Metal–to–particle charge transfer invoked photoelectrochemistry on ferroelectric SrTiO3 for split–mode and high–throughput aptasensing

Abstract

Split–mode aptasensing is highly desirable in photoelectrochemistry because of its distinctive advantages of high-throughput, avoided damage to biomolecules, and increased sensitivity and selectivity. However, the currently available photoelectrochemical (PEC) strategy conducible to split–mode aptasensing is still limited to the bioreaction mediated generation of photoactive species, in which a low photocurrent was usually attained, rending this strategy impotent for attaining high sensitivity. As a result, to explore new strategies that are amendable to highly efficient, split-mode PEC aptasensing are still challenging but demanding. Herein, ferrocyanide mediated metal–to–particle charge transition (MPCT) on ferroelectric strontium titanate (SrTiO₃) was explored as an innovative signal transduction strategy and was validated for high-performance aptasensing. By taking the 17β–Estradiol (E2) as a model analyte, the recognition between the target (E2) and its aptamer anchored on the Fe₃O₄@Au (named as Fe₃O₄@Au/Apt) destroyed the beforehand formed assembly between the Fe₃O₄@Au/Apt and the ssDNA labeled liposome encapsulated with [Fe(CN)₆]^4- (named as DLL–FeCN), which resulted in the release of the beforehand encapsulated [Fe(CN)₆]^4- into solution. The released [Fe(CN)₆]^4- then coordinated onto the surface of SrTiO₃ nanoparticles consisted photoelectrode, forming the MPCT process from metal ion (iron (II) in [Fe(CN)₆]^4-) to the conduction band (CB) of SrTiO₃ for anodic photocurrent signal output. The detection achieved linear range of 1.0 pM–100 nM, with a detection limit of 0.3 pM for E2. Benefiting from the cooperative effects of the MPCT process and the ferroelectric polarization in bulk SrTiO₃ for achieving highly efficient photocurrent generation capability, the developed split–type detection had the advantage of high sensitivity/selectivity and high throughput. This work not only opens up the MPCT process for innovative PEC sensing strategy but also blazes a new road for high performance PEC aptasensing.