High enzymatic activity preservation of malate dehydrogenase immobilized in a Langmuir-Blodgett film and its electrochemical biosensor application for malic acid detection

• Published in: RSC advances 2016-01, Vol.6 (83), p.79792-79797
• Main Authors: Gür, Bahri, I k, Mesut, K ran an, Kader Da c, Alanyal o lu, Murat, Beydemir, ükrü, Meral, Kadem
• Format: Article
• Language: English
• Subjects: Biosensors; Electrodes; Enzymes; Indium tin oxide; Langmuir-Blodgett films; Malate; Malic acid; Monolayers
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/c6ra17465e

In this study, malate dehydrogenase (MDH) enzyme was immobilized on a cation octadecylamine (ODA + ) monolayer at the air-water interface. Pressure-area ( π - A ) isotherm studies confirmed that the ODA-MDH system formed a stable monolayer at the air-water interface. The as-prepared MDH-ODA monolayer was transferred onto an indium tin oxide coated glass substrate (ITO) by the Langmuir-Blodgett (LB) method as an MDH-ODA/ITO LB film and characterized using FT-IR, SEM and UV-Vis absorption spectroscopy. The catalytic activity of the enzyme immobilized electrode (MDH-ODA/ITO) was assayed by sensing malic acid (MA) in the range of 10.0-50.0 mM. The high and preserved enzymatic activity of MDH in in vitro media was explored by following the absorbance ( A 340 nm ) of nicotinamide adenine dinucleotide (NADH). Moreover, the highly sensitive electrochemical biosensor behavior of the MDA-ODA/ITO electrode for MA detection was displayed by cyclic voltammetry studies. The electrochemical studies revealed that a voltammetric current from the MDA-ODA/ITO electrode was obtained, while the ODA/ITO electrode did not show this current response. The MDA-ODA/ITO ​demonstrated sensitive electrochemical sensor ability for quantification of MA in both standard solutions and real samples. Malate dehydrogenase was immobilized on a cation octadecylamine monolayer and transferred onto an indium tin oxide coated glass substrate. The enzyme immobilized electrode was then used to electrochemically sense malic acid in the range of 2.2-50 mM.