the temperature, the pH, the ionic strength, and parameters related to the charged species themselves (molecular mass, charge density, charge distribution, and so forth). It appeared however in the past few years that the interaction kinetics is also of fundamental importance; a fast mixing of the interacting species can lead to the formation of frozen and out-of-equilibrium structures. The present investigation is aimed to study the interactions between a small polyphosphate (sodium hexametaphosphate) (HMP) and a linear polyamine (poly(allylamine hydrochloride)) (PAH) from both a thermodynamic and kinetic point of view as a function of the ionic strength (in NaCl solutions). It is found, unexpectedly, that the interaction is of biphasic nature with a first exothermic regime followed by an endothermic regime. The transition between both regimes is ionic strength independent between 10 and 2000 mM emphasizing the strong interactions between both species. It occurs at a charge ratio of about 0.4 between the number of negative and positive charges and is correlated with proton release in the exothermic regime and a proton uptake in the endothermic regime. When HMP solutions are titrated in PAH solutions the turbidity of the mixtures is not the same as that obtained during the reverse titration at a given charge ratio, emphasizing the difficulty to establish an "equilibrium" phase diagram. Finally, the difference in complex formation mechanism defines conditions to obtain a macroscopic swollen material similar to compact polyelectrolyte complexes. [ABSTRACT FROM AUTHOR]

Tannic acid and other polyphenols adsorb spontaneously on almost all kinds of surfaces to yield hydrophilic coatings. However, the deposition kinetics of tannic acid as a function of its solution concentration has not yet been well characterized. Such fundamental aspects are of the highest importance for the protection against corrosion and other applications. Herein, it is shown by means of quartz crystal microbalance with dissipation monitoring that tannic acid (TA) deposition on gold and silica yield to monolayers independently of the TA concentration between 0.1 and 50 mg mL −1 . Significant but only partial desorption occurs when the film is put again in the presence of sodium acetate buffer. The reduction of Ag + cations in silver particles in the presence of tannic acid films is a slow and silver concentration dependent process. In addition TA monolayer films deposited on gold become impermeable to potassium hexacyanoferrate. This shows the high homogeneity and compacity of spontaneously deposited TA monolayers on silver and polycrystalline gold. [ABSTRACT FROM AUTHOR]

The step-by-step assembly of tannic acid (TA) and of Fe 3+ cations allows to produce films of controlled thickness using exclusively small multivalent ions. In the present investigation, it is shown that even if electrostatic interactions are dominant over ligand to metal charge transfer interactions in stabilizing such films, those electrostatic interactions display a small sensitivity to concentration in NaCl used as a supporting electrolyte as well as to the concentration in sodium acetate in the absence of NaCl. This finding highlights the strong stability of the films obtained through the step-by-step deposition of TA and Fe 3+ cations. Complementarily, the films made from 6 deposition cycles of TA and Fe 3+ cations do not form Prussian Blue when put in contact with hexacyanoferrate anions. This shows that Fe 3+ is so tightly bound to the film that it is not able to form a coordination polymer with Fe(CN) 6 4− anions. [ABSTRACT FROM AUTHOR]

Streaming potential measurement is one of the most frequently used characterization methods of polyelectrolyte multilayer films. In most cases, the adsorption of a polyelectrolyte occurs up to an overcompensation of the surface charge. Herein, we generalize previous findings that the obtained streaming potential (transformed into a relative ζ potential) is dependent on the history of the measurement and in particular that shear stresses due to the flow of the solution induce a reduction in the absolute values of the ζ potential. These findings show that huge care should be taken when defining an experimental protocol aimed to measure the zeta potential of polyelectrolyte multilayer films using the streaming potential method. Ideally, to avoid the influence of shear induced desorption of polyelectrolytes on the zeta potential values, polyelectrolyte multilayer films made from different number of layers should be characterized independently under overall identical conditions. [ABSTRACT FROM AUTHOR]

