Robust Antibacterial Activity Research Articles

Biomimetic Elastomeric Polypeptide-Based Nanofibrous Matrix for Overcoming Multidrug-Resistant Bacteria and Enhancing Full-Thickness Wound Healing/Skin Regeneration.

Overcoming the multidrug-resistant (MDR) bacterial infection is a challenge and urgently needed in wound healing. Few wound dressings possess the capacity to treat MDR bacterial infections and enhance wound healing. Herein, we develop an elastomeric, photoluminescent, and antibacterial hybrid polypeptide-based nanofibrous matrix as a multifunctional platform to inhibit the MDR bacteria and enhance wound healing. The hybrid nanofibrous matrix was composed of poly(citrate)-ε-poly lysine (PCE) and poly caprolactone (PCL). The PCL-PCE hybrid nanofibrous matrix showed a biomimetic elastomeric behavior, robust antibacterial activity including killing MDR bacteria capacity, and excellent biocompatibility. PCL-PCE nanofibrous system can efficiently prevent the MDR bacteria-derived wound infection and significantly enhance the complete skin-thickness wound healing and skin regeneration in a mouse model. PCL-PCE hybrid nanofibrous matrix might become a competitive multifunctional dressing for bacteria-infected wound healing and skin regeneration.

One-Pot Synthesis of Silver Nanoparticle Incorporated Mesoporous Silica Granules for Hemorrhage Control and Antibacterial Treatment.

Hemostasis is of critical importance for damage control and the initiation of tissue repair in surgery and trauma. Mesoporous silica materials, due to their favorable biocompatibility and excellent surface properties, have attracted increasing attention for their outstanding hemostatic performance. In this study, silver nanoparticle-incorporated mesoporous silica granules (AgNP-MSG) were prepared by means of one-pot sol-gel processing, which brought about a highly blood-absorbent composite capable of prompt hemostasis. Detailed studies were performed to evaluate its structure, cellular compatibility, and adsorption capacity, emphasizing the influence of the composite on in vivo degradability and hemostasis efficacy. The as-prepared composite showed good compatibility and sustained antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Further in vivo experimentation demonstrated that hemorrhage in a rat liver injury model was effectively controlled within 7 s by 5% AgNP-MSG, much more rapidly than commercially derived hemostatic gauze. Histological analysis further demonstrated that the fabricated composites could completely degrade at the site of liver injury 2 weeks later. These results suggest that as-prepared AgNP-MSG has great potential as a hemostatic material with robust antibacterial activity for future therapeutic translation.

ROS mediated destruction of cell membrane, growth and biofilms of human bacterial pathogens by stable metallic AgNPs functionalized from bell pepper extract and quercetin

Yellow pepper extract and quercetin (QDH) were used for YPE-AgNPs and Q-AgNPs fabrication. The AgNPs were thoroughly characterized using standard physico-chemical techniques and were found monodispersed, pleomorphic and had variable shape and size with a lattice fringe of 0.23 nm. YPE-AgNPs and Q-AgNPs revealed a characteristic SPR band at 438 nm and 431 nm. The XRD crystal size of YPE-AgNPs and Q-AgNPs was 10.16 and 12.20 nm while TEM analysis showed a size range of 5–40 and 1–25 nm. Bio-fabricated AgNPs remained stable for at least four weeks as the SPR did not deviate with time. FTIR data revealed functionalization of AgNPs by organics of reaction mixture. AgNPs had robust antibacterial and antibiofilm activity against ESβL(+) Escherichia coli, Pseudomonas aeruginosa, and methicillin sensitive and resistant Staphylococcus aureus. Staining of isolates with fluorescent probes displayed the increased production of ROS and membrane permeability. AgNPs hampered EPS production, endorsed DNA leakage, and generated superoxide radicals. Time and concentration dependent experiments demonstrated a consistent decrease in bacterial growth. Structural changes viz. irregular margins, distortion, depressions/indentations and shrinkage of cells were obvious under SEM. AgNPs due to strong antibacterial activity could be exploited as a supplement with antibacterial drugs to control resilient human infections.

