Myalowenkosi I. Sabela

Electrochemical Determination of Capsaicin and Silymarin Using a Glassy Carbon Electrode Modified by Gold Nanoparticle Decorated Multiwalled Carbon Nanotubes

The goal of this study was to develop a suitable electroanalytical method for the determination of primary compounds in the extracts of capsaicin and silymarin. For this purpose, a glassy carbon electrode immobilized with multiwalled carbon nanotubes decorated with gold nanoparticles was characterized by high resolution transmission electron microscopy and attenuated total reflectance infrared spectroscopy. The developed electrochemical sensor had a linear dynamic range from 0.15 to 35.0 µM. In addition, the limits of quantification for silymarin and capsaicin with the gold nanoparticle decorated multiwalled carbon nanotubes were 0.1564 and 0.2761 µg L−1 with relative standard deviations (n = 3) of 1.65% and 2.09% and equivalent mass percentages of 93.33% and 62.02%, respectively. The methodology may be employed for the determination of capsaicin and silymarin in pharmaceutical and food products.

Fabrication of copper nanoparticles decorated multiwalled carbon nanotubes as a high performance electrochemical sensor for the detection of neotame

A highly sensitive and novel electrochemical sensor for the detection of neotame using differential pulse voltammetry with a modified glassy carbon electrode is presented. The method was further customized by the fabrication of the electrode surface with copper nanoparticles-ammonium piperidine dithiocarbamate-mutiwalled carbon nanotubes assimilated with β-cyclodextrin. The multiwalled carbon nanotubes assimilated with β-cyclodextrin/glassy carbon electrode exhibited catalytic activity towards the oxidation of neotame at a potential of 1.3 V at pH 3.0. The transmission electron microscopy, thermogravimetric analysis, frontier transform infrared spectroscopy and cyclic voltammetry were employed to characterize the electrochemical sensor. The sensitivity and detection limits of the electrode increased two-fold in contrast to the β-CD-MWCNTs/GCE sensor. The developed method was successfully applied for the determination of neotame in food samples, with results similar to those achieved by our modified capillary electrophoresis method with a 96% confidence level.

Biosynthesis of ZnO nanoparticles using Jacaranda mimosifolia flowers extract: Synergistic antibacterial activity and molecular simulated facet specific adsorption studies.

The naturally occurring biomolecules present in the plant extracts have been identified to play an active role in the single step formation of nanoparticles with varied morphologies and sizes which is greener and environmentally benign. In the present work, spherical zinc oxide nanoparticles (ZnO NPs) of 2-4nm size were synthesized using aqueous extract of fallen Jacaranda mimosifolia flowers (JMFs), treated as waste. The microwave assisted synthesis was completed successfully within 5min. Thereafter, phase identification, morphology and optical band gap of the synthesized ZnO NPs were done using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and UV-Visible spectroscopy techniques. The composition of JMFs extract was analyzed by gas chromatography-mass spectrometry (GC-MS) and the ZnO NPs confirmation was further explored with fourier transform infrared spectroscopy (FTIR). The GC-MS results confirmed the presence of oleic acid which has high propensity of acting as a reducing and capping agent. The UV-Visible data suggested an optical band gap of 4.03eV for ZnO NPs indicating their small size due to quantum confinement. Further, facet specific adsorption of oleic acid on the surface of ZnO NPs was studied computationally to find out the impact of biomolecules in defining the shape and size of NPs. The viability of gram negative Escherichia coli and gram positive Enterococcus faecium bacteria was found to be 48% and 43%, respectively at high concentration of NPs.

Smartphone based bioanalytical and diagnosis applications: A review

A smartphone is a facile, handy-analytical device that makes our lives comfortable and stress-free in terms of health care diagnostic assessments. Due to recent advancements in the technology and the introduction of user friendly operating systems and applications, the smartphones have replaced laptops and desktop computers. Taking this fact into account, researchers have designed sensing systems which are more compatible with smartphones. Consequently, these devices are attracting the attention of researchers from fields such as telemedicine, biotechnology, chemical sciences and environmental sciences. In this review, our focus is on recent advances on smartphone based sensing and diagnosis applications.

An ultrasensitive performance enhanced novel cytochrome c biosensor for the detection of rebaudioside A.

In this study a novel cyctochrome c modified nanocomposite electrochemical biosensor was developed for the electrochemical determination of rebaudioside A in different food samples. The electrode surface was fabricated with graphene oxide assimilated with gold nanoparticles decorated on multiwalled carbon nanotubes/cytochrome c. The developed biosensor exhibited a 10-fold enhancement in the differential pulse voltammetry signal carried out at pH 11.0 in a 0.1M borate buffer. Under the optimized conditions, Ip (µA) was proportional to the rebaudioside A concentration in the range of 0.001-0.05 mM (R(2)=0.8308) and 0.075-1.25 mM (R(2)=0.9920) with a detection limit (S/N=3) of 0.264 µM. Results of this study revealed that cyctochrome c was adsorbed tightly onto the surface of the modified electrode and showed an enzymatic catalytic activity towards the quasi-reversible reduction of rebaudioside A at -0.1 V (vs Ag/AgCl). The direct electron transfer by cytochrome c was further supported by HOMO-LUMO calculations performed at the density functional theory level. Additionally, the molecular docking simulations predicted a stronger binding affinity of rebaudioside A towards cytochrome c, thus supporting their host-guest relationship. The use of novel electrode materials in this study demonstrates the application of the electrochemical biosensor in the food industry.

