The widespread occurrence of nosocomial infections and the emergence of new bacterial strands calls for the development of antibacterial coatings with localized antibacterial action that are capable ...of facing the challenges posed by increasing bacterial resistance to antibiotics. The Layer-by-Layer (LbL) technique, based on the alternating assembly of oppositely charged polyelectrolytes, can be applied for the non-covalent modification of multiple substrates, including medical implants. Polyelectrolyte multilayers fabricated by the LbL technique have been extensively researched for the development of antibacterial coatings as they can be loaded with antibiotics, antibacterial peptides, nanoparticles with bactericide action, in addition to being capable of restricting adhesion of bacteria to surfaces. In this review, the different approaches that apply LbL for antibacterial coatings, emphasizing those that can be applied for implant modification are presented.
Biofouling is one of the most serious problems in membrane filtration systems for water treatment. An easily applicable antimicrobial finish of polyethersulfone (PES) filter membranes is shown by ...derivatizing an approved chlorin photosensitizer drug with adhesive ortho‐catechol functionalities as known from l‐3,4‐dihydroxyphenylalanin (Dopa) residues of marine mussel glues. The chemical structure of the second‐generation photosensitizer 5,10,15,20‐tetrakis(3‐hydroxyphenyl)chlorin (m‐THPC) is modified by 2‐iodoxybenzoic acid (IBX) oxidation, transforming the peripheric meta‐phenols of m‐THPC into ortho‐catechols, and thus improving the adsorption properties of m‐THPC derivatives onto PES material. Stable coatings are formed that preserve chlorin's capability to generate singlet oxygen under visible light illumination. The modification of one or two phenol groups out of the four m‐THPC substituents leads to an optimum in the generation of active singlet oxygen, and thus the finish significantly reduces the bacterial growth of gram‐negative Escherichia coli and gram‐positive Micrococcus luteus on the PES membranes.
A chlorin‐based photosensitizer, known from photodynamic therapy, is derivatized to realize antimicrobial finishes for water‐filtration membranes. The introduced catechol moieties known from adhesive systems of marine mussels, improve the coating and affect both positioning and packing of the photosensitizers, to retain singlet oxygen production. Irradiating coated membranes by visible light significantly reduces bacterial growth of both gram‐positive and gram‐negative strains.
A three-layer system of nanocrystalline hydroxyapatite (first layer; 1000nm thick), silver nanoparticles (second layer; 1.5μg Ag cm
) and calcium phosphate (third layer, either 150 or 1000nm thick) ...on titanium was prepared by a combination of electrophoretic deposition of silver nanoparticles and the deposition of calcium phosphate by radio frequency magnetron sputtering. Scanning electron microscopy showed that the silver nanoparticles were evenly distributed over the surface. The adhesion of multilayered coating on the substrate was evaluated using the scratch test method. The resistance to cracking and delamination indicated that the multilayered coating has good resistance to contact damage. The release of silver ions from the hydroxyapatite/silver nanoparticle/calcium phosphate system into the phosphate-buffered saline (PBS) solution was measured by atomic absorption spectroscopy (AAS). Approximately one-third of the incorporated silver was released after 3days immersion into PBS, indicating a total release time of the order of weeks. There were no signs of cracks on the surface of the coating after immersion after various periods, indicating the excellent mechanical stability of the multilayered coating in the physiological environment. An antimicrobial effect against Escherichia coli was found for a 150nm thick outer layer of the calcium phosphate using a semi-quantitative turbidity test.
The fabrication of biocompatible and antibacterial coatings on metallic implants remains a significant challenge for load‐bearing orthopedic implants. This study focuses on the electrophoretic ...deposition of chitosan/gelatin/Ag‐Mn doped mesoporous bioactive glass nanoparticles (Ag‐Mn MBGNs) composite on the PEEK/bioactive glass layer (called as multi‐structured coatings), which had been deposited electrophoretically on 316L stainless steel. The EPD parameters for the deposition of the chitosan/gelatin/Ag‐Mn MBGNs coatings were optimized via Taguchi design of experiment approach. Scanning electron microscopy images confirmed that the chitosan/gelatin/Ag‐Mn MBGNS layer was deposited on the PEEK/BG layer. The addition of biologically active metallic ions (Mn and Ag) and molecules (chitosan) showed a strong effect on the growth of bacteria. Moreover, the inclusion of Mn and Ag showed a negligible toxic effect on the bioactivity (the ability of the coating to form a bond with the natural bone) of the coatings. Furthermore, the multi‐structured coatings presented appropriate wettability and surface roughness for orthopedic applications. Overall, this study provides a direct solution to improve the bioactivity, antibacterial activity, and surface properties of deposited chitosan/gelatin coatings on orthopedic implants that are more manufacturable and translational from research to an industrial scale.
