M. Ajmal Ali

Antimicrobial efficacy of green synthesized drug blended silver nanoparticles against dental caries and periodontal disease causing microorganisms

Development of biologically inspired green synthesis of silver nanoparticles is evolving into an important branch of nano-biotechnology. In the present investigation, we report the green synthesis of silver nanoparticles (AgNPs) employing the leaf extract of Justicia glauca. Water-soluble organics present in the leaf extract are mainly responsible for the reduction of silver nitrate (AgNO3) solution to AgNPs. The AgNPs are 10-20nm in dimensions as determined by TEM images. The antimicrobial activities of green synthesized AgNPs and drug blended AgNPs have been evaluated against the dental caries and periodontal disease causing microorganisms such as Streptococcus mutans, Staphylococcus aureus, Lactobacillus acidophilus, Micrococcus luteus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. The AgNPs and drug blended AgNPs show a significant antibacterial and antifungal activity. Minimum inhibitory concentration (MIC) value of AgNPs determined against the selected dental caries and periodontal disease causing microorganisms are noticeable between the range of 25-75μg/mL.

Palladium nanoparticles decorated on activated fullerene modified screen printed carbon electrode for enhanced electrochemical sensing of dopamine

In the present work, an enhanced electrochemical sensor for dopamine (DA) was developed based on palladium nanoparticles decorated activated fullerene-C60 (AC60/PdNPs) composite modified screen printed carbon electrode (SPCE). The scanning electron microscopy and elemental analysis confirmed the formation of PdNPs on AC60. The fabricated AC60/PdNPs composite modified electrode exhibited an enhanced electrochemical response to DA with a lower oxidation potential than that of SPCE modified with PdNPs and C60, indicating the excellent electrooxidation behavior of the AC60/PdNPs composite modified electrode. The electrochemical studies confirmed that the electrooxidation of DA at the composite electrode is a diffusion controlled electrochemical process. The differential pulse voltammetry was employed for the determination of DA; under optimum conditions, the electrochemical oxidation signal of DA increased linearly at the AC60/PdNPs composite from 0.35 to 133.35 μM. The limit of detection was found as 0.056 μM with a sensitivity of 4.23 μA μM(-1) cm(-2). The good recovery of DA in the DA injection samples further revealed the good practicality of AC60/PdNPs modified electrode.

Green synthesized silver nanoparticles decorated on reduced graphene oxide for enhanced electrochemical sensing of nitrobenzene in waste water samples

In the present work, an electrochemical sensor for nitrobenzene (NB) has been developed based on a green synthesized silver nanoparticles (AgNPs) decorated reduced graphene oxide (RGO) modified glassy carbon electrode (GCE). The AgNPs were synthesized using Justicia glauca leaf extract as a reducing and stabilizing agent. A RGO–AgNPs composite modified electrode was prepared by a simple electrochemical reduction of AgNPs dispersed GO solution. FESEM of RGO–AgNPs composite confirms that AgNPs are firmly attached on the RGO sheets and the average size of AgNPs is found to be 40 ± 5 nm. The modified electrode shows good efficiency with lower overpotential for electrocatalytic reduction of NB than that of other modified electrodes (AgNPs and RGO). The DPV response confirms that the reduction peak current of NB is linear over the concentrations from 0.5 to 900 μM. The sensitivity of the sensors is found to be 0.836 μA μM−1 cm−2 with the detection limit of 0.261 μM for NB. In addition, the RGO–AgNPs composite modified electrode shows good selectivity in the presence of potentially interfering similar compounds and good practicality in the waste water samples.

An electrocatalytic oxidation and voltammetric method using a chemically reduced graphene oxide film for the determination of caffeic acid.

The present work describes the characterization of a chemically reduced graphene oxide (CRGO) modified glassy carbon electrode (GCE) for electrochemical investigation of caffeic acid (CA). Cyclic voltammetry (CV), differential pulse voltammetry (DPV), amperometry, and electrochemical impedance spectroscopy (EIS) techniques were used to characterize the properties of the electrode. There was an obvious enhancement of the current response and a decreased over potential for the oxidation of CA. The interfacial electron transfer rate of CA was studied by EIS. Under optimal conditions, the CRGO displayed a linear response range of 1×10(-8) to 8×10(-4) M and the detection limit was 2×10(-9) M (S/N=3), with a sensitivity of 192.21 μA mM(-1) cm(-2) at an applied potential of +0.2V (vs. Ag/AgCl reference), which suggests that the CRGO is a promising sensing materials for the electrochemical investigation of CA. The results showed the good sensitivity, selectivity and high reproducibility of the CRGO modified electrode. Moreover, this modified electrode was further applied to investigate the CA in real samples of wine with satisfactory results.

