Electrochemical and Photoelectrochemical Immunosensors for the Detection of Ovarian Cancer Biomarkers.

Photoelectrochemical (PEC) sensing is an emerging technological innovation for monitoring small substances/molecules in biological or non-biological systems. In particular, there has been a surge of interest in developing PEC devices for determining molecules of clinical significance. This is especially the case for molecules that are markers for serious and deadly medical conditions. The increased interest in PEC sensors to monitor such biomarkers can be attributed to the many apparent advantages of the PEC system, including an enhanced measurable signal, high potential for miniaturization, rapid testing, and low cost, amongst others. The growing number of published research reports on the subject calls for a comprehensive review of the various findings. This article is a review of studies on electrochemical (EC) and PEC sensors for ovarian cancer biomarkers in the last seven years (2016-2022). EC sensors were included because PEC is an improved EC; and a comparison of both systems has, expectedly, been carried out in many studies. Specific attention was given to the different markers of ovarian cancer and the EC/PEC sensing platforms developed for their detection/quantification. Relevant articles were sourced from the following databases: Scopus, PubMed Central, Web of Science, Science Direct, Academic Search Complete, EBSCO, CORE, Directory of open Access Journals (DOAJ), Public Library of Science (PLOS), BioMed Central (BMC), Semantic Scholar, Research Gate, SciELO, Wiley Online Library, Elsevier and SpringerLink.

Comparative study of the photocatalytic degradation of 2-chlorophenol under UV irradiation using pristine and Ag-doped species of TiO2, ZnO and ZnS photocatalysts.

A comparative photocatalytic degradation of 2-chlorophenol (2CP) in aqueous solution was investigated using pristine and Ag-doped semiconductor photocatalysts obtained from TiO2, ZnO and ZnS. Varying percentages (1, 3 and 5%) of Ag nanoparticles were doped on the semiconductor photocatalysts via the sol-gel method. The pristine and Ag-doped photocatalysts were characterized using UV-Vis diffuse reflectance spectroscopy, photo-luminescence spectroscopy, X-Ray diffractometry, Fourier transform infrared spectroscopy and transmission electron microscopy; and these techniques confirmed the successful syntheses of the pristine and Ag-doped species. The photocatalytic activities of all species for the degradation of 2CP were carried in photo-reactor using UV irradiation intensity of 1.4 mW/cm2 for 150 min; and the effects of various operating parameters (such as catalyst loading, pH and 2CP initial concentrations) were studied. The results showed enhanced 2CP degradation in the Ag-doped species in comparison to the pristine species while alkaline pH region was most suitable for 2CP degradation especially at low concentration. Lower loadings of the photocatalysts were usually more effective for the 2CP degradation and the degradation trend in the TiO2 and ZnS species was 5% Ag-doped >3% Ag-doped >1% Ag-doped > Pristine, while it was 1% Ag-doped >3% Ag-doped >5% Ag-doped > Pristine in the ZnO. Thus, although the Ag doping enhanced 2CP by all semiconductor photocatalysts, the Ag-doped TiO2 was more effective than the ZnO and ZnS species.

Chitosan nanocomposites for water treatment by fixed-bed continuous flow column adsorption: A review.

Nowadays, access to clean water sources worldwide and particularly in Southern Africa is inadequate because of its pollution by organic, inorganic, and microorganism contaminants. A range of conventional water treatment techniques has been used to resolve the problem. However, these methods are currently facing the confronts posed by new emerging contaminants. Therefore, there is a need to develop simple and lower cost-effective water purification methods that use recyclable bio-based natural polymers such as chitosan modified with nanomaterials. These novel functional chitosan-based nanomaterials have been proven to effectively eliminate the different environmental pollutants from wastewater to acceptable levels. This paper aims to present a review of the recent development of functional chitosan modified with carbon nanostructured and inorganic nanoparticles. Their application as biosorbents in fixed-bed continuous flow column adsorption for water purification is also discussed.

A comparative study of acid-treated, base-treated, and Fenton-like reagent-treated biomass for Cr(VI) sequestration from aqueous solutions.