The step-by-step deposition of poly(allylamine hydrochloride) (PAH) and sodium hexameta­phosphate (PSP) leads to coatings displaying interesting intumescent properties and is a fascinating model system to understand the fundamental mechanism behind such a deposition process. In this investigation, the deposition kinetics of (PAH-PSP) n is followed in situ by means of a quartz crystal microbalance with dissipation monitoring, as a function of NaCl concentration. The evolution of the film deposition is analyzed in detail and the data are compared with previous data obtained by ellipsometry on dried films. These results are also compared with the expectations from the PAH/PSP phase diagram. The (PAH-PSP) n films are also able to incorporate hexacyanoferrate anions with an amount of an incorporated redox probe reflecting the film thickness as obtained in the presence of eletrolyte solutions of increasing ionic strength. The in situ measurements and the electrochemical probe experiments reveal details of the film deposition mechanism that are not accessible by dry-state characterization methods. [ABSTRACT FROM AUTHOR]

Highlights: [•] Alkaline phosphatase was adsorbed on “polydopamine” films. [•] The enzymatic activity was evaluated as a function of storage time. [•] “Polydopamine” films display some phosphatase like activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electrodeposition of pyrocatechol is compared with that of pyrogallol. • In case of CV deposition pyrogallol yields impermeable films of higher impedance. • In case of chronoamperometry, pyrocatechol yields impermeable films of higher impedance. The electrodeposition of films from redox active molecules has become an attractive surface functionalization method owing to its surface selectivity and one pot nature. Many investigations focused on the deposition mechanism of particular molecules such as aniline or thiophene. Fewer studies focused on derivatives of phenols and very few were aimed to compare the electrochemical properties of the obtained films when the chemical nature of the phenol derivative is changed, for instance upon the addition of an hydroxyl group on the benzene cycle, or when the nature of the deposition method is changed, namely variable (cyclic voltammetry, CV) or constant potential (chronoameprometry, CA). This investigation compares the influence of the film deposition method on the electrochemical properties of deposits made from pyrogallol or pyrocatechol on amorphous carbon electrodes. It is shown that CA is more efficient for the deposition of pyrocatechol based films than for pyrogallol based films. On the other hand, a lower number of CV cycles is required to obtained films impermeable to hexacyanoferrate anions in the case of pyrogallol compared to pyrocatechol. [ABSTRACT FROM AUTHOR]

Highlights: [•] Aged dopamine solutions contain small molecules. [•] These molecules have UV–vis spectra and CVs close to that of dopamine. [•] “Polydopamine” films contain a reservoir of molecules able to undergo oxidation. [•] “Polydopamine” films can be deposited on substrates from aged dopamine solutions. [Copyright &y& Elsevier]

Highlights: [•] Proteins allow to control the size of dopamine-eumelanin particles. [•] The kinetics of dopamine-eumelanin formation is also accelerated in the presence of those proteins. [•] Fibroblasts keep their viability in the presence of HAS dopamine-eumelanin nanoparticles. [Copyright &y& Elsevier]

Highlights: [•] The zeta potential of (PAH-polyoxometalate) n films is measured as a function of the ionic strength. [•] The zeta potential is stable as a function of time when the ionic strength is higher than 50mM. [•] At smaller ionic strengths, the zeta potential decreases without desorption. [ABSTRACT FROM AUTHOR]

Highlights: [•] Step-by-step assembly of dopamine-eumelanin and metal cations (Cu2+, Fe3+, La3+) is possible. [•] The coatings made from trivalent cations growth faster than those made from Cu2+. [•] Fe3+ does not undergo a change in its redox state upon incorporation in the coatings. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) are inorganic metal oxoanions with a negative charge, stabilized in the solid state by the corresponding number of countercations and possibly protons. In aqueous solution, the dissociation of all ion pairs is not necessarily quantitative because this would result in strong electrostatic repulsion among the polyanions. In the present communication, we show that the effective charge of the donut-shaped 30-tungsto-5-phosphate [NaPWO] (PW) is close to its 'structural charge' of 14 elementary negative charges in the presence of linear polyamines, namely, poly(allylamine hydrobromide) and poly( l-lysine hydrobromide) in a 10-mM NaBr electrolyte. When phase separation occurs, leading to a precipitate (rich in polyanion) and an almost clear supernatant, the charge ratio of the number of moles of cationic groups to polyanion is close to 14, showing that the effective charge in a solution of PW is indeed equal to −14 e in the presence of polycations. [ABSTRACT FROM AUTHOR]

