A pH-responsive hollow mesoporous SiO₂ nanocarrier designed for the ultrasensitive detection of alpha-fetoprotein

Effective signal amplification is necessary for the sensitive detection of low-abundance proteins. In this work, a sandwich-type immunosensor for the sensitive detection of alpha-fetoprotein (AFP) was prepared. Hollow mesoporous silica spheres (HMSS) with a large specific surface area and loading capacity were synthesized. Next, their adsorption performance was improved by a hyaluronic acid (HA) coating that could inhibit the escape of lead(II) ions adsorbed on the hollow silica spheres. After that, an "off-on" strategy was applied to the immunosensor to amplify delta I. The sensitive detection of AFP was obtained by square wave voltammetry (SWV). The antifouling material (HA) not only reduces non-specific binding, but also has good biocompatibility and increases the number of attached secondary antibodies. Finally, we confirmed the successful application of the "off-on" strategy by some electrochemical tests. The final electrochemical sensor has high sensitivity and a low detection limit of 9.9 fg mL(-1) (S/N = 3). The proposed "metal ion (organic small molecule)-HMSS@HA" bioresponsive release system has potential application value as a carrier for other electroactive substances.