Lori Rastogi

Enhancement of Antibacterial Activity of Capped Silver Nanoparticles in Combination with Antibiotics, on Model Gram-Negative and Gram-Positive Bacteria

The nanoparticles used in this study were prepared from AgNO3 using NaBH4 in the presence of capping agents such as citrate, sodium dodecyl sulfate, and polyvinylpyrrolidone. The formed nanoparticles were characterized with UV-Vis, TEM, and XRD. The generation of silver nanoparticles was confirmed from the appearance of yellow colour and an absorption maximum between 399 and 404 nm. The produced nanoparticles were found to be spherical in shape and polydisperse. For citrate, SDS, and PVP capped nanoparticles, the average particle sizes were 38.3 ± 13.5, 19.3 ± 6.0, and 16.0 ± 4.8 nm, respectively. The crystallinity of the nanoparticles in FCC structure is confirmed from the SAED and XRD patterns. Also, the combined antibacterial activity of these differently capped nanoparticles with selected antibiotics (streptomycin, ampicillin, and tetracycline) was evaluated on model Gram-negative and Gram-positive bacteria, employing disc diffusion assay. The activity of the tested antibiotics was enhanced in combination with all the stabilized nanoparticles, against both the Gram classes of bacteria. The combined effects of silver nanoparticles and antibiotics were more prominent with PVP capped nanoparticles as compared to citrate and SDS capped ones. The results of this study demonstrate potential therapeutic applications of silver nanoparticles in combination with antibiotics.

Gum kondagogu reduced/stabilized silver nanoparticles as direct colorimetric sensor for the sensitive detection of Hg2+ in aqueous system

A highly sensitive and selective method is reported for the colorimetric detection of Hg(2+) in aqueous system by using label free silver nanoparticles (Ag NPs). Ag NPs used in this method were synthesized by gum kondagogu (GK) which acted as both reducing and stabilizing agent. The average size of the GK-Ag NPs was found to be 5.0 ± 2.8 nm as revealed by transmission electron microscope (TEM) analysis and the nanoparticles were stable at various pH conditions (pH 4-11) and salt concentrations (5-100 mM). The GK reduced/stabilized Ag NPs (GK-Ag NPs) were directly used for the selective colorimetric reaction with Hg(2+) without any further modification. The bright yellow colour of Ag NPs was found to fade in a concentration dependent manner with the added Hg(+) ions. The fading response was directly correlated with increasing concentration of Hg(2+). More importantly, this response was found to be highly selective for Hg(2+) as the absorption spectra were found to be unaffected by the presence of other ions like; Na(+), K(+), Mg(2+), Ca(2+), Cu(2+), Ni(2+), Co(2+), As(3+), Fe(2+), Cd(2+), etc. The metal sensing mechanism is explained based on the turbidometric and X-ray diffraction (XRD) analysis of GK-Ag NPs with Hg(2+). The proposed method was successfully applied for the determination of Hg(2+) in various ground water samples. The reported method can be effectively used for the quantification of total Hg(2+) in samples, wherein the organic mercury is first oxidized to inorganic form by ultraviolet (UV) irradiation. The limit of quantification for Hg(2+) using the proposed method was as low as 4.9 × 10(-8) mol L(-1) (50 nM). The proposed method has potential application for on-field qualitative detection of Hg(2+) in aqueous environmental samples.

Highly stable, protein capped gold nanoparticles as effective drug delivery vehicles for amino-glycosidic antibiotics.

A method for the production of highly stable gold nanoparticles (Au NP) was optimized using sodium borohydride as reducing agent and bovine serum albumin as capping agent. The synthesized nanoparticles were characterized using UV-visible spectroscopy, transmission electron microscopy, X-ray diffraction (XRD) and dynamic light scattering techniques. The formation of gold nanoparticles was confirmed from the appearance of pink colour and an absorption maximum at 532 nm. These protein capped nanoparticles exhibited excellent stability towards pH modification and electrolyte addition. The produced nanoparticles were found to be spherical in shape, nearly monodispersed and with an average particle size of 7.8±1.7 nm. Crystalline nature of the nanoparticles in face centered cubic structure is confirmed from the selected-area electron diffraction and XRD patterns. The nanoparticles were functionalized with various amino-glycosidic antibiotics for utilizing them as drug delivery vehicles. Using Fourier transform infrared spectroscopy, the possible functional groups of antibiotics bound to the nanoparticle surface have been examined. These drug loaded nanoparticle solutions were tested for their antibacterial activity against Gram-negative and Gram-positive bacterial strains, by well diffusion assay. The antibiotic conjugated Au NP exhibited enhanced antibacterial activity, compared to pure antibiotic at the same concentration. Being protein capped and highly stable, these gold nanoparticles can act as effective carriers for drugs and might have considerable applications in the field of infection prevention and therapeutics.

