Environmental effects of chitosan as an immobilization medium for electrochemically active small molecules

Abstract

A number of challenges arise when using ferrocene as a component of electrochemical biosensors, including solubility in aqueous solutions. Therefore, entrapment of the biotin-ferrocene molecules within the chitosan film provides a route for immobilization on an electroactive surface such as an electrode while making the system water compatible. The use of the chitosan-ferrocene bioconjugate thin film on the electrode surface produces a signal that can be monitored in aqueous media. Herein, we discuss a series of modified ferrocene molecules that contain various linkers that provide non-covalent entanglement points to the chitosan medium. The electrochemical analysis and electron microscopy results show marked differences in the ferrocene loaded chitosan polymers when the termini of the ferrocene-linker vary between –SH and –NH₂. The –SH modified systems showed increased reversible and robust electrochemical signals relative to the –NH₂ congeners. Further studies showed that non-covalent impregnation strategy used is robust to degradation and less than 1% of the ferrocene molecules were leached over time. These results indicate that there are specific considerations needed when using chitosan-ferrocene systems as components in sensor arrays in future studies.

Keywords:

• Chitosan
• ferrocene
• electrochemistry

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors are grateful for generous financial support from TCU Andrews Institute of Mathematics & Science Education (to KNG), TCU Research and Creativity Activity Grant (to KNG), TCU Invests in Scholarship (to KNG), the INFOR Moncrief Foundation Support (to KNG), and the Robert A. Welch Foundation (Grant P-1212 to JLC).