Surface coatings obtained by a step-by-step(SBS) deposition process of polymers carrying mutually complementarymoieties (like polycations and polyanions) allow for a versatile multifunctionalizationof a vast kind of materials. However the SBS deposition process canbe extremely time-consuming when it is performed by alternativelydipping the substrates in the solutions carrying the interacting species.There is hence an important need to obtain coatings of similar compositionas those obtained in the SBS manner but in a “one pot”manner. Here we show that the sedimentation of stoichiometric polyelectrolytecomplexes can lead to a homogeneous coating. This is possible if thepolylectrolyte complexes display a high internal mobility. The filmgrowth rate is then in direct relation with the sedimentation rateof its constituting complexes. On the other hand when the interactionsbetween the oppositely charged polyelectrolytes are too strong, theobtained coating is neither continuous nor homogeneous. [ABSTRACT FROM AUTHOR]

Polyelectrolyte multilayer films are a versatile functionalization method of surfaces and rely on the alternated adsorption of oppositely charged species. Among such species, charged dyes can also be alternated with oppositely charged polymers, which is challenging from a fundamental point of view, because polyelectrolytes require a minimal number of charges, whereas even monovalent dyes can be incorporated during the alternated adsorption process. We will not only focus on organic dyes but also on their inorganic counterparts and on metal complexes. Such films offer plenty of possible applications in dye sensitized solar cells. In addition, dyes are massively used in the textile industry and in histology to stain textile fibers or tissues. However, the excess of non bound dyes poses serious environmental problems. It is hence of the highest interest to design materials able to adsorb such dyes in an almost irreversible manner. Polyelectrolyte multilayer films, owing to their ion exchange behavior can be useful for such a task allowing for impressive overconcentration of dyes with respect to the dye in solution. The actual state of knowledge of the interactions between charged dyes and adsorbed polyelectrolytes is the focus of this review article. [ABSTRACT FROM AUTHOR]

Abstract: The formation of “polydopamine” thin films becomes a popular method to confer multifunctionality to solid–liquid interfaces through the available catechol groups of such films. The mechanism of film formation is, however, not well elucidated, and most investigators use the protocol developed by Messersmith et al. (H. Lee, S.M. Dellatore, W.M. Miller, P.B. Messersmith, Science 318 (2007) 426.) using a dopamine solution at a constant concentration of 2gL−1 in the presence of Tris(hydroxymethyl aminomethane) at pH 8.5. A particular finding of this initial study was that the film thickness reaches a constant value (almost substrate independent) of about 40nm. Herein, we investigate the change in the polydopamine film thickness, morphology, surface energy and electrochemical properties as a function of the concentration of the dopamine solution put in the presence of silicon substrates. As a surprising finding, we observe a constant increase in the maximal film thickness with an increase in the dopamine solution between 0.1 and 5gL−1. The surface morphology is also markedly affected by the concentration of the dopamine solution, whereas the different components of the surface energy stay unaffected by the dopamine solution concentration. In addition, electrochemical impedance spectroscopy shows that the higher the initial dopamine concentration, the more rapidly compact and impermeable films are formed. Finally, we propose a model for the deposition of polydopamine films taking all our findings into account. This model relies on a rate equation taking into account both attractive and repulsive interactions between small polydopamine aggregates on the surface and in solution. [Copyright &y& Elsevier]

Abstract: Among various atmospheric pressure plasma deposition techniques, the so-called “Atmospheric Pressure Plasma Dielectric Barrier Discharges” (APDBD) has recently received a lot of attention due to the easy ignition of a stable discharge and its scalability. In the present work we aim at designing plasma polymer based films for biomedical applications, in which the drug to be released will be directly incorporated in the film during its deposition. Plasma polymer films made of methacrylic acid (MAA) and of ethylene glycol dimethacrylate (EGDMA) were prepared, allowing to obtain smart coatings able to release the molecule of interest, acetaminophen. A combination of different analytic tools shows that the functional groups of the film are well preserved with respect to the monomer structure and that the drug initially put in the gas phase is embedded in the plasma film with its structure being preserved. The physical and chemical characteristics of the elaborated film allowed for the progressive release of acetaminophen by simply dipping the film into a deionized water solution. However only 8% of the acetaminophen present in the monomer mixture could be released slowly in the presence of water. The significance of this result will be discussed. [Copyright &y& Elsevier]

