Electrochemical behavior of flufenamic acid at amberlite XAD-4 resin and silver-doped titanium dioxide/ amberlite XAD-4 resin modified carbon electrodes

Voltammetric determination of flufenamic acid and adsorption studies with biochar in the absence / presence of cetyltrimethylammonium bromide

In this article, a novel method for the determination of Flufenamic acid (FFA, pharmaceutical pollutant) is presented based on voltammetric oxidation at a carbon paste electrode (CPE) in-situ modified with cetyltrimethylammonium bromide (CTAB). The experimentally proved "erosion effect" of this surfactant enhanced the sensitivity of detection in the SWASV mode allowing us to quantify the analyte down to the low nanomolar level (with a LOD of 5.5 × 10-9 mol L-1 FFA). The respective (electro)analytical procedure has been shown to be applicable in monitoring the residua of FFA in model aqueous solutions simulating polluted and then purified industrial wastewater. Furthermore, the process of removal of FFA via adsorption onto selected carbonaceous materials was studied in detail, when two conventional active carbon adsorbents were compared with biochar (BC) - a cheaper alternative. It has been found that although the latter as such does not attain the adsorption capacities of both active carbons, in-situ modification of BC with CTAB enhances its adsorption capacity up to 40% (from 125 mg g-1 to ca. 175 mg g-1), as well as fastens the adsorption process (3x); both under conditions of testing. When considering the final procedure for removal of residual pollutant from model water samples with BC and the method of choice for quantification of the corresponding change(s) of FFA before and after purification, the principal role of CTAB has been revealed and defined. Namely, the functioning of CTAB had, in fact, double benefit: (i) enhancement of adsorptive capabilities of the BC adsorbent and (ii) improved sensitivity of the voltammetric detection with in-situ modified CPE.

Copper oxide nanoflowers/poly-l-glutamic acid modified advanced electrochemical sensor for selective detection of l-tryptophan in real samples

The main objective of this research work is to develop a low-cost sensor to detect l-tryptophan (L-tryp) in real sample medium based on a modified glassy carbon electrode. For this, copper oxide nanoflowers (CuONFs) and poly-l-glutamic acid (PGA) were used to modify GCE. The prepared NFs and PGA coated electrode was characterized using field emission scanning electron microscope (FE-SEM) with energy dispersive X-ray (EDX) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Furthermore, the electrochemical activity was performed by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The modified electrode showed excellent electro-catalytic activity towards L-tryp detection in PBS solution at neutral pH 7.0. Based on the physiological pH condition, the proposed electrochemical sensor can detect L-tryp concentration with a linear range of 1.0 × 10^-4-8.0 × 10^-8 molL^-1 with having a detection limit of 5.0 × 10^-8 molL^-1 and sensitivity of 0.6μA/μMcm². The selectivity of L-tryp was tested with a mixture of salt and uric acid solution at the above conditions. Finally, this strategy demonstrated excellent recovery value in real sample analysis like milk and urine.

Green Synthesis and Potential Antibacterial Applications of Bioactive Silver Nanoparticles: A Review

Green synthesis of silver nanoparticles (AgNPs) using biological resources is the most facile, economical, rapid, and environmentally friendly method that mitigates the drawbacks of chemical and physical methods. Various biological resources such as plants and their different parts, bacteria, fungi, algae, etc. could be utilized for the green synthesis of bioactive AgNPs. In recent years, several green approaches for non-toxic, rapid, and facile synthesis of AgNPs using biological resources have been reported. Plant extract contains various biomolecules, including flavonoids, terpenoids, alkaloids, phenolic compounds, and vitamins that act as reducing and capping agents during the biosynthesis process. Similarly, microorganisms produce different primary and secondary metabolites that play a crucial role as reducing and capping agents during synthesis. Biosynthesized AgNPs have gained significant attention from the researchers because of their potential applications in different fields of biomedical science. The widest application of AgNPs is their bactericidal activity. Due to the emergence of multidrug-resistant microorganisms, researchers are exploring the therapeutic abilities of AgNPs as potential antibacterial agents. Already, various reports have suggested that biosynthesized AgNPs have exhibited significant antibacterial action against numerous human pathogens. Because of their small size and large surface area, AgNPs have the ability to easily penetrate bacterial cell walls, damage cell membranes, produce reactive oxygen species, and interfere with DNA replication as well as protein synthesis, and result in cell death. This paper provides an overview of the green, facile, and rapid synthesis of AgNPs using biological resources and antibacterial use of biosynthesized AgNPs, highlighting their antibacterial mechanisms.

Bovine serum albumin-coated titanium dioxide modified electrochemical interface for enantioselective discrimination of D/L-aspartic acid

Due to the similar physicochemical properties, the discrimination of chiral isomers faces huge challenges in drug production and biochemical analysis. Herein, the bovine serum albumin-coated titanium dioxide (bovine serum albumin [BSA]/TiO₂ ) was modified as a novel electrochemical interface for efficient, simple, and enantioselective discrimination of aspartic acid enantiomers (D/L-Asp) based on the electrochemical impedance spectroscopy (EIS). Utilizing the structural characteristics of large cavity and high specific surface area, TiO₂ material provided sufficient space for adequate loading of BSA. The BSA/TiO₂ electrochemical interface was successfully fabricated to support abundant chiral recognition sites. The enantioselective discrimination of D/L-Asp was achieved on the interface with a good linear relationship against the impedance difference in the concentration range from 1 to 1000 nM with the detection limit of 0.37 nM for L-Asp and 0.94 nM for D-Asp, reaching the identification coefficient (I_c  = K_L /K_D ) of 1.85. The proposed interface is easy to form with a stable formation of BSA in TiO₂ microporous architecture, which maintained the desired stability and reproducibility. For the unknown racemic solution, I_c levels of different enantio-ratios of D/L-Asp were effectively obtained to evaluate the chiral percentage of racemic sample. The possible mechanism of chiral recognition by density function theory (DFT) was confirmed with a stronger adsorption to L-Asp in accordance with our experiment results, reinforcing the validity of our presented interface. The BSA/TiO₂ electrochemical interface with robust enantioselective discrimination of D/L-Asp has great potential for the practical application in pharmaceutical surveillance and food security.

