Effect of Amino Acid Types on the Mechanical and Antimicrobial Properties of Amino Acid-Based Polyionic Liquid Hydrogels

Polyionic liquid hydrogels attract increasing attention due to their unique properties and potential applications. However, research on amino acid-based polyionic liquid hydrogels is still in its infancy stage. Moreover, the effect of amino acid types on the properties of hydrogels is rarely studied to date. In this work, amino acid-based polyionic liquid hydrogels (D/L-PCAA hydrogels) are synthesized by copolymerizing vinyl choline-amino acid ionic liquids and acrylic acids using Al3+ as a crosslinking agent and bacterial cellulose (BC) as a reinforcing agent. The effects of amino acid types on mechanical and antimicrobial properties are systematically investigated. D-arginine-based hydrogel (D-PCArg) shows the highest tensile strength (220.7 KPa), D-phenylalanine-based hydrogel (D-PCPhe) exhibits the highest elongation at break (1346%), and L-aspartic acid-based hydrogel (L-PCAsp) has the highest elastic modulus (206.9 KPa) and toughness (1.74 MJ m-3). D/L-PCAsp hydrogels demonstrate stronger antibacterial capacity against Escherichia coli and Staphylococcus aureus, and D/L-PCPhe hydrogels possess higher antifungal activity against Cryptococcus neoformans. Moreover, the resultant hydrogels exhibit prominent hemocompatibility and low toxicity, as well as excellent self-healing capabilities (86%) and conductivity (2.8 S m-1). These results indicate that D/L-PCAA hydrogel provides a promise for applications in wound dressings.

Vanillin-Mediated Green-Synthesised Silver Nanoparticles' Characterisation and Antimicrobial Activity: An In-Vitro Study

Background and aim Nanoparticles in general due to their enhanced antimicrobial effects and other beneficial effects are used in dentistry. Silver nanoparticles (AgNPs) have emerged as the metal nanoparticle with the most advantages among the many types. The objective of the study was to synthesise vanillin-mediated AgNPs, then characterise those nanoparticles and assess their antimicrobial effectiveness. Materials and methods One-step synthesis of stable and crystalline AgNPs was done with vanillin as the reducing and capping agent. After being crushed into powder form, the produced AgNPs were subjected to characterisation. A scanning electron Microscope SEM) analysis was done for morphological details of the AgNPs. SEM with energy dispersive X-ray spectroscopy analysis (EDAX) and Fourier transform infrared (FTIR) testing were done for elemental analysis. AgNPs' antimicrobial properties were tested using the agar well diffusion technique. Results The SEM analysis revealed that the synthesized AgNps were porous and agglomerative clusters and varied in sizes between 30-35 nm. SEM-EDAX revealed the presence of 76.2 weight (wt)% Ag, 4.9 wt% carbon, and 18.9 wt% of oxygen. FTIR prominent peaks were observed at 1431.97 cm and 1361.20 cm indicating the presence of AgNPs. Both low and high concentrations of AgNps showed good antimicrobial effects against Streptococcus mutans (S. mutans). Conclusion Vanillin can be successfully used as a reducing agent for creating AgNPs. Due to their effective antimicrobial activity against S.mutans at various concentrations, vanillin-mediated AgNPs can be used with dental materials to reduce the risk of dental caries and enamel demineralization.

Synthesis and Characterization of Bioactive Glass and Zinc Oxide Nanoparticles with Enamel Remineralization and Antimicrobial Capabilities

BACKGROUND

We investigated the effect of bioactive glass and zinc oxide nanoparticles on enamel remineralization, as well as their antimicrobial effect on cariogenic microbes. This is the first study that investigated the properties of bioactive glass and zinc oxide nanoparticles with mixed materials.

METHODS

Fluoride gel (F), bioactive glass microparticles (µB), bioactive glass nanoparticles (nB), zinc oxide nanoparticles (Z), and a mixed suspension of nB and Z (nBZ) were prepared and characterized by scanning and transmission electron microscopy, zeta potential measurement, X-ray diffraction, and acid buffering capacity testing. Further, we performed a remineralization cycle test of 28 days, and nanoindentation testing was carried out during the immersion period, and then the enamel surfaces were examined using scanning electron microscopy. Additionally, the antimicrobial effects of the sample suspensions were evaluated by measuring their minimum microbicidal concentrations against various cariogenic microbes.

RESULTS

Our results revealed that nB had a near-circular shape with an amorphous structure and a considerably large specific surface area due to nanoparticulation. Additionally, nB possessed a rapid acid buffering capacity that was comparable to that of μB. In the remineralization test, faster recovery of mechanical properties was observed on the enamel surface immersed in samples containing bioactive glass nanoparticles (nB and nBZ). After remineralization, demineralized enamel immersed in any of the samples showed a rough and porous surface structure covered with mineralized structures. Furthermore, nBZ exhibited a broad antimicrobial spectrum.

CONCLUSIONS

These results demonstrated that bioactive glass and zinc oxide nanoparticles have superior demineralization-suppressing and remineralization-promoting effects.

