Low Temperature Synthesis of Superparamagnetic Iron Oxide (Fe3O4) Nanoparticles and Their ROS Mediated Inhibition of Biofilm Formed by Food-Associated Bacteria

In the present study, a facile environmentally friendly approach was described to prepare monodisperse iron oxide (Fe3O4) nanoparticles (IONPs) by low temperature solution route. The synthesized nanoparticles were characterized using x-ray diffraction spectroscopy (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) measurements, Fourier-Transform Infrared Spectroscopy (FTIR), and Thermogravimetric analysis (TGA) analyses. XRD patterns revealed high crystalline quality of the nanoparticles. SEM micrographs showed the monodispersed IONPs with size ranging from 6 to 9 nm. Synthesized nanoparticles demonstrated MICs of 32, 64, and 128 μg/ml against Gram negative bacteria i.e., Serratia marcescens, Escherichia coli, and Pseudomonas aeruginosa, respectively, and 32 μg/ml against Gram positive bacteria Listeria monocytogenes. IOPNs at its respective sub-MICs demonstrated significant reduction of alginate and exopolysaccharide production and subsequently demonstrated broad-spectrum inhibition of biofilm ranging from 16 to 88% in the test bacteria. Biofilm reduction was also examined using SEM and Confocal Laser Scanning Microscopy (CLSM). Interaction of IONPs with bacterial cells generated ROS contributing to reduced biofilm formation. The present study for the first time report that these IONPs were effective in obliterating pre-formed biofilms. Thus, it is envisaged that these nanoparticles with broad-spectrum biofilm inhibitory property could be exploited in the food industry as well as in medical settings to curtail biofilm based infections and losses

Pharmacokinetics

Pharmacokinetics may be defined as the study of the dynamic movements of foreign chemicals (xenobiotics) during their passage through the body and as such encompass the kinetics of absorption, distribution, biotransformation/metabolism and excretion (ADME). It can simply be described as how the body handles xenobiotics. Pharmacokinetics uses mathematical equations (models) to describe the time course of ADME of xenobiotics in the body enabling us to better understand, interpret and even predict the nature and the extent of the biological effects (therapeutic or toxic) of xenobiotics. Several approaches are used in pharmacokinetic to describe the fate of xenobiotics in the body, including considering the body as one or more homogenous compartments based either on mathematical fitting or physiological properties. Description of the rates of the movement of xenobiotics into tissue(s) allows better interpretation and prediction of the fate of xenobiotics inside the body. This article will introduce the reader to basic concepts and principles of pharmacokinetic analysis using both compartmental and physiologically based models

Metabolism (Biotransformation)

Metabolism is the sum of all chemical reactions occurring in organisms at the cellular level to sustain life. The main purpose of metabolism is to convert food to energy to run cellular processes, build macromolecule building blocks, i.e., proteins, lipids, nucleic acids and carbohydrates and eliminate nitrogenous wastes. Metabolism is catalyzed by enzymes, which are protein in nature. There are thousands of enzymes in an organism catalyzing a great variety of metabolic pathways (e.g., glycolysis, Krebs cycle), the sum of which is called metabolism, and the molecules that are produced during the process (intermediates or final products) are called metabolites. Metabolism allows organisms to grow, maintain their structures, respond to their environment, and reproduce. Metabolism is usually divided into two categories: catabolism or the breaking down of organic matter by cellular respiration, and anabolism or the building up of cellular components like proteins and nucleic acids. Usually, catabolism releases energy and anabolism consumes energy. These two processes are linked through cofactors, especially through widely distributed pyridine nucleotides in the form of NAD, NADP and adenine nucleotides in the form of ATP, ADP, and AMP. A primary catabolic process is cellular respiration where starting molecules such as glucose are oxidized in a stepwise fashion to pyruvate and the released energy is captured in the form of ATP and water and carbon dioxide are released as waste products of oxidation. The ATP is in turn used to drive anabolic processes such as amino acid and lipid biosynthesis. In addition to converting food to energy, biosynthesizing cellular components, and eliminating nitrogenous waste, metabolism also covers biotransformation of foreign chemicals (xenobiotics) through a series of enzyme-catalyzed processes. Biotransformation alters the physicochemical properties of xenobiotics making them from accessible into cells, by enhancing their absorption across biological membranes, to eliminate into urine or bile, by enhancing hydrophilicity. The enzymes responsible for the xenobiotic biotransformation are often called drug-metabolizing enzymes. In the absence of biotransformation, xenobiotics we routinely exposed to, unintentionally or intentionally, for example, pharmaceuticals, industrial chemicals, pesticides, pollutants, cooked food containing pyrolysis products, alkaloids, plant metabolites of pesticides/chemicals, and toxins produced by plants, fungi and microbes will accumulate and eventually reach to toxic levels. This article is part of the absorption, distribution, metabolism, and excretion or ADME series; the four main processes governing chemical (including drug) disposition in biological systems. Therefore, this article will summarize some fundamental principles of xenobiotic biotransformation (or metabolism) in mammals and major enzymes involved in this process

