Nanoscale materials have been employed in the past 2 decades in applications such as biosensing, therapeutics and medical diagnostics due to their beneficial optoelectronic properties. In recent years, silver nanoparticles (AgNPs) have gained attention due to their higher plasmon excitation efficiency than gold nanoparticles, as proved by sharper and stronger plasmon resonance peaks. The current work is focused on utilizing self-assembled DNA-AgNPs on microdevices for the detection of gynecological cancers. Human papilloma virus (HPV) mostly spreads through sexual transmittance and can cause various gynecological cancers, including cervical, ovarian and endometrial cancers. In particular, oncogene E7 from the HPV strain 16 (HPV-16 E7) is responsible for causing these cancers. In this research, the target sequence of HPV-16 E7 was detected by an AgNP-conjugated capture probe on a dielectrode sensor. The detection limit was in the range between 10 and 100 aM (by 3σ estimation). The sensitivity of the AgNP-conjugated probe was 10 aM and similar to the sensitivity of gold nanoparticle conjugation sensors, and the mismatched control DNA failed to detect the target, proving selective HPV detection. Morphological assessments on the AgNPs and the sensing surfaces by high-resolution microscopy revealed the surface arrangement. This sensing platform can be expanded to develop sensors for the detection various clinically relevant targets.
Continuously increasing energy demand and growing concern about energy resources has attracted much research in the field of clean and sustainable energy sources. In this context, zero-emission fuels are required for energy production to reduce the usage of fossil fuel resources. Here, we present the synthesis of Pd-Ag-decorated reduced graphene oxide (rGO) nanostructures using a green chemical approach with stevia extract for hydrogen production and antibacterial studies under light irradiation. Moreover, bimetallic nanostructures are potentially lime lighted due to their synergetic effect in both scientific and technical aspects. Structural characteristics such as crystal structure and morphological features of the synthesized nanostructures were analyzed using X-ray diffraction and transmission electron microscopy. Analysis of elemental composition and oxidation states was carried out by X-ray photoelectron spectroscopy. Optical characteristics of the biosynthesized nanostructures were obtained by UV-Vis absorption spectroscopy, and Fourier transform infrared spectroscopy was used to investigate possible functional groups that act as reducing and capping agents. The antimicrobial activity of the biosynthesized Pd-Ag-decorated rGO nanostructures was excellent, inactivating 96% of Escherichia coli cells during experiments over 150 min under visible light irradiation. Hence, these biosynthesized Pd-Ag-decorated rGO nanostructures can be utilized for alternative nanomaterial-based drug development in the future.
The volume of contaminated rivers in Malaysia continues to keep rising through the years. The
cost of instrumental monitoring is uneconomical and prohibits schedule monitoring of
contaminants particularly heavy metals. In this work, a rapid enzyme assay utilizing the
molybdenum-reducing enzyme as an inhibitive assay, prepared in crude form from the
molybdenum-reducing bacterium Serratia sp. strain DRY5 has been developed for monitoring
the heavy metals mercury, silver, copper and chromium in contaminated waters in the Juru
Industrial Estate. The crude enzyme extract transformed soluble molybdenum
(phosphomolybdate) into a deep blue solution, which is inhibited by heavy metals such as
mercury, silver, copper and chromium. The IC50 and Limits of Detection (LOD) values for
mercury, copper, silver and cadmium were 0.245, 0.298, 0.367, 0.326, and 0.124, 0.086, 0.088
and 0.094 mg L-1, respectively. The assay is rapid, and can be carried out in less than 10 minutes.
In addition, the assay can be carried out at ambient temperature. The IC50 values for these heavy
metals are more sensitive than several established assays. Water samples from various locations
in the month of November from the Juru Industrial Estate (Penang) were tested for the presence
of heavy metals using the developed assay. Enzyme activity was nearly inhibited for water
samples from several locations. The presence of heavy metals was confirmed instrumentally
using Atomic Emission Spectrometry and a Flow Injection Mercury System. The assay is rapid
and simple and can be used as a first screening method for large scale monitoring of heavy
metals.
