Impedimetric sensing of C-reactive protein using a novel molecularly imprinted polymer coupled with bismuth-enhanced cobalt ferrite nanocomposites for cardiovascular risk assessment

This study reports an approach of using a molecularly imprinted polymer (MIP) combined with Bi-doped cobalt ferrite (Bi_<i>x</i>CoFe₂O₄) nanoparticles (NPs) for detecting C-reactive protein (CRP), a marker associated with cardiovascular diseases (CVDs). Sudden cardiac arrest is a growing concern in India, where CVDs have become the leading cause of mortality. MIPs have recently drawn increasing interest over time; consequently, the objective of this study is to engineer an MIP-based electrochemical sensor due to their reliability, ease of electrochemical control for template removal, and cavity renewal. MIPs are selective polymers that can bind target molecules and are synthesised using a ratio of 1 : 4 : 20 of a novel functional monomer (4-nitrophenyl methacrylate), a template (CRP), and a crosslinker (EGDMA) <i>via</i> the bulk polymerisation method, along with Bi_<i>x</i>CoFe₂O₄ NPs (Bi = 0.05, 0.10, 0.15, and 0.20 M). These NPs and MIPs were characterised using powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray (EDX) analysis, dynamic light scattering (DLS), ultraviolet-visible (UV) spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and the Brunauer-Emmett-Teller (BET) method. The synthesised NPs and MIP were fabricated onto an indium tin oxide (ITO) electrode using the electrophoretic deposition (EPD) process. Moreover, an electrochemical analysis was conducted using voltammetry and electrochemical impedance sensing (EIS) techniques for CRP detection across two linear ranges: a lower range of 0.5-80 ng mL^-1 with a limit of detection (LOD) of 0.1609 ng mL^-1 and a sensitivity of 0.740 Ω ng^-1 cm^-2, and a higher range of 90-400 ng mL^-1, in which the LOD was 0.3262 ng mL^-1, sensitivity was 0.0631 Ω ng^-1 cm^-2 and the response time of the fabricated sensor was observed to be 10 seconds.