Immobilization of lactate dehydrogenase within multiwalled carbon nanotube-chitosan nanocomposite for application to lactate biosensors

A composite of multiwalled carbon nanotubes-chitosan (MWCNT-CHIT) was used as a matrix for entrapment of lactate dehydrogenase (LDH) onto a glassy carbon electrode in order to fabricate amperometric biosensor. The homogeneity of the resulting multiwalled carbon nanotubes-chitosan-lactate dehydrogenase (MWCNT-CHIT-LDH) nanobiocomposite film was investigated by atomic force microscopy (AFM). It shows that the enzyme is homogeneously immobilized within MWCNT-CHIT-LDH. The inclusion of MWCNT within MWCNT-CHIT-LDH exhibits the abilities to raise the current responses, to decrease the electrooxidation potential of β-nicotinamide adenine dinucleotide, reduced form (NADH), and to prevent the electrode surface fouling. The influence of several experimental parameters such as applied potential, solution pH value, NAD+ concentration, and enzyme loading was explored to optimize the electroanalytical performance of the biosensor. The optimized biosensor for the determination of lactate shows a sensitivity of 0.0083 A M−1 cm−2 and a response time of about 3 s. The proposed biosensor retained 65% of its original response after 7 days.