Molecularly Imprinted Polymer/Cu@g‐ C ₃ N ₄ Nanocomposite‐Based Bio

ABSTRACT

An electrochemical sensor was fabricated for selective detection of salivary 17β‐estradiol using interdigital capacitors (IDCs) functionalized with copper‐doped graphitic carbon nitride (Cu@g‐C ₃ N ₄ ) integrated within a molecularly imprinted polymer (MIP). Cu@g‐C ₃ N ₄ was characterized by Fourier‐transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Methacrylic acid and ethylene glycol dimethacrylate were selected as monomer/crosslinker for MIP formation in variable formulations, with capacitive measurements performed at 50 Hz, 100 Hz, and 1 kHz. The MIP‐Cu@g‐C ₃ N ₄ coated device exhibited linear capacitance response to 17β‐estradiol in concentration range of 50–800 nM with sensitivity of 115.94 nF/log(nM), which was about two times higher than pristine MIP. The calculated limit of detection (LOD) and limit of quantification (LOQ) were 14.9 and 45.16 nM, respectively. The sensor showed at least two‐fold higher response toward 17β‐estradiol compared to urea, glucose, ascorbic acid, tyrosine, creatinine, progesterone, and dydrogesterone. Mean recovery from spiked saliva samples was 101.18% ± 11.03%, demonstrating adequately reliable performance in complex matrices. Device‐to‐device variation was below 3% across three independently fabricated sensors, indicating good reproducibility. The sensor retained over 85% of its response after 4 weeks of storage, suggesting adequate stability. The Cu@g‐C ₃ N ₄ /MIP capacitive sensor could be potentially used for non‐invasive, reliable monitoring of salivary 17β‐estradiol.