The Research On Electrochemical Biosensors Based On Nanomaterials

Doped Carbon nanotubes (CNTs) have better electrochemical properties thanundoped CNTs because of the dope of other chemical elements, which can change theelectronic structure and crystal structure of undoped CNTs, so they have beenemployed widely in electrochemical biosensors. On the other hand, graphenepossesses unigue structural features and excellent physiochemical properties, whichmake it have good promising application. Based on the advantages of doped CNTs andgraphene, electrochemical biosensors based on boron-doped CNTs (BCNTs) andgraphene have been developed, and the main contents are summarized as follows:(1) Based on the excellent physicochemical properties of boron-doped carbonnanotubes (BCNTs), the electrochemical analysis of four free DNA bases at theBCNTs modified glassy carbon (GC) electrode was investigated. Herein, theBCNTs/GC electrode exhibited remarkable electrocatalytic activity towards theoxidation of purine bases (guanine (G), adenine (A)) and pyrimidine bases (thymine(T), cytosine (C)). The biosensor possessed high sensitivity, wide linear range andlow detection limit. for the electrochemical determination of G, A, T, and C. It may bedue to that BCNTs have the advantages of high electron transfer kinetics, largesurface area and electrode activity. On the other hand, the electrochemical oxidationof quaternary mixture of G, A, T, and C at the BCNTs/GC electrode was investigated.It was obtained that the peak separation between G and A, A and T, or T and C waslarge enough for their potential recognition in mixture without any separation orpretreatment. The BCNTs/GC electrode also displayed good stability, reproducibilityand excellent anti-interferent ability.(2) A novel, sensitive and enzymeless electrochemical sensor based onpolynucleotide-templated silver nanoclusters (DNA-AgNCs)/graphene composite filmwas developed for the detection of hydrogen peroxide. The graphene modified glassycarbon electrode (GCE) was employed because graphene has several advantagesincluding excellent conductivity, biocompatibility, and large surface area to volumeratio. In addition, it was found that DNA-AgNCs have remarkable electrocatalyticactivity towards the reduction of hydrogen peroxide, and can be easily immobilizedonto the surface of the graphene/GCE by π-π stacking. The sensor based on the(DNA-AgNCs)/graphene/GCE exhibited rapid response (ca.3s), low detection limit (3μM), wide linear range from15μM to23mM, high selectivity, as well as goodrepeatability. Moreover, the common interfering species, such as ascorbic acid, uricacid, dopamine, glutathione, and L-cysteine, did not result in any interference.(3) A lable-free and novel electrochemical biosensor based on graphene withunique structure and excellent electrochemical properties was fabricated for thedetection of uracil-DNA glycosylase activity. ssDNA can be adsorbed onto thesurface of graphene/GC electrode through π-π stacking, but dsDNA can’t. It’s becausethat the bases of dsDNA are matched with other bases, and can’t adsorbed ontographene by π-π stacking. Graphene was electrodeposited onto GC electrode, and thegraphene/GC electrode has many advantages, including good conductivity and largesurface area to volume ratio, which can adsorb abundant ssDNA and accelerate therate of electron transfer between guanine of ssDNA and graphene/GC electrode. Thisbiosensor displayed low-cost, ease of fabrication, a wide linear range (0.05-1.1U/mL),and excellent sensitivity with satisfactory repeatability.