Effect of Silver Nanoparticles on the Electron Transfer Reactivity and the Catalytic Activity of Myoglobin

A microfluidic organic transistor for reversible and real-time monitoring of H2O2 at ppb/ppt levels in ultrapure water

A microfluidic organic transistor functionalized with phenylboronic acid firstly succeeded in reversible and real-time monitoring of H₂O₂ at ppb/ppt levels in ultrapure water, which would be used not only as portable chemical sensors but also as monitoring tools to clarify unknown reaction mechanisms of phenylboronic acid with H₂O₂.

Comparative evaluation of the toxicological effect of silver salt (AgNO3 ) and silver nanoparticles on Cyprinus carpio synthesized by chemicals and marine algae using scanning electron microscopy

The widespread use of silver nanoparticles (AgNPs) results in the unintentional release into the water body. Therefore, understanding of the potentially harmful impacts of AgNPs and Ag-salt on aquatic animals is a need of time. This study was design to analyze the oxidative stress and histopathological damages in Cyprinus carpio. The synthesis of AgNPs from Halymenia porphyraeformis and by reduction of chemical was done. Nanoparticles were characterized with UV-Visible spectroscopy, SEM, XRD, and FTIR analysis. The comparative toxicological effect of chemically synthesized silver nanoparticles (Ch-AgNPs), green silver nanoparticles (Gr-AgNPs), and Ag-salt on C. carpio was analyzed. For oxidative stress analysis, different tests Lipid peroxidation (LPO), catalase, glutathione reduction (GST), and glutathione S-transferase (GST) were performed. The highest LPO 245.168 ± 0.034 was recorded in Ch-AgNPs-treated gills and the lowest 56.4532 ± 0.02 was found in Gr-AgNPs-treated liver. Maximum GSH 56.4065 ± 0.13 was observed in Gr-AgNPs liver and minimum 40.781 ± 0.54 was recorded in Ag-salt gills. The maximum quantity of catalase 68.0162 ± 0.09 was noted in the Ag-salt-treated liver and the minimum was calculated 17.3665 ± 0.01 in the liver of Ch-AgNPs and highest values of GST 765.829 ± 0.11 were recorded in gills of Gr-AgNPs and lowest 633.08 ± 0.26 in the liver of Ch-AgNPs-treated fish. In conclusion, maximum destruction was found in the gills and liver of the fish treated with chemical and green AgNPs followed by Ag-salt as compared to control. The adverse effects of AgNPs and Ag-salt were probably related to the oxidative stress in the fish that lead to histopathological damage of its vital organs.

Aptamer-Based Biosensors to Detect Aquatic Phycotoxins and Cyanotoxins

Aptasensors have a great potential for environmental monitoring, particularly for real-time on-site detection of aquatic toxins produced by marine and freshwater microorganisms (cyanobacteria, dinoflagellates, and diatoms), with several advantages over other biosensors that are worth considering. Freshwater monitoring is of vital importance for public health, in numerous human activities, and animal welfare, since these toxins may cause fatal intoxications. Similarly, in marine waters, very effective monitoring programs have been put in place in many countries to detect when toxins exceed established regulatory levels and accordingly enforce shellfish harvesting closures. Recent advances in the fields of aptamer selection, nanomaterials and communication technologies, offer a vast array of possibilities to develop new imaginative strategies to create improved, ultrasensitive, reliable and real-time devices, featuring unique characteristics to produce and amplify the signal. So far, not many strategies have been used to detect aquatic toxins, mostly limited to the optic and electrochemical sensors, the majority applied to detect microcystin-LR using a target-induced switching mode. The limits of detection of these aptasensors have been decreasing from the nM to the fM order of magnitude in the past 20 years. Aspects related to sensor components, performance, aptamers sequences, matrices analyzed and future perspectives, are considered and discussed.

