Research Of Electrode Surface For Cholesterol Molecularly Imprinted Sensor

Cholesterol is the most important steroid in human body and as the important partof the mammals bio-membrane, which is widely distributed in nature. The cholesterolcontent of the human body is closely related to human physiological and pathological,high cholesterol levels will lead to high blood cholesterol, and thus lead toatherosclerosis, coronary heart disease, nephropathy syndrome, as well as gallstonesand other diseases, therefore, cholesterol testing is particularly important.The molecular imprinting technique （MIT） has been progressive development inrecent years, which is a cross-disciplinary technology of integrated polymer chemistry,materials science and biochemistry disciplines. MIT integrates the template moleculeand functional monomer fixed template molecules in the polymer through themethods of self-assembled or pre-assembled in the cross-linking polymerizationprocess and elutes the template molecules finally. In the synthetic materials, somemolecular recognition sites are matched highly with the template molecule and havethe specific recognition of the template molecule. Because the molecularly imprintedpolymer has the characteristics of a good stability, high selectivity, affinity, and along service life, MIT has widely been developed in the field of electrochemicalbiosensors. However traditional molecularly imprinted electrochemical sensors stillhave many problems, such as few selection of the substrate electrode, smaller contactarea, the material of irregular shape etc., which hindered the development ofmolecular imprinting technique in the field of sensors to some extent.In this paper, the cholesterol was used as template molecules and nanomaterialswere applied in molecular imprinting technology to explore suitable substrateelectrode and prepared cholesterol molecularly imprinted sensor. Experiment resultsare as follows:1. The sol–gel method has been used to prepare colloidal solution with SnCl₂·2H₂Oand SbCl₃as the main raw material and optionally doped with other elements. Theporous titanium plates were coated with tin oxide doped by other elements and then molecularly imprinted membranes were formed by self-assembly route to fabricatethe cholesterol electrochemical biosensor in which the cholesterol and thedodecanethiol were used as the template molecule and the template matrix,respectively, to form a composite sensitive electrode. The surfaces of the compositeelectrode have been characterized by of x-ray diffraction （XRD）, scan electronmicroscopy （SEM,） and x-ray photoelectron spectrum （XPS）. The modificationprocess and the concentration response were analyzed by cyclic voltammetry.2. A porous silicon （PS） was prepared by photo-electrochemical etching single crystalsilicon wafer in HF-ethanol solution. The as-prepared PS was modified by Ce-Sbco-doped tin oxide optically transparent conductive thin layer with SnCl₂ 2H₂O andSbCl3as the main precursors. The modified PSs were used as cholesterol molecularimprinting photo-electrochemical sensor. The surface of modified electrodes hasbeen analyzed by SEM. The modification process and the concentration responsewere photo-electrochemically measured and characterized by cyclic voltammetryand chronoamperometry with two-electrode system, respectively.3. Various metal films such as platinum, nickel or platinum-nickel alloys etc. wascoated on the （111） surface of n-silicon. The backs of the silicon wafer were coatedAl film to for ohmic contact. A silicon-based molecular imprinting photo-electrochemical cholesterol molecule sensor has been assembled in which, thecholesterol acts as the template molecule and the dodecanethiol as the templatematrix to form a composite photo-electrochemical sensitive electrode. The surfacesof the composite electrode were analyzed by XPS. The modification process andthe concentration response are measured photo-electrochemically and characterizedby cyclic voltammetry and chronoamperometry with two-electrode system,respectively.