Facile construction of Ag nanoparticles encapsulated into carbon nanotubes with robust antibacterial activity

A facile glucose assisted one-step method for preparing highly dispersed Ag nanoparticles (Ag-NPs) encapsulated into carbon nanotubes (CNTs) was developed. The CNTs with open tips are employed as the nano-reactor and support, silver nitrite (AgNO3) is used as the precursor and glucose is employed both as the reducing and protecting agent in the whole preparation process. The Ag-NPs with diameters of 6–10 nm are uniformly assembled into the channel of CNTs. The detailed structure and morphology of Ag-NPs encapsulated into CNTs (Ag-NPs@CNTs) were systematically characterized. The obtained Ag-NPs@CNTs exhibits an enhanced antibacterial activity against Escherichia coli, comparing with those of Ag-NPs supported on activate carbon (Ag-NPs/AC) and on CNTs (Ag-NPs/CNTs) prepared by the traditional wetness impregnation method.

Mussel-Inspired Synthesis of NIR-Responsive and Biocompatible Ag-Graphene 2D Nanoagents for Versatile Bacterial Disinfections.

Pathogenic bacterial infection has been becoming a global threat toward people's health, especially the massive usage of antibiotics due to the lack of antibacterial agents with less side effects. Developing new nanoagents to fight pathogenic bacteria has provided enormous new possibilities in the treatment of bacterial infections, such as graphene-based two-dimensional (2D) antibacterial nanoagents with different bacterial inhibition capabilities; however, mussel-inspired design of near-infrared (NIR)-responsive and biocompatible Ag-graphene nanoagents possessing efficient and versatile bacterial disinfection activities have rarely been reported. In this study, we developed a new kind of antibacterial nanoagent, dopamine-conjugated polysaccharide sulfate-anchored and -protected Ag-graphene (Ag@G-sodium alginate sulfate ((SAS)) nanocomposite, to combat bacterial infection and contamination in different application fields. Ag@G-SAS exhibited robust antibacterial activity toward both Escherichia coli and Staphylococcus aureus; notably, the nanoagent can significantly inhibit S. aureus infection on wounded pig skin without or with NIR laser. Besides wound disinfection, the 2D Ag@G-SAS can also serve as a good layer-by-layer (LbL) building block for the construction of self-sterilizing coatings on biomedical devices. All of the results verified that the LbL-assembled Ag@G-SAS coating exhibited favorable bactericidal activity, extraordinary blood compatibilities, and good promotion ability for cell proliferation. Owing to the shielding effects of heparin-like polysaccharide sulfates, the Ag@G-SAS nanoagent showed limited cytotoxicity toward mammalian cells. Combining all of the advantages mentioned above, it is believed that the proposed Ag@G-SAS nanoagent and its LbL-assembled coatings may have versatile application potentials to avoid bacterial contaminations in different fields, such as wounded skin, disinfection of biomedical implants and devices, and food packaging sterilization.

Annealing-Induced Antibacterial Activity in TiO2 under Ambient Light

We demonstrate that annealing at 850 °C in the presence of Cu universally results in robust antibacterial activity under ambient illumination for TiO2 nanoparticles, different from those annealed in a quartz crucible without metal or in the presence of Ti. Resulting robust antibacterial activity occurred after annealing regardless of the initial properties and crystal structure of the starting samples (two anatase, one rutile, and P25). A clear difference in the powder color from white to gray and a pure rutile crystal structure is observed after annealing in all of the samples. ESR measurements, however, reveal obvious differences in the defects present in the samples annealed under different conditions. Strong antibacterial activity is observed under ambient illumination for samples annealed in the presence of Cu, despite the lower activity for photocatalytic degradation of common dyes such as methylene blue after annealing. Antibacterial activity could not be attributed to the presence of Cu (no activity in the dark) or to the ROS production (none detected under ambient illumination). This indicates that other mechanisms, such as direct charge transfer involving defect levels induced by annealing in the presence of copper, may play a role in the observed antibacterial activity.