Rethinking toxicity testing: Influence of aging on the outcome of long-term toxicity testing and possible remediation

Traditionally, toxicity testing is conducted at fixed dose rates (i.e., mg/kg/day) without considering life-changing events, e.g., stress, sickness, aging- and/or pregnancy-related changes in physical, physiological and biochemical parameters. In humans, life-changing events may cause systemic dose non-proportionality requiring modulation of drug dosage; similar changes occur in animals altering systemic dose during chronic/carcinogenic testing leading to late-occurring effects in some studies. For example, propylene monomethyl ether, an industrial chemical, initially induced sedation in rats and mice with recovery upon induction of hepatic CYPs after ~1 week. Sedation reappeared in rats but not in mice after ~12 months of exposure due to decreased CYP activity in rats, elderly mice were able to maintain slightly higher CYP activity avoiding recurrence of sedation. The systemic dose of two pharmaceuticals (doxazosin and brimonidine tartrate) increased up to 6-fold in ≥12-month old rats with no toxicity. In a rat reproductive toxicity study, systemic dose of 2,4-D, an herbicide, rapidly increased due to increased consumption of 2,4-D-fortified diet during pregnancy, lactation and neonatal growth, requiring adjustment to maintain the targeted systemic dose. Ideally, toxicological studies should be based on systemic dose with the option of modulating external dose rates to maintain the targeted systemic dose. Systemic dose can easily be monitored in selected core study animals at desired intervals considering recent developments in sampling and analysis at a fraction of the overall cost of a study

An environment Kuznets curve for ecological footprint: Evidence from GCC countries

Using country’s ecological footprint, the present empirical study aims to analyze the influence of the economic growth, energy consumption, and globalization on ecological footprint in the Environmental Kuznets curve (EKC) model for the Gulf Cooperation Council (GCC) countries; namely Bahrain, Oman, Qatar, Saudi Arabia and the UAE covering the period 1991-2017. By employing panel econometric approaches that considered issues of heterogeneity and cross sectional dependence, we find that all variables are first-difference stationary by using the cross-sectional augmented IPS (CIPS) and the cross-sectional augmented Dickey-Fuller (CADF) unit root tests. There exists a long-run relationship among examined variables tested by using the Westerlund cointegration tests statistics. By employing the dynamic ordinary least square (DOLS), and the fully modified ordinary least square (FMOLS), we also find that increase in the consumption of energy and globalization increases the ecological footprint, and the EKC hypothesis is not supported for the GCC countries. From the outcome of this empirical work a number of policy implications have been discussed in the study

Interference of phosphane copper (I) complexes of β-carboline with quorum sensing regulated virulence functions and biofilm in foodborne pathogenic bacteria: A first report

Foodborne pathogens are one of the major cause of food-related diseases and food poisoning. Bacterial biofilms and quorum sensing (QS) mechanism of cell–cell communication have also been found to be associated with several outbreaks of foodborne diseases and are great threat to food safety. Therefore, In the present study, we investigated the activity of three tetrahedrally coordinated copper(I) complexes against quorum sensing and biofilms of foodborne bacteria. All the three complexes demonstrated similar antimicrobial properties against the selected pathogens. Concentration below the MIC i.e. at sub-MICs all the three complexes interfered significantly with the quorum sensing regulated functions in C. violaceum (violacein), P. aeruginosa (elastase, pyocyanin and alginate production) and S. marcescens (prodigiosin). The complexes demonstrated potent broad-spectrum biofilm inhibition in Pseudomonas aeruginosa, E. coli, Chromobacterium violaceum, Serratia marcescens, Klebsiella pneumoniae and Listeria monocytogenes. Biofilm inhibition was visualized using SEM and CLSM images. Action of the copper(I) complexes on two key QS regulated functions contributing to biofilm formation i.e. EPS production and swarming motility was also studied and statistically significant reduction was recorded. These results could form the basis for development of safe anti-QS and anti-biofilm agents that can be utilized in the food industry as well as healthcare sector to prevent food-associated diseases. Keywords: Copper compounds, Biofilm, Quorum sensing, Food safety, Pathogen