NiCo2O4 Nano-/Microstructures as High-Performance Biosensors: A Review

Non-enzymatic biosensors based on mixed transition metal oxides are deemed as the most promising devices due to their high sensitivity, selectivity, wide concentration range, low detection limits, and excellent recyclability. Spinel NiCo2O4 mixed oxides have drawn considerable attention recently due to their outstanding advantages including large specific surface area, high permeability, short electron, and ion diffusion pathways. Because of the rapid development of non-enzyme biosensors, the current state of methods for synthesis of pure and composite/hybrid NiCo2O4 materials and their subsequent electrochemical biosensing applications are systematically and comprehensively reviewed herein. Comparative analysis reveals better electrochemical sensing of bioanalytes by one-dimensional and two-dimensional NiCo2O4 nano-/microstructures than other morphologies. Better biosensing efficiency of NiCo2O4 as compared to corresponding individual metal oxides, viz. NiO and Co3O4, is attributed to the close intrinsic-state redox couples of Ni3+/Ni2+ (0.58 V/0.49 V) and Co3+/Co2+ (0.53 V/0.51 V). Biosensing performance of NiCo2O4 is also significantly improved by making the composites of NiCo2O4 with conducting carbonaceous materials like graphene, reduced graphene oxide, carbon nanotubes (single and multi-walled), carbon nanofibers; conducting polymers like polypyrrole (PPy), polyaniline (PANI); metal oxides NiO, Co3O4, SnO2, MnO2; and metals like Au, Pd, etc. Various factors affecting the morphologies and biosensing parameters of the nano-/micro-structured NiCo2O4 are also highlighted. Finally, some drawbacks and future perspectives related to this promising field are outlined.

Tolfenamic acid on-line preconcentration strategy on carbon nanotubes minicolumn with fluorimetric detection

Nonsteroidal anti-inflammatory agents (NSAIDs) are a group of pharmaceuticals considered one of the most popular drugs used in clinical practice applied to the treatment of acute and chronic conditions. Some pharmaceuticals products are excreted reaching the environment and altering the balance of ecosystems. This work proposes a new fluorimetric flow injection (FI) methodology for the NSAID tolfenamic acid quantification based on the quenching effect of the analyte on fluorescent signal of bovine serum albumin fluorophore. Results put in evidence a mechanism of static quenching, with a Stern Volmer constant value of 1.8 × 10⁷ L mol^-1. To achieve the selective on-line preconcentration of analyte, a carbon nanotubes mini column was introduced in the FI configuration producing a beneficial effect on high sampling frequency, minimum sample and reagents consumption. The experimental factors that influence batch fluorescent signal and FI analysis have been studied and optimized. At optimal experimental conditions, an adequate tolerance to foreign species was shown. With the flow configuration, a LOD of 0.019 μg L^-1, a LOQ of 0.058 μg L^-1 were obtained with a sampling rate of 30 samples h^-1. The new methodology was successfully applied to analyte determination in tap water and pharmaceutical and factory waste samples with recuperation near to 100%.

A novel amperometric determination of flufenamic acid using CuMOF ribbons incorporated with activated carbon

Electrochemical detection of FFA using AC–CuMOF modified electrode.

Electrocatalytic behavior of a heterostructured nanocomposite sensor for aminotriazole

Heterostructured nano-composite sensor for aminotriazole.

ZnO-based nanostructured electrodes for electrochemical sensors and biosensors in biomedical applications

Fascinating properties of ZnO nanostructures have created much interest due to their importance in health care and environmental monitoring. Current worldwide production and their wide range of applications signify ZnO to be a representative of multi-functional oxide material. Recent nanotechnological developments have stimulated the production of various forms of ZnO nanostructures such as nano-layers, nanoparticles, nanowires, etc. Due to their enhanced sensing properties, improved binding ability with biomolecules as well as biological activities have enabled them as suitable candidates for the fabrication of biosensor devices in the biomedical arena. In this review, the synthesis of ZnO nanostructures, mechanism of their interaction with biomolecules and their applications as sensors in health care area are discussed considering the biosensors for molecules with small molecular weight, infectious diseases, and pharmaceutical compounds.

Porous carbon supported nanoceria derived from one step in situ pyrolysis of Jerusalem artichoke stalk for functionalization of solution-gated graphene transistors for real-time detection of lactic acid from cancer cell metabolism

Effective detection of biomarkers for tumor cells has been the focus of attention. In this work, we have successfully fabricated a highly sensitive sensor based on solution-gated graphene transistors (SGGT) for detecting lactic acid content accumulated in tumor cells through their glycolysis metabolism. The sensing mechanism of the lactic acid sensor is attributed to electrochemical catalysis of H₂O₂ produced by the oxidation of lactic acid by lactate oxidase near the gate electrode. The key component of the sensor is the functionalization of porous carbon loaded with ceria nanoparticles derived from a novel one step in situ pyrolysis of pretreated Jerusalem artichoke stalk, which significantly improved the sensor sensitivity, i.e. a detection limit as low as 300 nM and linear range from 3 μM to 300 μM. The optimized lactic acid sensor has successfully applied to the detection of lactic acid in practical cell culture samples with high credibility. The SGGT-based lactic acid biosensor shows great potential for the application in tumor microenvironment due to its superior biocompatibility and accuracy.