Toxicity effects of AgZnO nanoparticles and rifampicin on Mycobacterium tuberculosis into the macrophage

The World Health Organization acknowledges tuberculosis as a global threat. Tuberculosis infection is one of the top 10 causes of death worldwide. Nanotechnology and microbiology researchers are looking for new and safe nano drugs for eliminating Mycobacterium tuberculosis, the causative agent of tuberculosis. In this study, AgZnO nano-crystals (AgZnONCs) is synthesized via the decomposition of the precursor of oxalate method. Characterization of AgZnONCs were evaluated. Next, various concentrations of AgZnONCs, as well AgZnONCs+Rifampicin, were prepared. The MTT assay was employed to study the viability of human macrophage cell lines (THP-1) exposed to AgZnONCs. The bactericidal effects of AgZnONCs and AgZnONCs+Rifampicin were studied by Minimum Bactericidal Concentration (MBC) test. Subsequently, THP-1 were infected by H₃₇ Rv strain of M. tuberculosis (H₃₇ RvMtb). Also, bactericidal effects of AgZnONCs and AgZnONCs+Rifampicin were compared with ex-vivo conditions. The MBC of AgZnONCs and AgZnONCs+Rifampicin were ratios of 1:4 and 1:32 respectively (p-value <0.05). Also, more than 50% and 80% of THP-1 were alive in ratios of 1:4 and 1:32 in the presence of AgZnONCs, respectively. All phagocytic H₃₇ RvMtb were killed in the presence of AgZnONCs+Rifampicin (p-value <0.05), while AgZnONCs were not able to kill all the H₃₇ RvMtb (p-value >0.05). This study showed that, AgZnONCs+Rifampicin has the most anti-tubercular behavior with respect to the macrophages.

Electrochemical Aptatoxisensor Responses on Nanocomposites Containing Electro-Deposited Silver Nanoparticles on Poly(Propyleneimine) Dendrimer for the Detection of Microcystin-LR in Freshwater

A sensitive and reagentless electrochemical aptatoxisensor was developed on cobalt (II) salicylaldiimine metallodendrimer (SDD-Co(II)) doped with electro-synthesized silver nanoparticles (AgNPs) for microcystin-LR (L, l-leucine; R, l-arginine), or MC-LR, detection in the nanomolar range. The GCE|SDD-Co(II)|AgNPs aptatoxisensor was fabricated with 5' thiolated aptamer through self-assembly on the modified surface of the glassy carbon electrode (GCE) and the electronic response was measured using cyclic voltammetry (CV). Specific binding of MC-LR with the aptamer on GCE|SDD-Co(II)|AgNPs aptatoxisensor caused the formation of a complex that resulted in steric hindrance and electrostatic repulsion culminating in variation of the corresponding peak current of the electrochemical probe. The aptatoxisensor showed a linear response for MC-LR between 0.1 and 1.1 µg·L-1 and the calculated limit of detection (LOD) was 0.04 µg·L-1. In the detection of MC-LR in water samples, the aptatoxisensor proved to be highly sensitive and stable, performed well in the presence of interfering analog and was comparable to the conventional analytical techniques. The results demonstrate that the constructed MC-LR aptatoxisensor is a suitable device for routine quantification of MC-LR in freshwater and environmental samples.

Imaging electrocatalytic processes on single gold nanorods

Imaging electrochemical processes has attracted increasing attention in past decades. Particularly, monitoring electrochemical reactions rapidly at the nano-scale is still a challenge due to the ultra-low current detection and long scanning time required. The development of optical techniques provide a new way to demonstrate electrochemical processes through optical signals which enhance sensitivity and spatial resolution. Herein, we developed a novel method to image electrocatalytic processes on single gold nanorods (GNRs) during Cyclic Voltammetry (CV) scanning based on plasmon resonance scattering information by using dark-field microscopy. The electrocatalytic oxidation of hydrogen peroxide was selected as a typical reaction and the catalytic mechanism was revealed using the obtained spectra. Notably, observation on single GNRs avoided the averaging effects in bulk systems and confirmed that the individual nanoparticles had variable catalytic properties with different spectral change during the reaction process. Furthermore, a color-amplified system was introduced to convert light intensity into imaging information via the Matlab program which was able to image thousands of nanoparticles simultaneously. This approach offered the statistical intensity distribution of all of the nanoparticles in a dark-field image which dramatically enhanced the detection accuracy and avoided random events.