Formation of Umbilicaria decussata (Antarctic and Turkey) Extracts Based Nanoflowers with Their Peroxidase Mimic, Dye Degradation and Antimicrobial Properties

This work describes a unique and environmentally friendly approach for creating three-dimensional (3D) organic-inorganic flower shaped hybrid nanostructures called "nanoflower (NF)" by using Umbilicaria decussate (U. decussate) extract and copper ions (Cu2+ ). U. decussate species were collected from certain place in Antarctic and Turkey and extraction of each species were completed in methanol and water. The U. decussate extracts were used as organic components and Cu2+ acted as inorganic components for formation of U. decussate extracts based hybrid NFs. We rationally used these NFs as novel nanobiocatalyst and antimicrobial agents. These NFs exhibited peroxidase mimic, dye degradation and antimicrobial properties. The NFs were characterized with various techniques. For instance, the morphologies of the NFs were monitored by scanning electron microscope (SEM), presence of elements in the NFs were presented using Energy Dispersive X-Ray Analysis (EDX). Fourier-transform infrared spectroscopy (FT-IR) was used to elucidate corresponding bending and stretching of bonds in the NFs. The NFs acted as effective Fenton agents in the presence of hydrogen peroxide, and we demonstrated their peroxidase-like activity against guaiacol, dye degradation property towards malachite green and antimicrobial activity for Aeromonas hydrophila, Aeromonas sobria, Escherichia coli, Salmonella enterica and Staphylococcus aureus.

Antioxidant and Antimicrobial Properties and GC-MS Chemical Compositions of Makwaen Pepper (Zanthoxylum myriacanthum) Extracted Using Supercritical Carbon Dioxide

This research aimed to optimize pressure (10-20 MPa) and temperature (45-60 °C) conditions for supercritical fluid extraction (SFE) of Makwaen pepper (Zanthoxylum myriacanthum) extract (ME) in comparison to conventional hydro-distillation extraction. Various quality parameters, including yield, total phenolic compounds, antioxidants, and antimicrobial activities of the extracts, were assessed and optimized using a central composite design. The optimal SFE conditions were found to be 20 MPa at 60 °C, which resulted in the highest yield (19%) and a total phenolic compound content of 31.54 mg GAE/mL extract. IC₅₀ values for DPPH and ABTS assays were determined to be 26.06 and 19.90 μg/mL extract, respectively. Overall, the ME obtained through SFE exhibited significantly better physicochemical and antioxidant properties compared to ME obtained through hydro-distillation extraction. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that beta-pinene was the major component in the ME obtained through SFE (23.10%), followed by d-limonene, alpha-pinene, and terpinen-4-ol at concentrations of 16.08, 7.47, and 6.34%, respectively. On the other hand, the hydro-distillation-extracted ME showed stronger antimicrobial properties than the SFE-extracted ME. These findings suggest that both SFE and hydro-distillation have the potential for extracting Makwaen pepper, depending on the intended purpose of use.

Nematocidal and Bactericidal Activities of Green Synthesized Silver Nanoparticles Mediated by Ficus sycomorus Leaf Extract

Nanoparticles effectively control most plant pathogens, although research has focused more on their antimicrobial than their nematocidal properties. This study synthesized silver nanoparticles (Ag-NPs) through a green biosynthesis method using an aqueous extract of Ficus sycomorus leaves (FS-Ag-NPs). The nanoparticles were characterized using SEM, TEM, EDX, zeta sizer, and FTIR. The TEM results showed that the synthesized NPs were nanoscale and had an average particle size of 33 ± 1 nm. The elemental silver signal at 3 keV confirmed the formation of Ag-NPs from an aqueous leaf extract of F. sycomorus. The FTIR analysis revealed the existence of several functional groups in the prepared Ag-NPs. The strong-broad band detected at 3430 cm^-1 indicated the stretching vibration of -OH (hydroxyl) and -NH₂ (amine) groups. The nematocidal activity of biosynthesized FS-Ag-NPs has been evaluated in vitro against the root-knot nematode Meloidogyne incognita at 24, 48, and 72 h. The FS-Ag-NPs at a 200 µg/mL concentration applied for 48 h showed the highest effectiveness, with 57.62% nematode mortality. Moreover, the biosynthesized FS-Ag-NPs were also tested for their antibacterial activity against Pectobacterium carotovorum, P. atrosepticum, and Ralstonia solanacearum. With the application of nanoparticles, the reduction in bacterial growth gradually increased. The most potent activity at all concentrations was found in R. solanacearum, with values of 14.00 ± 2.16, 17.33 ± 2.05, 19.00 ± 1.41, 24.00 ± 1.41, and 26.00 ± 2.83 at concentrations of 5, 10, 15, 20, and 25 µg/mL, respectively, when compared with the positive control (Amoxicillin 25 µg) with a value of 16.33 ± 0.94. At the same time, the nanoparticles showed the lowest reduction values against P. atrosepticum when compared to the control. This study is the first report on the nematocidal activity of Ag-NPs using F. sycomorus aqueous extract, which could be a recommended treatment for managing plant-parasitic nematodes due to its simplicity, stability, cost-effectiveness, and environmentally safe nature.