Iatrogenic bacterial meningitis (IBM) is a rare but serious complication of neuraxial procedures, such as spinal and epidural anesthesia or lumbar puncture. We report a case of a 46-year-old female who presented to the emergency department with bacterial meningitis after spinal anesthesia. We review the existing literature outlining the pathogenesis, vector hypothesis, diagnosis, treatment, and prevention as they relate to IBM. We highlight the role of the emergency physician in the rapid diagnosis of this disease, and underscore the need for sterile technique when performing lumbar punctures. [ABSTRACT FROM AUTHOR]

The lateral diffusion of a protein (human serum albuminlabeledwith fluorescein isothiocyanate) within a highly hydrated polyelectrolytefilm is studied. The film is built up with poly(l-lysine)as polycation and hyaluronate as polyanion. Fluorescence recoveryafter photobleaching is used to evaluate the mobility of the labeledprotein. Spatial Fourier transformation is applied to the fluorescenceintensity recorded at various times after bleaching of a narrow rectangulararea within an image representative of the film. This approach necessitatesno hypothesis on the intensity distribution at the end of the bleachingprovided that the bleach has not appreciably changed the concentrationratios of the different diffusing species. Furthermore, under thehypothesis that molecules move according to Fick’s law, werepresent the Fourier transform by a weighted sum of exponentialseach containing another diffusion coefficient and evaluate the proportionattached to each term of this sequence using the simulated annealingmethod. A criterion, combining goodness-of-fit and the entropy characterizingthe diffusion coefficient spectrum, is proposed to avoid overinterpretationof the experimental data. The optimum spectrum of the diffusion coefficientis then extracted from the time evolution of the light intensity atvarious albumin concentrations within the films. It appears that themobility, quantified by the amount of tracer molecules having a diffusioncoefficient smaller than, e.g., 0.1 μm2/s, undergoesa transition between 20 and 2000 μg/mL of internal concentration.This suggests that the mutual interactions of the albumin moleculesand the interactions between fluorescently labeled albumin and thefilm network become increasingly important in the reduction of thealbumin mobility as the albumin concentration increases. [ABSTRACT FROM AUTHOR]

Abstract: The deposition of polyelectrolyte multilayer films (PEMs) appears more and more as a versatile tool to functionalize a broad range of materials with coatings having controlled thicknesses and properties. To increase the control over the properties of such coatings, a good knowledge of their deposition mechanism is required. Since Cohen Stuart et al. (Langmuir 18 (2002) 5607–5612) showed that the adsorption of one polyelectrolyte could induce desorption of polyelectrolyte complexes instead of regular deposition, more and more findings highlight peculiarities in the deposition of such films. Herein we demonstrate that the association of sodium polyphosphate (PSP) as the polyanion and either poly(-L-lysine hydrobromide) (PLL) or poly(allylamine chloride) (PAH) as the polycations may lead to non-monotonous film deposition as a function of time. Complementary, films containing PSP and PLL can be obtained from a (PLL–HA) n template films after the exchange of HA (hyaluronic acid) from the sacrificial template by PSP from the solution. This exchange is accompanied by pronounced film erosion. However, when starting from a (PAH–HA) n template, the film erosion and exchange due to the contact with PSP is by far less pronounced, nevertheless the film morphology changes. These findings show that the nature of the polycation used to deposit the PEM film may have a profound influence of the film’s response to a competing polyanion. [Copyright &y& Elsevier]