Ultrafine and well dispersed silver nanocrystals on 2D nanosheets: synthesis and application as a multifunctional material for electrochemical catalysis and biosensing

The strong coupling of inorganic nanocrystals with 2D nanosheets to produce function-enhanced nano-materials with uniform size, dispersion, and high coverage density has long been of interest to scientists from various research fields. Here, a simple and effective method has been described to fabricate ultrafine and well dispersed silver nanocrystals (AgNCs) on graphene oxide (GO), based on a facial-induced co-reduction strategy. The synthesized nanohybrid has shown uniform and well dispersed AgNCs (2.9 ± 1.4 nm), individually separated GO sheets, as well as highly covered surface (5250 nanocrystals per square micrometer), indicating the formation of a high-quality GO-based nanohybrid. Moreover, this material shows excellent catalytic activity for oxygen reduction reactions (ORRs) and exhibits enhanced signal readout for molecular sensing, demonstrating the potential application of this newly synthesized inorganic hybrid with strong synergistic coupling effects on advanced functional systems.

Investigation of Regenerated Cellulose/Poly(acrylic acid) Composite Films for Potential Wound Healing Applications: A Preliminary Study

Regenerated cellulose/poly(acrylic acid) composite films have been synthesized for wound dressing applications. The water absorbency of these films was studied as a function of amount of cross-linker N,N′-methylenebisacrylamide and cellulose contents in the feed mixture. The samples, having different compositions, showed tensile strength and percent elongation in the range of 9.98×105 to 13.40×105 N/m2 and 110 to 265, respectively. The water vapor transmission rate (WVTR) for various films was found to be in the range of 2.03 to 7.18 mg/cm2/h. These films were loaded with antibacterial drug miconazole nitrate and their release was studied in the physiological pH at 37°C. The release data was found to fit well the diffusion controlled Higuchi model. Finally the films demonstrated fair antibacterial and antifungal action, thus establishing their strong candidature as wound dressing materials.

Structural and functional effects of Cu metalloprotein-driven silver nanoparticle dissolution

Interactions of a model Cu-metalloprotein, azurin, with 10-100 nm silver nanoparticles (NPs) were examined to elucidate the role of oxidative dissolution and protein interaction on the biological reactivity of NPs. Although minimal protein and NP structural changes were observed upon interaction, displacement of Cu(II) and formation of Ag(I) azurin species under aerobic conditions implicates Cu(II) azurin as a catalyst of NP oxidative dissolution. Consistent with NP oxidation potentials, largest concentrations of Ag(I) azurin species were recorded in reaction with 10 nm NPs (>50%). Apo-protein was also observed under anaerobic reaction with NPs of all sizes and upon aerobic reaction with larger NPs (>20 nm), where NP oxidation is slowed. Cu(II) azurin displacement upon reaction with NPs was significantly greater than when reacted with Ag(I)(aq) alone. Regardless of NP size, dialysis experiments show minimal reactivity between azurin and the Ag(I)(aq) species formed as a result of NP oxidative dissolution, indicating Cu displacement from azurin occurs at the NP surface. Mechanisms of azurin-silver NP interaction are proposed. Results demonstrate that NP interactions not only impact protein structure and function, but also NP reactivity, with implications for targeting, uptake, and cytotoxicity.