Washable Antimicrobial Wipes Fabricated from a Blend of Nanocomposite Raw Cotton Fiber

In this study, a simple and effective way to produce washable antimicrobial wipes was developed based on the unique ability of raw cotton fiber to produce silver nanoparticles. A nanocomposite substructure of silver nanoparticles (25 ± 3 nm) was generated in raw cotton fiber without reducing and stabilizing agents. This nanocomposite raw cotton fiber (2100 ± 58 mg/kg in the concentration of silver) was blended in the fabrication of nonwoven wipes. Blending small amounts in the wipes-0.5% for antimicrobial properties and 1% for wipe efficacy-reduced the viability of S. aureus and P. aeruginosa by 99.9%. The wipes, fabricated from a blend of 2% nanocomposite raw cotton fiber, maintained their antibacterial activities after 30 simulated laundering cycles. The washed wipes exhibited bacterial reductions greater than 98% for both Gram-positive and Gram-negative bacteria.

Synthesis of CuO and PAA-Regulated Silver-Carried CuO Nanosheet Composites and Their Antibacterial Properties

With the aid of a facile and green aqueous solution approach, a variety of copper oxide (CuO) with different shapes and polyacrylic-acid (PAA)-regulated silver-carried CuO (CuO@Ag) nanosheet composites have been successfully produced. The point of this article was to propose a common synergy using Ag-carried CuO nanosheet composites for their potential antibacterial efficiency against three types of bacteria such as E. coli, P. aeruginosa, and S. aureus. By using various technical means such as XRD, SEM, and TEM, the morphology and composition of CuO and CuO@Ag were characterized. It was shown that both CuO and CuO@Ag have a laminar structure and exhibit good crystallization, and that the copper source and reaction duration have a sizable impact on the morphology and size distribution of the product. In the process of synthesizing CuO@Ag, the appropriate amount of polyacrylic acid (PAA) can inhibit the agglomeration of Ag NPs and regulate the size of Ag at about ten nanometers. In addition, broth dilution, optical density (OD 600), and electron microscopy analysis were used to assess the antimicrobial activity of CuO@Ag against the above three types of bacteria. CuO@Ag exhibits excellent synergistic and antibacterial action, particularly against S. aureus. The antimicrobial mechanism of the CuO@Ag nanosheet composites can be attributed to the destruction of the bacterial cell membrane and the consequent leakage of the cytoplasm by the release of Ag⁺ and Cu²⁺. The breakdown of the bacterial cell membrane and subsequent leakage of cytoplasm caused by Ag⁺ and Cu²⁺ released from antimicrobial agents may be the cause of the CuO@Ag nanosheet composites' antibacterial action. This study shows that CuO@Ag nanosheet composites have good antibacterial properties, which also provides the basis and ideas for the application research of other silver nanocomposites.

In vitro antimicrobial and cytotoxic activity of Neem and Kirata herbal formulation mediated Silver nanoparticles

Silver nanoparticles (AgNPs) gain great interest among noble metal nanoparticles due to their broad applications in medicine, dentistry, drug delivery, tissue and tumour imaging, biolabeling, and biosensing. The antibacterial, antifungal, antiviral, and antiparasitic activity of AgNPs is well documented in the literature. This study aimed to determine the antimicrobial and cytotoxic activity of Neem and Kirata herbal formulation-mediated silver nanoparticles against oral biofilm. The green synthesis of Neem and Kirata herbal formulation-mediated silver nanoparticles was done. The antimicrobial action against the strains of Candida albicans, Staphylococcus aureus, Enterococcus faecalis, and Streptococcus mutans were assessed. The results showed that the newly formulated nanoparticle had effective anti-microbial properties and decreased cytotoxic properties which make it advantageous for clinical applications and treatment modalities. It showed great potential for the nanoparticle in decreasing the bacterial effects and cytotoxic nature thereby providing future scope for clinical application in preventing oral biofilm formation and its deleterious effects.

Bioactivity and Thermal Stability of Collagen-Chitosan Containing Lemongrass Essential Oil for Potential Medical Applications

Bioactive collagen–chitosan–lemongrass (COL–CS–LG) membranes were prepared by casting method and analyzed for potential biomedical applications. For COL–CS–LG membranes, LG essential oil release, antioxidant properties, in vitro cytotoxicity and antimicrobial assessments were conducted, as well as free radical determination after gamma irradiation by chemiluminescence, and structural characteristics analysis through Attenuated Total Reflection–Fourier Transform Infrared Spectroscopy (ATR–FTIR) and Differential Scanning Calorimetry (DSC). The evaluation of non-isothermal chemiluminescence after gamma radiation exposure to COL–CS–LG membranes revealed a slowing down of the oxidation process at temperatures exceeding 200 °C, in correlation with antioxidant activity. Antimicrobial properties and minimum inhibitory concentrations were found to be in correlation with cytotoxicity limits, offering the optimum composition for designing new biomaterials.

