Polyelectrolyte complexes of chitosan and hyaluronic acid or carboxymethylpullulan and their aminoguaiacol derivatives with biological activities as potential drug delivery systems.

Polyelectrolyte complexes (PECs) were elaborated from chitosan as cationic polymer and carboxy-methylpullulan (CMP), hyaluronic acid (HA) and their derivatives grafted with aminoguaiacol (G) with different degrees of substitution (DSGA) with the aim of obtaining nanogels for drug delivery. For each couple of polysaccharides, the charge ratios giving the smaller size with the lower PDI were selected to produce PECs. CMP_CHIT and CMP-G_CHIT PECs had smaller sizes (220-280 nm) than HA_CHIT and HA-G_CHIT PECs (280-390 nm). PECs were stable at 4 °C during 28 days at pH 5. In phosphate buffer saline (PBS) at pH 7.4, at 4 °C, a better stability of PECs based on CMP-G derivatives was observed. The hydrophobic associations between aminoguaiacol groups (highlighted by measurements of pyrene fluorescence) led to a better PECs' stabilization in PBS. The PECs' antioxidant and antibacterial activities were demonstrated and related to the DSGA. Diclofenac and curcumin were used as drug models: their loading reached 260 and 53 µg/mg PEC, respectively. The release of diclofenac in PBS at 37 °C followed a quasi-Fickian diffusion mechanism with release constant between 0.88 and 1.04 h-1. The curcumin release followed a slow linear increase in PBS/EtOH (60/40 V/V) with an effect of DSGA.

SDGs and public health policies: implementing the S2D grid in the city of Lausanne, Switzerland.

Sustainable development goals (SDGs) and public health are often considered as separate policy fields, whereas there is a considerable potential in better coordinating their objectives and measures. Using an analytical grid (S2D grid) linking SDGs and public health objectives and comprising 6 thematic issues and 56 categories, the research team conducted an assessment of health promotion programs in the city of Lausanne, Switzerland. Their objective was to determine whether SDGs and public health concerns can translate into complementary policy objectives, and what was the level of achievement of Lausanne in terms of implementation, intersectoral collaboration and avoidance of redundancy, regarding the vast array of measures potentially dealing with SDGs and health promotion. Results show that measures implemented by Lausanne deal with 80% of categories included in the S2D grid, with a high level of intersectorality and a low level of redundancy. These results also emphasize the fact that linkages between SDGs and health promotion go well beyond the SDG 3 dedicated to 'good health and well-being', and that the S2D grid could be used as a tool in favor of organizational change, promoting the collaboration between stakeholders often reluctant to engage in public health policies.

Antibacterial Zirconia Surfaces from Organocatalyzed Atom-Transfer Radical Polymerization.

Antibacterial coatings are becoming increasingly attractive for application in the field of biomaterials. In this framework, we developed polymer coating zirconia with antibacterial activity using the "grafting from" methodology. First, 1-(4-vinylbenzyl)-3-butylimidazolium chloride monomer was synthesized. Then, the surface modification of zirconia substrates was performed with this monomer via surface-initiated photo atom transfer radical polymerization for antibacterial activity. X-ray photoelectron spectroscopy, ellipsometry, static contact angle measurements, and an atomic force microscope were used to characterize the films for each step of the surface modification. The results revealed that cationic polymers could be successfully deposited on the zirconia surfaces, and the thickness of the grafted layer steadily increased with polymerization time. Finally, the antibacterial adhesion test was used to evaluate the antibacterial activity of the modified zirconia substrates, and we successfully showed the antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa strains.

Implants coating strategies for antibacterial treatment in fracture and defect models: A systematic review of animal studies.

