Optical bio/chemical sensors for vitamin B ₁₂ analysis in food and pharmaceuticals: state of the art, challenges, and future outlooks

Vitamin B ₁₂ (VB ₁₂ ) is an essential Co ²⁺ -containing nutrient for neurological function, DNA synthesis, and red blood cell formation. Accurate and efficient VB ₁₂ quantification in food and pharmaceutical products is crucial due to its animal-derived dietary sources and the significant health implications of VB ₁₂ deficiency. Traditional methods for VB ₁₂ analysis, such as high-performance liquid chromatography and enzyme-linked immunosorbent assay, are often troublesome and time-consuming, and require high-tech laboratory setups. The current overview highlights the latest optical biosensing platforms in detecting Co ²⁺ ions and VB ₁₂ using RNA aptamer–gold nanoparticles colorimetric sensors, surface plasmon resonance sensors, chemiluminescence and electrochemiluminescence biosensors, and fluorescence biosensors (i.e., chemosensors, nanoclusters/nanoparticles-based sensors, and carbon dot (CD)- and quantum dot (QD)-based sensors). The advent of optical biosensing technologies has resulted in a new era for VB ₁₂ analysis, characterized by the development of innovative CD- and QD-based sensors. These nanomaterials offer several advantages over conventional methods, including enhanced sensitivity, specificity, rapid detection, and the ability for real-time analysis. CD- and QD-based biosensors with excellent optical properties such as photoluminescence enable the detection of VB ₁₂ at negligible concentrations and in real-world samples with complex matrices. Furthermore, integrating these biosensors into cellular bioimaging and the potential for non-invasive in vitro and in vivo analysis demonstrate their versatility and applicability across a broad spectrum of biomedical research, diagnostics, and nutrient analysis.