Study On The Effect Of Functional Nanomaterials/Hemin To L-tyrosine And Escherichia Coli O157:H7

Nowadays, the underlying pathogenic bacteria in food and drinking water still threatened human's life. There is no doubt that the development of sustained, rapid, effective means and methods for the bacteria detection and disinfection must be enforced. The chemical modified electrode (CME), in many ways, has the advantages, such as cheap, efficient, high sensitivity and environment-friendly. These advantages can be well meet the demand of disinfection at the present, and the electrochemical disinfection method has been widespread concerned. Gold nanoparticles (AuNPs)-based colorimetric biosensing assays have recently attracted considerable attention in diagnostic applications due to their simplicity and versatility. Although the development of this method has only more than ten years, it must be has great potential in the pathogenic bacteria detection field.In this paper, we have studied the effect of the functional materials to the biological molecules and their application in the field of bacteria detection and disinfection, which could be divided into three aspects as follow:(1) A novel amperometric sensor was fabricated based on the immobilization of hemin onto the poly (amidoamine)/multi-walled carbon nanotubes (PAMAM/MWCNT) nanocomposite film modified glassy carbon electrode (GCE). Electrochemical impendence spectroscopy (EIS), cyclic voltammetry (CV) and ultraviolet visible (UV-vis) adsorption spectroscopy were used to investigate the possible state and electrochemical activity of the immobilized hemin. In the Hemin/PAMAM/MWCNT nanocomposite film, MWCNT layer possessed excellent inherent conductivity to enhance the electron transfer rate, while the layer of PAMAM greatly enlarged the surface average concentration of hemin (Γ) on the modified electrode. Therefore, the nanocomposite film showed enhanced electrocatalytical activity towards the oxidation of L-tyrosine. In pH 7.0 phosphate buffer solution (PBS), the sensor exhibits a wide linear range from 0.1 to 28.8μM L-tyrosine with a detection limit of 0.01μM and a high sensitivity of 0.31μAμM-1 cm^-2. In addition, the response time of the L-tyrosine sensor is less than 5 s. The excellent performance of the sensor is largely attributed to the electro-generated high reactive oxoiron (IV) porphyrin (O=FeIV-P) which effectively catalyzed the oxidation of L-tyrosine. A mechanism was herein proposed for the catalytic oxidation of L-tyrosine by oxoiron (IV) porphyrin complexes.(2) The electrochemical inactivation of microorganisms using Escherichia coli (E. coli) as testing species by a hemin/graphite felt (GF) composite electrode was investigated. This composite electrode was constructed by chemical bonding hemin molecules onto the amino mineralized GF (AGF) surface. Then, it was characterized systematically by electrochemical methods, and the kinetic parameters of the modified electrode were investigated. The hemin molecules at the surface of the composite electrode have high activity to the reduction of O₂. When the composite electrode was applied with negative potentials, the dissolved oxygen was electrochemical catalytic reduced to reactive oxygen species (ROS, such as H₂O₂ and·OH) at the cathode surface. The ROS can cause biological damage and eventually result in the death of bacteria. The sterilizing rate could be obtained up to 99.9% in sixty minutes inactivation. Thus, this composite electrode was expected to be applied to the efficient disinfection of drinking water at low potential (-0.6 V vs. SCE) without any addition of chloride.(3) This report illustrates a new strategy in colorimetric assay for the direct detection of gram-negative bacteria - a commercially available compound, mercaptoethylamine (MEA), when presented on gold nanoparticles (AuNPs), could be used for the colorimetric detection of E. coli O157:H7.