Long-lasting Antibacterial Activity Research Articles

The preparation, characterization and antibacterial properties of chitosan/pectin silver nanoparticle films

Edible film production from natural biodegradable polymers that will not cause environmental waste problems has been increasing in recent years. Antibacterial materials can be added to these films to increase the shelf life and quality of products. In this work, chitosan-based and chitosan/pectin-based silver nanoparticle films which has eco-friendly and antibacterial properties were synthesized. The morphological test of the prepared films was performed by scanning electron microscope and transmission electron microscope. The presence of silver element was detected by energy-dispersive X-ray. Thermal analysis was tested with thermogravimetric analysis and differential scanning calorimeter analyzer. The crystallinity (%) of films was determined with X-ray diffraction analyzer. The presence of pectin increased the thermal stability and crystallinity%. The mechanical tests were examined with Zwick universal testing machine and the content of pectin improved the mechanical properties of film. The antibacterial test was done toward Gram-negative bacteria (Escherichia coli). Chitosan/pectin-based films compared with chitosan-based film displayed long-lasting antibacterial activity against E.coli.

A versatile chitosan nanogel capable of generating AgNPs in-situ and long-acting slow-release of Ag+ for highly efficient antibacterial

Development of multifunctional antibacterial agent with long-lasting antibacterial activity and biofilm ablation performance is significant for the effective treatment of bacterial infections. Here, by utilizing the electrostatic interaction between sulfonated chitosan (SCS) and Ag+ and chitosan (CS), and the sodium borohydride reduction method, a versatile antibacterial agent (AgNPs@CS/SCS) capable of generating silver nanoparticles (AgNPs) in-situ and long-acting slow-release Ag+ was developed. AgNPs@CS/SCS has a good physiological stability and can long-acting slow-release of Ag+ due to the pH-dependent Ag+ release behavior of AgNPs. Noteworthy, AgNPs@CS/SCS can exert both excellent short- and long-term antibacterial and biofilm ablation activity. Importantly, it also exhibits superior antibacterial activity in the treatment of implant infections, accompanied by good biocompatibility. Together, this study suggest that AgNPs@CS/CSC is indeed a versatile antibacterial agent, and is expected to provide an effective treatment modality for implant infections in the clinic settings.

Remarkable bactericidal traits of a metal-ceramic composite coating elated by hierarchically structured surface.

SummaryA ceramic-based coating with a hierarchical surface structure was synthesized via solid-state reaction enabled by a double cathode glow discharge technique. This innovative coating comprises two distinct layers, specifically an outer layer with a well-aligned micro-pillar array and a dense inner layer. Both are composed of a face-centered cubic Cu(Co,Ni,Fe) solid solution phase together with a spinel-type Fe(Al,Cr)2O4 oxide. This coating exhibits superhydrophobicity and, yet, a very strong adhesion to water, i.e., the so-called “rose petal effect”. This coating also exhibits highly efficient antibacterial ability against both Staphylococcus aureus and Escherichia coli bacteria under both dark and visible light conditions. The excellent antibacterial property originates from the synergistic effects through the release of Cu ions coupled with photothermal activity upon light activation.

Preparation and characterization of cinnamon essential oil nanocapsules and comparison of volatile components and antibacterial ability of cinnamon essential oil before and after encapsulation

