Palanivel Sathishkumar

Synthesis of flexirubin-mediated silver nanoparticles using Chryseobacterium artocarpi CECT 8497 and investigation of its anticancer activity

In this work, the synthesis of silver nanoparticles from a pigment produced by a recently-discovered bacterium, Chryseobacterium artocarpi CECT 8497, was achieved, followed by an investigation of its anticancer properties. The bacterial pigment was identified as flexirubin following NMR ((1)H NMR and (13)C NMR), UV-Vis, and LC-MS analysis. An aqueous silver nitrate solution was treated with isolated flexirubin to produce silver nanoparticles. The synthesised silver nanoparticles were subsequently characterised by UV-Vis spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), X-Ray Diffraction (XRD), and Fourier Transform Infrared (FTIR) Spectroscopy methodologies. Furthermore, the anticancer effects of synthesised silver nanoparticles in a human breast cancer cell line (MCF-7) were evaluated. The tests showed significant cytotoxicity activity of the silver nanoparticles in the cultured cells, with an IC50 value of 36μgmL(-1). This study demonstrates that silver nanoparticles, synthesised from flexirubin from C. artocarpi CECT 8497, may have potential as a novel chemotherapeutic agent.

Anti-acne, anti-dandruff and anti-breast cancer efficacy of green synthesised silver nanoparticles using Coriandrum sativum leaf extract.

In this present investigation, AgNPs were green synthesised using Coriandrum sativum leaf extract. The physicochemical properties of AgNPs were characterised using UV-visible spectrophotometer, field emission scanning microscopy/energy dispersive X-ray (FESEM/EDX), Fourier transformed infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis. Further, in vitro anti-acne, anti-dandruff and anti-breast cancer efficacy of green synthesised AgNPs were assessed against Propionibacterium acnes MTCC 1951, Malassezia furfur MTCC 1374 and human breast adenocarcinoma (MCF-7) cell line, respectively. The flavonoids present in the plant extract were responsible for the AgNPs synthesis. The green synthesised nanoparticles size was found to be ≈37nm. The BET analysis result shows that the surface area of the synthesised AgNPs was found to be 33.72m(2)g(-1). The minimal inhibitory concentration (MIC) of AgNPs for acne causative agent P. acnes and dandruff causative agent M. furfur was found to be at 3.1 and 25μgmL(-1), respectively. The half maximal inhibitory concentration (IC50) value of the AgNPs for MCF-7 cells was calculated as 30.5μgmL(-1) and complete inhibition was observed at a concentration of 100μgmL(-1). Finally, our results proved that green synthesised AgNPs using C. sativum have great potential in biomedical applications such as anti-acne, anti-dandruff and anti-breast cancer treatment.

PVDF–ErGO–GRC electrode: A single setup electrochemical system for separation, pre-concentration and detection of lead ions in complex aqueous samples

An effective electrode was developed based on electromembrane extraction (EME) and square wave voltammetry (SWV) for simultaneous separation, pre-concentration and determination of lead (II) (Pb(II)) ions in complex aqueous samples. Electrochemically reduced graphene oxide-graphite reinforced carbon (ErGO-GRC) was utilized in conjunction with the SWV. Pb(II) ions were extracted from an aqueous sample solution into an acidic acceptor phase (1M HCl) in the lumen of the polyvinylidene fluoride (PVDF) membrane bag by the application of voltage of maximum 6 V across the supported liquid membrane (SLM), consisting of organic solvent and di-(2-ethylhexyl)phosphoric acid (D2EHPA). The parameters affecting the EME were optimized for Pb(II) ions. The optimum EME conditions were found to be 20% D2EHPA in 1-octanol impregnated in the wall of PVDF membrane (PVDF17) as the SLM, extraction time of 20 min, pH of sample solution of 8 and a voltage of 5 V. The PVDF-ErGO-GRC electrode system attained enrichment factors of 40 times and 80% of extraction with relative standard deviations (n=5) of 8.3%. Good linearity ranging from 0.25 to 2 nM with coefficients correlation of 0.999 was obtained. The Pb(II) ions detection limit of PVDF-ErGO-GRC electrode was found to be 0.09 nM. The newly developed single setup electrochemical system was applied to complex aqueous samples such as tap, river and sea water to evaluate the feasibility of the method for applications.