Objective: Fracture-related infection (FRI) remains a major concern in orthopaedic trauma. Functionalizing implants with antibacterial coatings are a promising strategy in mitigating FRI. Numerous implant coatings have been reported but the preventive and therapeutic effects vary. This systematic review aimed to provide a comprehensive overview of current implant coating strategies to prevent and treat FRI in animal fracture and bone defect models. Methods: A literature search was performed in three databases: PubMed, Web of Science and Embase, with predetermined keywords and criteria up to 28 February 2023. Preclinical studies on implant coatings in animal fracture or defect models that assessed antibacterial and bone healing effects were included. Results: A total of 14 studies were included in this systematic review, seven of which used fracture models and seven used defect models. Passive coatings with bacteria adhesion resistance were investigated in two studies. Active coatings with bactericidal effects were investigated in 12 studies, four of which used metal ions including Ag+ and Cu2+; five studies used antibiotics including chlorhexidine, tigecycline, vancomycin, and gentamicin sulfate; and the other three studies used natural antibacterial materials including chitosan, antimicrobial peptides, and lysostaphin. Overall, these implant coatings exhibited promising efficacy in antibacterial effects and bone formation. Conclusion: Antibacterial coating strategies reduced bacterial infections in animal models and favored bone healing in vivo. Future studies of implant coatings should focus on optimal biocompatibility, antibacterial effects against multi-drug resistant bacteria and polymicrobial infections, and osseointegration and osteogenesis promotion especially in osteoporotic bone by constructing multi-functional coatings for FRI therapy. The translational potential of this paper: The clinical treatment of FRI is complex and challenging. This review summarizes novel orthopaedic implant coating strategies applied to FRI in preclinical studies, and offers a perspective on the future development of orthopaedic implant coatings, which can potentially contribute to alternative strategies in clinical practice.

Dual-functional antibacterial and osteogenic nisin-based layer-by-layer coatings.

Implanted biomaterials can be regarded in a cornerstone in the domain of bone surgery. Their surfaces are expected to fulfil two particular requirements: preventing the settlement and the development of bacteria, and stimulating bone cells in view to foster osseointegration. Therefore, a modern approach consists in the design of dual functional coatings with both antibacterial and osteogenic features. To this end, we developed ultrathin Layer-by-Layer (LbL) coatings composed of biocompatible polyelectrolytes, namely chondroitin sulfate A (CSA) and poly-l-lysine (PLL). The coatings were crosslinked with genipin (GnP), a natural and biocompatible crosslinking agent, to increase their resistance against environmental changes, and to confer them adequate mechanical properties with regards to bone cell behaviors. Antibacterial activity was obtained with nisin Z, an antimicrobial peptide (AMP), which is active against gram-positive bacteria. The coatings had a significant bactericidal impact upon Staphylococcus aureus, with fully maintained bone cell adhesion, proliferation and osteogenic differentiation.

Nisin-based antibacterial and antiadhesive layer-by-layer coatings.

Some removable medical devices such as catheters and cardiovascular biomaterials require antiadhesive properties towards both prokaryotic and eukaryotic cells in order to prevent the tissues from infections upon implantation and, from alteration upon removal. In order to inhibit cell adhesion, we developed ultrathin hydrated Layer-by-Layer (LbL) coatings composed of biocompatible polyelectrolytes, namely chondroitin sulfate A (CSA) and poly-l-lysine (PLL). The coatings were crosslinked with genipin (GnP), a natural and biocompatible crosslinking agent, to increase their resistance against environmental changes. In order to confer antibacterial activity to the coatings, we proceeded to the electrostatically-driven immobilization of nisin Z, an antimicrobial peptide (AMP) active against gram-positive bacteria. The nisin-enriched coatings had a significantly increased anti-proliferative impact on fibroblasts, as well as a strong contact-killing activity against Staphylococcus aureus in the short and long term.

Various methods to combine hyaluronic acid and antimicrobial peptides coatings and evaluation of their antibacterial behaviour.