Electrochemical sensing platform amplified with a nanobiocomposite of L-phenylalanine ammonia-lyase enzyme for the detection of capsaicin.

The present study involves the development of a sensitive electrochemical biosensor for the determination of capsaicin extracted from chilli fruits, based on a novel signal amplification strategy using enzyme technology. For the first time, platinum electrode modified with multiwalled carbon nanotubes where phenylalanine ammonia-lyase enzyme was immobilized using nafion was characterized by attenuated total reflectance infrared spectroscopy, transmittance electron microscopy and thermo-gravimetric analysis supported by computational methods. Cyclic and differential pulse voltammetry measurements were performed to better understand the redox mechanism of capsaicin. The performance of the developed electrochemical biosensor was tested using spiked samples with recoveries ranging from 98.9 to 99.6%. The comparison of the results obtained from bare and modified platinum electrodes revealed the sensitivity of the developed biosensor, having a detection limit (S/N=3) of 0.1863µgmL(-1) and electron transfer rate constant (ks) of 3.02s(-1). Furthermore, adsorption and ligand-enzyme docking studies were carried out to better understand the redox mechanisms supported by density functional theory calculations. These results revealed that capsaicin forms hydrogen bonds with GLU355, GLU541, GLU586, ARG and other amino acids of the hydrophobic channel of the binding sites thereby facilitating the redox reaction for the detection of capsaicin.

Determination of Neotame by High-Performance Capillary Electrophoresis Using ß-cyclodextrin as a Chiral Selector

An electrokinetic chromatographic method was developed for the chiral separation of neotame, a new high intensity artificial sweetener, using a chiral separating agent heptakis 2,3,6-tri-o-methylbetacyclodextrin. The purpose of this study was to better understand diastereomer-resolution interactions between neotame and the chiral separating agent. Molecular docking studies were performed to elucidate the mechanism of the separation. The optimum conditions were 50 mM phosphate buffer, pH 5.5, applied voltage 20 kV, cassette temperature of 30°C, and a 4 s sample injection time. The calibration curve showed good linearity (r2 > 0.99) with recoveries for both diastereomers, ranging from 95.66–99.00% and the limits of detection for L,L-neotame and D,D-neotame were 0.01857 and 0.08214 mM, respectively. The developed method showed analytical precision with relative standard deviations (n = 5) of 1.20% and 1.17% with respect to migration time and peak area, respectively. A large difference in the interaction energies observed between the diastereomers represents a significant differentiation. The results showed that both electrostatic and hydrophobic interactions played a significant role in stabilizing their inclusion complexes and consequently supported the elution order based on their differential stabilities.

Membrane technology for water purification

Managing higher water demands is a grand challenge of the twenty-first century due to pollution and climate change that are decreasing the amount of drinkable water. There is therefore a need for improved techniques to purify contaminated waters. Nanotechnology provides materials of unprecedented properties, which can be used to clean water. This article reviews recent developments in nanotechnology for wastewater treatment using novel polymeric membrane materials. The use of polymeric membrane materials and polymer brushes are discussed.

One-pot biosynthesis of silver nanoparticles using Iboza Riparia and Ilex Mitis for cytotoxicity on human embryonic kidney cells

Plant extracts continue gaining significant prominence in green synthesis of silver nanoparticles (AgNPs), due to their potential applications in nano-medicine and material engineering. This work reports on green synthesis of silver nanoparticles (AgNPs) from aqueous extracts of Iboza Riparia leaf and Ilex Mitis root bark with diterpenes (DTPs) and saponins (SPNs) as major components. After TEM, DLS, TGA/DSC, ATR, XRD and UV-Vis characterization, the relevant cytotoxicity studies were conducted with the MTT assay on human embryonic kidney cells (HEK293T) followed by antioxidant activity with ABTS. Overall, the AgNPs-DTPs (156nm) were found to be less toxic with 49.7% cell viability, while AgNPs-SPNs (50nm) and AgNPs-PVA (44nm) had cell viability of 40.8 and 28.0% respectively at 400μM. Based on the cytotoxicity and antioxidant activity, it is fair to report that these plant extracts have potential reducing and capping agents as they retain chemical properties on the surface of the nanoparticles.

Google Analytics and quick response for advancement of gold nanoparticle-based dual lateral flow immunoassay for malaria – Plasmodium lactate dehydrogenase (pLDH)

A rapid dual lateral flow diagnostic assay fabricated with quick response (QR) barcodes was developed to improve the quality control of malaria diagnostic tests, as well as to enhance systems for transferring data from survey studies among community healthcare workers at a point-of-care facility and centralized laboratories. The lateral flow kit has been modified with QR technology encoded with Google Analytics information for the detection and real-time tracking of Plasmodium lactate dehydrogenase (pLDH). The QR barcode was fabricated by attaching two QR barcodes which were encoded with websites that were linked to Google Analytics. The optical and structural properties of gold nanoparticles (AuNPs) were studied using UV-visible spectroscopy, transmission electron microscopy and a Biodot XYZ. The anti-mouse IgG antibody was used as a secondary antibody to act as a control and anti-pLDH. The antibody binding with pLDH antigens shows a test line indicating a positive test in the presence of phosphate buffer as a mobile phase. The diagnostic kit for the rapid detection of pLDH was developed and validated for the detection of malaria antigens at the lowest detectable recombinant concentration of 10 ng ml−1. The diagnostic kit was incorporated with quick QR barcodes for positive, negative and invalid tests readable with a smartphone. These QR barcodes successfully allowed us to track the precise location of the test through Google Analytics.