Chemical toxins and organic contaminants such as hydrocarbons and dyes are major global
contaminants with countless tones of those chemicals are created yearly with a significant
amount release to the environment. In this work we screen the ability of a molybdenum-reducing
bacterium isolated from contaminated soil to decolorize various azo and triphenyl methane dyes
independent of molybdenum reduction. Biochemical analysis resulted in a tentative identification
of the bacterium as Enterobacter sp. strain Zeid-6. The bacterium was able to decolorize the azo
dye Orange G. The bacterium reduces molybdate to Mo-blue optimally at pH between 5.5 and
8.0 and temperatures of between 30 and 37 oC. Other requirements include a phosphate
concentration of 5 mM and a molybdate concentration of 20 mM. The absorption spectrum of the
Mo-blue produced was similar to previous Mo-reducing bacterium, and closely resembles a
reduced phosphomolybdate. Molybdenum reduction was inhibited by copper, lead, mercury and
silver which showed 36.8, 16.9, 64.9 and 67.6% inhibition to Mo-reducing activity of
Enterobacter sp. strain Zeid-6, respectively. The resultant molybdenum blue spectrum closely
resembles the spectrum of molybdenum blue from the phosphate determination method. The
ability of this bacterium to detoxify molybdenum and decolorize azo dye makes this bacterium
an important tool for bioremediation.
Bacterial based remediation of environmental toxicants is a promising innovative technology
for molybdenum pollution. To date, the enzyme responsible for molybdate reduction to Moblue
from bacteria show that the Michaelis-Menten constants varies by one order of magnitude.
It is important that the constants from newer enzyme sources be characterized so that a
comparison can be made. The aim of this study is to characterize kinetically the enzyme from a
previously isolated Mo-reducing bacterium; Bacillus pumilus strain Lbna. The maximum
activity of this enzyme occurred at pH 5.5 and in between 25 and 35 oC. The Km and Vmax of
NADH were 6.646 mM and 0.057 unit/mg enzyme, while the Km and Vmax of LPPM were 3.399
mM and 0.106 unit/mg enzyme. The results showed that the enzyme activity for Bacillus
pumilus strain Lbna were inhibited by all heavy metals used. Zinc, copper, silver, chromium,
cadmium and mercury all caused more than 50% inhibition to the Mo-reducing enzyme activity
with copper being the most potent with an almost complete inhibition of enzyme activity
observed.
The indiscriminate released of heavy metals and xenobiotics into soils and aquatic bodies
severely alter soil organisms and the ecosystem. The isolation of xenobiotics degrading
microorganisms is cost-effective and naturally pleasant approach. Lately, the toxicological effect
of molybdenum to the spermatogenesis of several organisms has been record. This present study
is aimed at the isolation and characterization of a bacterium capable of converting molybdenum
to the colloidal molybdenum blue. Bacteria characterization was performed in a microplate
format using resting cells. Thus, the reduction process can be employed as a device for
molybdenum bioremediation. The results of the study revealed an optimum reduction at pH
between 6.0 and 6.3 and temperatures of between 25 and 40 oC. Similarly, it was also observed
that a phosphate concentration not greater than 5.0 mM and a sodium molybdate concentration
at 20 mM was required for reduction. Glucose was observed as the best carbon source to support
reduction. Following the scanning of molybdenum blue, it revealed an absorption spectrum
indicating the characteristics of molybdenum blue as a reduced phosphomolybdate. Molybdenum
reduction is inhibited by heavy metals like silver, lead, arsenic and mercury. Furthermore, the
ability of the bacterium (Pseudomonas sp. strain Dr.Y Kertih) to utilize several organic
xenobiotics such as phenol, acrylamide, nicotinamide, acetamide, iodoacetamide, propionamide,
acetamide, sodium dodecyl sulfate (SDS) and diesel as electron donor sources for aiding
reduction or as carbon sources for growth was also examined. Finding showed that none was
capable of aiding molybdenum reduction, however the bacterium was capable of growing on both
diesel and phenol as carbon sources. GC analysis was used to confirmed diesel degradation.
