Mashitah M. Yusoff

Biosynthesis of metallic nanoparticles using plant derivatives and their new avenues in pharmacological applications – An updated report

The field of nanotechnology mainly encompasses with biology, physics, chemistry and material sciences and it develops novel therapeutic nanosized materials for biomedical and pharmaceutical applications. The biological syntheses of nanoparticles are being carried out by different macro–microscopic organisms such as plant, bacteria, fungi, seaweeds and microalgae. The biosynthesized nanomaterials have been effectively controlling the various endemic diseases with less adverse effect. Plant contains abundant natural compounds such as alkaloids, flavonoids, saponins, steroids, tannins and other nutritional compounds. These natural products are derived from various parts of plant such as leaves, stems, roots shoots, flowers, barks, and seeds. Recently, many studies have proved that the plant extracts act as a potential precursor for the synthesis of nanomaterial in non-hazardous ways. Since the plant extract contains various secondary metabolites, it acts as reducing and stabilizing agents for the bioreduction reaction to synthesized novel metallic nanoparticles. The non-biological methods (chemical and physical) are used in the synthesis of nanoparticles, which has a serious hazardous and high toxicity for living organisms. In addition, the biological synthesis of metallic nanoparticles is inexpensive, single step and eco-friendly methods. The plants are used successfully in the synthesis of various greener nanoparticles such as cobalt, copper, silver, gold, palladium, platinum, zinc oxide and magnetite. Also, the plant mediated nanoparticles are potential remedy for various diseases such as malaria, cancer, HIV, hepatitis and other acute diseases.

Superior supercapacitive performance in electrospun copper oxide nanowire electrodes

Copper oxide (CuO) nanowires of diameter ∼30–50 nm were developed by an aqueous polymeric solution based electrospinning process and their structural, morphological, and electrochemical properties were studied with the aim to fabricate high performance supercapacitor devices. The wires consist of densely packed cuboidal particles of size ∼10 nm characterized by a low degree of crystal defects. Supercapacitor electrodes were fabricated on nickel foam substrates using 75 wt% CuO in 15 wt% conducting carbon and 10 wt% polyvinylidene fluoride. The supercapacitive properties of the electrodes were evaluated in a three-electrode configuration in aqueous electrolytes, viz. KOH and LiOH, employing cyclic voltammetry (CV), charge–discharge cycling (CDC) and electrochemical impedance spectroscopy (EIS). A record specific capacitance (CS) is observed for the present electrospun CuO nanowires: CS ∼ 620 F g−1 in KOH and 581 F g−1 in LiOH at a current density of 2 A g−1 with a Coulombic efficiency of ∼100%. Compared with the previous results on the electrochemical stability of CuO nanostructures, the material electrospun using an aqueous polymeric solution showed a much higher operational stability (98% at the end of 1000 cycles and 92% at the end of 2000 cycles) owing to its superior crystallinity. The electrochemical properties of the electrodes were determined using EIS to validate the CV and CDC results.

Nutraceuticals as potential therapeutic agents for colon cancer: a review

Colon cancer is a world-wide health problem and the second-most dangerous type of cancer, affecting both men and women. The modern diet and lifestyles, with high meat consumption and excessive alcohol use, along with limited physical activity has led to an increasing mortality rate for colon cancer worldwide. As a result, there is a need to develop novel and environmentally benign drug therapies for colon cancer. Currently, nutraceuticals play an increasingly important role in the treatment of various chronic diseases such as colon cancer, diabetes and Alzheimer׳s disease. Nutraceuticals are derived from various natural sources such as medicinal plants, marine organisms, vegetables and fruits. Nutraceuticals have shown the potential to reduce the risk of colon cancer and slow its progression. These dietary substances target different molecular aspects of colon cancer development. Accordingly, this review briefly discusses the medicinal importance of nutraceuticals and their ability to reduce the risk of colorectal carcinogenesis.

A Comprehensive Review on l-Asparaginase and Its Applications

Abstractl-asparaginase (LA) catalyzes the degradation of asparagine, an essential amino acid for leukemic cells, into ammonia and aspartate. Owing to its ability to inhibit protein biosynthesis in lymphoblasts, LA is used to treat acute lymphoblastic leukemia (ALL). Different isozymes of this enzyme have been isolated from a wide range of organisms, including plants and terrestrial and marine microorganisms. Pieces of information about the three-dimensional structure of l-asparaginase from Escherichia coli and Erwinia sp. have identified residues that are essential for catalytic activity. This review catalogues the major sources of l-asparaginase, the methods of its production through the solid state (SSF) and submerged (SmF) fermentation, purification, and characterization as well as its biological roles. In the same breath, this article explores both the past and present applications of this important enzyme and discusses its future prospects.

Near band-edge electron diffusion in electrospun Nb-doped anatase TiO2 nanofibers probed by electrochemical impedance spectroscopy

Charge transport through Nb-doped anatase TiO2 nanofibers (diameter ∼100 nm) developed by electrospinning is studied under the framework of hopping transport using electrochemical impedance spectroscopy measurements. It is observed that the Fermi level of TiO2 rise close to its conduction band and result in a band-edge type diffusion mechanism even at low bias voltages when 2 at % Nb atoms replaces the Ti atoms in the anatase lattice. The Nb-doped anatase electrospun nanofibers showed high chemical capacitance, high effective diffusion coefficient, and lower transport resistance compared to the undoped samples and conventional nanoparticles (25 nm).

