Critical Effect of Polyelectrolytes on the Electrochemical Response of Dehydrogenases Entrapped in Sol‐Gel Thin Films

Abstract

The influence of polyelectrolyte (PE) additives on the sol-gel encapsulation of dehydrogenases has been evaluated using d-sorbitol dehydrogenase (DSDH) as a model enzyme. Thin sol-gel films were prepared on glassy carbon electrodes (GCE), which were then evaluated with respect to the electrochemical detection of d -sorbitol. DSDH encapsulation in pure silica thin films resulted in undetectable electrochemical signal. Adding positively-charged PE that contributes to stabilize the negatively-charged DSDH in the biocomposite film led to much faster and higher response of DSDH to its substrate, as shown by the significant improvement in bioelectrochemical detection of NADH produced during the oxidation of d-sorbitol.

One Step Deposition of Sol‐Gel Carbon Nanotubes Biocomposite for Reagentless Electrochemical Devices

“…Again, no significant electrocatalytic response could be obtained. This result confirms the observation from previous investigations that the presence of positively charged polyelectrolyte (such as PEI) ensures suitable microenvironment for dehydrogenase encapsulation 10. This effect is mostly due to the stabilization of negatively charged dehydrogenase which in turn led to much faster and better response of GDH to its substrate.…”

“…The entrapment of biomolecules in a silica sol‐gel matrix and their use in biosensing applications have also been developed in the past decade. Research works have shown that an enzyme can be durably immobilized by simple entrapment in porous gel networks without requiring any covalent bond between the support and the enzyme, thus maintaining its native properties and biological activity 7–10. In addition, when coated onto the electrode surface, the response time of the device can be greatly reduced by controlling the thickness of the silica layer 11.…”

Dehydrogenase‐Based Reagentless Biosensors: Electrochemically Assisted Deposition of Sol‐Gel Thin Films on Functionalized Carbon Nanotubes

“…In the absence of NADH, no enhanced current was observed (dashed line). Upon addition of 0.5 mM NADH a well-defined voltammetric peak can be observed at a potential of about + 0.4 V (solid line) which is about 300 mV lower than NADH oxidation at the bare GCE [18]. The electrocatalytic effect was even more pronounced after microwave treatment of the MWCNT (Figure 2 B) with a further decrease of the anodic peak potential of NADH to 0 V caused by the formation of quinone groups at the MWCNT during microwave treatment [40].…”

“…For bioencapsulation, the protein is, in principle, simply introduced in the starting sol and is immobilized in the sol-gel thin film formed at the electrode during the gelification process. However, to allow safe encapsulation of sensitive proteins in their active form it is vital to carefully optimize the sol composition [11,18]. Dehydrogenases, which are very sensitive to the sol-gel environment often require the introduction of additive(s), such as positively-charged polyelectrolytes, to preserve their activity in the final electrodeposited matrices [12,19].…”

Enhancement of the direct electron transfer to encapsulated cytochrome c by electrochemical functionalization with a conducting polymer

“…It is recognized that silica constitutes a suitable inert matrix for the encapsulation of several biomolecules 11, [46][47][48][49] . However, this material presents a serious drawback from an electrochemical point of view, which is the lack of intrinsic electron conductivity.…”