Incorporation of silver nanoparticles into the bulk of the electrospun ultrafine polyimide nanofibers via a direct ion exchange self-metallization process

This paper reports our works on the preparation of the silver-nanoparticle-incorporated ultrafine polyimide (PI) ultrafine fibers via a direct ion exchange self-metallization technique using silver ammonia complex cation ([Ag(NH(3))(2)](+)) as the silver precursor and pyromellitic dianhydride (PMDA)/4,4'-oxidianiline (4,4'-ODA) polyimide as the matrix. The polyimide precursor, poly(amic acid) (PAA), was synthesized and then electrospun into ultrafine fibers. By thermally treating the silver(I)-doped PAA ultrafine fibers, where the silver(I) ions were loaded through the ion exchange reactions of the carboxylic acid groups of the PAA macromolecules with the [Ag(NH(3))(2)](+) cations in an aqueous solution, ultrafine polyimide fibers embedded with silver nanoparticles with diameters less than 20 nm were successfully fabricated. The fiber-electrospinning process, the ion exchange process, and various factors influencing the hybrid ultrafine fibers preparation process such as the thermal treatment atmospheres and the thermal catalytic oxidative degradation effect of the reduced silver nanoparticles were discussed. The ultrafine fibers were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA).

Surface functionalization of silver nanoparticles: novel applications for insect vector control

Every day, people and animals contract debilitating and life threatening diseases due to bites from infected flies, ticks, and mosquitoes. The current methods utilized to fight against these diseases are only partially effective or safe for humans and animals. When it comes to insect vector control, a conceptual paradigm shift is urgently needed. This work proposes a novel synthetic scheme to produce a nanoparticle-pesticide core-shell conjugate to be used as an active agent against arthropod vectors, such as mosquitoes. As a proof of concept, we conjugated nanosilver to the pyrethroid pesticide deltamethrin. First, electron microscopy and Fourier transform infrared spectroscopy verified the presence of a 15 nm nanosilver core surrounded by deltamethrin. Second, when the conjugate was exposed to mosquitoes for a 24 h bioassay, mortality was observed at 9 × 10(-4) M. Silver was detected in the hemolymph of mosquitoes exposed to the conjugate. We concluded that the newly developed nanoconjugate did not inactivate the primary function of the pesticide and was effective in killing mosquitoes at low concentrations. These results demonstrate the potential to use nanoparticle surfaces to kill insects, specifically vectors of human pathogens.

Dose-dependent in-vivo toxicity assessment of silver nanoparticle in Wistar rats

This study aims to suggest the limits of silver nanoparticle (AgNP) uses for medicinal purpose and was performed to explore the effect of various doses of silver nanoparticle in rats. Four different doses of AgNP (4, 10, 20, and 40 mg/kg) were injected intravenously. For safety evaluation of injected AgNP, body weight, organ coefficient, whole blood count, and biochemistry panel assay for liver function enzyme (AST, ALT, ALP, and GGTP), comet assay, ROS, and histological parameter were performed; 10-12 week old animals were randomly divided into groups of six individuals each for control, and doses of 40, 20, 10, and 4 mg/kg AgNP injected. Significant changes were observed (p < 0.01) in hematological parameters (WBC count, platelets counts, haemoglobin, and RBC count) in the 40 and 20 mg/kg groups. The changes were non-significant in the other groups (4 and 10 mg/kg group). In the 40 mg/kg group, a significant increase was also found in liver function enzymes like ALT and AST (p < 0.01), ALP (p < 0.01), GGTP (p < 0.01), and bilirubin (p < 0.01). ROS in blood serum increased in the high dose group. Tail migration in single cell gel electrophoresis in the 40, 20, 10, 4 mg/kg, and control groups was 34.9, 29.5, 17.8, 5.8, and 0.0 µm, respectively, which indicated damage in the DNA strand in the high dose group. EDXRF showed a ∼ 10-times increase in silver concentration in the 40 mg/kg group and TEM image also showed particle deposition in the 40 mg/kg group. This study indicates that the AgNP in doses (< 10 mg/kg) is safe for biomedical application and has no side-effects, but its high dose (> 20 mg/kg) is toxic.