A wide variety of biomass materials have been used for the removal of toxic chromium(VI) by biosorption. The current study investigated the efficacy of Macadamia nutshells treated with sodium hydroxide, nitric acid, and the Fenton-like reagent in the removal of Cr(VI). The adsorbents were characterized by FTIR, SEM, TGA, and elemental analysis. Effects of functional parameters influencing the adsorption of Cr(VI), solution pH (pH 1-11), contact time (5-250 min), concentration of adsorbent (1-10 g/L), and adsorbate concentration (10-200 mg/L) were investigated. The optimum conditions for biosorption were pH 1.4, adsorbent dose of 5 g/L, and 160 min of contact time. In all cases, the base-treated adsorbent displayed superior performance compared to others, with highest percent removal of 98%. The adsorbate-adsorbent interactions were better explained by the Freundlich isotherm and the pseudo-first-order rate model. The Macadamia-based adsorbents are potentially useful for Cr(VI) removal from aqueous solutions. PRACTITIONER POINTS: Three different chemical activators were investigated for the modification of Macadamia surface. The base-treated material exhibited the highest specific surface area of 12.1 m2 /g. The Cr(VI) adsorption performance for the base-treated material dwarfed the other materials. Excellent Cr(VI) removal efficiency in the presence of competitors was achieved.

Density functional theory study of gold(III)-dithiocarbamate complexes with characteristic anticancer potentials.

The application of gold as drug candidate dated back to 2500 BC and its relevance in medicine became more appealing following 1985 FDA approval of ingested Auranofin for the treatment of rheumatoid arthritis. In this study, we have provided a density functional theory (DFT) study of some gold(III)-dithiocarbamate complexes with characteristic anticancer potentials. DFT calculation of the reactivity and selectivity properties of these complexes with an enzyme template of thioredoxin reductase (TrxR) was carried out. The investigation proceeds with theoretical characterization of the selected compounds through spectroscopic analyses. IR and UV-vis analyses were carried out and the calculated values are comparable to experimental results. NMR assignment was determined for the gold compounds and the estimated theoretical chemical shift values agree with available experimental data from literature. The obtained DFT-based chemical parameters proved to be significant in evaluating the selectivity, reactivity and stability of the gold(III) complexes as potential anticancer moieties, specifically against TrxR. Calculated binding free energy gave similar order with the available in vitro inhibition profile of these gold(III)-dithiocarbamate complexes against TrxR. The outcome of this DFT study could serve as a useful guide towards future design of new and potent anticancer drug candidate. The investigated chemical reactivity properties could be considered and applied to a wide range of bioactive compounds and enzyme-inhibitor systems.

Antifouling Properties of Silver-Zinc Oxide Polyamide Thin Film Composite Membrane and Rejection of 2-Chlorophenol and 2,4-Dichlorophenol.

The silver-zinc oxide (Ag-ZnO) polyamide thin film composite (PA-TFC) membrane was prepared by interfacial polymerization. The Ag-ZnO/PA-TFC membrane was characterized by attenuated total reflectance fourier-transform infrared spectroscopy (ATR-FTIR) for polyamide functional groups and contact angle for surface hydrophilicity. The Ag-ZnO/PA-TFC membrane was further characterized by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) for morphology and surface roughness, respectively. The performance of the fabricated membrane was investigated using pure water flux, permeability, rejection, flux recovery, and fouling resistance using low molecular weight organic pollutants, 2-chlorophenol (2-CP) and 2,4-dichlorophenol (2,4-DCP). The results were compared to the neat (PA-TFC) membrane. It was observed that incorporation of Ag-ZnO nanocomposites into the PA-TFC membrane improved hydrophilicity, permeation, rejection, and fouling resistance properties of the membrane. The contact angle decreased from 62.8° to 54° for PA-TFC and the Ag-ZnO/PA-TFC membrane, respectively. The presence of Ag-ZnO enhanced permeability of the membrane from 0.9 (Lm-2h-1bar-1) to 1.9 (Lm-2h-1bar-1). Modification of the membrane with Ag-ZnO further showed an enhanced rejection of 2-CP and 2,4-DCP from 43% to 80% and 58% to 85%, respectively. The 2,4-DCP molecules were rejected more than 2-CP due to enhanced repulsive forces from the extra Cl ion. A high flux recovery of about 95% was achieved for the modified membrane compared to 64% for the neat membrane. The improved flux recovery was an indication of enhanced antifouling propensity.

