Synthesis of silver nanoclusters in colloidal scaffold for biolabeling and antimicrobial applications.

A robust method to prepare silver nanoclusters (AgNCs) inside a methacrylic acid-ethyl acrylate (MAA-EA) nanogel is proposed, where AgNCs were produced within the nanogel scaffold via UV-photoreduction. The impact of UV irradiation time on the formation of AgNCs and their application in biolabeling and antimicrobial properties were examined. The AgNCs formation is described by two stages; (1) Agn (n = 2-8) nanoclusters formation between 0 and 25 min, and (2) larger silver nanoparticles (AgNPs) formed via aggregation inside the nanogel. The antimicrobial performance depended on the size and concentration of silver ions (Ag+). A maximum inhibitory concentration (MIC) of 1.1 ppm was observed for antimicrobial test with yeast, and a MIC of 11 and 22 ppm was recorded for Escherichia. coli and Staphylococcus aureus respectively. Combining with the green illumination property of AgNCs (emitted at 525 nm) with dead yeast, it could be used for biolabeling. By tuning the size through photoirradiation, the nanogel templated AgNCs is a promising candidate for antimicrobial and biolabeling applications.

Bacterial cancer therapy: A turning point for new paradigms.

Cancer treatments have advanced considerably in recent years, appreciably enhancing the quality of life and survival of cancer patients. However, standard cancer treatments still have limitations that must be improved. In recent years, bacteria-based cancer therapy has gained much more attention owing to its unique properties that are unachievable with standard therapeutics. Bacteria species such as Salmonella, Clostridium, and Listeria have been shown to control tumor growth with improved prognosis in experimental animal models and clinical settings.

Encapsulation and controlled release of vitamin C in modified cellulose nanocrystal/chitosan nanocapsules.

Vitamin C (VC), widely used in food, pharmaceutical and cosmetic products, is susceptible to degradation, and new formulations are necessary to maintain its stability. To address this challenge, VC encapsulation was achieved via electrostatic interaction with glycidyltrimethylammonium chloride (GTMAC)-chitosan (GCh) followed by cross-linking with phosphorylated-cellulose nanocrystals (PCNC) to form VC-GCh-PCNC nanocapsules. The particle size, surface charge, degradation, encapsulation efficiency, cumulative release, free-radical scavenging assay, and antibacterial test were quantified. Additionally, a simulated human gastrointestinal environment was used to assess the efficacy of the encapsulated VC under physiological conditions. Both VC loaded, GCh-PCNC, and GCh-Sodium tripolyphosphate (TPP) nanocapsules were spherical with a diameter of 450 â€‹± â€‹8 and 428 â€‹± â€‹6 â€‹nm respectively. VC-GCh-PCNC displayed a higher encapsulation efficiency of 90.3 â€‹± â€‹0.42% and a sustained release over 14 days. The release profiles were fitted to the first-order and Higuchi kinetic models with R2 values greater than 0.95. VC-GCh-PCNC possessed broad-spectrum antibacterial activity with a minimum inhibition concentration (MIC) of 8-16 â€‹µg/mL. These results highlight that modified CNC-based nano-formulations can preserve, protect and control the release of active compounds with improved antioxidant and antibacterial properties for food and nutraceutical applications.

Enhanced visible light-driven photocatalysis of iron-oxide/titania composite: Norfloxacin degradation mechanism and toxicity study.

A simulated visible light-mediated iron oxide-titania (IoT) nanocomposite was employed to degrade the antibiotic norfloxacin (NFN) photocatalytically. The photocatalyst were prepared using a sol-gel method with controlled titania loadings to iron oxide by altering the fabrications step. The nanocomposites were structurally characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), field emission high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Diffuse reflectance UV-visible spectra (DRS-UV) spectroscopy, cyclic voltammetry, and X-ray photoelectron spectroscopy (XPS). It was observed that 100 mg/L of iron oxide doped titania loading at 1:4 (IoT-4) achieved the maximum photocatalytic activity in a 75 mg/100 mL of NFN solution within 60 min of the reaction time under visible light irradiation. The NFN degradation mechanism affirmed using HPLC-MS/MS analysis and the results confirmed the complete NFN degradation without residual intermediates. Significant, sustained recyclability was obtained by completely removing the contaminant up to 5 cycles with 90% degradation ability till nine cycles. Bacterial- and phytotoxicity data ascertain that the photocatalyzed and contaminant-free water is safe for the environment. The outstanding photocatalytic performance in removing organic pollutants indicates the potential application of IoT nanocomposites in real-time environmental remediation.