In the present study, cinnamon essential oil (CEO)-nanocapsules (CEO-NPs) were obtained through nanoprecipitation method by using chitosan and whey protein isolate (WPI) as wall materials. Effects of preparation conditions on the encapsulation efficiency (EE) were examined. The morphology and structures of CEO-NPs were analyzed through scanning electron microscopy (SEM), dynamic light scattering, fourier transformation infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Differences in volatile constituents of CEO before and after embedding were analyzed by gas chromatography-mass spectrometry (GC-MS). Additionally, the antibacterial activity differences between CEO and CEO-NPs were evaluated by measuring the diameter of inhibition zone (DIZ) and minimum inhibitory concentration (MIC). Results indicate that CEO-NPs having a size of 195.17 ± 1.35 nm and EE of 91.74 ± 1.10% are obtained when the wall material concentrations, pH, mass ratio of oil to wall materials, and emulsifier agent are 0.5% (w/w), 5, 1:1.8, and gelatin, respectively. FTIR revealed the encapsulation of CEO into nanocapsules, and DSC demonstrated the enhanced thermal stability of CEO after embedding. The zeta potential of CEO-NPs was found to be −31.7 ± 1.27 mV. Furthermore, GC-MS displayed the encapsulation of more than 90% ingredients of CEO into nanocapsules, and no significant difference in the main volatile constituents of CEO before and after embedding was observed. The MIC and DIZ values indicated a slightly decreased but more long-lasting and strong antibacterial activity of CEO-NPs against Staphylococcus aureus, Escherichia coli, Pseudomonas fragi, and Shewanella putrefaciens (sh2) during the 10-day storage period. Consequently, CEO-NPs could be employed as a potential natural preservative in food industry.

Synthesis and characterization of antibacterial polylactic acid film incorporated with cinnamaldehyde inclusions for fruit packaging

To maintain the quality of postharvest fruits continuously and meet the health requirements of consumers, a high barrier and long-lasting antibacterial polylactic acid film as packaging material was developed in this study. Polylactic acid-based antibacterial films incorporated with Cinnamaldehyde inclusions were used to achieve long-lasting antibacterial activity and improve the barrier properties. Cinnamaldehyde inclusions were prepared via the inclusion method and used as a sustained-release antibacterial agent and reinforcement to be incorporated into polylactic acid-based films within a concentration range of 0–30 wt%. The FT-IR spectrum demonstrated that the Cinnamaldehyde inclusions was physically interacting with PLA. The XRD results showed that the cinnamaldehyde inclusions at a concentration of 10 wt% enhanced the crystallinity of the antibacterial film. The oxygen and water vapor barrier properties of the film were respectively 14.29% and 12.38% higher than those of a pure PLA film. The tensile strength of the antibacterial film increased by 20%. And the antibacterial activity against Escherichia coli and Listeria monocytogenes was 100%. The release rate of cinnamaldehyde of the antibacterial film was slow and varied smoothly for 20 d.

Silver nanoparticles/graphene oxide nanoscroll composites synthesized by one step

Abstract In this work, silver nanoparticles/graphene oxide nanoscroll composites (Ag/GO nanoscroll composites) were fabricated by a one-step method at room temperature. The GO sheets were cut into pieces by the silver nanoparticles (AgNPs) due to their catalytic activity, and then the GO pieces rolled up resulting from the intermolecular hydrogen bonds. Transmission electron microscope images show that the Ag/GO nanoscroll composites have open-ended tubular hollow structures. The Escherichia coli (E. coli) was used to evaluate the antibacterial activity of synthesized nanoscroll composites. After against the E. coli for 3 days, the inhibition rate of Ag/GO nanoscroll composites can still up to 99.99%. This attributes to the open-ended tubular hollow structures, providing abundant channels and space to prevent AgNPs from aggregating and oxidizing. The result exhibits that the Ag/GO nanoscroll composites have the potential for long-lasting antibacterial activity. So, the Ag/GO nanoscroll composites can be applied in antibacterial materials for long-lasting use.

Hierarchical porous nanofibers containing thymol/beta-cyclodextrin: Physico-chemical characterization and potential biomedical applications.

As an effective natural antibacterial component, the low water solubility of thymol (THY) has stemmed its potential in biomedical application. Here, β-cyclodextrin (β-CD) and THY were self-assembled to form water-soluble inclusion complex (IC). The successful formation of IC was confirmed via 1H NMR. As an antibacterial agent, the resultant IC was then incorporated into cellulose acetate (CA) fibrous matrix with hierarchical structure (nanopores on porous fibrous webs) via electrospinning (CA/THY/β-CD), and the pure THY was also encapsulated into CA for comparison (CA/THY). In vitro dissolution tests demonstrated that CA/THY/β-CD fibrous membrane exhibited sustained drug release, which abided by non-Fickian diffusion. Besides, the CA/THY/β-CD fibrous membrane exhibited more effective and long-lasting antibacterial activity against S. aureus. Furthermore, the combination of hierarchical porous structure with sustained drug release endowed the CA/THY/β-CD fibrous membrane with good cytocompatibility. Taken together, the CA/THY/β-CD fibrous membrane could be an attractive candidate for wound dressing material.