In this study, a disposable and simple electrochemical immunosensor was fabricated for the detection of carcinoembryonic antigen. In this method, silver nanoparticles (AgNPs) were mixed with reduced graphene oxide (rGO) to modify the surface of screen-printed carbon electrode (SPE). Initially, AgNPs-rGO modified-SPEs were fabricated by using simple electrochemical deposition method. Then the carcinoembryonic antigen (CEA) was immobilized between the primary antibody and horseradish peroxidase (HRP)-conjugated secondary antibody onto AgNPs-rGO modified-SPEs to fabricate a sandwich-type electrochemical immunosensor. The proposed method could detect the CEA with a linear range of 0.05-0.50µgmL-1 and a detection limit down to 0.035µgmL-1 as compared to its non-sandwich counterpart, which yielded a linear range of 0.05-0.40µgmL-1, with a detection limit of 0.042µgmL-1. The immunosensor showed good performance in the detection of carcinoembryonic antigen, exhibiting a simple, rapid and low-cost. The immunosensor showed a higher sensitivity than an enzymeless sensor.
This work aims to shed light in the fabrication of poly(3-hydroxybutyrate-co-44%-4-hydroxybutyrate)[P(3HB-co-44%4HB)]/chitosan-based silver nanocomposite material using different contents of silver nanoparticle (SNP); 1-9 wt%. Two approaches were applied in the fabrication; namely solvent casting and chemical crosslinking via glutaraldehyde (GA). A detailed characterization was conducted in order to yield information regarding the nanocomposite material. X-ray diffraction analysis exhibited the nature of the three components that exist in the nanocomposite films: P(3HB-co-4HB), chitosan, and SNP. In term of mechanical properties, tensile strength, and elongation at break were significantly improved up to 125% and 22%, respectively with the impregnation of the SNP. The melting temperature of the nanocomposite materials was increased whereas their thermal stability was slightly changed. Scanning electron microscopy images revealed that incorporation of 9 wt% of SNP caused agglomeration but the surface roughness of the material was significantly improved with the loading. Staphylococcus aureus and Escherichia coli were completely inhibited by the nanocomposite films with 7 and 9 wt% of SNP, respectively. On the other hand, degradation of the nanocomposite materials outweighed the degradation of the pure copolymer. These bioactive and biodegradable materials stand a good chance to serve the vast need of biomedical applications namely management and care of wound as wound dressing.
The Silver Reed Model LK150 knitting machine is a home knitting machine which is
extremely lightweight and compact, making it preferable by most home knitters.
There are various knitwears with interesting patterns can be made using this model. In
the field of garments manufacturing by using flatbed knitting machines, it is
important to understand the physical properties of fabric so that their impact on
dimensional changes can be predicted to produce the most suitable end use. The
samples were produced by using a blended bamboo/cotton yarn, with a composition
of 30% cotton and 70% bamboo. The main objectives of this study are to to evaluate
the physical properties of single jersey fabric knitted on home knitting machine by
using different stitch dials and to relate the physical properties with different stitch
lengths. Then, all tests were conducted to compare the physical properties of samples
between three different stitch dials and the effects of before and after washing. The
physical properties measured in this research were stitch length, stitch density, weight,
thickness, absorbency and shrinkage. The result indicated that the longer the stitch
length, the higher the percentage of the water impact penetration. Meanwhile, there
was a slight reduction on the density, thickness and fabric weight. In addition, the
result after three times washing showed that the samples only had slight changes in
density, thickness, weight and stitch length, but has significant changes on the water
impact penetration.
Silver preparations are commonly used for burns, but evidence of their effectiveness remains poorly defined. The aim of the study was to evaluate the effectiveness of silver-containing dressings and topical silver for preventing infection and promoting healing in burns wounds through a meta-analysis of the available evidence. The Cochrane Central Register of Controlled Trials and relevant databases were searched. Drug companies and experts in this field were also contacted. Randomised controlled trials (RCTs) of silver dressings or topical silver (used with dressings) compared with non-silver dressings were eligible for inclusion. We identified 14 RCTs involving 877 participants. One small trial of a silver-containing dressing showed significantly better healing time compared to the control [MD -3.6; 95% CI -4.94 to -2.26 for partial thickness burns and MD -3.9; 95% CI -4.54 to -3.26 for superficial burns]. Topical silver showed significantly worse healing time compared to the non-silver group [WMD 3.96; 95% CI 2.41-5.51] and showed no evidence of effectiveness in preventing wounds infection [WMD 2.48; 95% CI 0.39-15.73]. Our review suggests that silver-containing dressings and topical silver were either no better or worse than control dressings in preventing wound infection and promoting healing of burn wounds.