Construction of Alizarin Conjugated Graphene Oxide Composites for Inhibition of Candida albicans Biofilms.

Biofilm inhibition using nanoparticle-based drug carriers has emerged as a noninvasive strategy to eradicate microbial contaminants such as fungus Candida albicans. In this study, one-step adsorption strategy was utilized to conjugate alizarin (AZ) on graphene oxide (GO) and characterized by ultraviolet-visible spectroscopy (UV-Vis), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray powder diffraction (XRD), dynamic light-scattering (DLS), and transmission electron microscopy (TEM). Crystal violet assay was performed to evaluate the antibiofilm efficacy of GO-AZs against C. albicans. Different characterizations disclosed the loading of AZ onto GO. Interestingly, TEM images indicated the abundant loading of AZ by producing a unique inward rolling of GO-AZ sheets as compared to GO. When compared to the nontreatment, GO-AZ at 10 µg/mL significantly reduced biofilm formation to 96% almost equal to the amount of AZ (95%). It appears that the biofilm inhibition is due to the hyphal inhibition of C. albicans. The GO is an interesting nanocarrier for loading AZ and could be applied as a novel antibiofilm agent against various microorganisms including C. albicans.

Supramolecular Self-Assembly of 3D Conductive Cellulose Nanofiber Aerogels for Flexible Supercapacitors and Ultrasensitive Sensors.

Nature employs supramolecular self-assembly to organize many molecularly complex structures. Based on this, we now report for the first time the supramolecular self-assembly of 3D lightweight nanocellulose aerogels using carboxylated ginger cellulose nanofibers and polyaniline (PANI) in a green aqueous medium. A possible supramolecular self-assembly of the 3D conductive supramolecular aerogel (SA) was provided, which also possessed mechanical flexibility, shape recovery capabilities, and a porous networked microstructure to support the conductive PANI chains. The lightweight conductive SA with hierarchically porous 3D structures (porosity of 96.90%) exhibited a high conductivity of 0.372 mS/cm and a larger area-normalized capacitance (Cs) of 59.26 mF/cm2, which is 20 times higher than other 3D chemically cross-linked nanocellulose aerogels, fast charge-discharge performance, and excellent capacitance retention. Combining the flexible SA solid electrolyte with low-cost nonwoven polypropylene and PVA/H2SO4 yielded a high normalized capacitance (Cm) of 291.01 F/g without the use of adhesive that was typically required for flexible energy storage devices. Furthermore, the supramolecular conductive aerogel could be used as a universal sensitive sensor for toxic gas, field sobriety tests, and health monitoring devices by utilizing the electrode material in lightweight supercapacitor and wearable flexible devices.

Direct one-pot synthesis of cinnamaldehyde immobilized on gold nanoparticles and their antibiofilm properties.

The objective of the present study was to develop a one-pot strategy to synthesis gold nanoparticle complexes using cinnamaldehyde, a potent antibiofilm agent which in its free form, exhibits high volatility and unstable nature. Hence, we developed cinnamaldehyde gold nanoparticles (CGNPs) in a single step to overcome the limitations of free cinnamaldehyde. Furthermore, reduction abilities of cinnamaldehyde under different experimental conditions, that is, varying precursor concentrations of cinnamaldehyde and gold, metal salts, pH, temperature, and light sources, were investigated. UV-vis spectroscopy, transmission electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and dynamic light-scattering measurements revealed that heat influenced the nanoparticle formation in the presence of cinnamaldehyde, and as produced cinnamaldehyde immobilized on gold nanoparticles were spherical, monodispersed, and stable by surface charge. CGNPs containing 0.01% cinnamaldehyde by weight exhibited effective biofilm inhibition of up to >80% against Gram positive bacteria (methicillin-sensitive and -resistant strains of Staphylococcus aureus, MSSA and MRSA, respectively) and Gram negative (Escherichia coli and Pseudomonas aeruginosa) and a fungus Candida albicans. In addition, CGNPs attenuated the virulence of C. albicans by inhibiting hyphae formation. Based on observations of their antibiofilm effects and confocal microscopy findings, CGNPs caused biofilm damage by direct contact. Thus, cinnamaldehyde appears to be a promising reduction material for the eco-friendly, one-pot synthesis of CGNPs with excellent antibiofilm activity.

