| Cysteine, an essential component of many proteins and organism, is involved in many important physiological chemical reactions.The accurate, rapid and in vivo detection of cysteine is significant for the diagnosis of diseases and unravelling the mechanism underlying the complex biological processes. Among the tremendous analysis methods, electrochemical methods have showed great prospective for the in vivo monitoring of cysteine due to their advantages of high sensitivity and easy minimized detection equipment. Recently, many electrochemical methods have been developed for the highly sensitive detection of cysteine, however, they still suffer from the problem of poor selectivity due to the high detection potential resulted from the sluggish electron transfer rate of mercapto group contained chemicals. To solve this problem, this thesis developed two methods which can achieve the goal of highly sensitivie and selective detection of cysteine, even when it is coexisted with other biothiols such as glutathione and homocysteine. The main work of the paper is listed as follows1. Electrochemically reduced graphene oxide for highly selective and sensitive cysteine sensing.A simple strategy for the sensitive and selective discrimination of cysteine was successfully established by assembling electrochemically reduced graphene oxide and Nation hybrid nanocomposite (Er-GRO-Nafion) on glassy carbon electrode. The amount and type of oxygen-containing functional groups were finely and readily controlled by electrochemical method, and their functions in the sensitive detection of cysteine were studied. The co-interaction of specific characters of Er-GRO such as superior conductivity, three dimensional interpenetrating network, and abundant amount of active chemical oxygen groups led to extremely high electro-catalytic activity of the Er-GRO-Nafion/GCE towards the electrochemical oxidation of cysteine at a low detection potential of-0.014V (vs. SCE). The electrocatalytic behaviour of Er-GRO was further used for the sensitive detection of cysteine. Under optimized conditions, the calibration curve was linear in the range from0.2μM to2.5mM. The electrochemical sensor showed strong antifouling ability, good stability and selectivity. It could effectively exclude the interferences from other biothiols and biological relevant species without coupling with any separation instruments, thus shows great perspective for in vivo analysis of biological samples. 2. Low potential and selective detection of eysteine on a hydrophilically treated commercial glassy carbon electrodeSelective discrimination of eysteine was achieved on a hydrophilically treated glassy carbon electrode, without the modification of any nanomaterials and biological reagents. The activation process performed in an acidic PBS made the commercial available electrode surface full of oxygen-containing functional groups and with improved wettability, which has been verified by EDX and surface water contact angle experiments, thus showed highly catalytic ability to the electrochemical oxidation of eysteine. The eysteine could be detected on the hydrophilically treated electrode at a low potential of+0.006V, which is much lower than most of the eysteine based electrochemical biosensors and is beneficial for improving the selectivity of the sensor. Under the optimized condition, the proposed electrochemical sensor showed a high sensitivity, a wide liner rang from16μM to6mM, good stability and reproducibility, and strong antifouling ability. In addition, it could effectively exclude the interferences from other biothiols and biological relevant species without coupling with any separation instruments, thus shows great perspective for in vivo analysis of biological samples... |
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