Toward the early evaluation of therapeutic effects: an electrochemical platform for ultrasensitive detection of apoptotic cells.

The ability for early evaluation of therapeutic effects is a significant challenge in leukemia research. To address this challenge, we developed a novel electrochemical platform for ultrasensitive and selective detection of apoptotic cells in response to therapy. In order to construct the platform, a novel three-dimensional (3-D) architecture was initially fabricated after combining nitrogen-doped carbon nanotubes and gold nanoparticles via a layer-by-layer method. The formed architecture provided an effective matrix for annexin V with high stability and bioactivity to enhance sensitivity. On the basis of the specific recognition between annexin V and phosphatidylserine on the apoptotic cell membrane, the annexin V/3-D architecture interface showed a predominant capability for apoptotic cell capture. Moreover, a lectin-based nanoprobe was designed by noncovalent assembly of concanavalin A on CdTe quantum dots (QDs)-labeled silica nanospheres with poly(allylamine hydrochloride) as a linker. This nanoprobe incorporated both the specific carbohydrate recognition and the multilabeled QDs-based signal amplification. By coupling with the QDs-based nanoprobe and electrochemical stripping analysis, the proposed sandwich-type cytosensor showed an excellent analytical performance for the ultrasensitive detection of apoptotic cells (as low as 48 cells), revealing great potential toward the early evaluation of therapeutic effects.