Physicochemical and Antigenic Properties of Experimental Preparations of Francisella tularensis.

Immuno-serological diagnostic tools particularly identifying pathogen antigens are the most important methods of pseudotuberculosis studies. The main immunodominant and species-specific antigens located in the surface structures of the bacterial cell are of practical interest. Thereby the aim of the work was to isolate and characterize biologically active surface structures of the pseudotuberculosis microbe. Here, the living cells of Y. pseudotuberculosis 3704 (O:1b) were lysed by using 9 M urea solution to extract antigens localized in the microbial surface structures. The subcellular fractions obtained such as outer membranes (OM), urea extract (UE) and isolated protein-lipopolysaccharide complex (PLPSC) are characterized by physical and chemical parameters. The protein content in the preparations ranged from 42% to 53%. The polypeptide band of the OM preparation, UE polypeptide and PLPSC for pseudotuberculosis microbe was presented by 14, 16 and 9 major polypeptides with molecular weight ranging from 13.9 kDa to 131.5 kDa, 13.5 kDa to 101.6 kDa, and 20.7 kDa to 66.6 kDa, respectively. Proteolytically active proteins and polypeptides were detected in isolated subcellular fractions (OM and UE) by using the radial enzyme diffusion test and substrate-gel electrophoresis found to be presented by 4 and 7 polypeptides with molecular weight ranging from 28.0 kDa to 118.0 kDa and 29.2 kDa to 97.7 kDa in the OM and UE preparation, respectively. The subcellular fractions obtained are capable to exhibit immunogenic activity after inoculation to experimental animals and antigenic activity while interacting with specific antibodies in the radial immunodiffusion (RID) assay and antibodies labeled with colloidal silver nanoparticles in dot immunoassay (DIA). OM and PLPSC preparations in DIA with immunoglobulins isolated from experimental antisera and labeled with colloidal silver nanoparticles were detected at a concentration of 0.12 g/ml (dry weight), cells of strain Y. pseudotuberculosis 3704 at a concentration of 3, 9 106 m.c./ml, which is similar to the results of DIA with immunoglobulins isolated from commercial pseudotuberculosis antiserum (St. Petersburg) and labeled with nanoparticles of colloidal silver. Thus, the subcellular fractions of pseudotuberculosis microbe isolated by using urea as a lysing and decontaminating agent retain their antigenic and immunogenic properties and enzymatic activity suggesting about their potential benefits for use to improve early diagnostics of pseudotuberculosis.

Nanoparticles synthesized through photochemical reduction using femtosecond involve reducing agent that reduces metal ions into nanoparticles. We synthesized Au50Ag50 from metal ions and colloidal nanoparticles in four different conditions: (i) gold metal ions and silver metal ion, (ii) colloidal gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs), (iii) gold metal ions and colloidal silver nanoparticles (AgNPs), and (iv) colloidal gold nanoparticles (AuNPs) and silver metal ions. Gold and metal ions were obtained from dilution of gold and silver metal salts. While gold and silver nanoparticles were obtained from gold and metal ions added into a quartz cuvette and irradiated by femtosecond laser in 10 minutes irradiation time. In the synthesis, every condition respectively mixed in 3 ml solution into a 10x10x45 mm quartz cuvette and irradiated by femtosecond laser in 5-, 10- and 15- minutes irradiation time. The result showed that Au50Ag50 alloy nanoparticles were successfully synthesized in four different conditions, and the LSPR (Localized Surface Plasmon Resonance) in 15 minutes irradiation time was observed at 454.51, 458.74, 459.60, and 457.29 nm in the condition (i), (ii), (iii), and (iv), respectively.

Surface-enhanced Raman scattering and quantum chemical studies of 2-trifluoroacetylpyrrole chemisorbed on colloidal silver and gold nanoparticles: A comparative study

Both negatively and positively charged colloids (in brief, PCS and NCS) of silver nano-particles were prepared. Quenching and enhancement of fluorescence fromrhodamine (RhB) and Fluorescein sodium (FS) molecules on the two colloids of silver nano-particles were recorded respectively and compared with each other. On PCS, the fluorescence of RhB is enhanced when the concentration is low, whilst when the concentration is high the fluorescence of RhB is quenched. However for FS, the fluorescence is always enhanced. On NCS, the fluorescence of FS and RhB are quenched.

We demonstrated the dependence on thickness of p-GaN spacer layer in the localized surface plasmons (LSPs)-enhanced near-ultraviolet light-emitting diodes (NUV-LEDs) by pneumatic spray process using colloidal silver (Ag) nanoparticles (NPs). The LSPs-enhanced NUV-LEDs with 10- and 20-nm-thick p-GaN spacer layer showed enhanced internal quantum efficiency (IQE) and reduced effective exciton lifetime by introducing the colloidal Ag NPs. The IQE of LSPs-enhanced NUV-LEDs with 10- and 20-nm-thick p-GaN spacer layer was increased by 18.8% and 24.2%, respectively. These results indicate that the spontaneous emission rate is increased by LSPs-excitons resonant coupling. However, the NUV-LEDs with 40- and 100-nm-thick p-GaN spacer layer showed decreased IQE and extended exciton lifetime due to the evanescent wave property of LSPs field from colloidal Ag NPs.

