A novel composite of covalent organic framework and molecularly imprinted polymer with 1,1′-bis(allylcarbamoyl)ferrocene as cross-linker for ratiometric electrochemical detection of 5-hydroxytryptamine

A novel covalent organic framework and molecularly imprinted polymer (COF-MIP) composite, incorporating 1,1'-bis(allylcarbamoyl)ferrocene (AC-Fc) as a cross-linker, was synthesized through free radical polymerization for the ratiometric electrochemical detection of 5-hydroxytryptamine (5-HT). The AC-Fc cross-linker was synthesized using 1,1'-ferrocenedicarboxylic acid as a reactant. Subsequently, the COF-MIP was prepared using surface imprinting technique, employing AC-Fc as the cross-linker, COF as the supporter, and 5-HT as the template. The COF-MIP was employed in the development of a ratiometric electrochemical sensor for 5-HT. Upon 5-HT introduction, the peak current of 5-HT exhibited a concentration-dependent increase, while that for ferrocene (Fc) remained nearly constant. By utilizing Fc and 5-HT peak currents as reference and indicator signals, respectively, 5-HT was quantitatively determined. The ratio of I5-HT/IFc for the COF-MIP sensor was 4.48, 3.57, and 1.98 times higher than those of non-imprinted polymer (NIP), traditional MIP, and COF-NIP sensors, respectively. The ratiometric sensor with COF-MIP demonstrated a linear ratiometric signal (I5-HT/IFc) in response to 5-HT concentrations within the range of 0.2-10 µM, with a detection limit of 0.03 µM. The relative standard deviation of the non-ratiometric and ratiometric sensors was 7.8% and 2.6%, respectively. This methodology was successfully employed for the detection of 5-HT in human serum.