Direct electrochemistry of glucose oxidase immobilized on ZrO2 nanoparticles-decorated reduced graphene oxide sheets for a glucose biosensor

We fabricated a glucose biosensor based on glucose oxidase (GOx) immobilized in a poly(L-lysine) (PLL) and reduced graphene oxide–zirconium oxide composite (RGO–ZrO2). First, a simple single step electrochemical approach was used to prepare the RGO–ZrO2 composite and its successful formation was confirmed by various techniques. Then, a mixture of GOx and PLL was immobilized to form the RGO–ZrO2 composite. Direct electrochemistry of the GOx was attained for the composite film showing well-defined redox peaks centered at the formal potential −0.403 V. Notably, the peak to peak separation (ΔEp) was very low (27 mV), while the heterogeneous rate constant for the fast electron transfer was calculated to be 5.03 (±0.14 s−1) revealed. The composite film modified electrode exhibited excellent electrocatalytic ability through the reductive detection of oxygen. A glucose biosensor was developed using the GOx–PLL/RGO–ZrO2 composite film modified electrode which functioned using differential pulse voltammetry (DPV). The fabricated biosensor exhibited good electrocatalytic ability for the determination of glucose with excellent analytical parameters such as wide linear range of 0.29 mM to 14 mM and high sensitivity of 11.65 (±0.17) μA mM−1 cm−2. The sensor results also exhibited appreciable repeatability, reproducibility and stability. Good recovery rates were achieved for the real sample studies proving the promise and practicality of the proposed sensor.

A sensitive and selective enzyme-free amperometric glucose biosensor using a composite from multi-walled carbon nanotubes and cobalt phthalocyanine

In the present study, a simple and sensitive amperometric enzyme-free glucose sensor was developed at a multiwalled carbon nanotube and cobalt tetrasulfonated phthalocyanine (MWCNT–CoTsPc) modified electrode. The morphology of the fabricated composite was characterized and confirmed by transmission electron microscopy and UV-Vis spectroscopy. UV-Vis spectroscopy results confirmed that the MWCNT–CoTsPc composite was formed via the strong π–π interaction between CoTsPc and MWCNT. Compared with pristine CoTsPc, the MWCNT–CoTsPc composite modified electrode showed a higher electrocatalytic activity and lower overpotential towards the oxidation of glucose. Amperometric i–t technique was used for the determination of glucose. The response of glucose was linear over the concentration ranging from 10 μM to 6.34 mM with a sensitivity of 122.5 μA mM−1 cm−2. The response time of the sensor was determined to be 2 s with a limit of detection of 0.14 μM (S/N = 3). The fabricated sensor also exhibited a good selectivity in the presence of common interfering species. In addition, the fabricated sensor exhibited special advantages, such as low working potential, good sensitivity along with good repeatability and reproducibility, for the determination of glucose.

Enhanced electrocatalytic oxidation of isoniazid at electrochemically modified rhodium electrode for biological and pharmaceutical analysis

A simple and sensitive electrochemical method has been proposed for the determination of isoniazid (INZ). For the first time, rhodium (Rh) modified glassy carbon electrode (GCE) has been employed for the determination of INZ by linear sweep voltammetry technique (LSV). Compared with the unmodified electrode, the proposed Rh modified electrode provides strong electrocatalytic activity toward INZ with significant enhancement in the anodic peak current. Scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) results reveal the morphology of Rh particles. With the advantages of wide linearity (70-1300μM), good sensitivity (0.139μAμM(-1)cm(-2)) and low detection limit (13μM), this proposed sensor holds great potential for the determination of INZ in real samples. The practicality of the proposed electrode for the detection of INZ in human urine and blood plasma samples has been successfully demonstrated using LSV technique. Through the determination of INZ in commercially available pharmaceutical tablets, the practical applicability of the proposed method has been validated. The recovery results are found to be in good agreement with the labeled amounts of INZ in tablets, thus showing its great potential for use in clinical and pharmaceutical analysis.