The effect of magnetic field of 0.3 T on the concentration, distribution of sizes in suspension and zeta potential of colloidal gold and colloidal silver nanoparticles, obtained by considering the pulsed laser ablation in double distilled water was studied. The magnetic field was transverse to the direction of incidence of the laser radiation and parallel to the surface of a submerged target. An Nd: YAG laser was used (1064 nm in wavelength, 10 ns in duration, repetition rate of 10 Hz and 37 mJ of energy) to ablate targets. The colloids were characterized by inductively coupled plasma optical emission spectroscopy, ultraviolet-visible spectroscopy, dynamic light scattering and zeta potential. Concentration analysis suggested that applying magnetic field of 0.3 T during nanoparticle synthesis leads to higher concentration. Applying magnetic field led to an eleven percent increase in the concentration of the colloid with gold nanoparticles and a five percent increase in the concentration of the colloidal silver nanoparticles. The absorption spectra suggested the presence of spherical nanoparticles. When analyzing the effect of the magnetic field on the hydrodynamic size distribution of the nanoparticles and the zeta potential of the colloids, no significant changes were evidenced. The magnetic confinement of the plasma induced by laser ablation caused changes in the characteristics of the colloids.

In this research work, colloidal silver nanoparticles were successfully produced via an electrolysis method and their antibacterial activity was evaluated. This study aims to determine the optimum concentration of colloidal silver nanoparticles to produce an effective inhibition zone for Escherichia coli bacteria growth. Based on the results obtained, the applied current and reaction times during the electrolysis played a crucial role in determining the colloidal silver nanoparticles’ concentration (ppm). It was found that a minimum content of colloidal silver nanoparticles (0.02 ppm) was required to perform the 0.1 mm inhibition zone diameter on agar medium spread with E. coli bacteria. Interestingly, high concentrations of colloidal silver nanoparticles could exhibit high conductivity (µS/cm) as well as the high intensity of the maximum plasmon peak from the UV/vis absorption spectra at about 390 nm. In conclusion, this research work revealed the destruction of the cytoplasmic membrane and the rupture of the internal organisation of E. -coli bacteria, leading to the leakage of the cytoplasmic contents and cell death after having contact with sufficient concentration of colloidal silver nanoparticles.

Colloidal silver and silver nanoparticles bioaccessibility in drinking water filters

Colloidal silver nanoparticles were successfully synthesized via the chemical reduction method. The synthesis used AgNO3 as the precursor, chitosan as the reducing and stabilizing agents, and NaOH as the accelerator. The synthesis parameters were optimized. The samples were tested with a UV-vis spectrophotometer to observe their localized surface plasmon resonance (LSPR) phenomenon, a transmission electron microscope (TEM), and a particle size analyzer (PSA) to investigate their particle shape and size distribution. Further, silver nanoparticles were tested for their storage stability and antibacterial performance. The UV-vis spectroscopy data exhibited that the silver nanoparticles have been successfully synthesized, validating via the emergence of the LSPR absorption band at 402–418 nm. At 50 °C, the optimum synthesis was achieved for 100 min of reaction time by adding 0.033 M NaOH and AgNO3 4.00% (w/w, AgNO3/chitosan). TEM results showed spherical silver nanoparticles of 1–8 nm, while the PSA results exhibited particles sizes of about 12–59 nm. The colloidal silver nanoparticles were stable in storage for 8 weeks and had good antibacterial performance against E. coli, S. aureus, extended-spectrum beta-lactamases (ESBL), and methicillin-resistant S. aureus (MRSA). Therefore, colloidal silver nanoparticles have the potential as a material for medical applications.

Silver colloidal nanoparticles have been incorporated into acrylic resins to induce antimicrobial properties. However, as additives, they can influence the mechanical properties of the final product. Mechanical properties are also dependent on different curing cycles. The aim of this study was to evaluate flexural strength of a denture base resin incorporated with different concentrations of silver colloidal nanoparticles subjected to two different curing cycles. Lucitone 199 denture base resin was used into which silver colloidal nanoparticles were incorporated at 0.5 and 5% by polymer mass. Specimens devoid of nanoparticles were used as controls. A total of 60 specimens were fabricated and divided into two groups. Each group was divided into three subgroups consisting of 10 specimens each. The specimens were fabricated according to American Dental Association (ADA) specification No. 12 and tested for flexural strength using universal testing machine. Silver colloidal nanoparticle incorporation at 0.5% concentration increased the mean flexural strength in both curing cycles by 7.5 and 4.4%, respectively, when compared with the control group. The study suggested that the mean flexural strength value of 0.5% silver colloidal nanoparticles in denture base resin was above the value of the control group both in short and long curing cycles, which makes it clinically suitable as a denture base material. However, at 5% concentration, the statistically significant amount of decrease in flexural strength compared with the value of control group both in short and long curing cycles gives it a questionable prognosis. The specimens incorporated with the antimicrobial agent 0.5% silver colloidal nanoparticles and processed by long curing cycles showed significant increase in its flexural strength compared with the control group, which makes it clinically suitable as a denture base material.