Development of gold nanoparticles coated with silica containing the antibiofilm drug cinnamaldehyde and their effects on pathogenic bacteria.

Emerging resistance to antibiotics is a mounting worldwide health concern and increases the need for nonantibiotic strategies to combat infectious diseases caused by bacterial pathogens. In this study, the authors used the antibiofilm activity of the naturally occurring antimicrobial cinnamaldehyde (CNMA) conjugated to the surface of gold nanoparticles (GNPs) to deliver CNMA efficiently and eradicate biofilms of Gram-negative organisms (enterohemorrhagic Escherichia coli O157:H7, and Pseudomonas aeruginosa), Gram positive (methicillin-sensitive Staphylococcus aureus organisms, and methicillin-resistant Staphylococcus aureus) bacteria. CNMA-GNPs containing 0.005% (v/v) of CNMA were found to inhibit biofilm formation efficiently. The distributions of nanoparticles in biofilm cells and their biofilm disruption activities, including distorted cell morphology, were determined by transmission electron microscopy. In addition to their antibiofilm activities, CNMA-GNPs attenuated S. aureus virulence and protected Caenorhabditis elegans (C. elegans) worms. Here, the authors report the antibiofilm effects of CNMA-GNPs and suggest that they could be used to treat pathogenic bacterial infections in vivo.

Recent Nanotechnology Approaches for Prevention and Treatment of Biofilm-Associated Infections on Medical Devices.

Bacterial colonization in the form of biofilms on surfaces causes persistent infections and is an issue of considerable concern to healthcare providers. There is an urgent need for novel antimicrobial or antibiofilm surfaces and biomedical devices that provide protection against biofilm formation and planktonic pathogens, including antibiotic resistant strains. In this context, recent developments in the material science and engineering fields and steady progress in the nanotechnology field have created opportunities to design new biomaterials and surfaces with anti-infective, antifouling, bactericidal, and antibiofilm properties. Here we review a number of the recently developed nanotechnology-based biomaterials and explain underlying strategies used to make antibiofilm surfaces.

Recyclable Photo-Thermal Nano-Aggregates of Magnetic Nanoparticle Conjugated Gold Nanorods for Effective Pathogenic Bacteria Lysis.

We describe the nucleophilic hybridization technique for fabricating magnetic nanoparticle (MNP) around gold nanorod (AuNR) for desired photo-thermal lysis on pathogenic bacteria. From the electromagnetic energy conversion into heat to the surrounding medium, a significant and quicker temperature rise was noted after light absorption on nanohybrids, at a controlled laser light output and optimum nanoparticle concentration. We observed a similar photo-thermal pattern for more than three times for the same material up on repeated magnetic separation. Regardless of the cell wall nature, superior pathogenic cell lysis has been observed for the bacteria suspensions of individual and mixed samples of Salmonella typhi (S.typhi) and Bacillus subtilis (B.subtilis) by the photo-heated nanoparticles. The synthesis of short gold nanorod, conjugation with magnetic nanoparticle and its subsequent laser exposure provides a rapid and reiterated photo-thermal effect with enhanced magnetic separation for efficient bactericidal application in water samples. Resultant novel properties of the nano-aggregates makes them a candidate to be used for a rapid, effective, and re-iterated photo-thermal agent against a wide variety of pathogens to attain microbe free water.

