Ferrofluids transport in bioinspired nanochannels: Application to electrochemical biosensing with magnetic-controlled detection.

Controllable transport of ions, molecules or fluids in bioinspired nanochannels is crucial to study biointeraction occurred in confined space and also develop biosensing platforms or devices. Herein, ferrofluids transport in biofunctionalized nanochannels was investigated and a novel electrochemical biosensing platform with the characteristic of label-free, high sensitivity and rapid response was constructed. The hydrophilic ferrofluids can flux swiftly through the antibody-immobilized nanochannels with the assistance of a permanent magnet. It was initially found that the presence of ferrofluids would depress the redox current of the electrochemical probe [Fe(CN)]. The mechanism of the depressing effect was ascribed to the constrained diffusion of [Fe(CN)] which lowered the concentration of it at the electrode surface and the weak adsorption of the ferrofluids which increased the charge transfer resistance of the interface. Therefore, redox current of the probe was applied to indicate the amount of the ferrofluids fluxing through the bioinspired nanochannels. The steric hindrance of the bioinspired nanochannels changed with the amount of the corresponding target being incubated, resulting in quantitative variation of the redox current. In this way, electrochemical biosensing platform based on ferrofluids transport was constructed. Using carbohydrate antigen 153 (CA153) as a model target, a low detection limit of 0.0013 U·mL was acquired. This magnetic-controlled bioelectrochemical platform was expected to be expanded to other applications such as genetic testing, drug analysis, and molecular identification.