Assessment of Mg(OH)_(2)/TiO_(2) coating in the Mg-Ca-Zn alloy for improved corrosion resistance and antibacterial performance

The high activity of metallic magnesium and alloys limits its potential in biomedical applications;in recent years,extensive efforts have been devoted to modulating this reactivity.In this work,we present Mg(OH)_(2) and TiO_(2)barrier coatings to reduce the degradation of magnesium alloy(Mg-Ca-Zn)surfaces.These coatings were deposited by the anodization method and the spin-coating technique,respectively.The anodized layer was coated with TiO_(2)generated from the hydrolysis of 3%weight of TTIP(Ti[OCH(CH_(3))_(2)]_(4),Titanium(IV)isopropoxide)in 2-Propanol deposited by the spin-coating method.Studying the degradation in Ringer’s solution by electrochemical impedance spectroscopy and OCP revealed a 98%reduction in pittings in uncoated samples after 14 days of immersion.The p H measurements revealed that the TiO_(2)coating reduced the alkalization of the physiological environment,keeping the pH at 6.0 values.In vitro studies of two types of bacteria(E.coli and S.aureus)exhibited zones of inhibition in the agar and activity bactericidal(kill time test).The mechanisms behind the improved degradation resistance and enhanced antibacterial activity are presented and discussed here.Surface modification with Mg(OH)_(2)/TiO_(2)coatings is a promising strategy to control the biodegradation of magnesium implants for bone regeneration.

Antibacterial and cytocompatible coatings based on poly(adipic anhydride) for a Ti alloy surface

This paper describes a formation of hybrid coatings on a Ti-2Ta-3Zr-36Nb surface.This is accomplished by plasma electrolytic oxidation and a dip-coating technique with poly(adipic anhydride)((C6H8O3)n)that is loaded with drugs:amoxicillin(C16H19N3O5S),cefazolin(C14H14N8O4S3)or vancomycin(C66H75Cl2N9O24·xHCl).The characteristic microstructure of the polymer was evaluated using scanning electron microscopy and confocal microscopy.Depending on the surface treatment,the surface roughness varied(between 1.53μm and 2.06μm),and the wettability was change with the over of time.X-ray photoelectron spectroscopy analysis showed that the oxide layer did not affect the polymer layer or loaded drugs.However,the drugs lose their stability in a phosphate-buffered saline solution after 6.5 h of exposure,and its decrease was greater than 7%(HPLC analysis).The stability,drug release and concentration of the drug loaded into the material were precisely analyzed by high-performance liquid chromatography.The results correlated with the degradation of the polymer in which the addition of drugs caused the percent of degraded polymer to be between 35.5%and 49.4%after 1 h of material immersion,depending on the mass of the loaded drug and various biological responses that were obtained.However,all of the coatings were cytocompatible with MG-63 osteoblast-like cells.The drug concentrations released from the coatings were sufficient to inhibit adhesion of reference and clinical bacterial strains(S.aureus).The coatings with amoxicillin showed the best results in the bacterial inhibition zone,whereas coatings with cefazolin inhibited adhesion of the above bacteria on the surface.

The Self-assembling and Application of Inorganic Anti-bacterial Material Made of Natural Nanoporous Carrier

The inorganic antimicrobial material was inhibited to the microbes with the added metal ion,Zn.The primary wet product carrying 5%-10% zinc ion was generated under the following conditions：temperature was 95 ℃,solution zinc concentration was 1.2-2.0 mol/L,and the ratio of Zn solution to zeolite weight was 5：1.The final stable product was manufactured after baking in an oven for 1-3 h at the temperature of 500-900 ℃.The baked material was tested for its disinfection effectiveness and coloring effect when mixed with paint coating.Based on the final batch of tests,the zinc content of this anti-microbial product was further optimized.

Glycopolymer N-halamine-modified biochars with high specificity for Escherichia coli eradication

Antibiotic-resistant bacteria contamination in environments imposes great threats to human life health.This research aims to develop novel targeted antibacterial biochars for achieving high selectivity to kill pathogenic Escherichia coli(E.coli).The glycopolymer N-halamine-modified biochars(i.e.,BCPMA-Cl)were synthesized by the modification of biochars with poly[2-(methacrylamido)glucopyranose-coacrylamide](P(MAG-co-AM),followed by chlorination treatment.Based on the results of FTIR,turbidity,XPS,and UV–vis,BCPMA-Cl was successfully synthesized and demonstrated to be able to eliminate Staphylococcus aureus(S.aureus)and E.coli.Especially,BCPMA-Cl possessed extremely potent to specific-killing 10^(4) CFU·ml^(-1) of E.coli with lower hemolytic activity(<5%).Additionally,the antibacterial mechanisms of BCPMA-Cl against bacteria were contact-killing and release-killing contributed by active chlorine(i.e.,Cl^(+)).Therefore,this work provided a cost-effective and facile approach for preparation of functional biochars used for bacteria-specific therapeutic applications via livestock pollutants as well as showing a promising strategy to avoid bacterial resistance.

Facile preparation of antibacterial polymer coatings via thiol-yne click photopolymerization

Novel antibacterial polymer coatings were prepared by a facile thiol-yne click photopolymerization of 1-propargyl-3-allYl-l,3-diazanyl-2,4-cyclopentadiene bromide （[PAIMIBr） and tetra（3-mercapto-pro- pionate）pentaerythritol （PETMP） （2：1 molar ratio） using 2,2-dimethoxy-2-phenylacetophenone （DMPA） as initiator. The antibacterial activity of the coatings was tested against Staphylococcus aureus （ATCC 292130） and Escherichia coli （ATCC 25922） by the dynamic shake method. The evaluation results revealed the antibacterial polymer coatings exhibited excellent inhibitory activity against S. aureus and E. coil, especially for S. aureus.