To prevent bacterial adhesion and contamination, biomaterials exhibiting both antiadhesive and biocidal properties are the most promising way. However, control of the properties combination is not so easy due, in particular, to antagonist mechanisms. Antibacterial surfaces against Staphylococcus epidermidis adhesion were here elaborated by using both nisin grafting and repelling polysaccharide coating. We evaluated two strategies aiming to improve the antimicrobial peptide (AMP) immobilization parameters (i.e., the accessibility and/or local density) in order to obtain the best antimicrobial activity on surfaces. We thus (i) grafted the nisin on a surface previously coated with hydrolyzed hyaluronic acid (HA) (to decrease the length of the polysaccharide chains) or (ii) coupled nisin and HA in solution before grafting this complex on surfaces. XPS analysis pointed out a lower amount of nisin on the surface for both approaches compared to the immobilization of nisin on native HA. However, an antibacterial activity was maintained, probably due to a higher local density of the AMP when surfaces were modified with hydrolyzed hyaluronic acid, leading to a better combination of antiadhesive-biocidal properties. Microscopy fluorescent observations demonstrated that accumulation of dead cells was also avoided by some coatings architecture.

Development of a novel functional core-shell-shell nanoparticles: From design to anti-bacterial applications.

This article reports the synthesis and functionalization of a novel CuO@SiO2-APTES@Ag0 core-shell-shell material using a simple and low-cost process. The growth, design strategies and synthesis approach are the key factors for the development of CuO@SiO2-APTES@Ag0 as efficient material with enhanced antibacterial activity. We investigated the morphology, surface charge, structure and stability of our new core-shell-shell by atomic force microscopy, scanning electron microscopy, energy dispersive X-ray, Fourier transform infrared and UV-visible spectroscopies, zeta potential measurements, and differential scanning calorimetry. The covalent surface grafting of APTES (3-(aminopropyl)triethoxysilane) onto CuO@SiO2 involving electrostatic interactions was confirmed. Size measurements and Scanning electron images showed that both APTES grafting and SiO2/Ag shells dropped on the surface of CuO produced structural compaction. UV-Vis spectroscopy proved to be a fast and convenient way to optically detect SiO2 shell on the surface of colloids. Additionally, the Ag-decorated CuO@SiO2-APTES surfaces were found to possess antibacterial activity and thermally more stable than undecorated surfaces. CuO@SiO2-APTES@Ag0 core-shell had antibacterial properties against Gram-positive bacteria making it a promising candidate for antibacterial applications.

Carboxymethylpullulan Grafted with Aminoguaiacol: Synthesis, Characterization, and Assessment of Antibacterial and Antioxidant Properties.

Aminoguaiacol, the aminated derivative of guaiacol, a natural phenolic compound, was chemically grafted onto a polysaccharide (carboxymethylpullulan, CMP) in the presence of the activator agent 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide hydrochloride (EDCI). The grafted polysaccharides were characterized by FTIR and 1H NMR spectroscopy to confirm and quantify the grafting. All polysaccharide derivatives (grafting rates of aminoguaiacol between 16% and 58%) were soluble in water. Their physicochemical properties were studied in a dilute regime and a semidilute regime by light scattering, fluorescence, and rheology, showing associative properties with peculiar polysoap behavior. The antibacterial activities of the synthesized products against Staphyloccocus aureus were assessed using a counting method. The antioxidant activities of the derivatives were also highlighted using the α,α-diphenyl-ß-picrylhydrazyl (DPPH) method. Finally, the cytotoxicity of the derivatives was studied with fibroblast cells and they showed a very good cytocompatibility. Such polymers could be used to replace chemical preservatives in food and cosmetic aqueous formulations.

Elaboration of antibacterial plastic surfaces by a combination of antiadhesive and biocidal coatings of natural products.

