Study On Electrochemical Biosensors For Biologically Active Substances Detection

Effective and sensitive quantification of biologically active substances involved in brain functions, such as glucose, lactate, ascorbic acid, dopamine and uric acid and so on, remains very imperative because of its great role in the diagnosis and therapy of diseases. The abnormal content of these biologically active substances would result in physiological changes of tissue and organ, therefore, the quantification of them has practical significance to exploit fast, sensitive and reliable methods to detect these biologically active substances. However, the chemical and physiological complexity of the central nervous system presents challenges for the development of analytical protocols for quantitatively monitoring neurochemicals. A great deal of efforts have been made for seeking to develop the rationally design of multifunctional electron-transfer interface between an immobilized enzyme and an electrode, the immobilization of enzymes, the improvement of the dynamics of electron transfer between the redox enzyme and the electrode and the retention of long-term stability, In this paper, several nanomaterials based electrobiosensors and aminated functional interface based electrosensor are developed to the sensitive detection of these biomoleculars, details are as follows:First, we prepare graphene by chemical approach and develop a strategy for one-step formed polymaleimidostyrene bonded-glucose oxidase (GOD micelle)/ferrocene (Fc)/graphene (GP)/polystyrene(PS) three-dimensional conductive nano-composite membrane successfully enables the stable immobilization of ferrocene, obviating the necessity of synthesizing certain chemical modification or conducting tedious complicated procedures. The composite film can be employed as a reliable sensing platform for the simple and robust on-line in vivo detection. By using glucose oxidase (GOD) as the model biorecognition units, the PMS-GOD/Fc/GP/PS modified electrode serves well as the selective detector for continuous online in vivo detecting of glucose in rat striatum, by integrating with in vivo microdialysis. The simplicity of manufacturing and the resulting performance provide wide application of the reported strategy for both fundamental research and practical applications.Second, hydrophilic functionalization of multiwall carbon nanotube (f-MWNT) was prepared and applied to the construction of biosensing interface with high performance. Both enzyme and mediator were immobilized stably in the polystyrene film due to the electrostatic interaction between glucose oxidase and ferrocene. By mixing with ferrocene, enzyme and hydrophilic f-MWNT, homogeneously three-dimensional conducting linking structur was formed, which greatly facilitate the electron transfer among the redox enzyme, ferrocene and electrode surface. Due to the favorable microenvironment which the elaborated structure provided, enzyme has a good biologically activity and stability in the composite membrane. The proposed strategy for one-step formation of GOD-Fc/f-MWNT/PS/GCE biosensing interface which is facile and has no need to conduct tedious complicated procedures for immobilization of mediator, the elaborated biosensor displaying a good analytical capability can serve as a promising platform effectively for continuously online in vivo measurements of glucose.At the end, the ammination of glass carbon electrode through electrochemical approach which is a simple, facile and manageable shows favorable electrocatalytic activity towards the oxidation of ascorbic acid, dopamine and uric acid. The observed electrocatalytic activity is relating to the different structure of target biomolecules and the interactions of hydrogen bond and π-π stack between the target biomolecules and amminated GCE, indicating that the amminated GCE can accelerate the electron transfer and decrease the overpotential of these three biomolecules oxidation with different degree. Therefore, this sensitive electrochemical sensor can be applied to individually or simultaneously determination of these biomolecules. In brief, the elaborated electrochemical sensor is a promising platform for AA, DA and UA individually in the complicated system when these three biomolecules coexisting, meanwhile, the proposed strategy provide a simple, effective and green approach for nurochemicals detection.