Colorimetric Detection Of Lead And Metallothioneins Based On The Conformational Switching Of TBA By Lead

Lead is an environmental pollutant, with severe adverse effect on human health.It can induce the synthesis of metallothioneins (MTs), which have been proposed as apotential biomarker for metal pollution due to their significant responses to heavymetal exposure such as lead. Therefore, it is of significance to develop a sensitive,specific assay for both MTs and lead to evaluate heavy metal pollution inenvironment and explore the function of MTs. In this paper, we established botha dual channel assay for both MTs and lead and a detection method for MTsusing gold nanoparticles as probe, which all used thrombin binding aptamer(TBA) as molecular recognition element. The proposed methods have beenapplied for the determination of the practical samples, which are reliable andsatisfying.In Chapter2, a dual channel assay for lead ion and MTs detection has beendeveloped based on TBA-Pb2+-hemin DNAzyme. TBA is induced by Pb2+toform the stable G-quadruplex, which can bind to hemin to form mimickingperoxidase. The peroxidase catalyses the oxidation of ABTS by H2O2togenerate a blue-green product ABTS˙+, leading to the enhancement of theabsorbance of the system at415nm. Adjusting cPb2+to excessive extent, thecatalytic activity of the system was decreased. When Pb2+was captured by MTs,the catalytic activity of the system resumed. With increasing amount of MTs, theabsorbance of the system at415nm was increased gradually. Thereby, a dual channelassay for lead ion and MTs was developed. Under the optimum condition, the ΔAwas directly proportional to the concentration of Pb2+in the range of1.07×10-10~2.01×10-9mol·L-1. The equation of linear regression was ΔA==0.409c（×10-9mol·L-1）+40.7with a correlation coefficient (r2) of0.9932. The limit of detection(LOD) was3.21×10-11mol·L-1. And a linear correlation existed between the A andthe concentration of MTs in the range of5.60×10-8~3.70×10-7mol·L-1. The equationof linear regression was ΔA==0.133c（×10-7mol·L-1）+0.068, r2=0.9945. The limit of detection (LOD) was1.68×10-8mol·L-1.In Chapter3, a colorimetric method for MTs detection was developedbased on TBA-Pb2+complex using gold nanoparticle as probe. The aggregationof gold nanoparticles was changed by adding MTs to TBA-Pb2+complex solution,leading to color change of the system. The ΔA was directly proportional to theconcentration of MTs in the range of2.06×10-8~6.93×10-7mol·L-1. The equation oflinear regression was ΔA=0.454+0.115c (10-8mol·L-1), r2=0.9915. The limit ofdetection (LOD) was6.18×10-8mol·L-1. The proposed method is simple, rapid andselective, and allows direct analysis of the samples by the naked eyes without costlyinstruments.