Rapid Solar Heating of Antimicrobial Ag and Cu2O Nanostructured Plasmonic Textile for Clean Water Production

Solar steam generation is an attractive method to produce clean water, and high steam generation rates have been achieved using nanostructured light absorbers. However, since it usually takes minutes to reach the temperature for steady-state steam generation under solar illumination, a material that responds quickly to intermittent sunlight is strongly desired. Here, we report an unprecedented heating rate in an ultralight freestanding textile consisting of interconnected Ag and Cu₂O nanoparticles. The textile demonstrated high solar absorption with low reflectance and transmittance, which were rationalized using our multiphysics simulations. A commercial polystyrene foam wrapped with this broadband light-absorbing textile showed the fastest response to sunlight together with a good steam generation rate compared to reported inorganic nanostructured steam generators. Furthermore, the textile exhibited antibacterial property, which might lower the risk of the vapor-induced transfer of bacteria during long-term intermittent use and the cost of subsequent water sanitization.

Spatial Delivery of Triple Functional Nanoparticles via an Extracellular Matrix-Mimicking Coaxial Scaffold Synergistically Enhancing Bone Regeneration

It remains a major challenge to simultaneously achieve bone regeneration and prevent infection in the complex microenvironment of repairing bone defects. Here, we developed a novel ECM-mimicking scaffold by coaxial electrospinning to be endowed with multibiological functions. Lysophosphatidic acid (LPA) and zinc oxide (ZnO) nanoparticles were loaded into the poly-lactic-co-glycolic acid/polycaprolactone (PLGA/PCL, PP) sheath layer of coaxial nanofibers, and deferoxamine (DFO) nanoparticles were loaded into its core layer. The novel scaffold PP-LPA-ZnO/DFO maintained a porous nanofibrous architecture after incorporating three active nanoparticles, showing better physicochemical properties and eximious biocompatibility. In vitro studies showed that the bio-scaffold loaded with LPA nanoparticles had excellent cell adhesion, proliferation, and differentiation for MC3T3-E1 cells and synergistic osteogenesis with the addition of ZnO and DFO nanoparticles. Further, the PP-LPA-ZnO/DFO scaffold promoted tube formation and facilitated the expression of vascular endothelial markers in HUVECs. In vitro antibacterial studies against Escherichia Coli and Staphylococcus aureus demonstrated effective antibacterial activity of the PP-LPA-ZnO/DFO scaffold. In vivo studies showed that the PP-LPA-ZnO/DFO scaffold exhibited excellent biocompatibility after subcutaneous implantation and remarkable osteogenesis at 4 weeks post-implantation in the mouse alveolar bone defects. Importantly, the PP-LPA-ZnO/DFO scaffold showed significant antibacterial activity, prominent neovascularization, and new bone formation in the rat fenestration defect model. Overall, the spatially sustained release of LPA, ZnO, and DFO nanoparticles through the coaxial scaffold synergistically enhanced biocompatibility, osteogenesis, angiogenesis, and effective antibacterial properties, which is ultimately beneficial for bone regeneration. This project provides the optimized design of bone regenerative biomaterials and a new strategy for bone regeneration, especially in the potentially infected microenvironment.

Liquid metal polymer composite: Flexible, conductive, biocompatible, and antimicrobial scaffold

Gallium and its alloys, such as eutectic gallium indium alloy (EGaIn), a form of liquid metal, have recently attracted the attention of researchers due to their low toxicity and electrical and thermal conductivity for biomedical application. However, further research is required to harness EGaIn-composites advantages and address their application as a biomedical scaffold. In this research, EGaIn-polylactic acid/polycaprolactone composites with and without a second conductive filler, MXene, were prepared and characterized. The addition of MXene, into the EGaIn-composite, can improve the composite's electrochemical properties by connecting the liquid metal droplets resulting in electrically conductive continuous pathways within the polymeric matrix. The results showed that the composite with 50% EGaIn and 4% MXene, displayed optimal electrochemical properties and enhanced mechanical and radiopacity properties. Furthermore, the composite showed good biocompatibility, examined through interactions with fibroblast cells, and antibacterial properties against methicillin-resistant Staphylococcus aureus. Therefore, the liquid metal (EGaIn) polymer composite with MXene provides a first proof-of-concept engineering scaffold strategy with low toxicity, functional electrochemical properties, and promising antimicrobial properties.