Orthopedic infections pose severe societal and economic burden and interfere with the capability of the implanted devices to integrate in the host bone, thus significantly increasing implants failure ...rate. To address infection and promote integration, here nanostructured antibacterial and bioactive thin films are proposed, obtained, for the first time, by Ionized Jet Deposition (IJD) of silver-substituted tricalcium phosphate (Ag-TCP) targets on titanium. Coatings morphology, composition and mechanical properties are characterized and proof-of-concept of biocompatibility is shown. Antimicrobial efficacy is investigated against four Gram positive and Gram negative bacterial strains and against C. albicans fungus, by investigating the modifications in planktonic bacterial growth in the absence and presence of silver. Then, for all bacterial strains, the capability of the film to inhibit bacterial adhesion is also tested. Results indicate that IJD permits a fine control over films composition and morphology and deposition of films with suitable mechanical properties. Biological studies show a good efficacy against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis and against fungus Candida albicans, with evidences of efficacy against planktonic growth and significant reduction of bacterial cell adhesion. No cytotoxic effects are evidenced for equine adipose tissue derived mesenchymal stem cells (ADMSCs), as no reductions are caused to cells viability and no interference is assessed in cells differentiation towards osteogenic lineage, in the presence of silver. Instead, thanks to nanostructuration and biomimetic composition, tricalcium phosphate (TCP) coatings favor cells viability, also when silver-substituted. These findings show that silver-substituted nanostructured coatings are promising for orthopedic implant applications.
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•Silver-substituted TCP films on titanium are prepared by Ionized Jet Deposition•Films are nanostructured, hard, with submicron thickness•Adipose mesenchymal stem cells differentiate into osteogenic lineage on the surface of films•Films show antimicrobial and anti-adhesive activity against several microorganisms•Films are promising for application in orthopedic titanium implants
In this study, we propose new polymeric coatings for metallic implants that impart biocompatibility and antibacterial features to such surfaces. The starting material, poly(cyclic ...carbonate)-polydimethylsiloxane, was prepared from carbon dioxide fixation and then sequentially reacted by aminolysis with an organoaminosilane, affording the formation of an urethanic polydimethylsiloxane-based material. Finally, a hybrid coating was obtained by performing a sol-gel process on the metallic surfaces, catalyzed by phosphotungstic acid. We provide evidence that due to the polydimethylsiloxane segments governing the surface termination, the hybrid coatings show a hydrophobic character. Furthermore, due the presence of phosphotungstic acid in the upper surface, the adhesion of Gram-positive and Gram-negative bacteria is suppressed in 4 h of contact with aqueous bacterial cultures. In addition, the coatings presented a >70% cytocompatibility besides a low cytotoxicity, making them interesting candidates as biocompatible materials and an alternative to avoiding the biofilm associated with bacterial infections.
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•Hybrid polyurethane coatings were fabricated in a sustainable way by carbon dioxide fixation•The hybrid coatings presented osteoblast and fibroblast cell compatibility and, bacteriostatic behaviour•Bacteriostatic behaviour were evidenced in the presence of hybrid polyurethane PDMS-based coatings•Phosphotungstic acid catalyses the sol-gel reaction and cooperates with the suppression of bacterial adhesion•PDMS segments provide hydrophobic surfaces by coating substrates with hybrid polyurethane PDMS-based
Bacterial adhesion to surfaces is the onset of biofilm formation and a hard problem to tackle, aggravated by the rise in drug-resistant bacteria, responsible for more than 500 000 deaths ...globally/year. This work reports few-layer graphene (FLG) and few-layer graphene oxide (FLGO) as stand-alone light-responsive platforms to develop smart antibacterial surfaces. Films exposure to low-intensity NIR drastically improve their ability to kill planktonic (up to ∼99%) and adherent (up to ∼85%) methicillin-resistant S. aureus and S. epidermidis. Upon irradiation, a mild photothermal effect is observed in supernatant, with temperature rising from 37.0 °C to 39.0 °C–42.0 °C, while surface temperature of non-oxidized FLG films increases to 51.3 °C versus 56.0 °C for oxidized films. Both films prompt total glutathione oxidation when irradiated, despite FLG films induce higher ROS generation than FLGO, suggesting antioxidants depletion occurs preferentially by ROS-dependent pathway (photodynamic effect) for FLG versus ROS-independent pathway for FLGO films. This proof-of-principle study demonstrates that safe, low-intensity NIR irradiation is a valuable and effective tool to boost graphene surfaces’ antibacterial performance through a synergistic photothermal and photodynamic effect. These stand-alone NIR-activated graphene-based platforms arise as simple and economical disinfection surfaces/systems, with widespread use in medical and non-medical applications.