Antibacterial polyolefins surfaces, combining biocidal and antiadhesive properties, were elaborated by a covalent grafting of antimicrobial peptides (AMPs), able to kill adherent bacteria, on a pre-immobilized hyaluronic acid (HA) layer, able to repel the micro-organisms. Different HA activation rate for its immobilization, were used to change HA layer morphology and number of residual free carboxylic acid functions for AMPs grafting. Based on adhesion tests on Staphylococcus epidermidis and microscopy fluorescent observations, the presence of the two combined properties was shown to be depended on the HA activation rate. Thus, the best addition effect was observed for an AMP grafting on a surface based on a high HA activation, data pointing out a decrease of the bacterial adhesion up to 99.8% and a perturbation of the bacterial membrane integrity of adhered bacteria. On the contrary, a decrease of the antibacterial activity was observed for an AMP grafting on a surface based on a low HA activation.

Design of an anti-adhesive surface by a pilicide strategy.

Biofilm formation on surfaces is one of major problems in medical, cosmetic and food industries. Nowadays any efficient treatment is known, as consequence, research of new strategies to inhibit biofilm formation is urgent. Recently, virstatin, which interferes with bacterial type IV pili formation, has demonstrated a capacity to inhibit biofilm formation developed by Acinetobacter baumannii after 24h. In this study, we aim to elaborate anti-adhesive surfaces preventing biofilm development by the covalent immobilization of virstatin on silicon surface. Surfaces were functionalized by self-assembled monolayers of two aminosilanes (11-aminoundecyltrimethoxysilane (AUTMS) and 3-aminopropyltrimethoxysilane (APTMS)). Then, virstatin (2mM) was immobilized on those modified surfaces. We observed an increase in surface hydrophobicity of AUTMS modified substratum leading to an increase of A. baumannii ATCC 17978 adhesion (after 4h). Immobilization of virstatin molecule on APTMS modified surface was efficient to decrease cell attachment by 32.1±5.7% compared to unmodified surface. As virstatin is known to inhibit type IV pili formation in solution, the observed decrease of bacterial adhesion might be due to this pilicide action. We also demonstrated that hydrophobicity of strains plays a role in adhesion according to surface properties. In conclusion, immobilized virstatin succeeded to inhibit bacterial attachment of various Acinetobacter baumannii strains comparing to APTMS modified support.

Polysaccharide-based antibiofilm surfaces.

Surface treatment by natural or modified polysaccharide polymers is a promising means to fight against implant-associated biofilm infections. The present review focuses on polysaccharide-based coatings that have been proposed over the last ten years to impede biofilm formation on material surfaces exposed to bacterial contamination. Anti-adhesive and bactericidal coatings are considered. Besides classical hydrophilic coatings based on hyaluronic acid and heparin, the promising anti-adhesive properties of the algal polysaccharide ulvan are underlined. Surface functionalization by antimicrobial chitosan and derivatives is extensively surveyed, in particular chitosan association with other polysaccharides in layer-by-layer assemblies to form both anti-adhesive and bactericidal coatings. STATEMENT OF SIGNIFICANCE: Bacterial contamination of surfaces, leading to biofilm formation, is a major problem in fields as diverse as medicine, first, but also food and cosmetics. Many prophylactic strategies have emerged to try to eliminate or reduce bacterial adhesion and biofilm formation on surfaces of materials exposed to bacterial contamination, in particular implant materials. Polysaccharides are widely distributed in nature. A number of these natural polymers display antibiofilm properties. Hence, surface treatment by natural or modified polysaccharides is a promising means to fight against implant-associated biofilm infections. The present manuscript is an in-depth look at polysaccharide-based antibiofilm surfaces that have been proposed over the last ten years. This review, which is a novelty compared to published literature, will bring well documented and updated information to readers of Acta Biomaterialia.

Elucidation of innovative antibiofilm materials.