Thermosensitive and pH-responsive tannin-containing hydroxypropyl chitin hydrogel with long-lasting antibacterial activity for wound healing

Polysaccharide hydrogels have been widely used as wound dressings because of their biocompatibility and ability to provide moist environment for wound healing. However, bacterial infection often delays the healing process. Herein, a novel thermosensitive and pH-sensitive hydroxypropyl chitin/tannic acid/ferric ion (HPCH/TA/Fe) composite hydrogel was fabricated by a simple assembly. The pre-cooled hydrogel precursor solution can be injected onto the irregular wound area and gel rapidly at physiological temperature. The TA not only acted as a crosslinker to enhance mechanical properties of the hydrogel, but also as an antibacterial agent which could be sustainably released in response to the acidic environment. The composite hydrogel showed excellent broad-spectrum antibacterial activity up to 7 days with negligible cytotoxicity. Moreover, the hydrogel can inhibit bacterial infection and accelerate the wound healing process without scars in the mouse experiment. These results indicate the potential application of this composite hydrogel for the infected wound healing.

Long-lasting anti-bacterial activity and bacteriostatic mechanism of tea tree oil adsorbed on the amino-functionalized mesoporous silica-coated by PAA

Tea tree oil (TTO) is an efficient natural antibacterial agent. However, the bacteriostatic effect of TTO does not prevail for a long period because of the volatile nature of the oil. Therefore, a novel sustained-release formulation of TTO should be developed for improving the applicability of TTO. Herein, the mesoporous silica was selected for constructing a carrier for TTO. Mesoporous silica is non-toxic, easy to modify and exhibited an adjustable pore size. First, the mesoporous silica was modified by an aminated silane coupling agent (NH2-MCM-41). Then, the polyacrylic acid (PAA) was bonded by electrostatic bonds (PAA-NH2-MCM-41), which imparted the sustained-release effect in the TTO, supported in the mesoporous silica channel (TTO/PAA-NH2-MCM-41). The prepared bacteriostatic agent can achieve long-term sustained-release properties. At room temperature (26 ℃), the release rate of TTO after 11 h release reached 50 %. However, the release rate of TTO from TTO/PAA-NH2-MCM-8 reached only 42 % after 24 h. Furthermore, the sustained release behavior of TTO/PAA-NH2-MCM-41 was consistent with the Korsmeyer-Peppas kinetic model. Compared to TTO, TTO/PAA-NH2-MCM-41 exhibited a stable and sustained bacteriostatic effect even after 50 days in a natural environment. The minimum inhibitory concentration (MIC) value of the TTO/PAA-NH2-MCM-41 against Escherichia coli (E. coli) was 0.37∼0.44 mg/mL. TTO altered the cell morphology of E. coli and broke the integrity of the cell membrane, leading to cell death.

Fabrication of a novel antibacterial TPU nanofiber membrane containing Cu-loaded zeolite and its antibacterial activity toward Escherichia coli

A novel antibacterial thermoplastic polyurethane (TPU) nanofiber membrane was fabricated by electrospinning with the aid of Cu-loaded NaX zeolite (CuX), which showed excellent and long-lasting antibacterial activity against Escherichia coli (E. coli). The crystalline structure, morphology and composition of the obtained NaX zeolite, CuX and CuX/TPU nanofiber membrane were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray fluorescence (XRF), respectively. The antibacterial activity of CuX/TPU nanofiber membrane against E. coli was investigated by inhibition zone method and plate-counting method, and it is indicated that the inactivation efficiency was increased from 58.40 to 99.85% with increasing the addition of CuX from 5 to 30% in 4 h. The result of kinetics study indicated that the disinfection process accorded with the pseudo-first-order model. The possible antibacterial mechanism was also proposed that the released Cu2+ by CuX in nanofiber membrane destroyed the cell wall and penetrated plasma membrane of E. coli. It is expected that this CuX/TPU nanofiber membrane with excellent antibacterial activity would be a promising candidate for biomedical applications.