One-pot preparation of nanoporous Ag-Cu@Ag core-shell alloy with enhanced oxidative stability and robust antibacterial activity

Metallic core–shell nanostructures have inspired prominent research interests due to their better performances in catalytic, optical, electric, and magnetic applications as well as the less cost of noble metal than monometallic nanostructures, but limited by the complicated and expensive synthesis approaches. Development of one-pot and inexpensive method for metallic core–shell nanostructures’ synthesis is therefore of great significance. A novel Cu network supported nanoporous Ag-Cu alloy with an Ag shell and an Ag-Cu core was successfully synthesized by one-pot chemical dealloying of Zr-Cu-Ag-Al-O amorphous/crystalline composite, which provides a new way to prepare metallic core–shell nanostructures by a simple method. The prepared nanoporous Ag-Cu@Ag core-shell alloy demonstrates excellent air-stability at room temperature and enhanced oxidative stability even compared with other reported Cu@Ag core-shell micro-particles. In addition, the nanoporous Ag-Cu@Ag core-shell alloy also possesses robust antibacterial activity against E. Coli DH5α. The simple and low-cost synthesis method as well as the excellent oxidative stability promises the nanoporous Ag-Cu@Ag core-shell alloy potentially wide applications.

Antibacterial activity of PLAL synthesized nanocinnamon

Natural cinnamon containing polyphenolic compound is well known for diverse biological activities, broad range of pharmacological and therapeutic properties. However, the potential of nanocinnamon for antibacterial usage was not widely explored. Highly crystalline elliptical shaped cinnamon nanoparticles (CNPs) were prepared via pulse laser ablation in liquid (PLAL) by immersing a cinnamon target in methanol. Effects of varying laser fluence on the structure, morphology and optical properties of as-grown CNPs were determined. Samples were characterized via UV-Vis, FTIR, XRD, TEM, HRTEM, SAED, EDX, DLS and HPLC measurements. Methanol was found to be favorable for the growth of CNPs at optimum fluence of 5.73J/cm2. These CNPs revealed robust antibacterial activity against Gram-negative and Gram-positive bacterial strains including Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. Antibacterial activity of CNPs was evaluated via agar well diffusion assay and optical density (OD600) tests. It was established that the PLAL may constitute a basis for the production CNPs with desired size distribution potential for nanomedicinal applications.

A novel chimeric lysin with robust antibacterial activity against planktonic and biofilm methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most threatening pathogens due to its multi-drug resistance (MDR) and strong biofilm-forming capacity. Here, we described the screening of a novel chimeolysin (ClyF) that was active against planktonic and biofilm MRSA. Biochemical tests showed that ClyF was active against all S. aureus clinical isolates tested under planktonic and biofilm conditions. Structure analysis revealed that ClyF has an enhanced thermostability and pH tolerance than its parental lysin Pc by forming a hydrophobic cleft in the catalytic domain and an Ig-like structure in the cell-wall binding domain. A single intraperitoneally or topically administration of ClyF showed good MRSA removing efficacy in mouse models of bacteremia and burn wound infection, respectively. Our data collectively demonstrated that ClyF has good bactericidal activity against planktonic and biofilm MRSA both in vitro and in vivo, and therefore represents a useful antibacterial to combat MDR S. aureus.

Bioinspired and biocompatible carbon nanotube-Ag nanohybrid coatings for robust antibacterial applications

Bacterial infection of medical devices has been considered to be a world-wide clinical threat towards patients' health. In this study, a bioinspired and biocompatible antibacterial coating was prepared via the spray-assisted layer-by-layer (LbL) assembly. The silver nanopartilces loaded oxidized carbon nanotube (AgNPs@oCNT), which were coated by functional polymers (chitosan and synthetic heparin mimicking polymers), were prepared via mussel inspired chemistry; and the spray-assisted assembly process allowed the fast construction on devices. Owing to the antibacterial efficiency of the loaded AgNPs, the coating showed robust bacterial killing activity and resistance towards bacterial adhesion. Moreover, since that the AgNPs were shielded by the polymers, the coating exhibited no clear toxicity at blood or cellular level. Benefiting from the universal and large-scale fabrication advancements of the spray assisted LbL coating; it is believed that the proposed strategy can be applied in designing many other kinds of self-sterilizing biomedical implants and devices.

