With this configuration, a wide linear response range from 50 M to 5.0 mM with a detection limit of about 10 M for choline was achieved. Song et al. fabricated an another choline biosensor by immobilizing ChO into a sol gel silicate film on MWCNTs modified platinum electrode. This biosensor was BMS-554417 from lecithin by phospholipase D in serum samples with high sensitivity and the detection limit was 0.1 M. A stable and sensitive acetylthiocholine sensor based on immobilization of acetylcholinesterase on the CS MWCNTs composite was developed by Du et al. GA was used as cross linker to covalently bond AChE and efficiently prevent leakage of the enzyme from the film. Lee et al. developed an amperometric tyrosinase biosensor based on MWCNTs dispersed in mesoporous composite films of sol gel derived titania and Nafion.
Tyrosinase was immobilized within the composite film and phenolic compounds were determined by the direct reduction of biocatalytically liberated quinone species. This sensor exhibited Belinostat remarkably fast response time less than 3 sec and a good performance in terms of the sensitivity and the detection limit due to the large pore size of the composite film. An amperometric biosensor was based on the immobilization of HRP on MB modified MWCNTs for phenolic compounds and it showed a very wide linear response with a good sensitivity for catechol. Recently, Lopez et al. described a biosensor fabricated by the modification of GCE with a matrix based on MWCNTs, tetrahydrofuran mixed with poly, and with a GA solution for NADH detection. The modified electrode showed a relatively higher sensitivity, a promotion of electron transfer, and it facilitated the amperometric determination of NADH starting in a potential of 0.
40 V. Male et al. developed a biosensor for arsenite by depositing molybdenum containing arsenite oxidase galvanostatically onto the active surface of a MWCNTs on GCE. The detection limit of 1 ppb was found for arsenite but there was a severe interference caused by common metal ions found in tap and river waters. Mita et al. constructed a bisphenol A biosensor using a various tyrosinase containing CPE and they optimized the experimental condition with the composition of 10% tyrosinase, 45% SWCNTs, and 45% mineral oil. It showed a good reproducibility with a detection limit of 20 nM. Liu and Lin fabricated an amperometric biosensor based on LBL selfassembling AChE on CNTs modified GCE and integrated it within a flow injection detection system.
It was highly sensitive for organophosphate pesticides and nerve agents and showed a good precision, reproducibility, and stability. CNTs play a dual significant role in this structure. It provides a robust immobilization sites for a suitable microenvironment to retain the enzyme activity and as a transducer, which amplifies the electrochemical signal of the product of the enzymatic reaction. Rahman et al. fabricated an amperometric lactate biosensor based on MWCNTs and conducting polymer by covalently immobilizing the lactate dehydrogenase and NADH onto the MWCNTs/CP assembly. The MWCNTs/CP nanocomposite assembly was obtained through the electrochemical polymerization of monomer containing MWCNTs. The analytical results such as sensitivity, selectivity, and stability were found to be improved significantly using MWCNTs/ CP nanocomposite assembly.