Potent antimicrobial and antibiofilm activities of bacteriogenically synthesized gold-silver nanoparticles against pathogenic bacteria and their physiochemical characterizations.

The objective of this study was to develop a bimetallic nanoparticle with enhanced antibacterial activity that would improve the therapeutic efficacy against bacterial biofilms. Bimetallic gold-silver nanoparticles were bacteriogenically synthesized using γ-proteobacterium, Shewanella oneidensis MR-1. The antibacterial activities of gold-silver nanoparticles were assessed on the planktonic and biofilm phases of individual and mixed multi-cultures of pathogenic Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive bacteria (Enterococcus faecalis and Staphylococcus aureus), respectively. The minimum inhibitory concentration of gold-silver nanoparticles was 30-50 µM than that of other nanoparticles (>100 µM) for the tested bacteria. Interestingly, gold-silver nanoparticles were more effective in inhibiting bacterial biofilm formation at 10 µM concentration. Both scanning and transmission electron microscopy results further accounted the impact of gold-silver nanoparticles on biocompatibility and bactericidal effect that the small size and bio-organic materials covering on gold-silver nanoparticles improves the internalization and thus caused bacterial inactivation. Thus, bacteriogenically synthesized gold-silver nanoparticles appear to be a promising nanoantibiotic for overcoming the bacterial resistance in the established bacterial biofilms.

Enhanced detection sensitivity of Escherichia coli O157:H7 using surface-modified gold nanorods.

Escherichia coli O157:H7 (O157) is a Gram negative and highly virulent bacteria found in food and water sources, and is a leading cause of chronic diseases worldwide. Diagnosis and prevention from the infection require simple and rapid analysis methods for the detection of pathogens, including O157. Endogenous membrane peroxidase, an enzyme present on the surface of O157, was used for the colorimetric detection of bacteria by catalytic oxidation of the peroxidase substrate. In this study, we have analyzed the impact of the synthesized bare gold nanorods (AuNRs) and silica-coated AuNRs on the growth of E. coli O157. Along with the membrane peroxidase activity of O157, other bacteria strains were analyzed. Different concentrations of nanorods were used to analyze the growth responses, enzymatic changes, and morphological alterations of bacteria by measuring optical density, 3,3',5,5'-tetramethylbenzidine assay, flow cytometry analysis, and microscopy studies. The results revealed that O157 showed higher and continuous membrane peroxidase activity than other bacteria. Furthermore, O157 treated with bare AuNRs showed a decreased growth rate in comparison with the bacteria with surface modified AuNRs. Interestingly, silica-coated AuNRs favored the growth of bacteria and also increased membrane peroxidase activity. This result can be particularly important for the enzymatic analysis of surface treated AuNRs in various microbiological applicants.

Ultraviolet light and laser irradiation enhances the antibacterial activity of glucosamine-functionalized gold nanoparticles.

Here we report a novel method for the synthesis of glucosamine-functionalized gold nanoparticles (GlcN-AuNPs) using biocompatible and biodegradable glucosamine for antibacterial activity. GlcN-AuNPs were prepared using different concentrations of glucosamine. The synthesized AuNPs were characterized for surface plasmon resonance, surface morphology, fluorescence spectroscopy, and antibacterial activity. The minimum inhibitory concentrations (MICs) of the AuNPs, GlcN-AuNPs, and GlcN-AuNPs when irradiated by ultraviolet light and laser were investigated and compared with the MIC of standard kanamycin using Escherichia coli by the microdilution method. Laser-irradiated GlcN-AuNPs exhibited significant bactericidal activity against E. coli. Flow cytometry and fluorescence microscopic analysis supported the cell death mechanism in the presence of GlcN-AuNP-treated bacteria. Further, morphological changes in E. coli after laser treatment were investigated using atomic force microscopy and transmission electron microscopy. The overall results of this study suggest that the prepared nanoparticles have potential as a potent antibacterial agent for the treatment of a wide range of disease-causing bacteria.

Role of surface modification in zinc oxide nanoparticles and its toxicity assessment toward human dermal fibroblast cells.