Impedimetric graphene-based biosensor for the detection of Escherichia coli DNA

A label-free impedimetric DNA biosensor based on graphene nanosheets has been developed for the detection of Escherichia coli O157:H7 strain GZ-021210. Probe DNA (pDNA) of E. coli was immobilized onto graphene nanosheets by the surface functionalization of graphene with 1-pyrenebutyric acid (PyBA) followed by carbodiimide linkage. The hybridization of complementary DNA (cDNA) of E. coli with the immobilized pDNA increased the electron transfer resistance of the graphene nanosheets, as observed by electrochemical impedance spectroscopy (EIS). The E. coli DNA biosensor displayed a wide range of linear response (1.0 × 10−10 M to 1.0 × 10−14 M), low detection limit (0.7 × 10−15 M), single-base mismatch selectivity, high robustness and good reproducibility. The current work demonstrates an important advancement in the development of a sensitive biosensor for E. coli detection.

New pyrimidine-based photo-switchable bent-core liquid crystals

The first examples of liquid crystalline pyrimidine-based photo-switchable bent-core monomers incorporating azobenzene as side arms linked with terminal double bonds as polymerizable functional groups are synthesized and characterized. Polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction analysis reveal that the bent-shaped lower homologue compounds are crystalline in nature whereas higher homologue compounds display the stable enantiotropic B6 phase. They exhibit fast photoisomerization effects in solution and relatively slow photoisomerization effects in liquid crystal cells. In solution both trans–cis and cis–trans occur at around 3 s and 200 s, respectively, whereas in solids they occur at around 10 s to 200 min. These are some of the first examples of azobenzene liquid crystals which exhibit very fast switching properties in solutions.

Highly active thiol-functionalized SBA-15 supported palladium catalyst for Sonogashira and Suzuki–Miyaura cross-coupling reactions

Highly ordered mesoporous silica SBA-15 with pendent 3-mercaptopropyl groups has been prepared by condensation of surface silanols and (3-mercaptopropyl)trimethoxysilane. Treatment of the mercaptopropylated SBA-15 with (CH3CN)2PdCl2 gave a heterogeneous Pd-catalyst. The immobilized Pd-catalyst served as an efficient heterogeneous catalyst for Sonogashira and Suzuki–Miyaura cross coupling reactions of aryl halides. Furthermore, the SBA-15 supported Pd-catalyst was recovered by a simple filtration from the reaction mixture and reused five times without significant loss of its catalytic activity.

An accelerated route of glycerol carbonate formation from glycerol using waste boiler ash as catalyst

Waste boiler ash was successfully utilised as catalyst for the direct synthesis of glycerol carbonate from glycerol and urea. A series of catalysts were prepared using various calcination temperatures. The physico-chemical properties of the catalysts have been investigated by using XRD, BET, TGA, FESEM-EDX, ICP-MS, Hammett test and CO2-TPD. From the study it was found that boiler ash had significant catalytic activity towards conversion of glycerol into glycerol carbonate. It is believed that the potassium metal ion which detaches from potassium silicate had a major impact on the catalytic data where the potassium ion being a weak Lewis acid causes selective catalytic transformation of glycerol into glycerol carbonate. The mechanistic pathway through glycerol carbamate intermediate was confirmed through time online analysis study using 13C-NMR and ATR-FTIR, respectively. However, the selective transformation of glycerol carbamate into glycerol carbonate is reported to be different where it is formed in an accelerated manner. The highest catalytic activity resulted in an average percentage of 93.6 ± 0.4% glycerol conversion, 90.1 ± 1.0% glycerol carbonate selectivity and 84.3 ± 1.1% glycerol carbonate yield. Besides, for the first time the novel idea of using waste material, specifically boiler ash, is proposed as a catalyst for synthesis of glycerol carbonate from glycerol and urea. The current research employed suggests an alternative route for proper disposal of waste boiler ash.

Standardization of photoelectrode area of dye-sensitized solar cells

This study is aimed to provide new insights on the scalability of dye-sensitized solar cells (DSCs). The DSCs of electrode area up to ∼2 cm2 were fabricated using commercially available P25 TiO2 particles, N3 dye, and iodide/triiodide electrolyte. The photovoltaic conversion efficiency follows a biexponential decay, the main contributor to which is the short circuit current density (JSC). Interesting features were observed in the electrochemical impedance spectra and charge transport parameters in the devices as the photoelectrode areas were increased. Results show that electrons from an area above a threshold are not collected due to varied choice of diffusion pathways. Furthermore, this study identifies that the area of the photoelectrode for reporting the efficiency needs to be fixed at ∼0.5 cm2 for 25 nm TiO2 particles because below this value it strongly varies. On the other hand, the study provides opportunities to build high efficiency dye-sensitized solar cells using the current choice of materials.