Polymethylmethacrylatebased antibacterial coating in vitro and in vivo

Nowadays, the infection recurrence rate in osteomyelitis is still high. New hardware not only allowing one to stabilize bone fragments, but also having antibacterial activity seems to be an extremely useful and promising task. The goal of the study was to assess the effectiveness of use of an antibacterial coating based on polymethylmethacrylate cement in experiment and in infected nonunions of long tubular bones of the lower limbs. Bone cement-based coatings impregnated with antibiotics were formed on titanium plates. A plate rinse was carried out; antibiotic concentrations in the rinsed solutions were estimated by a serial broth microdilution method. The antibacterial activity of control and rinsed samples against the antibiotic-sensitive and multiple-antibiotic-resistant Staphylococcus aureus and Pseudomonas aeruginosa strains was estimated by a bilayer agar method. Clinical part. The study included 70 patients divided into 2 groups: osteosynthesis with antibacterial-coated interlocking nail (40 patients, main group) and osteosynthesis with an external fixation device (30 patients, control group) comparable in age, sex and disease duration. The effectiveness of the antibacterial coating was analyzed by the duration of systemic use of antibiotics and infection recurrence rate. The concentrations of meropenem and phosphomycin in the rinsed solutions obtained at one-fold and two-fold treatments were sufficient to suppress the growth of control strains. Vancomycin-containing samples possessed sufficient antibacterial activity against both methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) S. aureus strains, double rinse of the samples eliminated their bactericidal properties. The duration of systemic antibacterial therapy in the main group was statistically significantly lower than in the control group (U = 77.5, p < 0.001), and in the main group the infection recurrence rate was lower than 32.5 % vs. 86.7 % (χ2 = 20.39, p < 0.001). The PMMA-based coating impregnated with phosphomycin, meropenem or vancomycin possesses sufficient and long-lasting antibacterial activity, mainly against antibiotic-sensitive strains. An adequate use of such a coating in clinical practice allows one to obtain the desired result of treatment.

Bonding durability, antibacterial activity and biofilm pH of novel adhesive containing antibacterial monomer and nanoparticles of amorphous calcium phosphate

ObjectivesThe dentin bonding often fails over time, leading to secondary caries and restoration failure. The objectives of this study were to develop an adhesive with dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and investigate the effects of storage in artificial saliva for six months on the bonding durability, antibacterial activity, ion release and biofilm pH properties for the first time. MethodsDMAHDM was added at 5% (by mass) to Scotchbond Primer and Adhesive (SBMP). NACP was added at 10%, 20%, and 30% to SBMP adhesive. Dentin bonding durability, antibacterial activity against Streptococcus mutans biofilms, and calcium (Ca) and phosphate (P) ion liberation properties were investigated after 1 day and 6months of storage in artificial saliva. ResultsDentin bond strength (n = 50) had 25% loss after 6 months of aging for SBMP control. However, SBMP + DMAHDM+10NACP and SBMP + DMAHDM+20NACP showed no loss in bond strength after storage in artificial saliva for 6 months. The DMAHDM + NACP incorporation method dramatically reduced the biofilm metabolic activity and acid production, and decreased the biofilm CFU by four orders of magnitude, compared to SBMP control, even after 6 months of aging (p < 0.05). DMAHDM + NACP had long-lasting Ca and P ion releases, and raised the biofilm pH to 6.8, while the control group had a cariogenic biofilm pH of 4.5. ConclusionsIncorporating DMAHDM + NACP in bonding agent yielded potent and long-lasting antibacterial activity and ions liberation ability, and much higher long-term dentin bond strength after 6-month of aging. The new bonding agent is promising to inhibit caries at the restoration margins and increase the resin-dentin bonding longevity. Clinical significanceThe novel bioactive adhesive is promising to protect tooth structures from biofilm acids and secondary caries. NACP and DMAHDM have great potential for applications to a wide range of dental materials to reduce plaque and achieve therapeutic effects.