The wide-scale applications of zinc oxide (ZnO) nanoparticles (NPs) in photocatalysts, gas sensors, and cosmetics may cause toxicity to humans and environments. Therefore, the aim of the present study was to reduce the toxicity of ZnO NPs by coating them with a silica (SiO2) layer, which could be used in human applications, such as cosmetic preparations. The sol-gel method was used to synthesize core ZnO with SiO2-shelled NPs (SiO2/ZnO NPs) with varying degrees of coating. Diverse studies were performed to analyze the toxicity of NPs against cells in a dose- and time-dependent manner. To ensure the decreased toxicity of the produced SiO2/ZnO NPs, cytotoxicity in membrane damage and/or intracellular reactive oxygen species (ROS) were assessed by employing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, lactate dehydrogenase, 2',7'-dichlorofluorescin, and lipid peroxide estimations. The cores of ZnO NPs exhibited cytotoxicity over time, regardless of shell thickness. Nevertheless, the thicker SiO2/ZnO NPs revealed reduced enzyme leakage, decreased peroxide production, and less oxidative stress than their bare ZnO NPs or thinner SiO2/ZnO NPs. Therefore, thicker SiO2/ZnO NPs moderated the toxicity of ZnO NPs by restricting free radical formation and the release of zinc ions, and decreasing surface contact with cells.

Antibacterial activity of ordered gold nanorod arrays.

Well-packed two- and three-dimensional (2D and 3D) gold nanorod (AuNR) arrays were fabricated using confined convective arraying techniques. The array density could be controlled by changing the concentration of the gold nanorods solution, the velocity of the moving substrate, and the environment air-temperature. The hydrophilic behavior of glass substrates before and after surface modification was studied through contact angle measurements. The affinity and alignment of the AuNR arrays with varying nanorod concentrations and the resulting different array densities were studied using field emission scanning electron microscopy (FE-SEM). Under stable laser intensity irradiation, the photothermal response of the prepared arrays was measured using a thermocouple and the results were analyzed quantitatively. Synthesized AuNR arrays were added to Escherichia coli (E. coli) suspensions and evaluated for photothermal bactericidal activity before and after laser irradiation. The results showed promising bactericidal effect. The severity of pathogen destruction was measured and quantified using fluorescence microscopy, bioatomic force microscopy (Bio-AFM) and flow cytometry techniques. These results indicated that the fabricated AuNR arrays at higher concentrations were highly capable of complete bacterial destruction by photothermal effect compared to the low concentration AuNR arrays. Subsequent laser irradiation of the AuNR arrays resulted in rapid photoheating with remarkable bactericidal activity, which could be used for water treatment to produce microbe-free water.

Magnetic, optical gold nanorods for recyclable photothermal ablation of bacteria.

A new antibacterial gold nanorod (GNR) conjugated magnetic nanoparticle (MNP) composite (GNR-MNP) was synthesized successfully for the eradication of antibiotic resistant nosocomial pathogens in water to improve the water quality. The composite was fabricated via the reaction of nucleophilic amine and epoxide carbon moieties with silanes. Tagging of MNP over GNR was confirmed using electron microscopy. Zeta potential measurements were used to study the fundamental surface chemical states of GNR and MNP (before and after surface modification). The synthesized GNR-MNP composite was directly mixed with a bacterial culture suspension and the photo-thermally induced bactericidal effects were evaluated before and after laser treatment. Optical, spectral and electron microscopy results revealed that laser irradiated GNR-MNP show a more pronounced bactericidal effect than other disinfecting agents. Further, the results indicate that there is a positive correlation between the bacterial cell mortality and nanoparticle concentration and laser energy used. Interestingly, GNR-MNPs are capable of generating a rapid and reiterated photothermal effect for more than three consecutive cycles with enhanced magnetic separation for repeatable bactericidal application. These results suggest that the fabricated GNR-MNPs are a highly efficient photothermal agent against a wide variety of bacteria, suitable for cleaning real samples like water. Importantly, our method showed superior cell lysing results for both Escherichia coli (E. coli) and Enterococcus faecalis (E. faecalis) compared to conventional heat treatment.