Long-lasting Antibacterial Activity Research Articles

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.

O-Acrylamidomethyl-2-hydroxypropyltrimethyl ammonium chloride chitosan and silk modified mesoporous bioactive glass scaffolds with excellent mechanical properties, bioactivity and long-lasting antibacterial activity

Mesoporous bioactive glass (MBG) is a promising scaffold in bone tissue engineering because its large specific surface area facilitates bioactive behavior and allows mesopores to be loaded with osteogenic agents for promoting the formation of new bone. In the present study, a biocompatible MBG-based scaffold for bone regeneration applications with long-lasting antibacterial activity were fabricated via surface modification with O-acrylamidomethyl-2-hydroxypropyltrimethyl ammonium chloride chitosan (NMA-HACC) and silk. The NMA-HACC–silk (NHS) modified MBG scaffolds were prepared by evaporation-induced self-assembly using polyurethane sponges and the P123 surfactant as co-templates. The microstructure of the scaffold was characterized using scanning electron microscopy (SEM) and synchrotron radiation microcomputer tomography (SRμCT). Fourier transform infrared spectroscopy (FTIR), SEM, X-ray diffraction (XRD), and mechanical experiments were used to analyze the product's composition, inner microstructure, morphology, and mechanical strength before and after its surface modification. These methods were also used to assess the degree to which minerals became deposited on the scaffold after soaking in simulated body fluid (SBF). Confocal laser scanning microscopy (CLSM) was used to evaluate the antibacterial properties and biocompatibility of the scaffolds at various time intervals. Finally, biocompatibility was demonstrated by studying the in vitro proliferation and viability of human mesenchymal stem cells (hMSCs). The results showed that the fabricated scaffolds possessed well-ordered, three-dimensional structures and the NMA-HACC–silk modification rendered the pore network more uniform and continuous, leading to the significant improvement in bioactivity and in hMSC attachment, cell spreading and cell proliferation. Furthermore, the NMA-HACC–silk modification significantly prolonged the antibacterial activity of the MBG scaffold.

Synthesis of High Valence Silver-Loaded Mesoporous Silica with Strong Antibacterial Properties.

A simple chemical method was developed for preparing high valence silver (Ag)-loaded mesoporous silica (Ag-ethylenediaminetetraacetic acid (EDTA)-SBA-15), which showed strong antibacterial activity. Ag-EDTA-SBA-15 exhibited stronger and more effective antibacterial activity than commercial Ag nanoparticles did, and it offered high stability of high valence silver in the porous matrix and long-lasting antibacterial activity. The synthesized materials were characterized using Fourier transform infrared spectroscopy, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) analysis, and transmission electron microscopy (TEM). Ag existed in both surface complexation and Ag particles. EDTA anchored within a porous structure chelated Ag ions in higher oxidation states and prevented their agglomeration and oxidation reduction. The XRD results showed that most Ag in the Ag-EDTA-SBA-15 existed in higher oxidation states such as Ag(II) and Ag(III). However, the XPS and TEM results showed that Ag easily reduced in lower oxidation states and agglomerated as Ag particles on the exterior layer of the SBA-15.

Enhanced bone tissue regeneration by antibacterial and osteoinductive silica-HACC-zein composite scaffolds loaded with rhBMP-2

Next-generation orthopedic implants with both osteoinductivity and antibacterial ability are greatly needed. In the present study, biodegradable rhBMP-2 loaded zein-based scaffolds with a macroporous structure were synthesized, and SBA-15 nanoparticles and hydroxypropyltrimethyl ammonium chloride chitosan (HACC) were incorporated into the scaffolds to produce an anti-infective composite scaffold for delivery of osteogenic factors that facilitate the functional repair of bone defects. The silica/HACC/zein scaffolds developed here showed bioactivity, biocompatibility, and effective antibacterial activity. Confocal laser scanning microscopy (CLSM) was used to quantitatively measure the bactericidal efficacy with respect to bacterial adhesion. Results showed that the sample zein-HACC-S20 exhibited long-lasting antibacterial activity against Escherichia coli and Staphylococcus aureus up to 5 d. At a low dosage of rhBMP-2 (ca. 80 μg), the scaffolds released rhBMP-2 protein efficiently at a relatively slow rate, even after 27 d. An ALP activity and ECM mineralization assay showed that the zein-HACC-S20 scaffolds exhibited significant early osteogenic differentiation by generating enhanced ALP product on day 14 and ECM mineralization on day 21. In a mouse model of thigh muscle pouches, zein-S20 and zein-HACC-S20 groups resulted in obvious bone formation and gave more extensive mineralization to the implants than silica free groups, indicating effective bone induction in vivo. In a rabbit model of critical-sized radius bone defects (20 mm in length and 5 mm in diameter), the bone defects were almost fully repaired and bone marrow cavity recanalization was detectable by 3D micro-CT technique and histological analysis after 12 weeks. In this way, the zein-HACC-S20 scaffolds were proven to significantly promote the bone repair. They also demonstrated considerable promise for tissue engineering. Silica/HACC/zein scaffolds with both antibacterial activity and the ability to induce osteogenesis have immense potential in orthopedics and other biomedical applications.