A sensitive, selective and rapid determination of lead(II) ions in real-life samples using an electrochemically reduced graphene oxide-graphite reinforced carbon electrode

In this study, a sensitive and cost-effective electrochemically reduced graphene oxide (ErGO) on graphite reinforced carbon (GRC) was developed for the detection of lead (Pb(II)) ions present in the real-life samples. A film of graphene oxide (GO) was drop-casted on GRC and their electrochemical properties were investigated using cyclic voltammetry (CV), amperometry and square wave voltammetry (SWV). Factors influencing the detection of Pb(II) ions, such as grades of GRC, constant applied cathodic potential (CACP), concentration of hydrochloric acid and drop-casting drying time were optimised. GO is irreversibly reduced in the range of -0.7 V to -1.6 V vs Ag/AgCl (3 M) in acidic condition. The results showed that the reduction behaviour of GO contributed to the high sensitivity of Pb(II) ions detection even at nanomolar level. The ErGO-GRC showed the detection limit of 0.5 nM and linear range of 3-15 nM in HCl (1 M). The developed electrode has potential to be a good candidate for the determination of Pb(II) ions in different aqueous system. The proposed method gives a good recovery rate of Pb(II) ions in real-life water samples such as tap water and river water.

Photocatalytic activity and reusability of ZnO layer synthesised by electrolysis, hydrogen peroxide and heat treatment

ABSTRACT In this study, the zinc oxide (ZnO) layer was synthesised on the surface of Zn plates by three different techniques, i.e. electrolysis, hydrogen peroxide and heat treatment. The synthesised ZnO layers were characterised using scanning electron microscopy, X-ray diffraction, UV–visible diffuse reflectance and photoluminescence spectroscopy. The photocatalytic activity of the ZnO layer was further assessed against methylene blue (MB) degradation under UV irradiation. The photocatalytic degradation of MB was achieved up to 84%, 79% and 65% within 1 h for ZnO layers synthesised by electrolysis, heat and hydrogen peroxide treatment, respectively. The reusability results show that electrolysis and heat-treated ZnO layers have considerable photocatalytic stability. Furthermore, the results confirmed that the photocatalytic efficiency of ZnO was directly associated with the thickness and enlarged surface area of the layer. Finally, this study proved that the ZnO layers synthesised by electrolysis and heat treatment had shown better operational stability and reusability.

Plant extract as environmental-friendly green catalyst for the reduction of hexavalent chromium in tannery effluent

ABSTRACT The aqueous extract of various plants like Coriandrum sativum (AECS), Alternanthera tenella colla (AEAT), Spermacoce hispida (AESH) and Mollugo verticillata (AEMV) was studied for its hexavalent chromium (CrVI) reduction property. Even though antioxidant activity was present, AEAT, AESH and AEMV did not reduce CrVI. AECS showed rapid and dose-dependent CrVI reduction. The efficient reduction of 50 mg/L of CrVI using AECS was attained in the presence of 250 µg/mL of starting plant material, incubating the reaction mixture at pH 2, 30°C and agitation at 190 rpm. Under such conditions, about 40 mg/L of CrVI was reduced at 3 h of incubation. FT-IR analysis revealed the involvement of phenols, alcohols, alpha-hydroxy acid and flavonoids present in the AECS for the CrVI reduction. These results indicate that not all the plant extracts with rich antioxidants are capable of reducing CrVI. Using the conditions standardized in the present study, AECS reduced about 80% of CrVI present in the tannery effluent. These results signify the application of AECS as an eco-friendly method in the wastewater treatment.

Fabrication of a composite modified glassy carbon electrode: a highly selective, sensitive and rapid electrochemical sensor for silver ion detection in river water samples

In this study, a glassy carbon electrode (GCE) was modified with multi-walled carbon nanotubes (MWCNTs), 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6), N,N′-bis(2-hydroxyacetophenone)ethylenediamine (BZE) and Nafion to form a MWCNT-BZE-[bmim]PF6-Nafion-GCE. The electrochemical behaviour of the modified electrode with respect to silver (Ag(I)) ion detection was studied by cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV). Furthermore, the experimental parameters including the pH value of Britton–Robinson Buffer (BRB), Nafion, MWCNTs, BZE and ([bmim]PF6) concentrations and the deposition potential and time were optimized. The detection limit of the modified electrode for the Ag(I) ion was found to be 70 ng L−1 (6.49 × 10−10 mol L−1). Repetitive measurements revealed good reproducibility with a relative standard deviation (RSD) value of 0.4%. The system performance of the modified electrode was highly satisfactory and the recoveries for river water samples were found to be 96–121%. This study proved that the MWCNT-BZE-[bmim]PF6-Nafion-GCE is a highly selective and sensitive modified electrode for the detection of the Ag(I) ion in river water samples with good recovery value.

