Hydrotalcite Synthesis, Characterization And Biosensor Applications

1. Layered double hydroxides inorganic matrix materials: Characterization and application to the design of amperometric biosensorLayered double hydroxides (LDHs), also calld"anionic clays", have been demonstrated as attractive materials for the immobilization of biomolecules onto physical transducers, due to their hydrophilic, swelling, and porosity properties. The LDHs consist of MⅡ(OH)6 and MⅢ(OH)6 edge-sharing octahedral forming sheets similar to those of brucite. Net positive charges of the layer are balanced by exchangeable anions intercalated between the sheets. We synthesized LDHs ([Zn3-Al-Cl]) via the method of coprecipitation, and showed that the entrapment of biomolecules in this synthetic lamellar material constitutes an inexpensive, fast and easy method for the elaboration of enzymes electrodes. The procedure consists of the adsorption of an enzyme/clay aqueous colloid mixture onto the electrode surface. This method of deposition offers the possibility of entrapping a large and well-known amount of enzyme into the clay film.2. Amperometric Detection of Glucose with Glucose Oxidase Immobilized in Layered Double HydroxidesA novel cheap and simple amperometric biosensor, based on the immobilization of glucose oxidase(GOD) into anionic clay; layered double hydroxides(LDHs) [Zn3-Al-Cl] is presented. GOD can be entrapped in the LDHs gel via electrostatic interaction. Amperometric Detection of Glucose with an unmediated sensor at 0.6V (vs.SCE) results in a rapid response (5s), a wide linear range of 0.001-12mM, as well as good operational stability. The low detection limit was 0.1uM at 3σ. The apparent Michaelis-Menten constant (KMapp) is 4.4 mM. The general interferences that coexisted in blood serum do not affect glucose determination, except for uric acid. In addition, optimization of the biosensor construction and the effects of the applied potential on the amperometric response of the sensor were investigated and discussed herein.3. Electrochemical study of ferrocenemethanol modified layered double hydroxides composite matrix: Potential application in the development of amperometric biosensorsWith the attempt of amperometric biosensor development, a mediated glucose biosensor with simultaneous immobilization of both ferrocenemethanol (MeOHFc) mediator and glucose oxidase (GOD) in the layered double hydroxides (LDHs) was initially investigated. MeOHFc played effectively the role of an electron shuttle between the redox site of enzyme and the electrode. The biosensor (LDHs/MeOHFc/GOD) electrode showed good sensitivity (60 mA M-1 cm-2) with a good detection limit of 3μM at 3σ, small Michaelis-Menten constant (2.25 mM) and very fast response time of approximately 5s. In addition, the entrapped MeOHFc mediator permitted sensor operation at 0.25 V (vs. SCE), thereby reducing susceptibility toward common endogenous, easily oxidizable interferences.4. Amperometric Detection of Choline with Choline Oxidase Immobilized in Layered Double HydroxidesLayered double hydroxides (LDHs) can effectively immobilize the biological macro-molecules. Choline oxidase (ChOx) can be entrapped in the LDHs gel via electrostatic interaction. The research discovered that detection of Choline with an unmediated sensor at 0.5V (vs.SCE) resulted in a rapid response (5 s), a wide linear range of 3.7×10-6~6.3×10-4M, as well as good operational stability. The apparent Michaelis constanst and activation energy for the immobilized Chox are 1.38 mM and 26.69 kJmol-1, respectively. The sensitivity is 9.51 mA M-1cm-2. The low detection limit was 0.3uM. In addition, the effects of the applied potential, pH value of the solution, and system temperature on the amperometric response of the sensor were investigated and discussed herein.