Microwave-Assisted Green Synthesis of Small Gold Nanoparticles Using Aqueous Garlic (Allium sativum) Extract: Their Application as Antibiotic Carriers

ABSTRACT This article establishes a rapid, microwave-assisted green synthetic method for the production of gold nanoparticles (AuNPs) using garlic extract as a reducing and stabilizing agent and seeks their application as antibiotic carriers. The appearance, crystalline nature, size, and shape of nanoparticles are understood by different physical techniques like UV-vis spectroscopy, transmission electron microscopy, and X-ray diffraction. The AuNPs of size varying from 1.8 ± 0.85 nm to 23.2 ± 4.1 nm were synthesized successfully by varying the power of microwave irradiation. Further, AuNPs (of size 23.2 ± 4.1 nm) were functionalized with ciprofloxacin (cfH), a broad-spectrum antibiotic. A red shift in absorption and emission maxima with decreased intensity suggested successful binding of cfH to AuNPs. AuNPs-conjugated cfH (cfH@AuNPs) were found to have better antibacterial activities in terms of zone of inhibition compared to free cfH against the tested bacterial strains.

Facile synthesis of palladium nanocatalyst using gum kondagogu ( Cochlospermum gossypium ): a natural biopolymer

Palladium nanoparticles (Pd NPs) were synthesised by using gum kondagogu (GK), a non-toxic ecofriendly biopolymer. GK acted as both reducing and stabilising agent for the synthesis of Pd NPs. Various reaction parameters, such as concentration of gum, Pd chloride and reaction pH were standardised for the stable synthesis of GK reduced stabilised Pd NPs (GK-Pd NPs). The nanoparticles have been characterised using ultraviolet-visible spectroscopy, transmission electron microscopy and X-ray diffraction. Physical characterisation revealed that the gum synthesised Pd NPs were in the size range of 6.5 ± 2.3 nm and crystallised in face centred cubic (FCC) symmetry. Fourier transform infrared spectroscopy implicated the role of carboxyl, amine and hydroxyl groups in the synthesis. The synthesised Pd NPs were found to be highly stable in nature. The synthesised nanoparticles were found to function as an effective green catalyst (k = 0.182 min⁻¹) in the reduction of 4-nitrophenol by sodium borohydride, which was evident from the colour change of bright yellow (nitrophenolate; λ(max) - 400 nm) to colourless (4-AP; λ(max) - 294 nm) solution. The overall objectives of the current communication were: (i) to synthesize the Pd NPs using a green reducing/capping agent; GK and (ii) to determine the catalytic performance of the synthesised Pd NPs.

A novel Cu–BSA nanocomposite based vapour generation approach for the rapid determination of mercury in aqueous media by cold vapour atomic absorption spectrometry and on-line flow injection inductively coupled plasma mass spectrometry

The present study reports, for the first time, novel Copper–Bovine Serum Albumin nanocomposites (Cu–BSA NCs) based vapor generation as a simple, rapid and reliable approach for the sensitive determination of mercury in water. Copper nanoparticles in the form of Cu–BSA NCs acted as reductant to convert mercury ions to elemental mercury (Hg0) which was subsequently quantified using cold vapour atomic absorption spectrometry (CVAAS) and on-line flow injection inductively coupled plasma mass spectrometry (FI-ICPMS). The basic experimental parameters such as reaction time, amount of copper nanoparticles, pH and temperature of sample solution related to chemical vapour generation (CVG), have been optimized for both inorganic mercury (iHg) and methyl mercury (MeHg) species using CVAAS in batch mode. These studies indicate that the reduction process is very rapid (<20 s) when the pH and temperature of the sample solution is maintained at ≥4.0 and ∼90 °C, respectively. After optimizing the conditions by CVAAS, further studies were performed with on-line FI-ICPMS. The recoveries of mercury species were found to be in the range of 97–104%. The absolute limits of detection of the developed method in conjunction with FI-ICPMS were 2.8 pg and 4.1 pg for iHg and MeHg, respectively. Interference of concomitant ions and possible mechanism of the Cu–BSA NCs induced vapor generation of mercury have been discussed in detail. The proposed CVG method was applied to the analysis of total mercury in various natural water samples.

Physico-chemical and bacteriological screening of Hussain Sagar lake: An urban wetland

