The Design And Research Of Label-free Electrochemical Biosensor Based On Graphene Hybird Nanosheets

Chapter 1:Firstly, the properties, application, synthetic methods, and functionalized methods of graphene were introduced in this chapter. The methods for synthetizing graphene by using method of oxidation graphite deoxidation and the functionalization of graphene have been summarized. Secondly, the constitution, classification and development of biosensor have been introduced. Lastly, the principle, classification and characteristics of aptasensor have been introduced especially electrochemical aptasensor.Chapter 2:This chapter reported an ultrasensitive and label-free electrochemical DNA biosensing platform based on a newly synthesized water-soluble electroactive dye azophloxine-functionalized graphene nanosheets (AP-GNs). Azophloxine can be attached on the graphene surface through synergistic noncovalent charge-transfer and π-π stacking interactions with graphene. The attachment of azophloxine on the graphene surface not only acts as a stabilizer for graphene but also as the in situ probe for the electrochemical DNA detection. Under optimum conditions, this biosensor exhibited high sensitivity and low detection limit for detecting DNA. The linear range is from 1.0×10-15 M to 1.0×10-11 M and the detection limit is 4.0×10-16 M. Furthermore, this biosensor showed extraordinary capability for single nucleotide polymorphisms (SNPs) assay. The results demonstrate that this AP-GNs based biosensor has potential application in sensitive and selective DNA detection.Chapter 3:In this paper, we provided a facil way for synthesizing Au nanoparticles (AuNPs) and azophloxine (AP, a water-soluble dye with electroactivity) functionalized graphene nanohybrids (AuNPs/AP-GNs). By integrating the properties of AuNPs/AP-GNs (high conductivity, electroactive, signal amplication and good biocompatibility) and aptamers (high affinity and specificity), we developed a label-free sensitive electrochemical aptasensor for adenosine triphosphate (ATP, as model analyte) detection using azophloxine as in-situ electrochemical probe and Au nanoparticles for amplification. The AuNPs/AP-GNs based aptasensor showed good performance in detection of ATP. The linear range was from 1×10-15 M to 1×10-12 M with a low detection limit of 3.3×10-16 M. The analogues of ATP and mutant ATP binding aptamer exhibited no obvious current response in contrast to the presence of ATP. Compared with the common laborious and expensive ATP aptasensors, this aptasensor was label-free, sensitive and the sensing procedure was highly simply.