Antibacterial activity of novel Cu2ZnSnS4 nanoparticles against pathogenic strains

Cu2ZnSnS4 nanoparticles exhibited robust antibacterial activity against the pathogenic Gram-positive and Gram-negative bacteria.

Slow release of ions from internalized silver nanoparticles modifies the epidermal growth factor signaling response

Due to their distinctive physiochemical properties, including a robust antibacterial activity and plasmonic capability, hundreds of consumer and medical products contain colloidal silver nanoparticles (AgNPs). However, even at sub-toxic dosages, AgNPs are able to disrupt cell functionality, through a yet unknown mechanism. Moreover, internalized AgNPs have the potential to prolong this disruption, even after the removal of excess particles. In the present study, we evaluated the impact, mechanism of action, and continual effects of 50nm AgNP exposure on epidermal growth factor (EGF) signal transduction within a human keratinocyte (HaCaT) cell line. After AgNP expose, EGF signaling was initially obstructed due to the dissolution of particles into silver ions. However, at longer durations, the internalized AgNPs increased EGF signaling activity. This latter behavior correlated to sustained HaCaT stress, believed to be maintained through the continual dissolution of internalized AgNPs. This study raises concerns that even after exposure ceases, the retained nanomaterials are capable of acting as a slow-release mechanism for metallic ions; continually stressing and modifying normal cellular functionality.

A silicon-based antibacterial material featuring robust and high antibacterial activity.

In this article, we present a kind of silicon-based antibacterial material made of silver nanoparticle (AgNP)-decorated silicon wafers (AgNP@Si), which is facilely and rapidly (30 min) synthesized via a one-step reaction. Significantly, such a resultant silicon-based antibacterial material features stable and high antibacterial activity, preserving >99% antibacterial efficiency against E. coli during 30 day storage.

Ag-silica composite nanotube with controlled wall structures for biomedical applications

A range of Ag-silica composite nanotubes with tailored wall structures were successfully synthesized in situ by single-nozzle electrospinning. By increasing AgNO3 concentration, the wall structure of Ag-silica tubes changes from dense to porous, and eventually turns into a ‘lace-like’ structure. This is attributed to Ag ions doping into the SiOSi network of precursors, as illustrated in FTIR study. More importantly, Ag-silica composite nanotubes show robust antibacterial activity against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli microorganisms. Therefore, it is a breakthrough of the nanostructure biomaterial research for future medical applications that require strong antibacterial properties.

Reactive oxygen species and the bacteriostatic and bactericidal effects of isoconazole nitrate

Bacterial superinfections often occur in dermatomycoses, resulting in greatly inflamed or eczematous skin. The objective of this study was to evaluate the antibacterial efficacy of isoconazole nitrate (ISN), a broad-spectrum antimicrobial imidazole, commonly used to treat dermatomycoses. Several gram-positive bacteria minimal inhibitory concentrations (MICs) for ISN (ISN solution or ISN-containing creams: Travogen or corticosteroid-containing Travocort) and ampicillin were obtained using the broth-dilution method. Speed of onset of the bactericidal effect was determined with bacterial killing curves. Reactive oxygen species (ROS) were visualised by staining cells with singlet oxygen detector stain. Compared with ampicillin MICs, ISN MICs for Bacillus cereus, Staphylococcus haemolyticus and Staphylococcus hominis were lower and ISN MICs for Corynebacterium tuberculostearicum and Streptococcus salivarius were similar. Incubation with ISN led to a 50% kill rate for Staphylococcus aureus and methicillin-resistant strains (MRSA). Post-ISN incubation, 36% (30 min) and 90% (60 min) of S. aureus cells were positive for ROS. Isoconazole nitrate has a broad bacteriostatic and bactericidal action, also against a MRSA strain that was not reduced by the corticosteroid in the Travocort cream. Data suggest that the antibacterial effect of ISN may be ROS dependent. An antifungal agent with robust antibacterial activity can provide a therapeutic advantage in treating dermatomycoses with suspected bacterial superinfections.