Abstract Hussain Sagar is a man-made lake originally designed for drinking water purpose that receives domestic sewage and industrial effluents through drainage canals due to rapid residential and industrial growth. Also, every year thousands of idols are immersed into the lake during festivals. In this context, a comprehensive study was initiated for monitoring the lake water quality. Various physico-chemical parameters such as temperature, pH, EC, TDS, COD and chlorophyll a were analyzed using APHA standard methods Water was also monitored for heterotrophic bacteria, total coliforms, Escherichia coli and antibiotic resistant bacteria. The average values for heterotrophs were found to be 8.6 × 104 and 2.8 × 104 CFU/mL before and after idol immersion, respectively. While the average values for total coliforms and E. coli were 5 × 104 and 5 × 102; 1.2 × 104 and 7.2 × 101 CFU/mL, for the respective sampling periods. The mean values for ampicillin and gentamicin resistant bacteria were 5.9 × 103 and 6.9 × 102; and 2.2 × 103 and 5.4 × 102 CFU/mL, respectively. It was found that TDS, COD and chlorophyll a values were decreased after idol immersion due to extensive cleaning. The statistical results showed no correlation between faecal bacteria and physico-chemical parameters and one way-ANOVA indicated statistically significant differences between the mean values of different sampling locations, with respect to COD and E. coli at 95% confidence. However, enormous load of coliforms and E. coli indicated severe contamination of the lake with domestic sewage and human excreta. Thus, the water is not suitable for human consumption/drinking purpose. Notably, incidence of antibiotic resistant bacteria in lake water is a potential threat to both public health and the environment. Thus, regular monitoring and applying appropriate corrective actions are needed to improve the water quality.

Bacteriogenic synthesis of selenium nanoparticles by Escherichia coli ATCC 35218 and its structural characterisation

A biosynthetic method for the production of selenium nanoparticles under ambient temperature and pressure from sodium selenite was developed using Gram-negative bacterial strain Escherichia coli ATCC 35218. Bacteriogenic nanoparticles were methodologically characterized employing UV-vis, XRD, Raman spectroscopy, SEM, TEM, DLS and FTIR techniques. Generation of nanoparticles was visualized from the appearance of red colour in the selenite supplemented culture medium and broad absorption bands in the UV-vis. Biofabricated nanoparticles were spherical, polydisperse, ranged from 100-183 nm and the average particle size was about 155 nm. Based on selected-area electron diffraction, XRD patterns; and Raman spectroscopy the nanospheres were found to be amorphous. IR spectrum revealed the involvement of bacterial proteins in the reduction of selenite and stabilization of nanoparticles. Used bacterial strain demonstrated efficient selenite reduction capability which was evident from 89.2% of selenium removal within 72 h at a concentration of 1 mM. Observation noted in the current study highlight the importance of bacterial reduction in selenium nanoparticle generation which can be scaled up for commercial production. Also, the bacteriogenic, amorphous nanoparticles can also be used as nutritional supplements for humans since selenium nanoparticles of 5-200 nm are bioavailable and known to induce seleno enzymes involved in antioxidant defence.

Traceable quantitation of cyanocobalamin (vitamin B12) via measurement of cobalt and phosphorus: a comparative assessment using inductively coupled plasma atomic emission spectrometry (ICP-AES) and ion chromatography (IC)

Traceable and precise quantitative measurements of cyanocobalamin (CN-Cbl) have been hampered by the lack of well characterized standards and pure materials of this bio-inorganic analyte that belongs to the water-soluble vitamins of the B-group known as vitamin B12. Measurement of cobalt and/or phosphorus content of vitamin B12 offer an approach for its quantitation that is traceable to the International System of Units (SI) with low measurement uncertainty. Cobalt and phosphorus measurements of CN-Cbl were carried out by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and Ion Chromatography (IC). Use of a mixed bed ion exchange column coupled with post column reaction, IC provides a means to differentiate free cobalt from the cobalt complexed inside the corrin ring of the CN-Cbl molecule. In the case of ICP-AES and IC, a prerequisite for quality measurement is the purity of the starting vitamin B12 material. The relative expanded uncertainties (% U) expressed at 95% confidence for these analyses range from 0.3 to 1%.

Accurate quantitation standards of glutathione via traceable sulfur measurement by inductively coupled plasma optical emission spectrometry and ion chromatography

The quantitative analysis of glutathione (GSH) is important in different fields like medicine, biology, and biotechnology. Accurate quantitative measurements of this analyte have been hampered by the lack of well characterized reference standards. The proposed procedure is intended to provide an accurate and definitive method for the quantitation of GSH for reference measurements. Measurement of the stoichiometrically existing sulfur content in purified GSH offers an approach for its quantitation and calibration through an appropriate characterized reference material (CRM) for sulfur would provide a methodology for the certification of GSH quantity, that is traceable to SI (International system of units). The inductively coupled plasma optical emission spectrometry (ICP-OES) approach negates the need for any sample digestion. The sulfur content of the purified GSH is quantitatively converted into sulfate ions by microwave-assisted UV digestion in the presence of hydrogen peroxide prior to ion chromatography (IC) measurements. The measurement of sulfur by ICP-OES and IC (as sulfate) using the “high performance” methodology could be useful for characterizing primary calibration standards and certified reference materials with low uncertainties. The relative expanded uncertainties (% U) expressed at 95% confidence interval for ICP-OES analyses varied from 0.1% to 0.3%, while in the case of IC, they were between 0.2% and 1.2%. The described methods are more suitable for characterizing primary calibration standards and certifying reference materials of GSH, than for routine measurements.