Antibacterial Hydrogel with Self-Healing Property for Wound-Healing Applications

Hydrogels with inherent antibacterial ability are a focus in soft tissue repair. Herein, a series of antibacterial hydrogels were fabricated by quaternized N-[3-(dimethylamino)propyl] methacrylamide (quaternized P(DMAPMA-DMA-DAA)) bearing copolymers with dithiodipropionic acid dihydrazide (DTDPH) as cross-linker. The hydrogels presented efficient self-healing capability as well as a pH and redox-triggered gel-sol-gel transition property that is based on the dynamic acylhydrazone bond and disulfide linkage. Furthermore, the hydrogels showed good antibacterial activity, biocompatibility, degradability, and sustained release ability. More importantly, the in vivo experiments demonstrated that the hydrogels loaded with mouse epidermal growth factor (mEGF) significantly accelerated wound closure by preventing bacterial infection and promoting cutaneous regeneration in the wound model. The antibacterial hydrogels with self-healing behavior hold great potential in wound treatment.

Epsilon-poly-L-lysine: Recent Advances in Biomanufacturing and Applications

ε-poly-L-lysine (ε-PL) is a naturally occurring poly(amino acid) of varying polymerization degree, which possesses excellent antimicrobial activity and has been widely used in food and pharmaceutical industries. To provide new perspectives from recent advances, this review compares several conventional and advanced strategies for the discovery of wild strains and development of high-producing strains, including isolation and culture-based traditional methods as well as genome mining and directed evolution. We also summarize process engineering approaches for improving production, including optimization of environmental conditions and utilization of industrial waste. Then, efficient downstream purification methods are described, including their drawbacks, followed by the brief introductions of proposed antimicrobial mechanisms of ε-PL and its recent applications. Finally, we discuss persistent challenges and future perspectives for the commercialization of ε-PL.

Biological Synergy and Antimicrobial Mechanism of Hydroxypropyltrimethyl Ammonium Chloride Chitosan with Benzalkonium Chloride

Preservatives in eye drops have always been the focus of people's attention. Benzalkonium chloride (BAC) is one of the most frequently used bacteriostatic agents in eye drops, which has broad-spectrum and efficient bactericidal ability. However, the inappropriate dosage of BAC may lead to high cytotoxicity. Therefore, adding low-toxic hydroxypropyltrimethyl ammonium chloride chitosan (HACC) can not only achieve antimicrobial effect, but also have the advantages of moisturizing and biocompatibility. In this paper, the minimum inhibitory concentrations (MICs) of HACC and BAC were evaluated against Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Diphtheroid bacillus and Candida albicans. Based on the MIC of each antimicrobial agent, an antimicrobial assay was performed to investigate the antimicrobial ability of disinfectant solution. Besides, cytotoxicity had also been assessed. When the HACC/BAC solution at weight ratio of 150/1 showed a highest antimicrobial efficiency and the cell proliferation rates were the highest in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. Furthermore, the cell leakage was examined by UV absorption, indicating the great synergistic antimicrobial effect between HACC and BAC. What is more, the results of micromorphology research suggested that as the result of repulsive force between the two molecules, the average particle size of HACC would decrease. Finally, the impedance experiment showed that with the addition of BAC, current density would increase significantly, suggesting that more positive charge group was exposed to aqueous solution, leading the the increase of antimicrobial ability. Based on these results, HACC-BAC combination solution might be a promising novel antimicrobial group for biomedical applications.

Isolating High Antimicrobial Ability Lignin From Bamboo Kraft Lignin by Organosolv Fractionation

Lignin from different biomasses possess biological antioxidation and antimicrobial activities, which depend on the number of functional groups and the molecular weight of lignin. In this work, organosolv fractionation was carried out to prepare the lignin fraction with a suitable structure to tailor excellent biological activities. Gel permeation chromatography (GPC) analysis showed that decreased molecular weight lignin fractions were obtained by sequentially organosolv fractionation with anhydrous acetone, 50% acetone and 37.5% hexanes. Nuclear magnetic resonance (NMR) results indicated that the lignin fractions with lower molecular weight had fewer substructures and a higher phenolic hydroxyl content, which was positively correlated with their antioxidation ability. Both of the original lignin and fractionated lignins possessed the ability to inhibit the growth of Gram-negative bacteria (Escherichia coli and Salmonella) and Gram-positive bacteria (Streptococcus and Staphylococcus aureus) by destroying the cell wall of bacteria in vitro, in which the lignin fraction with the lowest molecular weight and highest phenolic hydroxyl content (L3) showed the best performance. Besides, the L3 lignin showed the ability to ameliorate Escherichia coli-induced diarrhea damages of mice to improve the formation of intestinal contents in vivo. These results imply that a lignin fraction with a tailored structure from bamboo lignin can be used as a novel antimicrobial agent in the biomedical field.