Abstract: Dopamine–melanin films produced through the oxidation of dopamine in the presence of oxygen as an oxidant allow to reduce silver ions onto silver particles as already described in the paper by Lee et al. (H. Lee, S.M. Dellatore, W.M. Miller, P.B. Messersmith, Science 318 (2007) 426.). This reduction process has to occur through the oxidation of moieties present in the melanin film. This investigation shows that the free radicals present in the pseudomelanin film, quantified by means of electron spin resonance spectroscopy (ESR) for the first time, are not used in the transformation of Ag+ cations to deposit silver. The ESR signal is hardly affected by the deposition of silver particles. On the other hand, X-ray photoelectron spectroscopy shows a small increase in the density of quinone groups and a small decrease of catechol groups on the surface of the film during the deposition of silver. This suggests that the deposited pseudomelanin films contain a significant fraction of catechol groups able to trigger reduction processes of metallic cations. These silver nanoparticles remain adherent to the melanin films and allow for a quantitative killing of Escherichia coli over a broad range of bacterial dilutions. However, the presence of the bacteria induces a release of the nanoparticles. The pseudomelanin films cannot be reused again for a silver ion reduction step. Nevertheless, the easy preparation of the pseudomelanin–silver composite and its effective one shot bacterial killing activity renders the strategy presented in this paper attractive. Some fundamental questions about redox process allowed by the pseudomelanin films will also be asked. [Copyright &y& Elsevier]

Abstract: Background: Benign acute childhood myositis (BACM) is a rare transient muscle syndrome classically occurring in children after a viral upper respiratory infection (URI). BACM causes difficulty walking due to severe bilateral calf pain. The incidence of this well-described phenomenon is uncertain but infrequent, and it is typically appreciated during times of large influenza outbreaks and epidemics. The URI symptoms that precede BACM are consistent with an uncomplicated viral influenza infection and include fever, malaise, cough, sore throat, headache, and rhinitis. Objectives: Little is written in the Emergency Medicine literature regarding this clinical entity. In this report, a brief review of BACM from the current literature is provided, as well as tools to aid in differentiating it from more severe but similar disorders such as rhabdomyolysis and Guillain-Barré syndrome. Case Report: We present a case of BACM in a 7-year-old boy who presented to the emergency department after a resolving URI with the acute onset of calf pain causing alarming difficulty in his ability to walk. His presentation was typical for BACM and his condition improved with supportive treatment. Conclusions: Although quite alarming and potentially puzzling to the physician who is not familiar with BACM, this syndrome is self limited and spontaneously resolves with no specific intervention. Recognition of this rare but distinct clinical entity by the emergency physician can spare a patient from potentially unneeded invasive testing and hospital admission. [ABSTRACT FROM AUTHOR]

Isothermal titration microcalorimetry (ITC) is mostly used to investigate the thermodynamics of "specific" host-guest interactions in biology as well as in supramolecular chemistry. The aim of this review is to demonstrate that ITC can also provide useful information about non-specific interactions, like electrostatic or hydrophobic interactions. More attention will be given in the use of ITC to investigate polyelectrolyte-polyelectrolyte (in particular DNA-polycation), polyelectrolyte-protein as well as protein-lipid interactions. We will emphasize that in most cases these "non specific" interactions, as their definition will indicate, are favoured or even driven by an increase in the entropy of the system. The origin of this entropy increase will be discussed for some particular systems. We will also show that in many cases entropy-enthalpy compensation phenomena occur. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the different molecular recognition systems used for inducing adhesion, fusion of vesicles as well as their physical properties. A third part concerns the control of the release of vesicles at the solid interface thanks to an optimized polyelectrolyte coating. Various chemical strategies based on the incorporation of recognition lipids are presented and compared to induce and control the interaction between membranes. The kinetics effects in the adhesion and fusion processes are demonstrated by complementary techniques such as the micropipettes, fluorimetry and reflexion interference contrast microscopy. [Copyright &y& Elsevier]