It is known for roughly a decade that bacterial communities (called biofilms) are responsible for significant enhanced antibiotherapy resistance. Biofilms are involved in tissue persistent infection, causing direct or collateral damage leading to chronic wounds development and impairing natural wound healing. In this study, we are interested in the development of supported protein materials which consist of asymmetric membranes as reservoir supports for the incorporation and controlled release of biomolecules capable of dissolving biofilms (or preventing their formation) and their use as wound dressing for chronic wound treatment. In a first step, polyhydroxyalkanoates (PHAs) asymmetric membranes were prepared using wet phase inversion technique. Scanning microscopy (SEM) analysis has showed the influence of different processing parameters. In a second step, the porous side of the membranes were functionalized with a surface treatment and then loaded with the antibiofilm agent (dispersin B). In a third step, the properties and antibiofilm performance of the loaded-membranes were evaluated. Exposure of Staphylococcus epidermidis biofilms to such systems weakly inhibited biofilm formation (weak preventive effect) but caused their detachment and disaggregation (strong curative effect). These initial results are promising since they open the way to a new generation of effective tools in the struggle against persistent bacterial infections exhibiting enhanced antibiotherapy resistance, and in particular in the case of infected chronic wounds.

Two methods for one-point anchoring of a linear polysaccharide on a gold surface.

Two strategies to achieve a one-point anchoring of a hydrolyzed pullulan (P9000) on a gold surface are compared. The first strategy consists of forming a self-assembled monolayer of a 6-amino-1-hexanethiol (AHT) and then achieving reductive amination on the surface between the aminated surface and the aldehyde of the polysaccharide reductive end sugar. The second consists of incorporating a thiol function at the extremity of the pullulan (via the same reductive amination), leading to P9000-AHT and then immobilizing it on gold by a spontaneous reaction between solid gold and thiol. The modified pullulan was characterized by NMR and size-exclusion chromatography coupled to a light-scattering detector. P9000-AHT appears to be in a disulfide dimer form in solution but recovers its unimer form with dithiothreitol (DTT) treatment. The comparison of the two strategies by contact angle and XPS revealed that the second strategy is more efficient for the pullulan one-point anchoring. P9000-AHT even in its dimer form is easily grafted onto the surface. The grafted polymer seems to be more in a coil conformation than in a rigid brush. Furthermore, QCM measurements highlighted that the second strategy leads to a grafting density of around 3.5 × 10(13) molecules·cm(-2) corresponding to a high surface coverage. The elaboration of a dense and oriented layer of polysaccharides covalently linked to a gold surface might enhance the use of such modified polysaccharides in various fields.

Role of molecular properties of ulvans on their ability to elaborate antiadhesive surfaces.

Antiadhesive properties of polysaccharides (such ulvans) once immobilized on a surface are described in the literature but the parameters governing their antifouling properties are not yet well identified. In the present study, the relationship between molecular parameters of ulvans and the inhibition of bacterial adhesion was investigated. To this aim, various ulvans were grafted on silicon wafers under two different experimental immobilization conditions. Results showed that the experimental immobilization conditions and the polysaccharides molecular weight led to specific layer conformations which exhibited a key role in the surface antiadhesive properties.

Antiadhesive activity of ulvan polysaccharides covalently immobilized onto titanium surface.

Bacterial adhesion leading to biofilm formation on the surface of implants is responsible for pathogenesis infections. One promising strategy to reduce the risk of infection consists of modifying implant surfaces by antibacterial coating. In the present study, the ability of ulvan, a non biocidal algal polysaccharide, to limit bacterial adhesion on titanium was investigated. To this end, titanium surfaces were modified by two different ulvans. Polysaccharides were covalently immobilized on titanium surfaces which had been previously functionalized by self assembled monolayers of aminoundecyltrimethoxysilane (AUTMS). Each step in the modification process was characterized by contact angle, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Bacterial adhesion assays showed that immobilized ulvans on titanium surface strongly decreased by about 90% the adhesion of Pseudomonas aeruginosa. Moreover, AFM observations showed that the polysaccharide also inhibited the bacterial spreading on the surface but not cell-to-cell interaction. The permanence of the anti-adhesive effect of the surfaces was finally tested on a non-motile organism, i.e., Staphylococcus epidermidis. The results showed that the effect was maintained for at least 24h.

