Electrochemical Studies On The Adenosine Deaminase’s Activity And Direct Electron Transfer Between Proteins

Electrochemistry-based biosensors offer sensitivity, selectivity and low cost for the detection of selected DNA sequences or protein. Over the past20years, it was being widely applied in medical health, biotechnology, and environmental protection. Graphene, due to its special properties, are able to improve the function of biosensors when incorporated with biological elements. And this should bring up new phenomena that may well sustain. And our work is also concerning this theme.1. A new strategy to fabricate electrochemical aptasensor:application to the assay of adenosine deaminase activityA novel strategy for the fabrication of electrochemical aptasensor is proposed in this work, and the strategy has been employed to develop an aptasensor for the assay of adenosine deaminase activity. While a well-designed oligonucleotide containing three functional regions (an anti-adenosine aptamer region, a split anti-hemin aptamer region, and a linker region) is adopted in our strategy as the core element, the enzymatic reaction of adenosine catalyzed by adenosine deaminase plays key role as well in the regulation of the binding of the split anti-hemin aptamer with hemin, the electroactive probe, which is to reflect the activity of the enzyme indirectly but accurately. The detection limit of the fabrication biosensor can be lowered to0.2U ml-1of adenosine deaminase, and1nM of the inhibitor erythro-9-(2-Hydroxy-3-nonyl) adenine hydrochloride is enough to present distinguishable electrochemical response. Moreover, since the electroactive probe is not required to be bound with the oligonucleotide, this strategy may integrate the advantages of both labeled and label-free strategies.2. Direct electron transfer between proteins within a graphene oxide multilayersAlthough many kinds of film materials and modification techniques have been employed for the development of protein-film electrochemistry, ordered assembly of the molecules to platform for the achievements of direct electron transfer between proteins is highly required. For this purpose, cyt c and the enzyme bilirubin oxidase (BOD) or glucose oxide (GOx) are coimmobilized in a multilayer on gold electrodes. We here employ graphene oxide as scaffolds for the construction of multilayered uniform self-assembled structure. The currents increase with the addition of protein layers, which means that by increasing the number of catalytic sites, the bioelectro-catalytic conversion can be enhanced. Furthermore, the system does not need an external mediator but relies on the in situ generation of a mediating radical, and thus allows signal transfer protein via the substrate-converting enzyme to the electrode. Direct electro transfer avoids the use of redox mediators, thus reducing potential interferences and side reactions, as well as being more compatible with in vivo conditions.