Green and facile fabrication of silver nanoparticles loaded activated carbon fibers with long-lasting antibacterial activity

Silver nanoparticles (AgNPs) with diameter of about 50 nm were successfully loaded on the surface of activated carbon fibers (ACFs) via a facile and green hydrothermal route. The XRD and XPS results demonstrated that the silver loaded on ACFs surfaces was in metallic form of Ag0. Effects of preparation conditions of pH and reaction time were investigated. pH of the reaction solution was essential for the formation of AgNPs on the ACFs surface. The possible formation mechanism was proposed on the basis of the XPS results. The prepared material was tested for its antibacterial property against typical Gram-positive and Gram-negative bacteria of S. aureus and E. coli, both of which showed good bactericidal efficiency. The stability of the loading was justified by washing the material with water. The long-lasting antibacterial property of the material is of significant practical importance for water purification. Electricity introduced into the system can drastically improve the bactericidal efficiency to 100% in 10 min.

Antibacterials loaded electrospun composite nanofibers: release profile and sustained antibacterial efficacy

Synthetic polyacrylonitrile (PAN)/agar composite nanofibers were fabricated by introducing agar during the electrospinning process, and it was found that the nanofibers could be used for efficient, controlled drug release. Hydrophilic drugs such as ampicillin (AMC) were successfully encapsulated inside the agar, allowing the formation of uniform and smooth AMC/agar/PAN composite nanofibers. Cell viability assays showed that the as-prepared agar/PAN composite nanofibers had a good biocompatibility, and the antibacterial activity of the designed drug delivery system was investigated against Gram negative E. coli with a sustained release profile. The good biocompatibility and enhanced thermal properties—as well as the long-lasting antibacterial activity—of these agar/PAN composite nanofiber-containing drugs indicate their significant promise for a variety of potential medicinal applications. We believe that this approach could serve as a model technique in the fields of drug delivery and controlled release when considering the compatibility between polymers and drugs.

A preliminary study on antibacterial mechanisms of silver ions implanted stainless steel

Silver-containing stainless steels have shown broad spectrum antibacterial activities and exhibit potential applications in food industries and medical appliances. However, few results associated with the antibacterial process have been reported to uncover the interaction of silver implanted stainless steel and bacteria. In this paper we made a preliminary study on antibacterial mechanisms of silver implanted AISI 420 stainless steel. Silver ions exist in metallic state fitted by the Gaussian functions in the implanted layer, with the maximum silver concentration of 3.3 at.% appearing at 45 nm beneath the surface at the extracting voltage of 50 kV. Silver implanted stainless steel possesses excellent antibacterial activities against Escherichia coli at the implantation dose greater than 100 × 1015 ions/cm2. Antibacterial rate against E. coli improves with the increase of silver implantation dose, from 77.7% at 5 × 1015 ions/cm2 to 98.4% at 1000 × 1015 ions/cm2. Dissolved silver ions are crucial for the bactericidal effect. The concentration of released silver ions increases from 35 ± 16 ppb at silver implantation dose of 5 × 1015 ions/cm2 to 255 ± 20 ppb at silver implantation dose of 1000 × 1015 ions/cm2. Silver implanted stainless steel exhibits long-lasting antibacterial activity (antibacterial rate >90%) after exposure to air or immersion in tap water for over one year.