Coupling Biocompatible Au Nanoclusters and Cellulose Nanofibrils to Prepare the Antibacterial Nanocomposite Films

Cellulose nanofibrils (CNF) is considered as an inexhaustible precursor to produce antibacterial materials, such as antibacterial hydrogel, antibacterial paper, and antibacterial film. However, the poor antimicrobial property of neat CNF required it should be coupled with an antibacterial ingredient. Herein, biocompatible Au nanoclusters (AuNCs) were synthesized and added into the CNF dispersion to prepare a novel antibacterial film (AuNCs@CNF film). The effects of addition of AuNCs with different amount on the morphology and physicochemical properties of AuNCs@CNF films were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), FTIR (Fourier-transform infrared), light transmittance spectra, and thermogravimetric analysis (TGA). The results showed that AuNCs did not affect the nano-structural features of the CNF film and its basic structures, but could greatly increase the hydrophilicity, the flexibility and the thermal stability of CNF film, which might improve its application in antimicrobial wound-healing dressing. The prepared AuNCs@CNF films demonstrated high antibacterial properties toward Escherichia coli (E. coli) and Streptococcus mutans (S. mutans) both in vitro and in vivo, which can prohibit their growths and promote the healing of bacteria-infected wound, respectively. Thus, the prepared AuNCs@CNF film with great antibacterial properties could be applicable in biomedical field.

Bactericidal and Bioresorbable Calcium Phosphate Cements Fabricated by Silver-Containing Tricalcium Phosphate Microspheres

Bacterial adhesion to the calcium phosphate surface is a serious problem in surgery. To prevent bacterial infection, the development of calcium-phosphate cements (CPCs) with bactericidal properties is indispensable. The aim of this study was to fabricate antibacterial CPCs and evaluate their biological properties. Silver-containing tricalcium phosphate (Ag-TCP) microspheres consisting of α/β-TCP phases were synthesized by an ultrasonic spray-pyrolysis technique. The powders prepared were mixed with the setting liquid to fabricate the CPCs. The resulting cements consisting of β-TCP and hydroxyapatite had a porous structure and wash-out resistance. Additionally, silver and calcium ions could be released into the culture medium from Ag-TCP cements for a long time accompanied by the dissolution of TCP. These data showed the bioresorbability of the Ag-TCP cement. In vitro antibacterial evaluation demonstrated that both released and immobilized silver suppressed the growth of bacteria and prevented bacterial adhesion to the surface of CPCs. Furthermore, histological evaluation by implantation of Ag-TCP cements into rabbit tibiae exhibited abundant bone apposition on the cement without inflammatory responses. These results showed that Ag-TCP cement has a good antibacterial property and good biocompatibility. The present Ag-TCP cements are promising for bone tissue engineering and may be used as antibacterial biomaterials.

Iron Magnetic Nanoparticle-Induced ROS Generation from Catechol-Containing Microgel for Environmental and Biomedical Applications

Reactive oxygen species (ROS) can degrade organic compounds and function as a broad-spectrum disinfectant. Here, dopamine methacrylamide (DMA) was used to prepare catechol-containing microgels, which can release ROS via metal-catechol interaction. A combination of the microgel and iron magnetic nanoparticle (FeMNP) significantly reduced the concentration of four organic dyes (Alizarin Red S, Rhodamine B, Crystal Violet, and Malachite Green) and an antibiotic drug, ciprofloxacin, dissolved in solution. Degradation of dye occurred across a wide range of pH levels (pH 3-9). This simple combination was also antimicrobial against both Escherichia coli and Staphylococcus aureus. Electron paramagnetic resonance spectroscopy (EPR) results indicate that singlet oxygen was generated during the reaction between catechol and FeMNP at both pH 3 and 7.4, which was responsible for the degradation of organic compounds and bactericidal features of the microgel. Unlike autoxidation that only occurs at a neutral to basic pH, FeMNP-induced catechol oxidation generated singlet oxygen over a wide range of pH level. Additionally, catechol chelates heavy metal ions, resulting in their removal from solution and repurposed these metal ions for dye degradation. This multifunctional microgel can potentially be used for environmental applications for the removal of organic pollutants and heavy metal ions from wastewater, as well as reducing bacterial infection in biomedical applications.

Polydopamine Nanosphere with In-Situ Loaded Gentamicin and Its Antimicrobial Activity

The mussel inspired polydopamine has acquired great relevance in the field of nanomedicines, owing to its incredible physicochemical properties. Polydopamine nanoparticles (PDA NPs) due to their low cytotoxicity, high biocompatibility and ready biodegradation have already been widely investigated in various drug delivery, chemotherapeutic, and diagnostic applications. In addition, owing to its highly reactive nature, it possesses a very high capability for loading drugs and chemotherapeutics. Therefore, the loading efficiency of PDA NPs for an antibiotic i.e., gentamicin (G) has been investigated in this work. For this purpose, an in-situ polymerization method was studied to load the drug into PDA NPs using variable drug: monomer ratios. Scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) confirmed the successful loading of drug within PDA NPs, mainly via hydrogen bonding between the amine groups of gentamicin and the hydroxyl groups of PDA. The loading amount was quantified by liquid chromatography-mass spectrometry (LC-MS) and the highest percentage loading capacity was achieved for G-PDA prepared with drug to monomer ratio of 1:1. Moreover, the gentamicin loaded PDA NPs were tested in a preliminary antibacterial evaluation using the broth microdilution method against both Gram-(+) Staphylococcus aureus and Gram-(-) Pseudomonas aeruginosa microorganisms. The highest loaded G-PDA sample exhibited the lowest minimum inhibitory concentration and minimum bactericidal concentration values. The developed gentamicin loaded PDA is very promising for long term drug release and treating various microbial infections.

