The role of tannic acid and sodium citrate in the synthesis of silver nanoparticles.

We describe herein the significance of a sodium citrate and tannic acid mixture in the synthesis of spherical silver nanoparticles (AgNPs). Monodisperse AgNPs were synthesized via reduction of silver nitrate using a mixture of two chemical agents: sodium citrate and tannic acid. The shape, size and size distribution of silver particles were determined by UV-Vis spectroscopy, dynamic light scattering (DLS) and scanning transmission electron microscopy (STEM). Special attention is given to understanding and experimentally confirming the exact role of the reagents (sodium citrate and tannic acid present in the reaction mixture) in AgNP synthesis. The oxidation and reduction potentials of silver, tannic acid and sodium citrate in their mixtures were determined using cyclic voltammetry. Possible structures of tannic acid and its adducts with citric acid were investigated in aqueous solution by performing computer simulations in conjunction with the semi-empirical PM7 method. The lowest energy structures found from the preliminary conformational search are shown, and the strength of the interaction between the two molecules was calculated. The compounds present on the surface of the AgNPs were identified using FT-IR spectroscopy, and the results are compared with the IR spectrum of tannic acid theoretically calculated using PM6 and PM7 methods. The obtained results clearly indicate that the combined use of sodium citrate and tannic acid produces monodisperse spherical AgNPs, as it allows control of the nucleation, growth and stabilization of the synthesis process. Graphical abstractᅟ.

Electrodes Modified with Composite Layers Based on Poly(3,4-ethylenedioxythiophene) as Sensors for Paracetamol.

Two sensors for paracetamol were obtained on the basis of a GC electrode modified with poly(3,4-ethylenedioxythiophene) (PEDOT). The first sensor was a GC electrode modified with a conductive composite layer of PEDOT doped with poly(4-lithium styrenesulfonic acid) (PSSLi), and the second one was a GC electrode modified by a composite of PEDOT doped with PSSLi and multiwall carbon nanotubes (MWCNT). A conductive PEDOT polymer film was used as an electron mediator with a rich electron cloud. Both sensors were developed for the determination of paracetamol (ACOP) in the presence of interference compounds. Differential pulse voltammetry (DPV) and adsorptive stripping differential pulse voltammetry (AdsDPV) were applied as analytical methods. The modified electrodes were successfully employed for the determination of ACOP in a pharmaceutical formulation.

Paraoxonase activity as a marker of exposure to xenobiotics in tobacco smoke.

The paraoxonase (PON) family is composed of 3 proteins (PON1, PON2, and PON3), each of which plays a crucial role in the body, displaying antioxidant, anti-inflammatory, and antiatherosclerotic properties. The activities and properties of PON proteins can be modulated by a number of environmental factors, including cigarette smoke. In the present article, a review of existing literature is employed to analyze both the direct and the indirect impact of cigarette smoking on the activity of members of the PON family. Cigarette smoking leads to direct inhibition of the hydrolytic activity of PON enzymes by modification of thiol groups, by the reactions of free radicals, or by inhibiting enzyme-active regions with heavy metals. It has been shown that cigarette smoking correlates with a decrease in high-density lipoprotein (HDL) concentration as well as with an increase in other components of the lipid profile (low-density lipoprotein (LDL), triglycerides, and total cholesterol). By decreasing HDL levels, cigarette smoking likely acts indirectly to induce a decline in PON1 activity. Inhibition of PON1 activity by smoking is a reversible process after cessation of exposure to the xenobiotics in tobacco smoke.

Review: The role of paraoxonase in cardiovascular diseases.

Paraoxonase (PON) is a group of proteins present in three forms (PON1, PON2, PON3) encoded by genes PON1, PON2, and PON3. PON1 and PON3 are plasma enzymes, structurally and functionally related to HDL, while PON2 is characterized by an intracellular location. Many polymorphisms of PON have been observed. The most widely and accurately described is the single nucleotide polymorphism, which impacts the conversion of glutamine (Q) to arginine (R) and has the effect of altering the hydrolytic activity of the PON1 form. Each PON form plays an important role in the human body, and they exhibit antioxidant, antiatherosclerotic, and anti-inflammatory influences. The PON family inhibits LDL oxidative modification and suppresses the differentiation of monocytes into macrophages, which is the first stage in the development of atherosclerosis. Furthermore, PON1 prevents the accumulation of oxidized LDL and stimulates cholesterol efflux from macrophages. Establishing these functions has led researchers to study the relationship between PON family and lipids in healthy subjects and in patients with diagnosed cardiovascular diseases. There is a certain relation between PON1 polymorphism and HDL and LDL particles. The PON1192RR genotype is associated with lower HDL levels and higher LDL levels. Lower concentrations of LDL in people with genotype PON155LL have been noted. These dependencies have been observed among healthy people, but the relation disappears in patients with cardiovascular diseases.

Immobilization of glucose oxidase on modified electrodes with composite layers based on poly(3,4-ethylenedioxythiophene).

Two modified electrodes with immobilized glucose oxidase were developed. Modification with poly(3,4-ethylenedioxythiophene) (PEDOT) and polyacrylic acid (PAA) doped with poly(4-lithium styrenesulfonic acid) (PSSLi) in a newly elaborated procedure was used in the first electrode. The second one presents innovative solution and consists of two sublayers; one of them was PEDOT doped with PSSLi and the other was composed of PEDOT and anthranilic acid (AA) doped with poly(4-styrenesulfonic acid) (PSSH). Glucose oxidase was covalently bonded with the carboxyl groups of the polymer through N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (WSC). The activity of immobilized enzyme was confirmed by spectrophotometry using the reaction of the produced hydrogen peroxide with o-dianisidine. The procedure for immobilization was optimized. It was found that the choice of an appropriate doping agent and its concentration were significant and 0.1M PSSLi proved to be the best doping agent. The most efficient immobilization was established for WSC and GOD concentration at the level of 4mg/ml and 5mg/ml respectively. In both cases, it was found that a small deviation from the concentrations determined to cause a sharp decrease in the activity of the enzyme, which was proven by spectrophotometric measurements. Prepared electrodes were active over a month with repeatable measurement results.