Graphite oxide (GO) was successfully silylated by 3‐mercaptopropyltrimethoxysilane. The surface‐enhanced Raman scattering spectrum of the silylated GO sheets sandwiched between colloidal silver nanoparticles and silver piece is presented. The Raman signal shows a 104 enhancement compared to that of bulk GO. The large Raman enhancement is most likely a result of electromagnetic (EM) coupling between the colloidal silver nanoparticles (localized surface plasmon) and the silver piece (surface plasmon polariton), creating large localized EM fields at their interface, where the silylated GO sheets reside in this sandwich architecture. Copyright © 2009 John Wiley & Sons, Ltd.

Gamma-radiation synthesis, characterization and nonlinear optical properties of highly stable colloidal silver nanoparticles in suspensions

Mosquitoes spread terrible diseases like chikungunya, yellow fever, malaria, dengue, Japan encephalitis and lymphatic filariasis in human beings even causes many deaths in every year. Chemical insecticides cause adverse effect in human beings, also to the environment. In this work, we sought a credible, eco friendly tool to control the vector mosquitoes at their larva stage. It reveals an eco-friendly and effective larvicidal activity of the Deoxyribonucleic acid (DNA) capped colloidal Silver nanoparticles. Characterizations of the Silver nanoparticles were done using absorption spectra and SEM. Spectra shows a predominant peak at 425nm and the SEM image shows the particles size is about 45nm. The third instars of Culex larvae were treated using these colloidal Silver nanoparticles, also the mortality rate for 24 hours was observed with 100% mortality rate at 10 ppm. The LC50, LC90 and confidence interval at 95% were investigated. Colour analysis and the SEM image of the treated larva were performed and confirm that the colloidal Silver nanoparticles were accumulated all over the skin surface of the larva which causes death.

Background. The growth of antibiotic resistance of Helicobacter pylori, a microorganism significant in the development of gastrointestinal diseases and inflammatory periodontal diseases, makes us think about the search for new approaches to the eradication of the microorganism. One solution to this problem may be to develop immunobiological preparations based on microorganisms inactivated with colloidal silver nanoparticles (CSNPs).The aim. To evaluate the inactivating ability of colloidal silver nanoparticles in vitro and in vivo with respect to H. pylori to determine the possibility of their use in the development of a specific immunobiological preparation.Materials and methods. The study design consisted in sequential execution of the steps of synthesis of colloidal silver nanoparticles with an assessment of the conditionality of the prepared preparations; isolating and identifying pure H. pylori culture; inactivation of H. pylori by synthesized silver nanoparticles; evaluation of the result of H. pylori inactivation in vitro and in vivo.Results. The conditionality of the synthesized colloidal silver nanoparticles of size 30 ± 3 nm, obtained using a step-by-step technique, was estimated by electron microscopy. Testing the inactivating activity of CSNPs on H. pylori showed that their effect on the culture for 3 hours at a ratio of volumes of CSNPs and 1:1 culture leads to a gradual decrease in the concentration of the microorganism until its complete death and lack of growth on the fifth passage. During the evaluation of the effect of CSNPs on H. pylori, it was shown that the inactivated culture retains its cultural and tinctorial properties; alters morphological properties and biochemical activity; becomes more sensitive to antibiotics and L. acidophilus; ceases to establish in the body of mice with an immunosuppression condition.Conclusions. Proposed method of synthesis of silver nanoparticles with proven inactivating activity against H. pylori can become a stage of biotechnological process of development of vaccine preparation both on the basis of given microorganism and in complex with CSNPs possessing multilevel antimicrobial effect, antioxidant and immunomodulating activity.

This study investigated the effect of molar concentration of colloidal silver nanoparticles that enhanced Raman signal on Surface-Enhanced Raman Scattering (SERS) substrate performance. Colloidal silver nanoparticles were fabricated as SERS substrate on a glass microscope using drop-casting method. Colloidal silver nanoparticles have been synthesized separately in different concentrations of 5 x 10−4 M (sample 1) and 20 x 10−4 M (sample 2) from silver nitrate (AgNO3) irradiated by femtosecond laser in 5 minutes irradiation times. SERS substrates were fabricated on glass using a hot plate in around 100°C. The performance of SERS substrates was tested for the detection of 500 ppm deltamethrin pesticides using Raman spectroscopy. The result shows that there were increasing Raman signal in sample 2. This indicated that the increased molar concentration of colloidal silver nanoparticles enhances Raman signal. The samples were also characterized using FE SEM to know the particle size of nanoparticles in SERS substrate. Sample 2 that have a higher molar concentration of silver nanoparticles showed bigger particle size than sample 1. The particle size in sample 1 and 2 were 27.46 nm and 37.27 nm, respectively.