Polyanionic Composite Membranes Based on Bacterial Cellulose and Amino Acid for Antimicrobial Application

Ideal wound dressing materials should be active components in the healing process. Bacterial cellulose (BC) has attracted a great deal of attention as novel wound dressing materials; however, it has no intrinsic antimicrobial activity. To explore the practical application values of BC and develop novel wound dressing materials, a series of composite membranes based on BC and polymeric ionic liquids (BC/PILs, composed of BC, and PILs formed by choline and different amino acids) with antimicrobial activity were synthesized by an ex situ method. The physicochemical and antimicrobial properties and biocompatibility of these membranes were systematically investigated. The results indicated that BC/PIL membranes with excellent properties could be obtained by adjusting the concentration and type of PILs. Several kinds of BC/PIL membranes exhibited good biocompatibility and high antimicrobial activity against Gram-positive and Gram-negative bacteria and fungus. The anionic PILs played important roles in the antimicrobial activity of BC/PIL membranes. The obtained membranes provided a novel promising candidate for wound dressing materials.

Novel polymeric microspheres: Synthesis, enzyme immobilization, antimutagenic activity, and antimicrobial evaluation against pathogenic microorganisms

New polymeric microspheres containing azomethine (1a-1c and 2a-2c) were synthesized by condensation to compare the enzymatic properties of the enzyme glucose oxidase (GOx) and to investigate antimutagenic and antimicrobial activities. The polymeric microspheres were characterized by elemental analysis, infrared spectra (FT-IR), proton nuclear magnetic resonance spectra, thermal gravimetric analysis, and scanning electron microscopy analysis. The catalytic activity of the glucose oxidase enzyme follows Michaelis-Menten kinetics. Influence of temperature, reusability, and storage capacity of the free and immobilized glucose oxidase enzyme were investigated. It is determined that immobilized enzymes exhibit good storage stability and reusability. After immobilization of GOx in polymeric supports, the thermal stability of the enzyme increased and the maximum reaction rate (V_max ) decreased. The activity of the immobilized enzymes was preserved even after 5 months. The antibacterial and antifungal activity of the polymeric microspheres were evaluated by well-diffusion method against some selected pathogenic microorganisms. The antimutagenic properties of all compounds were also examined against sodium azide in human lymphocyte cells by micronuclei and sister chromatid exchange tests.

Stability and Antimicrobial Activity of Nisin-Loaded Mesoporous Silica Nanoparticles: A Game-Changer in the War against Maleficent Microbes

Antimicrobial agents, such as nisin, are used extensively in the food industry. Here, we investigated various approaches to load nisin onto mesoporous silica nanoparticles (MSNs, 92 ± 10 nm in diameter), to enhance its stability and sustained release. The morphology, size, and surface charge of the as-prepared nanoparticles were analyzed using scanning transmission electron microscopy, dynamic light scattering, and ζ potential measurement. Nisin was either physically adsorbed or covalently attached to the variously functionalized MSNs, with high loading capacities (>600 mg of nisin g^-1 of nanoparticles). The results of antibacterial activity analysis of nisin against Staphylococcus aureus showed that, despite the very low antibacterial activity of nisin covalently conjugated onto MSNs, the physical adsorption of nisin onto the unfunctionalized nanoparticles enhances its antimicrobial activities under various conditions, with no significant cytotoxicity effects on mouse fibroblast L929 cells. In conclusion, MSNs can be recommended as suitable carriers for nisin under various conditions.

Antimicrobial property of lemongrass (Cymbopogon citratus) oil against pathogenic bacteria isolated from pet turtles

The usage of essential oils as antimicrobial agents is gaining attention. Besides, pet turtles were known to harbor a range of pathogenic bacteria while the turtle keeping is a growing trend worldwide.The current study examined the antimicrobial activity of lemon grass oil (LGO) against seven species of Gram negative bacteria namely; Aeromonas hydrophila, A. caviae, Citrobacter freundii, Salmonella enterica, Edwardsiella tarda, Pseudomonas aeruginosa, and Proteus mirabilis isolated from three popular species of pet turtles. Along with the results of disc diffusion, minimum inhibitory and minimum bactericidal concentration (MIC and MBC) tests, LGO was detected as effective against 6 species of bacteria excluding P. aeruginosa. MIC of LGO for the strains except P. aeruginosa ranged from 0.016 to 0.5% (V/V). The lowest MIC recorded in the E. tarda strain followed by A. hydrophilla, C. freundii, P. mirabilis, and S. enterica. Interestingly, all the bacterial species except E. tarda were showing high multiple antimicrobial resistance (MAR) index values ranging from 0.36 to 0.91 upon the 11 antibiotics tested although they were sensitive to LGO.