Abstract: In this review we summarize novel aspects of the hydration and internal properties of polyelectrolyte multilayers formed by layer-by-layer assembly. Reflectivity techniques monitor the water content and swelling behavior, while spin relaxation monitors water mobility. Odd–even effects in dependence on the number of layers are discussed in terms of an influence of the terminating layer. Other novel methodological approaches like X-ray microscopy or NMR cryoporometry address the water content in hollow capsules, and the water pore size distribution, respectively. Multilayer material properties are relevant for different applications. As a novel concept, dielectric properties are monitored in a field effect transistor device. Ion mobility and redox processes in multilayers are revealed by the electrochemical properties. Mechanical properties of multilayers, studied by colloidal probe atomic force microscopy depend on the conformation of the polymers involved. [Copyright &y& Elsevier]

Abstract: Complexation between linear poly-l-lysine (PLL) and negatively charged phosphocholine unilamellar liposomes has been investigated by means of dynamic light scattering, microelectrophoresis, and differential scanning calorimetry. It is found that complexation results in charge inversion (vesicle coating/stabilization) or vesicle aggregation depending on various experimental conditions. Complexation in dependence on PLL concentration and molecular mass, lipid phase state, rate and order of liposome and PLL mixing and time evolution of complexes are investigated and discussed. Aggregation profiles are determined and size distribution of the aggregates formed is studied, leading to the possibility of aggregation control. The time evolution of vesicle aggregation shows particle enlargement consisting in particle growth up to the irreversible formation of thermodynamically stable aggregates of about 2 μm in diameter. The formation of stable aggregates is in agreement with theoretical predictions of colloid particles aggregation by an interplay of long range electrostatic repulsion and short range attraction. Differential scanning calorimetry reveals that physical adsorption occurs exclusively on the vesicle surface and the lipidic organization is not significantly disturbed. The present study describes multivariable aspects of the complexation process between liposomes and polyions which results in the formation of a new class of still poorly defined colloids. These results allow establishing and optimization of a procedure for fabrication of polycation-stabilized vesicles to be used for various applications such as drug delivery. [Copyright &y& Elsevier]

Abstract: In this work, incorporation of plasmid DNA, pre-complexed with PEI, into polyelectrolyte multilayers has been studied to further develop platforms for local gene delivery. Polyplex embedding in synthetic and naturally degradable architectures was efficient for transfection of human hepato-cellular carcinoma cells. [Copyright &y& Elsevier]

The understanding of the role of biological macromolecules in the nucleation of calcium carbonates and calcium phosphates is of primary importance for the development of biomimetic surfaces able to mimic the proteins used by living organisms to produce such composite materials. In this study we show how polyelectrolyte multilayers made from poly-l-lysine (PLL) as the polycation and from a mixture of two polyanions, poly-l-glutamic acid (PGA) and poly-l-aspartic acid (Pasp), at different ratios are able to affect the duration of the lag time preceding crystal growth at constant supersaturation. These polyelectrolyte multilayers appear as interesting candidates for biomimetic surfaces, since they display a content of β-sheets that can be controlled by changing the PGA proportion in the polyanion mixture. The duration of the lag times preceding fast crystal growth is measured in situ with three complementary techniques, namely quartz crystal microbalance with dissipation (QCM-D), optical waveguide lightmode spectroscopy (OWLS), and infrared spectroscopy in the attenuated total reflection mode (ATR-FTIR). The three techniques lead to comparable results, and ATR-FTIR spectroscopy allows us to demonstrate that the growing inorganic particles are calcium phosphates. The obtained mineral is most probably octacalcium phosphate or poorly crystalline hydroxyapatite, whatever the PGA content of the multilayer film. However, the duration of the lag time as well as the morphology of the obtained particles cannot be simply correlated with the β sheet content of the multilayer film. In this study we show how polyelectrolyte multilayers made from poly-l-lysine (PLL) as the polycation and from a mixture of two polyanions, poly-l-glutamic acid (PGA) and poly-l-aspartic acid (Pasp), at different ratios are able to affect the duration of the lag time preceding crystal growth at constant supersaturation. These polyelectrolyte multilayers appear as interesting candidates for biomimetic surfaces, since they display a content of β-sheets that can be controlled by changing the PGA proportion in the polyanion mixture. [ABSTRACT FROM AUTHOR]

