Design Of The Interface Of Novel Biosensor's And Its Application

Biosensor is a very active research and engineering technical field. It is in cross area of life science and information science with bioinformation, biochip, biocybernetics, bionics and biocomputer. Research about biosensor derived from 1960s. Updike and Hicks assembled glucose oxidase (GOD) on the oxygen electrode in1967. This is the first biosensor - glucose oxidase electrode. The field of biosensors research has basically formed in 1980s, the significant matters of which are that the international publication "biosensor" was founded in Britain, the classics work of biosensors is published by Oxford Press; and the 1st World Biosensor Academic Conference was holded in Singapore in 1990, in additional, this conference was arranged to be hold every two years.Biomolecule immobilization is one of the most important research fields and is cared more and more. For example, the controlled adsorption of proteins is essential in the fields of investigating structure function relationship of proteins, thermodynamics of protein electron transfer, enzymatic catalysis, designing the third-generation electrochemical and disease diagnostics. Layer-by-layer assembled technique has brought a new opportunity for biofunctional nano material, owing to its easy preparation method and facile controlling every layer's composition, thickness and orientation. Layer-by-layer assembly technique is frontal research direction in microcosmic physics and chemisty field, and supply new idea for developing next molecular instrument.The main work of this paper is focus on one of the most active field where nano technique combines with assembled technique and electroanalytical chemistry, developing and fabrication novel modified electrodes based on nano materials (electrochemical sensors). The emphasis of this paper is to find out and study the assembled electrodes modified by difference materials based on layer-by-layer assembled technique. Besides, the other emphasis of the paper is to apply these novelmodified electrodes to realizing the detection and analysis of some biological molecules, which may provide many important analytical methods for the life science and relative fields. What we have done is to try our best to combine the nano technique, life science with electroanalytical chemistry firmly. The details are listed below:Chapter I: PrefaceLayer-by-layer (LbL) assembly is a kind of effective approach to fabricate organic nano-thin films. According to all these factors, this part reviews the Layer-by-layer assembled technique's preparation, characteristic, and studies on application in biomolecular immobilization and bioanalysis.Chapter II : Direct electrochemistry of hemoglobin immobilized on a Au-SiO2-modified bare glassy carbon electrode and its application indetection of glucose level as glucose biosensorSBA-15 family of silicate mesoporous materials is a new type of SiO₂ base materials, which possesses regular pore structure, large surface areas, tunable pore sizes and volumes, and good mechanical strength. The structural characteristics of mesoporous silica materials are expected to be suitable for the immobilization of enzymes. The activity of Hb immobilized on SBA-15 by electrochemical method was investigated. SBA-15 can provide a "near water" microenvironment for Hb and prevent the direct contact between Hb and electrode.In the present contribution, we reported the encapsulation Hb on mesoporous silicas SBA-15 and Au-doped SBA-15 (Au-SBA-15), respectively. The results of experiments show that Hb/SBA-15 and Hb/Au-SBA-15 all have good electrocatalytic activity toward H₂O₂. However, the electrocatlytic ability of Hb/Au-SBA-15 is better than that of Hb/SBA-15 because of the existence of Au nanoparticles. The Hb/Au-SBA-15/GC modified electrode is used to immobilize glucose oxidase (GOD) and a novel glucosebiosensor is developed. Moreover, this biosensor displays high sensitivity and is potentially useful for glucose sensing in vitro or in vivo.Chapter III : Layer-by-layer assembled mesoporous SBA-15 for selective determination of dopamine in the presence of ascorbic acidDopamine (3-hydroxytyramine) is a important neurotransmitter in mammalian central nervous systems. A loss of DA-containing neurons may result in sane serious disease such as Parkinson's disease. Hence, the determination of the concentration of this neurochemical is important. Mesoporous SBA-15 is perfect candidate for its relatively high surface areas, well-define three-dimensional structure, varied surface functionality, and unique properties. We combine mesoporous SBA-15 with LbL assembled technique to prepare SBA-15 modified electrode.Layer-by-layer assembled SBA-15 modified electrode, offers substantial improvements in sensitivity and selectivity towards the determination of dopamine (DA). It can inhibit the response of ascorbic acid (AA) while the redox reaction of dopamine is promoted. Under the chosen conditions, the peak currents are correspondent linearly to the concentrations of DA in the range of 1.0× 10^-9～1.0× 10^-4 M with a limit of detection of 5.0 ×10^-10 M. The proposed method can be applied to detect DA in real samples.Chapter IV : Research of enzyme immobilized on layer-by-layer assembled (PB/PDDA)n modified electrode and its application in detection of acetylcholineThe determination of acetylcholine (ACh) and choline (ChO) are important clinically. Determination of ACh in the brain is important for understanding the mechanisms of neurotransmission and neuroregulation, which in turn should be beneficial to early detection and effective treatment of neurodegradative diseases, such as Alzheimer's disease and myasthenia gravis. Being one of the most commonlyused electrochemical mediators for analytical applications, Prussian blue bas found a wide use in the biosensor field during the last years.Amperometric enzyme biosensors for the determination of acetylcholine (or choline) have been described. For the fabrication of the biosensors, pure nanoparticals Prussian blue (PB) within layers of polyelectrolyte has been achieved by a multiple sequential adsorption (MSA) approach of positively and negatively charged ions on a charged support. The thickness of assembled films has been investigated by AFM. Linear increase in UV-visible light absorbance with the number of assembled layers indicates that an homogeneous film growth. Acetylcholinesterase (AChE) with choline oxidase (ChO) was co-immobilized in a polycation PDDA membrane on the (PB/PDDA)₈ modified glassy carbon electrode for a acetylcholine (ACh) sensor, and only choline oxidase immobilized for an choline (Ch) sensor. The resulting sensors were characterized by fast response, expanded linear range and low interference. The optimal ACh sensor gave a detection limit (S/N =3) of 5.0×10^-9M within the range of a definite concentration.