| Electrochemiluminescence (ECL), which combines electrochemical and luminescent techniques, is a means of converting electrochemical energy into radiative energy at the surface of an electrode through an applied potential. ECL biosensors apply ECL techniques to detectimine bioactive materies, which have the advantages of simple setup, low cost, high sensitivity and low background signal. Graphene, has received a great deal of attention because of its unique electronic and mechanical properties. Due to the unique physical and chemical properties, graphene provides an ideal base for electronics, electric devices and biosensors. Nano-materials play a great importance in biosensor due to its high surface-to-volume ratio and good biocompatibility. The combination of grapheme and nano-materials has been an important method in constructing biosensors.The main works are included as follows: Part1Electrochemiluminescence of luminol enhanced by AuNPs for determination of cholesterolA biosensor was prepared based on gold nanoparticles-catalyzed luminol ECL for the determination of cholesterol. Firstly, L-cysteine-reduced graphene oxide composites were modified on the surface of a glassy carbon electrode. Then, gold nanoparticles (AuNPs) were self-assembled on it. Subsequently, cholesterol oxidase (ChOx) was adsorbed on the surface of AuNPs to construct a cholesterol biosensor. The stepwise fabrication processes were characterized with cyclic voltammetry and atomicforce microscopy. The ECL behaviors of the biosensor were also investigated. It was found that AuNPs not only provided larger surface area for higher ChOx loading but also formed the nano-structured interface on the electrode surface to improve the analytical performance of the ECL biosensor. Besides, based on the efficient catalytic ability of AuNPs to luminol ECL, the response of the biosensor to cholesterol was linear range from3.3 μmol·L-1to1.0mmol·L-1with a detection limit of1.1μmol·L-1(S/N=3). In addition, the prepared ECL biosensor exhibited satisfying reproducibility, stability and selectivity. Taking into account the advantages of ECL, we confidently expect that ECL would have potential applications in biotechnology and clinical diagnosis. Part2Electrochemiluminescence of luminuol using cerium oxide-graphene for determination of cholesterolA simple ECL cholesterol biosensor was prepared based on cerium oxide-graphene (CeO2-graphene) composites as an efficient matrix. CeO2-grapheme composites were characterized by scanning electron microscopy (SEM). The CeO2-graphene composites catalyze the ECL of luminol-H2O2system. In addition, the use of CeO2-graphene provided a good biocompatible microenvironment for ChOx, resulting in excellent stability the ECL cholesterol biosensor. The surface assembly process and ECL behaviors of the biosensor were investigated. The quantity of cholesterol was in the linear range from12μmol·L-1to7.2mmol·L-1with a detection limit of4.0μmol·L-1(S/N=3). In addition, the biosensor exhibited outstanding selectivity, long-term stability and reproducibility. Moreover, the biosensor offers an alternative analytical method with high speed and low cost. Part3A cathodic electrogenerated chemiluminescence biosensor based on luminol and hemin-graphene nanosheets for cholesterol detectionA cathodic ECL sensing platform was developed, which is utilizing hemin-graphene nanosheets as an ECL sensing element and amplification for cholesterol. Hemin-graphene nanosheets were synthesized and used to detect cholesterol. First, hemin-graphene nanosheets were dropped onto a bare glassy carbon electrode (GCE). Then it was allowed to dry at room temperature. Following, in virtue of the huge surface areas and strong adsorptive ability of hemin-graphene, cholesterol oxidase (ChOx) was modified onto the surface of the electrode to construct a biosensor. To the best of our knowledge, there is no report on a cathodic ECL behavior of luminol based on hemin-graphene for the determination of cholesterol. |
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