Biosensing Application of Electrodeposited Nanoparticles As an Electron Transfer Facilitator for Protein Immobilization

Reactive oxygen species (ROS), including hydrogen peroxide, hydroxyl radical, superoxide anion, and peroxynitrite are involved in some diseases. Among the ROS, H₂O₂ is the most durable species which is a product of several biological, enzyme-catalyzed reactions. In addition, it is toxic to cellular life and is an indicator of oxidative stress. Therefore, a selective and sensitive method for determination of H₂O₂is practically important, especially in the field of biosensor fabrication.

Biosensors have attracted attention for use in biodiagnostics [1]. The capability of biosensors will be completely changed by advances in nanoscience and nanotechnology.

Nanostructured metals and metal oxides have various applications in sensors and actuators due to their unique semiconducting and piezoelectric properties [2]. Good biocompatibility, nontoxicity, high surface area, and in particular, chemical stability and fast electron transfer features make them appropriate to apply in various fields.

In this work, cerium oxide nanoparticles (CeO₂ NPs) on the electrode surface were electrodeposited. Cerium was firstly electrodeposited at -0.75 V from a 1.0 mM cerium nitrate in ammonium nitrate buffer solution. Afterwards, the electrode was placed into a buffer solution pH 7.0 and was electrochemically passivated. Scanning electron microscopy has been used as diagnostic tools to identify the synthesized CeO₂ NPs. For the preparation of biosensor, the hemoglobin immobilized on the CeO₂NPs. Immobilized Hb showed an electrochemical redox

 behavior pertained to Hb(Fe(III)-Fe(II)) by direct electron transfer between protein and nanoparticles with a formal potential of -55.5 mV in phosphate buffer solution (PBS).

The anodic charge transfer coefficient (α) and heterogeneous electron transfer rate constant (k_s) were 0.42 and 0.75 s^-1, respectively. The prepared biosensor showed a satisfactory sensitivity and reproducibility for H₂O₂.

 References:

1. Y. Ding, J. Li, R.E. Campbell, Nature Methods, 12, 195 (2015).

2. R.C. Ashoori, Nature, 379, 413 (1996).