Poly[(mercaptopropyl)methylsiloxane](PMMS)-based antibacterial polymer coatings prepared by a two-step sequential thiol–ene click chemistry

Poly[（mercaptopropyl）methylsiloxane] （PMMS）-based antibacterial polymer coatings have been prepared through a two-step sequential thiol-ene click chemistry utilizing 1-allyl-3-decylimidazolium bromide （ADIm） as antibacterial monomer and triallyl cyanurate （TAC） as the crosslinker. These films with different content of ADIm were characterized by thermogravimetric analysis （TGA）, dynamic mechanical analysis （DMA） and pencil hardness. It was found that the mechanical and thermal properties of these films were largely influenced by the content of ADIm in the films. Films with imidazolium bromide groups displayed excellent antimicrobial activity against Staphylococcus aureus with 100% killing efficiency.

In vitro degradation and multi-antibacterial mechanisms ofβ-cyclodextrin@curcumin embodied Mg(OH)_(2)/MAO coating on AZ31 magnesium alloy

It is a challenging task to prepare a coating on Mg alloys for desirable corrosion resistance,good antibac-terial ability and biocompatibility.In this research work,an in-situ Mg(OH)_(2)coating incorporated with sodium alginate(SA)andβ-cyclodextrin(β-CD)@curcumin(Cur)was formed on the surface of micro arc oxidation(MAO)coated AZ31 alloy via a low temperature hydrothermal method.Characterization tech-niques such as X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Fourier transform infrared spectrometer(FT-IR)and scanning electron microscope(SEM)were employed to characterize the chemi-cal composition and surface morphology of the coatings.The corrosion protection ability of the coatings was monitored via electrochemical polarization,hydrogen evolution and immersion tests.Photothermal antibacterial ability and cytocompatibility of the coatings were evaluated by plate counting method under the irradiation of 808 nm-near infrared light,in vitro cytotoxicity tests(MTT)and live/dead cell staining.The results indicate that a chelation of the organic molecules led to the formation of a MAO/(β-CD@Cur)-SA-Mg(OH)_(2)coating with excellent corrosion protection,multi-antibacterial ability and almost no toxic-ity to the cells.Especially,the coating provided photothermal performance through the light absorption of Cur,which was encapsulated byβ-CD to improve its bioavailability.SA enhanced the binding force between the drug and the substrate.This novel coating designated the potential application on bioab-sorbable magnesium alloys.

Ionized jet deposition of antimicrobial and stem cell friendly silver-substituted tricalcium phosphate nanocoatings on titanium alloy

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.

Recent Advance in Polymer Coatings Combating Bacterial Adhesion and Biofilm Formation

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.

Electrostatic assembly functionalization of poly(γ-glutamic acid)for biomedical antibacterial applications

Poly(γ-glutamic acid)(γ-PGA)has been found widespread applications in biomedical field because of its excellent water solubility,biocompatibility,and bioactivity.Herein,a water-insoluble γ-PGA antibacterial compound is facilely fabricated via one-pot electrostatic assembly of γ-PGA with cationic ethyl lauroyl arginate(ELA).The functionalized γ-PGA compound(γ-PGA-ELA)ethanol solution can facilely produce colorless and transparent coatings on various inorganic,metal,and polymeric substrates,especially for the lumen of slender catheters(length up to 2 m,and inner diameter down to 1 mm).The functionalized γ-PGA coating presents remarkable antibacterial efficacy in vitro and in vivo.In addition,the γ-PGA compound is used as antibacterial additives of polyolefin via melting extrusion,and the asprepared antibacterial polyolefin demonstrates advantageous antibacterial efficacy.More importantly,the functionalized γ-PGA coating exhibit good hemocompatibility,low cytotoxicity,and satisfactory histocompatibility.The as-proposed γ-PGA compound has a great potential to serve as a safe and multifunctional antibacterial candidate to combat biomedical devices-related infections.

A Biomimetic Surface for Infection-resistance through Assembly of Metal-phenolic Networks

Despite the fact that numerous infection-resistant surfaces have been developed to prevent bacterial colonization and biofilm formation, developing a stable, highly antibacterial and easily produced surface remains a technical challenge. As a crucial structural component of biofilm, extracellular DNA（eDNA） can facilitate initial bacterial adhesion, subsequent development, and final maturation. Inspired by the mechanistic pathways of natural enzymes（deoxyribonuclease）, here we report a novel antibacterial surface by employing cerium（Ce（Ⅳ）） ion to mimic theDNA-cleavage ability of natural enzymes. In this process, the coordination chemistry of plant polyphenols and metal ions was exploited to create an in situ metal-phenolic film on substrate surfaces. Tannic acid（TA） works as an essential scaffold and Ce（Ⅳ） ion acts as both a cross-linker and a destructor of eDNA. The Ce（Ⅳ）-TA modified surface exhibited highly enhanced bacteria repellency and biofilm inhibition when compared with those of pristine or Fe（Ⅲ）-TA modified samples. Moreover, the easily produced coatings showed high stability under physiological conditions and had nontoxicity to cells for prolonged periods of time. This as-prepared DNA-cleavage surface presents versatile and promising performances to combat biomaterial-associated infections.