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•Graphene films irradiated with low-power (0.15 W/cm2) NIR (812 nm) have bactericidal action.•Oxidized films (FLGO) have higher bactericidal performance than non-oxidized (FLG).•NIR-irradiated FLGO films kill ∼99% planktonic bacteria (MRSA and S. epidermidis).•Antibacterial performance occurs through synergistic PTT and PDT effects.•FLG acts mainly by ROS-dependent and FLGO by ROS-independent pathways.
Introduction
The use of spinal implants for the treatment of back disorders is largely affected by the insurgence of infections at the implantation site. Antibacterial coatings have been proposed as ...a viable solution to limit such infections. However, despite being effective at short-term, conventional coatings lack the ability to prevent infections at medium and long-term. Hydrogel-based drug delivery systems may represent a solution controlling the release of the loaded antibacterial agents while improving cell integration. Agarose, in particular, is a biocompatible natural polysaccharide known to improve cell growth and already used in drug delivery system formulations. In this study, an agarose hydrogel-based coating has been developed for the controlled release of gentamicin (GS).
Methods
Sand blasted Ti6Al4V discs were grafted with dopamine (DOPA) solution. After, GS loaded agarose hydrogels have been produced and additioned with tannic acid (TA) and calcium chloride (CaCl
2
) as crosslinkers. The different GS-loaded hydrogel formulations were deposited on Ti6Al4V-DOPA surfaces, and allowed to react under UV irradiation. Surface topography, wettability and composition have been analyzed with profilometry, static contact angle measurement, XPS and FTIR spectroscopy analyses. GS release was performed under pseudo-physiological conditions up to 28 days and the released GS was quantified using a specific ELISA test. The cytotoxicity of the produced coatings against human cells have been tested, along with their antibacterial activity against
S. aureus
bacteria.
Results
A homogeneous coating was obtained with all the hydrogel formulations. Moreover, the coatings presented a hydrophilic behavior and micro-scale surface roughness. The addition of TA in the hydrogel formulations showed an increase in the release time compared to the normal GS-agarose hydrogels. Moreover, the GS released from these gels was able to significantly inhibit
S. aureus
growth compared to the GS-agarose hydrogels. The addition of CaCl
2
to the gel formulation was able to significantly decrease cytotoxicity of the TA-modified hydrogels.
Conclusions
Due to their surface properties, low cytotoxicity and high antibacterial effects, the hereby proposed gentamicin-loaded agarose-hydrogels provide new insight, and represent a promising approach for the surface modification of spinal implants, greatly impacting their application in the orthopedic surgical scenario.
Comprehensive Summary
Implantable medical device‐associated infections (DAIs) originating from bacterial adhesion and biofilm formation have threatened to the health and life of patients. ...Antibacterial polymer coatings with antifouling and/or bactericidal properties have showed great potentials to combat DAI issues. In this review, we report recent advances in antibacterial polymer coatings fighting bacterial adhesion and biofilm formation on implantable biomaterial surfaces. We summarize the mechanisms of bacterial adhesion and biofilm formation, which provides guidance for the design of antibacterial coatings. We describe the polymer and coating preparation methods and discuss the structure‐property relationships of antibacterial polymer coatings. Applications of these polymer coatings in medical catheters, orthopaedic implants, and other applications are elaborated. Future challenges and prospects associated with antibacterial polymer coatings for implantable medical devices are discussed.
The article briefly reviews recent advances in antibacterial polymer coatings with antibacterial adhesion and antibiofilm properties for implantable medical device applications.
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