Antibacterial Activity of Antibiotic-Impregnated Bone Cement Based Coatings Against Microorganisms with Different Antibiotic Resistance Levels

Purpose — to evaluate the presence and duration of antibiotic activity of antibiotic-impregnated bone cement based coatings samples against antibiotic-sensitive and antibiotic-resistant microorganisms.Material and Methods. Bone cement based coatings impregnated with antibiotics (gentamycin, vancomycin, colistin, meropenem, fosfomycin) are formed on titanium (Ti) plates. A plate rinse was carried out; antibiotic concentrations in the rinsed solutions were estimated by a serial broth microdilution method. Antibacterial activity of the control and rinsed samples against the antibiotic-sensitive and multiple-antibiotic-resistant Staphylococcus aureus and Pseudomonas aeruginosa strains was estimated by a bilayer agar method.Results. The meropenem and fosfomycin concentrations in the rinsed solutions obtained at a one-fold (16 μg/ml for both antibiotics) and two-fold treatment (2 μg/ml for meropenem and 8 μg/ml for fosfomycin) were sufficient to suppress the growth of the control strains. One-fold rinse of samples with colistin eliminated their antibacterial activity completely. The marked activity of the samples with meropenem and fosfomycin persisted against the antibiotic-sensitive P. aeruginosa ATCC 27853 strain after 2 rinse cycles; single-rinsed samples with fosfomycin also maintained the activity against the extensively antibioticresistant P. aeruginosa BP-150 strain. Vancomycin-containing samples possessed the sufficient antibacterial activity against both methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) S. aureus strains; two-fold rinse of the samples eliminated their bactericidal properties.Conclusion. Bone cement based coatings impregnated with fosfomycin and meropenem possess the most marked and long-lasting antibacterial activity, manifested mainly against the antibiotic-sensitive strains.

An Antifouling Hydrogel Containing Silver Nanoparticles for Modulating the Therapeutic Immune Response in Chronic Wound Healing.

Patients with diabetic wounds have deficient local and systemic cellular immunity. Herein, a new silver nanoparticle-containing hydrogel with antifouling properties was developed for enhancing the immune response in diabetic wound healing. The antifouling property was obtained by adjusting the composition of cationic chitosan and anionic dextran to approach zero charge. Furthermore, this hybrid hydrogel showed long-lasting and broad-spectrum antibacterial activity. Rapid wound contraction was observed after the treatment with the hydrogel, which suggested its superior healing activity to promote fibroblast migration, granulation tissue formation, and angiogenesis. The upregulation of CD68+ and CD3+ expression levels demonstrated that the hydrogel could trigger immune responses in the treatment of wound healing. These results show that this antifouling hybrid hydrogel as a wound dressing provided a promising strategy for the treatment of diabetic ulcers.

Preparation and properties of cinnamon-thyme-ginger composite essential oil nanocapsules

Essential oils (EO) as one of natural antimicrobials possess excellent antibacterial, antifungal and antioxidant properties. However, their main components are easy to be oxidated and deteriorated when EO was exposed to the oxygen, light and heat. In this study, cinnamon-thyme-ginger composite essential oil nanocapsules (CEO-NPs) were prepared with chitosan as the wall via ionic gelification reaction. The effect of the mass ratio of chitosan (CS) to tripolyphosphate (TPP), composite essential oils (CEO) and surfactant concentration and pH on the properties of the CEO-NPs were investigated in detail. The morphology and structures of CEO-NPs were measured by dynamic light scattering (DLS), fourier transformation infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), gas chromatography–mass spectrometry (GC–MS) and ultraviolet spectrum (UV). Meanwhile, the antibacterial property of CEO-NPs was determined by inhibition zone method. CEO-NPs with the size of 215 nm and zeta potential of 25.12 mv were obtained when the mass ratio of CS/TPP, CEO and fatty alcohol polyoxyethylene ether-9 (AEO-9) concentration and pH were 8:1, 1.8 g/L, 0.7 g/L and 5.26. FTIR demonstrated that CEO has been encapsulated into NPs. TGA showed that the thermal stability of CEO-NPs was improved compared with CEO and the loading capacity of CEO was 13.4%. GC–MS displayed that more than 90% ingredients of CEO had been encapsulated into NPs. UV indicated that CEO-NPs had the excellent sustained-release property. Furthermore, CEO-NPs showed a long-lasting antibacterial activity against Escherichia coli, Bacillus subtilis and Staphylococcus aureus. In all, CEO-NPs can be used as a potential long-term natural preservative.

