An amperometric microbial biosensor for the determination of vitamin B12

Abstract

In this study we describe a sensitive amperometric microbial biosensor that is fast, economic, reliable, and can compete with the existing proposed methods for vitamin B₁₂ determination. Taking advantage of the bacterial strain Tetrasphaera duodecadis which oxidizes vitamin B₁₂ with oxygen consumption, we shaped a promising alternative tool for the direct and specific determination of vitamin B₁₂ in different samples without pre-treatment. For this purpose, a vitamin B₁₂ amperometric microbial biosensor was constructed based on one-step immobilization of the bacterium by filtration of a concentrated bacterial mass through a 0.15 μm pore size cellulose filter and fixed on a Clark-type oxygen probe, serving as a transducer, and exploiting the described processes. The results obtained indicate a sensitive capability with a linear sensor concentration range from 10⁻⁷ mol L⁻¹ to 10⁻⁵ mol L⁻¹ and the response time of about 700 seconds at 10⁻⁶ mol L⁻¹. Furthermore, the Tetrasphaera duodecadis membrane attached to the Clark type oxygen probe has an estimated 1 month lifetime at room temperature. In addition, the developed prototype allowed the assessment of B₁₂ status directly in samples prepared for that purpose. The results were well correlated with those obtained with commercial samples, thus demonstrating that the proposed microbial sensor offers an accurate and useful analytical tool that can be easily applied to prevent diseases caused by the lack of vitamin B₁₂.