Acceptor properties of "carbon nanotubes-redox-active polymer based on bovine serum albumin modified with ferrocenecarboxaldehyde" composite for creating a BOD biosensor with BKM Y-2677 yeast.

The possibility of using a composite material based on bovine serum albumin (BSA) covalently bonded with ferrocenecarboxaldehyde and containing carbon nanotubes (CNT) for the immobilization of BKM Y-2677 () yeast is discussed. The optimal ratio of ferrocenecarboxaldehyde to BSA for the redox-active polymer synthesis is 1:2, since the heterogeneous electron transfer constant is 0.45 ± 0.01 s. When carbon nanotubes (CNTs) are added to this polymer, the heterogeneous electron transfer constant increases: at a CNT specific density of 2.5 µg/mm, it reaches a maximum value of 0.55 ± 0.01 s. The addition of CNTs into the conducting system leads to increasing of the rate constant of interaction redox species with yeast by an order: the rate constant of interaction between yeast and electroactive particles in a redox-active polymer is 0.056 ± 0.005 dm/g × s and in a composite material based on CNTs is 0.51 ± 0.02 dm/g × s. The yeast specific density at the electrode of 0.1 mg/mm and electrolyte pH of 6.2 was chosen as the working value for the receptor system operation. Immobilized in a composite material, yeast oxidizes a wider range of substrates compared with a similar receptor element based on the ferrocene mediator. The biosensors formed on the basis of hybrid polymers have a high sensitivity with a lower limit of determined concentrations of 1.5 mg/dm with an assay time of 5 min and a high correlation ( = 0.9945) with the results of the standard method for determining biochemical oxygen demand (BOD) in nine real surface water samples of the Tula region.