Effects of silver segregation on sputter deposited antibacterial silver-containing diamond-like carbon films

Silver-containing diamond-like carbon (DLC) films for antibacterial applications were prepared on 316L stainless steel and slide glass substrates by magnetron sputtering at different silver target current. Scanning electron microscopy and atomic force microscopy analyses show that the film surface becomes rough due to the formation of nanoparticles/clusters and even a surface layer with the increase of silver target current. The Ag content was measured as 0, 2.1, 6.1 and 14.3 at.%, respectively by energy dispersive X-ray analysis. X-ray diffraction and X-ray photoelectron spectroscopy reveal the dominant metallic nature of silver for the Ag-containing films. Silver segregation from the carbon matrix to film surface is confirmed by the above analyses. Microhardness indentation, contact angle measurement and potentiodynamic polarization test in a Ca-free Hank's balanced salt solution indicate that the addition of silver has decreased hardness, elastic modulus, H/E and H3/E2 ratios, wettability, surface energy and corrosion resistance of the DLC films, respectively. The antibacterial tests by agar disk diffusion assay and agar plate counting method against Escherichia coli demonstrate long-lasting and reusable antibacterial activity of the Ag-containing films. The study shows that silver segregation plays a crucial role in microstructure, mechanical, chemical and biological properties of the antibacterial Ag-containing DLC films.

Transparent gel composite films with multiple functionalities: Long-lasting anti-fogging, underwater superoleophobicity and anti-bacterial activity

Transparent gel-based composite films with multiple functionalities, showing long-lasting anti-fogging properties, underwater superoleophobicity, and anti-bacterial activity were successfully prepared from polyvinylpyrrolidone (PVP) and aminopropyl-functionalized clay (AMP-clay). Due to the addition of glutaraldehyde (GA, cross-linker) into the PVP matrices, and AMP-functionalities to the substrate surfaces, both the adhesion properties in water and durability of the anti-fogging properties were significantly improved. In addition, this durability was also found to be markedly improved by increasing the film thickness via deposition of several PVP/AMP/GA layers, while still retaining excellent transparency.

Development of a novel resin-based dental material with dual biocidal modes and sustained release of Ag+ ions based on photocurable core-shell AgBr/cationic polymer nanocomposites.

Research on the incorporation of cutting-edge nano-antibacterial agent for designing dental materials with potent and long-lasting antibacterial property is demanding and provoking work. In this study, a novel resin-based dental material containing photocurable core-shell AgBr/cationic polymer nanocomposite (AgBr/BHPVP) was designed and developed. The shell of polymerizable cationic polymer not only provided non-releasing antibacterial capability for dental resins, but also had the potential to polymerize with other methacrylate monomers and prevented nanoparticles from aggregating in the resin matrix. As a result, incorporation of AgBr/BHPVP nanocomposites did not adversely affect the flexural strength and modulus but greatly increased the Vicker's hardness of resin disks. By continuing to release Ag+ ions without the impact of anaerobic environment, resins containing AgBr/BHPVP nanoparticles are particularly suitable to combat anaerobic cariogenic bacteria. By reason of the combined bactericidal effect of the contact-killing cationic polymers and the releasing-killing Ag+ ions, AgBr/BHPVP-containing resin disks had potent bactericidal activity against S. mutans. The long-lasting antibacterial activity was also achieved through the sustained release of Ag+ ions due to the core-shell structure of the nanocomposites. The results of macrophage cytotoxicity showed that the cell viability of dental resins loading less than 1.0 wt% AgBr/BHPVP was close to that of neat resins. The AgBr/BHPVP-containing dental resin with dual bactericidal capability and long term antimicrobial effect is a promising material aimed at preventing second caries and prolonging the longevity of resin composite restorations.

