The Effect of the Duration and Temperature of Infusion on the Heavy Metal Content of Green Tea

Tea is one of the most popular drinks in the world, which contains several important essential micro nutrients that are beneficial to human health. On the other hand, the contamination of tea leaves by heavy metals may pose serious problems to human health. In this research, the concentration of toxic metals (Al, As, Pb, Cr, Cd, and Ni) and essential heavy metals (Fe, Zn, Cu and Mn) in Iranian green tea (IGT) leaves and its infusion were determined using atomic absorption spectrometry. Additionally, the effect of the duration (10, 30 and 90 min) and temperature (80 and 100 ºC) of tea infusion on the content of heavy metals was studied. There was a significant difference between all samples at different time and temperatures. The concentrations range of heavy metals in IGT leaves was 1332-0.023 mg/kg. The highest and lowest metal content was observed for Al and Cd, respectively. The results showed that the heavy metal contents in IGT infusion varied between 11.7 mg/L for Al to 0.0002 mg/L for Cd. The highest and lowest percentage of metal extracted into IGT infusion was observed for Ni and Fe as 73.6 and 2.4, respectively

Intellectual modifying a bare glassy carbon electrode to fabricate a novel and ultrasensitive electrochemical biosensor: Application to determination of acrylamide in food samples

Acrylamide (AA) is a neurotoxin and carcinogen which is mainly formed in foods containing large quantities of starch processed at high temperatures and its determination is very important to control the quality of foods. In this work, a novel electrochemical biosensor based on hemoglobin-dimethyldioctadecylammonium bromide (HG-DDAB)/platinum-gold-palladium three metallic alloy nanoparticles (PtAuPd NPs)/chitosan-1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (Ch-IL)/multiwalled carbon nanotubes-IL (MWCNTs-IL)/glassy carbon electrode (GCE) is proposed for ultrasensitive determination of AA in food samples. Development of the biosensor is based on forming an adduct by the reaction of AA with α-NH2 group of N-terminal valine of HG which decreases the peak current of HG-Fe+3 reduction. The modifications were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), energy dispersive X-ray spectroscopic (EDS) and scanning electron microscopy (SEM). Under optimized conditions, the biosensor detected AA by square wave voltammetry (SWV) in two linear concentration ranges of 0.03?39.0 nM and 39.0?150.0 nM with a limit of detection (LOD) of 0.01 nM. The biosensor was able to selective detection of AA even in the presence of high concentrations of common interferents which confirmed that the biosensor is highly selective. Also, the results obtained from further studies confirmed that the proposed biosensor has a short response time (less than 8 s), good sensitivity, long term stability, repeatability, and reproducibility. Finally, the proposed biosensor was successfully applied to determine AA in potato chips and its results were comparable to those obtained by gas chromatography-mass spectrometry (GC-MS) as reference method.Fil: Varmira, Kambiz. Kermanshah University Of Medical Sciences; IránFil: Abdi, Omid. Kermanshah University Of Medical Sciences; IránFil: Gholivand, Mohammad Bagher. Razi University; IránFil: Goicoechea, Hector Casimiro. Universidad Nacional del Litoral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Jalalvand, Ali R.. Kermanshah University Of Medical Sciences; Irá

A gold nanoparticle colorimetric probe-based biosensor for rapid detection of VIM-2 and IMP-1 metallo-beta lactamase genes

Despite actions to reduce the prevalence of antibiotic resistance, antibiotic resistance remains a major threat in the treatment and control of infections. Therefore, the development of rapid diagnostic methods plays a significant role in the detection of antibiotic resistance genes and the management of hospital infections. This study aimed to design and develop a gold nanoparticle colorimetric probe-based biosensor was developed for faster and more accurate detection of VIM-2 and IMP-1 Metallo-Beta-Lactamases (MBLs) genes in different clinical samples. After identifying 248 clinical isolates of bacteria with standard biochemical methods and evaluation of antibiotic resistance and identifying MBL-producing strains, PCR method was carried out for detecting VIM-2 and IMP-1 genes as a gold standard. Synthesis of AuNPs were done by citrate reduction method and AuNP -IMP-1 biosensor was used for detecting IMP-1 gene, after functionalization of thiol modified oligonucleotides. AuNP biosensor and IMP-1 PCR were compared in terms of detection indices. Method PCR was defined as the gold standard. Bacteria examined, 87 isolates were resistant to carbapenems. Out of the 87 carbapenem-resistant isolates, 85 (34.2%) were phenotypically positive for MBLs. Also, 7 isolates had IMP-1 gene, but none of them carried VIM-2 gene. The AuNP biosensor had 100% sensitivity, specificity, PPV and NPV, respectively. The final detection limit of IMP-1 genomic DNA (LOD) by PCR and AuNP-IMP-1 biosensor technique was 0.1 fg/μl (2.5 fg/25 reactions) and 0.001 fg/μl (0.025 fg/25 reaction), respectively. According to the promising results of Diagnostic indices, AuNP biosensor is a more efficient and accurate method for direct and indirect detection of antibiotic resistance genes in clinical samples

Fabrication of a novel enzymatic electrochemical biosensor for determination of tyrosine in some food samples

In this work, fabrication of a novel and ultrasensitive electrochemical biosensor based on immobilization oftyrosine hydroxylase onto palladium-platinum bimetallic alloy nanoparticles/chitosan-1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide/graphene-multiwalled carbon nanotubes-IL/glassycarbon electrode for determination of L-tyrosine in some high tyrosine foods including cheese, egg and yogurtwas reported. Immobilization of tyrosine hydroxylase onto the surface of the biosensor was performed bycross-linking tyrosine hydroxylase and chitosan through the addition of glutaraldehyde. Enzymatic biosensorsemploy the affinity and selectivity of catalytically active proteins towards their target molecules and here, thetyrosine hydroxylase selectively catalyzes the conversion of tyrosine to levodopa which can be oxidized atlower potentials than tyrosine. The modifications were characterized by electrochemical impedancespectroscopy, cyclic voltammetry, energy dispersive X-ray spectroscopic and scanning electron microscopy.Under optimal conditions, the biosensor detected tyrosine in concentration ranges of 0.01×10-9 to 8.0×10-9 molL-1 and 8.0×10-9 to 160.0×10-9 mol L-1 with a limit of detection of 0.009×10-9 mol L-1. The biosensor was ableto selective determination of tyrosine even in the presence of common interferents therefore, the biosensor washighly selective. The biosensor also showed good operational stability, antifouling properties, sensitivity,repeatability and reproducibility.Fil: Varmira, Kambiz. Kermanshah University Of Medical Sciences; IránFil: Mohammadi, Ghobad. Kermanshah University Of Medical Sciences; IránFil: Mahmoudi, Majid. Kermanshah University Of Medical Sciences; IránFil: Khodarahmi, Reza. Kermanshah University Of Medical Sciences; IránFil: Rashidi, Khodabakhsh. Kermanshah University Of Medical Sciences; IránFil: Hedayati, Mehdi. The Cellular And Molecular Endocrine Research Center; IránFil: Goicoechea, Hector Casimiro. Universidad Nacional del Litoral; ArgentinaFil: Jalalvand, Ali R.. Kermanshah University Of Medical Sciences; Irá