Abstract
Polymer-multiwalled carbon nanotube (MWCNT) nanohybrids, which differ in surface charge have been synthesized to study the bioelectrocatalysis of adsorbed cellobiose dehydrogenase (CDH) from Phanerochaete sordida on gold electrodes. To obtain negatively charged nanohybrids, poly(3-amino-4-methoxybenzoic acid-co-aniline) (P(AMB-A)) was covalently linked to the surface of MWCNTs while modification with p-phenylenediamine (PDA) converted the COOH-groups to positively charged amino groups. Fourier transform infrared spectroscopy (FTIR) measurements verified the p-phenylenediamine (PDA) modification of the polymer-CNT nanohybrids. The positively charged nanohybrid MWCNT-P(AMB-A)-PDA promoted direct electron transfer (DET) of CDH to the electrode and bioelectrocatalysis of lactose was observed. Amperometric measurements gave an electrochemical response with KMapp = 8.89 mM and a current density of 410 nA/cm2 (15 mM lactose). The catalytic response was tested at pH 3.5 and 4.5. Interference by ascorbic acid was not observed. The study proves that DET between the MWCNT-P(AMB-A)-PDA nanohybrids and CDH is efficient and allows the sensorial detection of lactose.
Highlights
Substrate detection with electrochemical biosensors allows the sensitive and selective measurement of analytes
cellobiose dehydrogenase (CDH) was immobilized on amino- or carboxy-modified polymer carbon nanotubes (CNTs) nanohybrids on gold electrodes and the electron transfer was studied
Au-mercaptopropionic acid (MPA)-[multiwalled carbon nanotube (MWCNT)-P(AMB-A)-PDA]/CDH or Au-cysteamine-[MWCNT-P(AMB-A)]/CDH were placed into a measuring chamber and acetate buffer was added
Summary
Substrate detection with electrochemical biosensors allows the sensitive and selective measurement of analytes. Direct electron transfer (DET) between electrode and enzyme can compensate several obstacles of mediator-based second generation biosensors, e.g., diffusion of mediators, expensive heavy metal complexes or toxicity of the shuttle molecule. Electropolymers have been used as a simple immobilization matrix with no role in transferring electrons to the SWCNTs [32,33,34] In such a structure the polymer improves the immobilization while the CNTs increase the overall conductivity and decrease the operation potential. This allows the measurement of slow oxidation processes and may suppress interferences by oxidizable substances, e.g., ascorbic acid or uric acid [30,35]. CDH was immobilized on amino- or carboxy-modified polymer CNT nanohybrids on gold electrodes and the electron transfer was studied
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