Evidence from animal studies and trials suggests that honey may accelerate wound healing. The objective of this review was to assess the effects of honey compared with silver dressings on the healing of burn wounds. Relevant databases for randomized controlled trials (RCTs) of honey compared with silver sulfadiazine (SSD) were searched. The quality of the selected trials was assessed using the Cochrane Risk of Bias Assessment Tool. The primary endpoints considered were wound healing time and the number of infected wounds rendered sterile. Nine RCTs met the inclusion criteria. Based on moderate quality evidence there was a statistically significant difference between the two groups, favoring honey in healing time (MD -5.76days, 95% CI -8.14 to -3.39) and the proportions of infected wounds rendered sterile (RR 2.59; 95% CI 1.58-2.88). The available evidence suggests that honey dressings promote better wound healing than silver sulfadiazine for burns.
Colorectal cancer (CRC) is a global public health issue which poses a substantial humanistic and economic burden on patients, healthcare systems and society. In recent years, intestinal dysbiosis has been suggested to be involved in the pathogenesis of CRC, with specific pathogens exhibiting oncogenic potentials such as Fusobacterium nucleatum, Escherichia coli and enterotoxigenic Bacteroides fragilis having been found to contribute to CRC development. More recently, it has been shown that initiation of CRC development by these microorganisms requires the formation of biofilms. Gut microbial biofilm forms in the inner colonic mucus layer and is composed of polymicrobial communities. Biofilm results in the redistribution of colonic epithelial cell E-cadherin, increases permeability of the gut and causes a loss of function of the intestinal barrier, all of which enhance intestinal dysbiosis. This literature review aims to compile the various strategies that target these pathogenic biofilms and could potentially play a role in the prevention of CRC. We explore the potential use of natural products, silver nanoparticles, upconverting nanoparticles, thiosalicylate complexes, anti-rheumatic agent (Auranofin), probiotics and quorum-sensing inhibitors as strategies to hinder colon carcinogenesis via targeting colon-associated biofilms.
Silver and copper nanoparticles were produced by chemical reduction of their respective nitrates by ascorbic acid in the presence of chitosan using microwave heating. Particle size was shown to increase by increasing the concentration of nitrate and reducing the chitosan concentration. Surface zeta potentials were positive for all nanoparticles produced and these varied from 27.8 to 33.8 mV. Antibacterial activities of Ag, Cu, mixtures of Ag and Cu, and Ag/Cu bimetallic nanoparticles were tested using Bacillus subtilis and Escherichia coli. Of the two, B. subtilis proved more susceptible under all conditions investigated. Silver nanoparticles displayed higher activity than copper nanoparticles and mixtures of nanoparticles of the same mean particle size. However when compared on an equal concentration basis Cu nanoparticles proved more lethal to the bacteria due to a higher surface area. The highest antibacterial activity was obtained with bimetallic Ag/Cu nanoparticles with minimum inhibitory concentrations (MIC) of 0.054 and 0.076 mg/L against B. subtilis and E. coli, respectively.
In this article, silver and magnetite nanofillers were synthesized in modified κ-carrageenan hydrogels using the in situ method. The effect of metallic nanoparticles in gastro-intestinal tract (GIT) release of a model drug (methylene blue) has been investigated. The effect of nanoparticles loading and genipin cross-linking on GIT release of nanocomposite is also studied to finally provide the most suitable drug carrier system. In vitro release studies revealed that using metallic nanocomposites hydrogels in GIT studies can improve the drug release in intestine and minimize it in the stomach. It was found that cross-linking and nanofiller loading can significantly improve the targeted release. Therefore, applying metallic nanoparticles seems to be a promising strategy to develop GIT controlled drug delivery.
In the present study, the novel Ag/cellulose nanocrystal (CNC)-doped CeO2 quantum dots (QDs) with highly efficient catalytic performance were synthesized using one pot co-precipitation technique, which were then applied in the degradation of methylene blue and ciprofloxacin (MBCF) in wastewater. Catalytic activity against MBCF dye was significantly reduced (99.3%) for (4%) Ag dopant concentration in acidic medium. For Ag/CNC-doped CeO2 vast inhibition domain of G-ve was significantly confirmed as (5.25-11.70 mm) and (7.15-13.60 mm), while medium- to high-concentration of CNC levels were calculated for G + ve (0.95 nm, 1.65 mm), respectively. Overall, (4%) Ag/CNC-doped CeO2 revealed significant antimicrobial activity against G-ve relative to G + ve at both concentrations, respectively. Furthermore, in silico molecular docking studies were performed against selected enzyme targets dihydrofolate reductase (DHFR), dihydropteroate synthase (DHPS), and DNA gyrase belonging to folate and nucleic acid biosynthetic pathway, respectively to rationalize possible mechanism behind bactericidal potential of CNC-CeO2 and Ag/CNC-CeO2.