Acylprolinamides: A new class of peptide deformylase inhibitors with in vivo antibacterial activity

A new class of PDF inhibitor with potent, broad spectrum antibacterial activity is described. Optimization of blood stability and potency provided compounds with improved pharmacokinetics that were suitable for in vivo experiments. Compound 5c, which has robust antibacterial activity, demonstrated efficacy in two respiratory tract infection models.

Durable antibacterial Ag/polyacrylonitrile (Ag/PAN) hybrid nanofibers prepared by atmospheric plasma treatment and electrospinning

Durable antibacterial Ag/polyacrylonitrile (Ag/PAN) hybrid nanofibers were prepared by atmospheric plasma treatment and electrospinning. Atmospheric helium plasma treatment was first used to reduce the AgNO 3 precursor in pre-electrospinning solutions into metallic silver nanoparticles, followed by electrospinning into continuous and smooth nanofibers with Ag nanoparticles embedded in the matrix. SEM, TEM, and EDX spectra were used to study the structure and surface elemental composition of the nanofibers. Silver nanoparticles, with diameters ranging between 3 and 6 nm, were found to be uniformly dispersed in the nanofiber matrix. The Ag/PAN nanofibers exhibited slow and long-lasting silver ion release, which provided robust antibacterial activity against both Gram-positive Bacillus cereus and Gram-negative Escherichia coli microorganisms.

Silver-modified iron oxide nanoparticle impregnated fiberglass for disinfection of bacteria and viruses in water

Recent work has shown that a new material system composed of iron oxide (Fe 2O 3) nanoparticles loaded onto a fiberglass support displays excellent antiviral properties against the model virus, MS2 phage, but is ineffective against bacteria, specifically Escherichia coli ( E. coli). To increase the antibacterial properties and still maintain antiviral activity, silver (Ag) nanoparticles were added to this system through an aqueous hydrothermal reduction process with 0.25 M silver nitrate (AgNO 3). A 0.05 mg/mL loading of the new Ag modified oligodynamic nanoparticle impregnated fiberglass system consisting of Fe 2O 3 (9.1 wt.%) and Ag (0.1 wt.%)/g-fiber, displayed robust antibacterial activity by achieving a 2 log removal of 10 6 CFU/mL E. coli in 1 min. The inactivation rate of the Ag-modified Fe 2O 3 impregnated fiberglass (FG-Fe 2O 3/Ag) system was comparable to previously reported Ag nanoparticle impregnated fiberglass. The FG-Fe 2O 3/Ag displayed excellent dynamic performance, effectively eliminating 10 6 E. coli CFU /mL with no bacterial breakthrough up to 250 bed volumes.

One-step synthesis of silver nanoparticle-filled nylon 6 nanofibers and their antibacterial properties

A novel and facile one-step approach to in situ synthesize silver nanoparticle-filled nylon 6 nanofibers by electrospinning is reported. The method does not need post-treatments and can be carried out at ambient conditions without using additional chemicals. It employs the electrospinning solvent as a reducing agent for in situ conversion of AgNO3 into silver nanoparticles during the solution preparation. The resultant silver nanoparticle-filled nylon 6 hybrid nanofibers show an excellent fibrous structure (fiber diameter at 50–150 nm), with narrow size 2–4 nm silver nanoparticles uniformly dispersed throughout the nylon 6 matrix. DSC analysis shows that the in situ incorporation of silver nanoparticles increased the Tg and crystallinity of the resultant nanofibers. These silver nanoparticle-filled nylon 6 nanofibers exhibit a steady and long-lasting silver ion release behavior, and robust antibacterial activity against both Gram-positive B. cereus and Gram-negative E. coli microorganisms.

Sustainable and bio-inspired chemistry for robust antibacterial activity of stainless steel

We report on the original synthesis of a poly(methacrylamide) bearing (oxidized) 3,4-dihydroxyphenylalanine specially designed to (i) insure film growth by covalent coupling, (ii) covalently bind an antibacterial peptide and (iii) contribute to the film cross-linking that is essential for the durability of the properties.