Rapid biosynthesis of Bauhinia variegata flower extract-mediated silver nanoparticles: an effective antioxidant scavenger and α-amylase inhibitor

Abstract Silver nanoparticles (AgNPs) were biosynthesized using Bauhinia variegata flower extract (BVFE). The BVF-AgNPs was found to be spherical shaped with the size of 5–15 nm. The phytoconstituents analysis and FTIR spectrum indicated that bioactive compounds like, phenols, flavonoids, benzophenones, nitro compounds, aromatics and aliphatic amines from BVFE might absorb on the surface of BVF-AgNPs. The synthesized BVF-AgNPs showed potent antioxidant property and α-amylase enzyme activity inhibition. The IC50 value of BVF-AgNPs was found to be 4.64 and 16.6 µg/ml for DPPH and ferric reducing power assay, respectively. The IC50 value of BVF-AgNPs for α-amylase inhibition was found to be 38 µg/ml. The Ki value of BVF-AgNPs for α-amylase inhibitory effect was found to be 21 µg/ml with the non-competitive mode of inhibition. These results suggest that BVF-AgNPs might be an effective nano-drug to treat diabetic conditions.

Determination of para-arsanilic acid with improved diazotization reaction using differential pulse cathodic stripping voltammetry in aqueous system

Para-arsanilic acid (p-ASA) has been widely used in the poultry industry to promote growth and prevent dysentery. It is excreted unchanged in the manure and released into non-target sites causing organoarsenic pollution risk to the environment and living system. Therefore, simple and effective analytical strategies are demanded for determining the samples that contain p-ASA. However, direct determination of both p-ASA and ortho-arsanilic acid (o-ASA) using differential pulse cathodic stripping voltammetry (DPCSV) gives the similar voltammograms that directly hamper the analysis used by the DPCSV technique. In this study, a method to determine and differentiate p-ASA from o-ASA via diazotization and coupling reaction of the amine groups followed by the direct DPCSV determination of diazo compounds is presented. The diazotization reaction carried out at pH 1.5 and 0 ± 1°C for 10 min showed two reduction peaks in DPCSV at–70 mV and –440 mV vs. Ag/AgCl (KCl 3 M). However, when the diazotization reaction was performed at pH 12.5 and 0 ± 1°C for 40 min, a coloured azo compound was produced and the DPCSV showed only one reduction peak that appeared at –600 mV vs. Ag/AgCl (3 M of KCl). The results of this study show that only p-ASA compound gave a reduction peak, whereas o-ASA compound did not give any peak. The detection limit of p-ASA was found to be 4 × 10−8 M. As a result, the proposed electro-analytical technique might be a good candidate to determine and differentiate the p-ASA present in the poultry and environmental samples.

Modified phyto-waste Terminalia catappa fruit shells

This study investigated the preparation of a reusable adsorbent from the phyto-waste Terminalia catappa fruit shells by acid-thermal modification and utilization for the removal of diclofenac from aqueous systems. The structural characteristic features of the modified T. catappa fruit shells (MTCFS) were analysed using Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy and Brunauer–Emmett–Teller analysis. Batch experiments proved that temperature and pH mainly influenced the adsorption process. The Langmuir and Freundlich isotherms were obeyed for the diclofenac adsorption. The Temkin isotherm model revealed that increasing temperature affected the adsorption of diclofenac. The Dubinin–Radushkevich isotherm indicated that the present adsorption system was achieved through physical interactions. A pseudo-second-order kinetic model was well fitted for the diclofenac adsorption. Intraparticle diffusion results indicated increases in the rate of adsorption and in the boundary layer thickness. The thermodynamic results revealed that increasing the temperature inversely affected the diclofenac adsorption. Recycling experiments confirmed that the MTCFS were found to be quite stable and retained their adsorption efficiency for up to eight cycles of diclofenac removal.