Enhancement in Sustained Release of Antimicrobial Peptide from Dual-Diameter-Structured TiO2 Nanotubes for Long-Lasting Antibacterial Activity and Cytocompatibility

Novel films on Ti-based orthopedic implants for localized antimicrobial delivery, which comprises dual-diameter TiO2 nanotubes with the inner layers of compact and fluorine-free oxide tightly bonding to Ti, were formed by voltage-increased anodization with F- sedimentation procedure. The nanotubes were closely aligned and structured with upper 35 and 70 nm diametric tubes as nanocaps, respectively, and the underlying 140 nm diametric tubes as nanoreservoirs. Followed by loading ponericin G1 (a kind of antimicrobial peptide (AMP)) into the dual-diameter nanotubes with vacuum-assisted physisorption, the resultant films were investigated for loading efficiency and release kinetics of AMP, antibacterial activity against Staphylococcus aureus, and osteoblastic compatibility, together with the AMP-loaded single-diameter (140 nm) nanotube film. The loaded films had no statistical difference in the loading efficiency of AMP and revealed burst release within 6 h followed by steady release of AMP in phosphate-buffered solution. At day 42, almost all of AMP was released from the single-diameter nanotube film. However, the dual-diameter nanotube films loaded with AMP still showed sustained release at least up to 60 days, and the sustained efficacy was enhanced with decreasing diameter of nanocaps. In the case of nominal AMP loading amount of 125 μg, the resultant 35 nm capped dual-diameter nanotube film exhibited significant short- and long-term (even for 49 days) antibacterial activity not only against planktonic bacteria, which is ascribed to the release-killing efficacy of AMP, but also against adhered bacteria, which is ascribed to the AMP-derived killing efficacy and the nanocaps-derived adhesion resistance. Moreover, this loaded film presented cytocompatibility comparative to that of Ti but higher than that of the other AMP-loaded films. Increasing the nominal loading amount of AMP to 200 μg improved antibacterial activity but gave rise to obvious cytotoxicity of the loaded films.

Optically transparent silver-loaded mesoporous thin film coating with long-lasting antibacterial activity

Infectious diseases caused by microorganisms affect millions of people worldwide. In an effort to prevent infections induced by bacteria, a variety of antibacterial coatings have been designed. In this sense, the possibility to combine broad-range bactericidal agents such as silver and chemically and mechanically stable matrices such as mesoporous oxide thin films has been encouraging. In this study, titania–silica bilayer mesoporous thin film (MTF) coatings have been produced and loaded with silver species, and their bactericidal efficiency against Pseudomonas aeruginosa and Staphylococcus aureus was assessed over time. In this sense, coatings loaded with silver ions (MTF + Ag+) were analyzed in comparison with coatings confining silver nanoparticles (MTF + AgNP). EDS analysis revealed that both types of MTF coatings were loaded with high amounts of silver (MTF + Ag+ = 25%; MTF + AgNP = 34%). MTF + Ag+ showed extremely high bactericidal efficiency (percent reduction of 99.5 to >99.999) against both strains along 10 cycles of use, comparable to that observed with MTF + AgNP. Interestingly, silver release from both types of coatings was similar over the same testing period. However, contrary to MTF + AgNP, MTF + Ag+ have shown absolute optical transparency. This is relevant for any type of coating, as conservation of optical properties of the material surface where they are intended to be applied, is highly desirable. Moreover, the maximum silver ion sorption capacity of film coatings was 3 μg cm−2 and MTF + Ag+ were still loaded with silver after 10 cycles of use which indicates that the bactericidal effect could be extended beyond. These results spotlight the potentiality of MTF + Ag+ as antibacterial coatings for any ceramic and/or metallic surface with no alteration of optical and mechanical properties.