Adsorptive Removal of Hexavalent Chromium by Diphenylcarbazide-Grafted Macadamia Nutshell Powder.

Macadamia nutshell powder oxidized by hydrogen peroxide solutions (MHP) was functionalized by immobilizing 1,5'-diphenylcarbazide (DPC) on its surface. The effectiveness of grafting was confirmed by the Fourier transform infrared spectrum due to the presence of NH and C=C stretches at 3361, 1591, and 1486 cm-1, respectively, on the grafted material which were absent in the nongrafted material. Thermogravimetric analysis revealed that the presence of DPC on the surface of Macadamia shells lowered the thermal stability from 300°C to about 180°C owing to the volatile nature of DPC. Surface roughness as a result of grafting was appreciated on the scanning electron microscopy images. Parameters influencing the adsorptive removal of Cr(VI) were examined and found to be optimal at pH 2, 120 min, 150 mg/L, and 2.5 g/L. Grafting MHP with DPC leads to an increase in the Langmuir monolayer capacity from 37.74 to 72.12 mg/g. Grafting MHP with DPC produced adsorbent with improved removal efficiency for Cr(VI).

Solvent-solvent fractionations of Combretum erythrophyllum (Burch.) leave extract: Studies of their antibacterial, antifungal, antioxidant and cytotoxicity potentials.

OBJECTIVE: To evaluate the biological activities of Combretum erythrophyllum (C. erythrophyllum) leaf extracts against infectious diseases' pathogenesis and their cytotoxicity potentials. METHODS: Powdered leaf material (300 g) of C. erythrophyllum was extracted (1:10 w/v) using acetone to obtain the crude extract. Liquid-liquid fractionation was performed on the crude acetone extract (30 g) using solvents of different polarity. The bioautographic method was used to detect the inhibition of bacterial and fungal growth by active compounds present in the crude and fractions. The extracts were then tested on bacterial strains: Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa; fungal strains: Candida albicans (C. albicans), Cryptococcus neoformans, and Aspergillus fumigatus, by microtitre dilution method for MIC determination. RESULTS: The extracts MIC values ranged between 0.08 and 2.50 mg/mL against the tested pathogens. Water fraction had the highest activity against bacteria strains, while the fungal assay revealed crude acetone extract and ethyl acetate fraction to be active against C. albicans (1.25 mg/mL), dichloromethane extract against C. albicans and A. fumigatus (0.16 mg/mL). Extract fractions showed a good antioxidant activity via DPPH, ABTS and hydroxyl radical scavenging assays, in the order: ethyl acetate > water > acetone > dichloromethane > hexane. The toxicity level of crude extract and fractions evaluated in Vero monkey kidney cells ranged from 34 to 223 µg/mL, while doxorubicin (IC50 = 7.19 µg/mL) served as the positive control. CONCLUSIONS: It can be concluded that the extracts of C. erythrophyllum are safe for medicinal use in folk medicine for treating infectious and stress related diseases.

Acetylcholinesterase-polyaniline biosensor investigation of organophosphate pesticides in selected organic solvents.

The behavior of an amperometric organic-phase biosensor consisting of a gold electrode modified first with a mercaptobenzothiazole self-assembled monolayer, followed by electropolymerization of polyaniline in which acetylcholinesterase as enzyme was immobilized, has been developed and evaluated for organophosphorous pesticide detection. The voltammetric results have shown that the formal potential shifts anodically as the Au/MBT/PANI/AChE/PVAc thick-film biosensor responded to acetylthiocholine substrate addition under anaerobic conditions in selected organic solvent media containing 2% v/v 0.05 M phosphate buffer, 0.1 M KCl (pH 7.2) solution. Detection limits in the order of 0.147 ppb for diazinon and 0.172 ppb for fenthion in acetone-saline phosphate buffer solution, and 0.180 ppb for diazinon and 0.194 ppb for fenthion in ethanol-saline phosphate buffer solution has been achieved.