The adsorption and desorption kinetics of six polypeptides, denoted by 1, 2, 3A, 3B, 4 and bee venom melittin, close in molecular weight but differing in their apparent charge state and hydrophobicity are investigated at a given bulk concentration (10−6 M) by means of optical waveguide light mode spectroscopy at an Si0.8Ti0.2O2–aqueous solution interface. At pH 8.0 and a salt concentration of 0.01 M, it is found that four of these polypeptides, 1, 2, 4 and melittin display quasi identical adsorption kinetics and differ only significantly with respect to their desorption kinetics. These observations could be rationalized by the calculation of their charge state in the framework of the Linderstro¨m-Lang model: in contrast with predictions based on their amino acid sequence, all these molecules display only a very small charge due to pKa modifications in this low ionic strength medium. In marked contrast to the four other polypeptides, the molecules 3A and 3B, identical in their amino acid composition but differing in the localization of four amino acids (through two point mutations), display smaller adsorption rates when put in contact with the sorbent. Moreover, their desorption kinetics could be fitted by means of only one exponential decay function whereas two exponentials where necessary for the first class of polypeptides. No evident reason is found to explain this peculiar adsorption behavior since 3A and 3B display the same average (calculated) charge state and hydrophobicity as the other investigated molecules. The polypeptides 1, 2, 3A, 3B display an adsorption hysteresis: their desorption rate constant depends markedly on the contact time between the polypeptide solution and the sorbent. In that sense, the interfacial behavior of these molecules is quite similar to that of large globular proteins. [Copyright &y& Elsevier]

• The reaction of aminomalononitrile (AMN) at pH = 8.6 allows to produce coatings displaying redox activity. • This redox activity affords antioxidant properties to the AMN based films. • Those antioxydant properties depend on the film thickness and morphology. Conformal films obtained through polymerization of aminomalononitrile in solution at pH = 8.6 display an irreversible electrochemical oxidation current and a thickness/ morphology dependant antioxidant activity as measured by the quenching of 2,2-diphenyl-1-picrylhydrazyl. These findings illustrate that materials issued from molecules suspected to have played an important role in prebiotic chemical process offer application potentials in biomaterials science. [ABSTRACT FROM AUTHOR]

• Close similarity between polydopamine and eumelanin. • Several templating agents allow to obtain polydopamine based nanomaterials. • Biomimetic approaches appear the most successful. • Description of these nanomaterials as therapeutic agents and sensing materials. The mussel inspired chemistry of dopamine leading to versatile coatings on the surface of all kinds of materials in a one pot process was considered as the unique aspect of catecholamine for a long time. Only recently, research has been undertaken to valorize the simultaneous oxidation and colloid formation in dopamine solutions in the presence of an oxidant. This mini review summarizes the synthesis methods allowing to get controlled nanomaterials, either nanoparticles, hollow capsules or nanotubes and even chiral nanomaterials from dopamine solutions. Finally the applications of those nanomaterials will be described. [ABSTRACT FROM AUTHOR]

Polyphenols like tannic acid, and others, adsorb spontaneously to the surface of a vast repertoire of materials to coat them with a conformal and functional thin film. Since polyphenols can be oxidized, their deposition can also be controlled at the surface of conductive materials. Since the oxidized form of polyphenols contains reactive quinone groups it could be of interest to electropolymerize them in the presence of nucleophiles, like polyamines to obtain composite coatings with properties different from those displayed by a coating obtained from the polyphenol alone. However in conditions where polyamines are reactive and unprotonated, polyphenols undergo spontaneous, non controlled oxidation. In this article, the electropolymerization of tannic acid (TA) by means of cyclic voltammetry is performed at pH = 5.0. The obtained TA based coatings are compared to those obtained from blends with poly(allylamine hydrochloride) (PAH) as a primary polyamine and with poly(diallyldimethyl ammonium chloride) (PDADMAC) containing quaternary ammonium groups. In these conditions, the polyamines form complexes with TA. It will be shown by means of electrochemical impedance spectroscopy, that the higher the PAH concentration in the blend, the higher is the pseudocapacitance of the film. This finding is explained by the incorporation of positively charged PAH or PDADMAC into the film during the oxidation of TA and by the increase in film roughness/porosity in the presence of the polycation. [ABSTRACT FROM AUTHOR]