Characterization of Antimicrobial Poly (Lactic Acid)/Nano-Composite Films with Silver and Zinc Oxide Nanoparticles

Antimicrobial active films based on poly (lactic acid) (PLA) were prepared with nano-silver (nano-Ag) and nano-zinc oxide (nano-ZnO) using a solvent volatilizing method. The films were characterized for mechanical, structural, thermal, physical and antimicrobial properties. Scanning electron microscopy (SEM) images characterized the fracture morphology of the films with different contents of nano-Ag and nano-ZnO. The addition of nanoparticles into the pure PLA film decreased the tensile strength and elasticity modulus and increased the elongation of breaks-in other words, the flexibility and extensibility of these composites improved. According to the results of differential scanning calorimetry (DSC), the glass transition temperature of the PLA nano-composite films decreased, and the crystallinity of these films increased; a similar result was apparent from X-ray diffraction (XRD) analysis. The water vapor permeability (WVP) and opacity of the PLA nano-composite films augmented compared with pure PLA film. Incorporation of nanoparticles to the PLA films significantly improved the antimicrobial activity to inhibit the growth of Escherichia coli. The results indicated that PLA films with nanoparticles could be considered a potential environmental-friendly packaging material.

Antibacterial and Antifungal Activities of Spices

Infectious diseases caused by pathogens and food poisoning caused by spoilage microorganisms are threatening human health all over the world. The efficacies of some antimicrobial agents, which are currently used to extend shelf-life and increase the safety of food products in food industry and to inhibit disease-causing microorganisms in medicine, have been weakened by microbial resistance. Therefore, new antimicrobial agents that could overcome this resistance need to be discovered. Many spices-such as clove, oregano, thyme, cinnamon, and cumin-possessed significant antibacterial and antifungal activities against food spoilage bacteria like Bacillus subtilis and Pseudomonas fluorescens, pathogens like Staphylococcus aureus and Vibrio parahaemolyticus, harmful fungi like Aspergillus flavus, even antibiotic resistant microorganisms such as methicillin resistant Staphylococcus aureus. Therefore, spices have a great potential to be developed as new and safe antimicrobial agents. This review summarizes scientific studies on the antibacterial and antifungal activities of several spices and their derivatives.

Essential oils as natural food antimicrobial agents: a review

Food-borne illnesses pose a real scourge in the present scenario as the consumerism of packaged food has increased to a great extend. Pathogens entering the packaged foods may survive longer, which needs a check. Antimicrobial agents either alone or in combination are added to the food or packaging materials for this purpose. Exploiting the antimicrobial property, essential oils are considered as a "natural" remedy to this problem other than its flavoring property instead of using synthetic agents. The essential oils are well known for its antibacterial, antiviral, antimycotic, antiparasitic, and antioxidant properties due to the presence of phenolic functional group. Gram-positive organisms are found more susceptible to the action of the essential oils. Essential oils improve the shelf-life of packaged products, control the microbial growth, and unriddle the consumer concerns regarding the use of chemical preservatives. This review is intended to provide an overview of the essential oils and their role as natural antimicrobial agents in the food industry.

UV Light-Induced Generation of Reactive Oxygen Species and Antimicrobial Properties of Cellulose Fabric Modified by 3,3',4,4'-Benzophenone Tetracarboxylic Acid

3,3',4,4'-Benzophenone tetracarboxylic acid (BPTCA) could directly react with hydroxyl groups on cellulose to form ester bonds. The modified cotton fabrics not only provided good wrinkle-free and ultraviolet (UV) protective functions, but also exhibited important photochemical properties such as producing reactive oxygen species (ROS) including hydroxyl radicals (HO(•)) and hydrogen peroxide (H2O2) under UV light exposure. The amounts of the produced hydroxyl radical and hydrogen peroxide were measured, and photochemical reactive mechanism of the BPTCA treated cellulose was discussed. The results reveal that the fabrics possess good washing durability in generation of hydroxyl radicals and hydrogen peroxide. The cotton fabrics modified with different concentrations of BPTCA and cured at an elevated temperature demonstrated excellent antimicrobial activities, which provided 99.99% antibacterial activities against both E. coli and S. aureus. The advanced materials have potential applications in medical textiles and biological material fields.

Quaternary ammonium salt of chitosan: preparation and antimicrobial property for paper

A series of 2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC) was prepared by the reaction of chitosan with glycidyl trimethyl ammonium chloride. Structure of HACC was characterized by FT IR and 1H NMR spectroscopies, and it was proved that substitution reaction mainly occurs on the N element. Antimicrobial activities of HACC was examined against S. aureus, E. coli, and A. niger. Results indicatd that the inhibitory effects of HACC solutions were varied with HACC concentration, quaternization degrees, pH values, metal ions, and heat treatment. The antimicrobial properties of handsheets prepared from HACC were studied by the inhibition zone method, and the sheets had good antimicrobial properties against S. aureus and E. coli, and low inhibition rate against A. niger.