Molecularly imprinted polymers-based electrochemical sensors for tracking vitamin B12 released from spray-dried microcapsules during in vitro simulated gastrointestinal digestion

Abstract

Highly sensitive detection of vitamin B₁₂ (VB₁₂) is crucial for assessing its bioavailability and diagnosing deficiency-related disorders. VB₁₂ with 87.69 % efficiency was microencapsulated by spray drying complex coacervation-based emulsions of Arabic gum and sonicated insect protein, forming 5.4 μm semi-spherical microcapsules with smooth or wrinkled surfaces. The optimized VB₁₂-specific o-aminophenol (AP)-based molecularly imprinted polymer (MIP) film demonstrated efficient molecular recognition and significant electrochemical responsiveness, enabling VB₁₂ detection in PBS buffer with an LOD of 0.5 μM within a linear range of 0.5–10 μM (R² = 0.991). Surface characterization revealed remarkable property changes during sensor fabrication. A significant reduction in the hydrophilicity of the VB₁₂-AP-MIP film after template removal (TR) was observed due to the increased contact angle from 33.1° to 55.82° (p < 0.05). Morphological analysis using atomic force microscopy (AFM) showed the highest roughness (90.57 nm) for the VB₁₂-AP-MIP film, decreasing after TR (30.56 nm) and increasing upon VB₁₂ capture (46.04 nm). Scanning electron microscopy (SEM) revealed smoother, more uniform surfaces for MIP films than non-imprinted polymer (NIP) films, indicating the template's critical role in polymerization. The developed electro-MIP sensor exhibited good template-selectivity and a 15-day storage stability at 4 °C. The electrochemical VB₁₂-AP-MIP sensor successfully detected VB₁₂ in digested microcapsules under simulated salivary (3.30 ± 0.46 μM), gastric (64.87 ± 2.66 μM), and intestinal (76.68 ± 2.16 μM) conditions. The VB₁₂ analysis using HPLC and UV–Vis spectrophotometry showed that the electro-MIP sensor outcomes were comparable to those obtained with HPLC. The developed electro-MIP sensor would be a promising tool for determining VB₁₂ levels in complex biological samples.