(1) Background: polyphenols are a broad class of molecules extracted from plants and have a large repertoire of biological activities. Biomimetic inspiration from the effects of tea or red wine on the surface of cups or glass lead to the emergence of versatile surface chemistry with polyphenols. Owing to their hydrogen bonding abilities, coordination chemistry with metallic cations and redox properties, polyphenols are able to interact, covalently or not, with a large repertoire of chemical moieties, and can hence be used to modify the surface chemistry of almost all classes of materials. (2) Methods: the use of polyphenols to modify the surface properties of dental materials, mostly enamel and dentin, to afford them with better adhesion to resins and improved biological properties, such as antimicrobial activity, started more than 20 years ago, but no general overview has been written to our knowledge. (3) Results: the present review is aimed to show that molecules from all the major classes of polyphenolics allow for low coast improvements of dental materials and engineering of dental tissues. [ABSTRACT FROM AUTHOR]

The diaphragm, which forms a physical barrier between the thoracic and the abdominal cavities, is also the major part of the respiratory system. Congenital diaphragmatic hernia (CDH) is a malformation of that partition muscle. Expanded polytetrafluoroethylene (e-PTFE), a synthetic nondegradable biomaterial, is currently used for the repair of diaphragm defects. Indeed, this hydrophobic biomaterial does not promote rapid and dense cell colonization. Surface modifications are needed to favor or even guide cellular responses. In this context, we present here a practical and effective way of functionalization of the e-PTFE material. We investigated, by using electron microscopy, the coating with PRF (Platelet-Rich Fibrin) of PDA (Polydopamine) treated e-PTFE implant material. We demonstrate that this straightforward chemical functionalization with PDA increases the hydrophilicity of e-PTFE and thus improves tissue integration. Then, we demonstrated that whatever the contact time between PRF and e-PTFE and the centrifugation speed, the PDA coating on the e-PTFE biomaterial promotes further biological events like cell adhesion and spreading. Our findings clearly show that this composite coating (chemically by using PDA + biologically by using PRF) method of e-PTFE is a simple, interesting and promising way to favor tissular integration of such biomaterials. [ABSTRACT FROM AUTHOR]

Review: 46 refs. [ABSTRACT FROM AUTHOR]

The article discusses the postassembly reversible loading and unloading of nanoparticles in polyelectrolyte film. The layer-by-layer assembly technique is used as a method for the preparation of thin films with controlled properties. It is mentioned that the structure of the variations of these layers and nanoparticles can control the release as well as the incorporation of the nanoparticles.

Polyphenols are important molecules in living organisms, particularly in plants, where they serve as protectants against predators. They are also of fundamental importance in pharmacology for their antioxidant and antibacterial activities. Since a few years polyphenols are also used in surface functionalization mimicking the tannin deposition observed when tea or red wine are in contact with the surface of cups or glasses respectively. The interaction of polyphenols with proteins to yield colloids and of polyphenol with surfaces will be reviewed in this article to provide an overview of such particles and surface functionalization methods in modern surface science. Particular emphasis will be given to biological applications of polyphenols at interfaces. [ABSTRACT FROM AUTHOR]

Layer-by-layer-deposition of enzymes and polyphenols, like tannic acid may provide a reservoir of antioxidant and antibacterial molecules of controlled thickness and degradability with an additional activity due to the presence of the enzyme. The layer-by-layer deposition of films made from tannic acid and alkaline phosphatase is shown to yield an exponential growth with the number of deposited layer pairs. The films display the electrochemical behavior of tannic acid and the enzymatic activity of alkaline phosphatase. However, it is shown that only the enzyme close to the film-solution interface is active and follows the Michaelis-Menten mechanism. Similarly, only tannic acid close to the electrode-film interface can be oxidized. The enzymatic activity is almost completely lost when the multilayer film is treated with sodium periodate which oxidizes tannic acid even if the solubilized enzyme is not affected by the oxidant. This shows that the formation of covalent bonds between alkaline phosphatase and tannic acid is deleterious for its conformation and activity. [ABSTRACT FROM AUTHOR]