The application of nanomaterials has gained considerable momentum in various fields in recent years due to their high reactivity, excellent surface properties and quantum effects in the nanometer range. The properties of zinc oxide (ZnO) vary with its crystallite size or particle size and often nanocrystalline ZnO is seen to exhibit superior physical and chemical properties due to their higher surface area and modified electronic structure. ZnO nanoparticles are reported to exhibit strong bacterial inhibiting activity and silver (Ag) has been extensively used for its antimicrobial properties since ages. In this study, Ag doped ZnO nanoparticles were synthesized by mechanochemical processing in a high energy ball mill and investigated for antimicrobial activity. The nanocrystalline nature of zinc oxide was established by X-ray diffraction (XRD) studies. It is seen from the XRD data obtained from the samples, that crystallite size of the zinc oxide nanoparticles is seen to decrease with increasing Ag addition. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) data also supported the nanoparticle formation during the synthesis. The doped nanoparticles were subjected to antimicrobial investigation and found that both increase in Ag content and decrease in particle size contributed significantly towards antimicrobial efficiency. It was also observed that Ag doped ZnO nanoparticles possess enhanced antimicrobial potential than that of virgin ZnO against the studied microorganisms of Escherichia coli and Staphylococcus aureus.
An organometallic/silica nanocomposite of a 1D cylindrical assembly of a trinuclear gold(I)-pyrazolate complex ([Au(3)Pz(3)]) that was confined inside the nanoscopic channels of hexagonal mesoporous silica ([Au(3)Pz(3)]/silica(hex)), emitted red light with a luminescence center at 693 nm upon photoexcitation at 276 nm owing to a Au(I)-Au(I) metallophilic interaction. When a film of [Au(3)Pz(3)]/silica(hex) was dipped into a solution of Ag(+) in tetrahydrofuran (THF), the resulting nanocomposite material (Ag@[Au(3)Pz(3)]/silica(hex)) emitted green light with a new luminescence center at 486 nm, which was characteristic of a Au(I)-Ag(I) heterometallic interaction. Changes in the emission/excitation and XPS spectra of Ag@[Au(3)Pz(3)]/silica(hex) revealed that Ag(+) ions permeated into the congested nanochannels of [Au(3)Pz(3)]/silica(hex), which were filled with the cylindrical assembly of [Au(3)Pz(3)].
Indoles are amongst the most important class of heteroaromatics in organic chemistry, being commonly found in biologically active natural products and therapeutically useful compounds. The synthesis of indoles is therefore important and several methods for their synthesis that make use of silver(I) catalysts and reagents have been developed in recent years. This Focus Review contains, to the best of our knowledge, a comprehensive coverage of silver-mediated indole forming reactions since the first reaction of this type was reported in 2004.
miRNA (miR)-155 is a potential biomarker for breast cancers. We aimed at developing a nanosensor for miR-155 detection by integrating hybridization chain reaction (HCR) and silver nanoclusters (AgNCs). HCR serves as an enzyme-free and isothermal amplification method, whereas AgNCs provide a built-in fluorogenic detection probe that could simplify the downstream analysis. The two components were integrated by adding a nucleation sequence of AgNCs to the hairpin of HCR. The working principle was based on the influence of microenvironment towards the hosted AgNCs, whereby unfolding of hairpin upon HCR has manipulated the distance between the hosted AgNCs and cytosine-rich toehold region of hairpin. As such, the dominant emission of AgNCs changed from red to yellow in the absence and presence of miR-155, enabling a ratiometric measurement of miR with high sensitivity. The limit of detection (LOD) of our HCR-AgNCs nanosensor is 1.13 fM in buffered solution. We have also tested the assay in diluted serum samples, with comparable LOD of 1.58 fM obtained. This shows the great promise of our HCR-AgNCs nanosensor for clinical application.