Electrochemical immunosensor for detection of prostate specific antigen based on an acid cleavable linker into MSN-based controlled release system

A mesoporous silica nanoparticle (MSN)-based controlled release system with acid cleavable linkage was developed to fabricate an electrochemical immunosensor for the quantitative detection of the prostate-specific antigen (PSA). 3,9-Bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5.5]undecane functionalized mesoporous silica nanoparticles (MSN-Acetal) were used to immobilize the electron mediator thionine (Th). The encapsulation of Th molecules was achieved by capping the pores of MSN-Acetal with carboxylic acid modified Au nanoparticles (defined as MSN-Th-Au). Under the acidic conditions, the capped Au nanoparticles were removed from MSN-Th-Au through the hydrolysis of the acid-labile acetal linker, resulting in the release of encapsulated Th. In this work, the pH-responsive cargo release system was firstly used as the label of secondary anti-PSA for developing an electrochemical immunosensor, and amination Fe3O4 was used as the sensing matrix for immobilizing primary anti-PSA on magnetic carbon electrode surfaces. The specific recognition of PSA resulted in the attachment of MSN-Th-Au-secondary anti-PSA (MSN-Th-Au-Ab2) onto the electrode surfaces. Subsequently, the released Th was detected by differential pulse voltammetry under the acidic conditions. The developed cargo release system provided an innovative and reliable method for the detection of PSA because the response signal was correlated with the concentration of PSA. Under the optimal conditions, the electrochemical immunosensor exhibited a wide linear range of 0.001-5.0 ng/mL with a low detection limit of 0.31 pg/mL. Moreover, the developed immunosensor showed superior reproducibility and long-term stability, which has promising applications in bioassay and biosensing.