Tailoring nanostructures using copolymer nanoimprint lithography.

The generation of defect-free polymer nanostructures by nanoimprinting methods is described. Long-range nanorheology and shorter-range surface energy effects can be efficiently combined to provide alignment of copolymer lamellae over several micrometers. As an example, a perpendicular organization with respect to circular tracks is shown, demonstrating the possibility of writing ordered radial nanostructures over large distances.

Elaboration of antibiofilm materials by chemical grafting of an antimicrobial peptide.

A peptide antibiotic, gramicidin A, was covalently bound to cystamine self-assembled monolayers on gold surfaces. Each step of the surface functionalization was characterized by polarization modulation infrared reflection absorption spectroscopy and X-ray photoelectron spectroscopy. The antimicrobial activity of the anchored gramicidin was tested against three Gram-positive bacteria (Listeria ivanovii, Enterococcus faecalis, and Staphylococcus aureus), the Gram-negative bacterium Escherichia coli and the yeast Candida albicans. The results revealed that the adsorbed gramicidin reduced, from 60% for E. coli to 90% for C. albicans, the number of culturable microorganisms attached to the surface. The activity was proven to be persistent overtime, up to 6 months after the first use. The bacteria attached to the functionalized surfaces were permeabilized as shown by confocal microscopy. Taken together, these results indicate a bacteriostatic mode of action of the immobilized peptide. Finally, using green fluorescent protein-expressing bacteria, it was shown that the development of a bacterial biofilm was delayed on peptide-grafted surfaces for at least 24 h.

Investigation of an allergen adsorption on amine- and acid-terminated thiol layers: influence on their affinity to specific antibodies.

This work describes the controlled immobilization of a recognized allergen, beta-lactoglobulin, onto gold transducers with the aim of optimizing the elaboration of a biosensor directed against allergen-produced antibodies. This protein was immobilized on both amine- and acid-terminated thiol self-assembled monolayers, and the influence on its affinity to a specific IgG was investigated. For amine-terminated layers, the beta-lactoglobulin was immobilized via its surface acid functions implying an activation step with 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride/ester of N-hydroxysuccinimide (EDC-NHS). Conversely, the grafting on acid-terminated layer takes advantage of the accessible amine groups that react with the activated acidalkylthiols. The resulting layers of beta-lactoglobulin were then submitted to various concentrations of rabbit serum containing beta-lactoglobulin specific rabbit immunoglobulin (rIgG), and the antigen/antibody affinity was evaluated using modulated polarization-infrared absorption spectroscopy (PM-IRRAS) and Fourier transform surface plasmon resonance (FT-SPR). Even though for similar concentration, the amount of adsorbed beta-lactoglobulin was identical on both surfaces, atomic force microscopy (AFM) images showed a better dispersion for amine-terminated layers. Moreover, the affinity to specific IgG, estimated under static conditions by PM-IRRAS and under dynamic conditions by SPR, was different. Grafting beta-lactoglobulin via its acid groups gave an affinity constant 3 times higher than its immobilization via its amine groups despite the fact that the amount of accessible recognition sites appeared to be similar for both systems. This work underlines the importance of the involved chemical groups upon protein immobilization on their biological activity and will be essential for the construction of nondirect biosensors for detecting specific immunoglobulin E (IgE) of allergens.

Contact-active microbicidal gold surfaces using immobilization of quaternary ammonium thiol derivatives.

Contact-active auto-bactericidal surfaces were obtained by grafting of specially designed thiol derivatives containing antimicrobial quaternary ammonium moieties on gold substrates. The formation and quality of the self-assembled monolayers (SAMs) were characterized by X-ray photoelectron spectroscopy, cyclic voltammetry and contact angle measurements. The bactericidal activity of the modified gold surface was evaluated against Staphylococcus aureus using an original procedure. This activity was demonstrated to be dependent on the length of the alkyl chain borne by the charged nitrogen atom of the quaternary ammonium moiety, and on the contact time.