A novel furanone-modified antibacterial dental glass ionomer cement

A novel furanone derivative and a polyacid constructed from it were synthesized, characterized and formulated into experimental high strength cements. The compressive strength (CS) and Streptococcus mutans viability were used to evaluate the mechanical strength and antibacterial activity of the cements. The effect of human saliva and aging were investigated. The antibacterial activity against Lactobacillus sp. and cytotoxicity to human pulp cells were also evaluated. The results show that all the formulated furanone-containing cements showed antibacterial activity, with an initial reduction in CS. The effect of the furanone derivative loading was significant. Increasing loading enhanced the antibacterial activity but reduced the initial CS of the formed cements. The derivative showed antibacterial activity against both S. mutans and Lactobacillus sp. Human saliva did not affect the antibacterial activity of the cement. The cytotoxicity study with human dental pulp cells shows that the furanone-modified cement was biocompatible. A 30day aging study indicated that the cements may have long-lasting antibacterial activity. Within the limitations of this study it appears that the experimental cement could be a clinically attractive dental restorative due to its high mechanical strength and antibacterial function.

Synthesis and Characterization of Waterborne Polyurethane/Cu(II)-Loaded Hydroxyapatite Nanocomposites with Antibacterial Activity

A novel kind of environmentally friendly nanocomposites, waterborne polyurethane (WBPU)/Cu(II)-loaded hydroxyapatite (CuHAp), with improved physical properties and antibacterial activity have been prepared via in-situ polymerization from functionalized CuHAp nanoparticles (CuHAp NPs). The interaction of the CuHAp NPs with isophorone diisocyanate to form the functionalized CuHAp NPs containing isocyanate groups (CuHAp-g-NCO) has been studied. The microstructure and particle distribution of the nanocomposites were observed using scanning electron microscopy. The improvements of mechanical properties, thermal stability and water resistance of the nanocomposites have also been evaluated. Finally, the antibacterial activity was tested against G(-) Escherichia coli and G(+) Staphylococcus aureus by the zone of inhibition test and the direct contact test. The long-lasting antibacterial activity was studied by measuring antibacterial ability of the nanocomposites after being immersed in water. The results indicate that WBPU incorporation with CuHAp NPs shows strong antibacterial activity upon contact, and long-lasting antibacterial property.

Preparation and characterization of NaY/PVDF hybrid ultrafiltration membranes containing silver ions as antibacterial materials

A novel antibacterial ultrafiltration (UF) membrane obtained by blending poly (vinylidene fluoride) (PVDF) with Ag + exchanged NaY zeolite particles (AgNaY) was prepared using phase inversion methods. The AgNaY hybrid PVDF membranes exhibited excellent and long-lasting antibacterial activity against Escherichia coli ( E. coli) . Its antibacterial activity was improved with increased Ag + content. The hydrophilicity of P-AgNaY-3 was improved with a low contact angle of 81.6°. Compared with P-0, the permeate performance, thermal stability, and mechanical properties of P-AgNaY were improved with a steady bovine serum albumin (BSA) retention above 92%. Antibacterial activity of the membranes against E. coli was measured using the halo zone test. The characterization of AgNaY/PVDF hybrid membranes was investigated by scanning electron microscope, X-ray diffraction, tensile stress tests, thermogravimetric analysis, contact angle tests, pure water flux, and permeation flux.

Antibacterial properties of 4 orthodontic cements

White spot lesions are observed in nearly 50% of patients undergoing orthodontic treatment. Long-lasting antibacterial properties of orthodontic cements can reduce this phenomenon. The antibacterial properties of 4 orthodontic cements were evaluated by direct contact test (DCT) and agar diffusion test (ADT). With the DCT technique, octet specimens of glass ionomer (CX-Plus; Shofu, Kyoto, Japan), reinforced glass ionomer (GC Fuji ORTHO LC; GC Corporation, Tokyo, Japan), and 2 composite (Transbond XT and Transbond Plus; 3M Unitek, Monrovia, Calif) orthodontic cements were placed on the sidewalls of wells of a 96-microtiter plate. Streptococcus mutans cells (ca. 1 x 10(6) ) were placed on the surface of each specimen for 1 hour at 37 degrees C. Then, fresh media was added to each well, and bacterial growth was monitored for 16 hours with a temperature-controlled spectrophotometer. This was repeated on specimens aged in phosphate-buffered saline for 1 day, 1 week, and 1 month. The ADT was performed by placing specimens in wells punched in agar plates. Measurement of the halo in bacterial lawn after 48 hours showed that only the glass ionomer cement (CX-Plus) produced an inhibition zone (1.2 mm around the sample). Results at the DCT showed that only the reinforced glass ionomer cement (GC Fuji ORTHO LC) exhibited potent antibacterial activity, which lasted 1 week and diminished over the next 3 weeks. The reinforced glass ionomer cement possessed the most potent and long-lasting antibacterial activity.