A highly sensitive and selective electrochemical determination of non-steroidal prostate anti-cancer drug nilutamide based on f-MWCNT in tablet and human blood serum sample

A novel electrochemical sensor based on the functionalized multiwalled carbon nanotube (f-MWCNT) was successfully developed for the sensitive and selective determination of non-steroidal prostate anti-cancer drug nilutamide in tablet and blood serum samples. The f-MWCNT was prepared by the simple reflux method and characterized by the scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, X-ray powder diffraction (XRD) and fourier transform infrared spectroscopy (FT-IR). Interestingly, the f-MWCNT was exhibited a superior electrocatalytic activity towards the anti-cancer drug nilutamide when compared with pristine MWCNT and unmodified electrodes. Besides, the electrochemical sensor was revealed an excellent current response for the determination of nilutamide with wide linear ranges (0.01-21μM and 28-535μM), high sensitivity (11.023 and 1.412μA μM-1cm2) and very low detection limit (LOD) 0.2nM. The developed electrochemical sensor was showed an excellent selectivity even in the presence of electrochemically active biological substances and nitro aromatic compounds. Moreover, it manifested a good reproducibility and stability. In addition, the f-MWCNT modified glassy carbon electrode (GCE) sensor was successfully applied for the detection of nilutamide in tablet and blood serum sample.

Assessing Molecular Signature for Some Potential Date (Phoenix dactylifera L.) Cultivars from Saudi Arabia, Based on Chloroplast DNA Sequences rpoB and psbA-trnH

Phoenix dactylifera L. (date palm), being economically very important, is widely cultivated in the Middle East and North Africa, having about 400 different cultivars. Assessment of date cultivars under trading and farming is a widely accepted problem owing to lack of a unique molecular signature for specific date cultivars. In the present study, eight different cultivars of dates viz., Khodry, Khalas, Ruthana, Sukkari, Sefri, Segae, Ajwa and Hilali were sequenced for rpoB and psbA-trnH genes and analyzed using bioinformatics tools to establish a cultivar-specific molecular signature. The combined aligned data matrix was of 1147 characters, of which invariable and variable sites were found to be 958 and 173, respectively. The analysis clearly reveals three major groups of these cultivars: (i) Khodary, Sefri, Ajwa, Ruthana and Hilali (58% BS); (ii) Sukkari and Khalas (64% BS); and (iii) Segae. The economically most important cultivar Ajwa showed similarity with Khodary and Sefri (67% BS).The sequences of the date cultivars generated in the present study showed bootstrap values between 38% and 70% so these sequences could be carefully used as molecular signature for potential date cultivars under trading and selection of genuine cultivars at the seedling stage for farming.

Flame synthesis of nitrogen doped carbon for the oxygen reduction reaction and non-enzymatic methyl parathion sensor

Growing concerns about the economical feasibility of materials synthesis means that simple methodologies to furnish materials are needed. Moreover, the multi-functional activity of these as-prepared materials is of great importance. Hence, here we report nitrogen-doped carbon nanoparticles from a one-step flame synthesis by directly burning pyrrole at room temperature and in an air atmosphere. The as-synthesized N-doped carbon was scrutinized as a cathode material for the oxygen reduction reaction and was also demonstrated in an electrochemical sensor. Furthermore, X-ray photoelectron spectroscopy (XPS) and Raman analysis was carried out to confirm the percentage of nitrogen content, the bonding environment and the disorder of carbon. The as-prepared N-doped carbon exhibits superior electrocatalytic activity towards the ORR compared with a commercial Pt/C catalyst. Moreover, the N-doped carbon modified glassy carbon electrode manifests a sensitive electrochemical response towards the detection of methyl parathion. A linear response was demonstrated by the fabricated sensor across two concentration ranges, from 0.0025 to 1 μM and 1 to 100 μM, with a lower detection limit of 0.068 nM. The proposed method is very simple, low cost and it can be utilized for practical applications to produce carbon materials on a large scale.