Reliable and sensitive in situ detection of molecules released from live cells attracts tremendous research interest, as it shows significance in pathological and physiological investigation. In the present work, a novel electrochemiluminescent (ECL) luminophore, N-(aminobutyl)- N-(ethylisoluminol)-functionalized Ag nanoparticles modified three-dimensional (3D) polyaniline-phytic acid conducting hydrogel (ABEI-Ag@PAni-PA), is synthesized to adhere cells for in situ sensitive ECL detection of hydrogen peroxide (HO) released from live cells. The obtained 3D nanostructured ABEI-Ag@PAni-PA conducting hydrogels synergize the advantages of a conducting hydrogel and a nanoparticle catalyst, in which the PAni-PA conducting hydrogels benefit the cell adhesion and high loading density of the ABEI-Ag luminescent material due to their good biocompatibility, porous structure, and 3D continuous framework. Importantly, compared with the traditional procedure for detection of HO released from cells in solution, adhesion of cells on ABEI-Ag@PAni-PA conducting hydrogels provides a short diffusion distance to reaction sites for HO, thus realizing sensitive in situ monitoring of HO released from cells under drug stimulation. With good biocompatibility, high sensitivity, and easy preparation, the ECL biosensor based on ABEI-Ag@PAni-PA conducting hydrogels can be expanded to detect other molecules released from cells, which may facilitate the investigation of pathology and physiology.

Herein, we fabricated a novel electrochemiluminescence (ECL) biosensor for ultrasensitive detection of mucin 1 (MUC1) based on a three-dimensional (3-D) DNA nanomachine signal probe powered by protein-aptamer binding complex. The assembly of 3-D DNA nanomachine signal probe achieved the cyclic reuse of target protein based on the protein-aptamer binding complex induced catalyzed hairpin assembly (CHA), which overcame the shortcoming of protein conversion with enzyme cleavage or polymerization in the traditional examination of protein. In addition, CoFeO, a mimic peroxidase, was used as the nanocarrier of the 3-D DNA nanomachine signal probe to catalyze the decomposition of coreactant HO to generate numerous reactive hydroxyl radical OH as the efficient accelerator of N-(aminobutyl)-N-(ethylisoluminol) (ABEI) ECL reaction to amplify the luminescence signal. Simultaneously, the assembly of 3-D DNA nanomachine signal probe was executed in solution, which led to abundant luminophore ABEI be immobilized around the CoFeO surface with amplified ECL signal output since the CHA reaction was occurred unencumberedly in all directions under homogeneous environment. The prepared ECL biosensor showed a favorable linear response for MUC1 detection with a relatively low detection limit of 0.62 fg mL. With excellent sensitivity, the strategy may provide an efficient method for clinical application, especially in trace protein determination.

Herein, a high-efficiency electrochemiluminescence (ECL) indicator of an abundant N-(aminobutyl)-N-(ethylisoluminol) functionalized metal-organic framework (ABEI@Fe-MIL-101) was synthesized to construct a biosensor for the ultrasensitive assay of mucin1 on MCF-7 cancer cells with a coreactant HO-free strategy.

In the present work, we first found that mercury ion (Hg(2+)) has an efficient quenching effect on the electrochemiluminescence (ECL) of N-(aminobutyl)-N-(ethylisoluminol) (ABEI). Since we were inspired by this discovery, an aptamer-based ECL sensor was fabricated based on a Hg(2+) triggered signal switch coupled with an exonuclease I (Exo I)-stimulated target recycling amplification strategy for ultrasensitive determination of Hg(2+) and mucin 1 (MUC1). Concretely, the ECL intensity of ABEI-functionalized silver nanoparticles decorated graphene oxide nanocomposite (GO-AgNPs-ABEI) was initially enhanced by ferrocene labeled ssDNA (Fc-S1) (first signal switch "on" state) in the existence of H2O2. With the aid of aptamer, assistant ssDNA (S2) and full thymine (T) bases ssDNA (S3) modified Au nanoparticles (AuNPs-S2-S3) were immobilized on the sensing surface through the hybridization reaction. Then, via the strong and stable T-Hg(2+)-T interaction, an abundance of Hg(2+) was successfully captured on the AuNPs-S2-S3 and effectively inhibited the ECL reaction of ABEI (signal switch "off" state). Finally, the signal switch "on" state was executed by utilizing MUC1 as an aptamer-specific target to bind aptamer, leading to the large decrease of the captured Hg(2+). To further improve the sensitivity of the aptasensor, Exo I was implemented to digest the binded aptamer, which resulted in the release of MUC1 for achieving target recycling with strong detectable ECL signal even in a low level of MUC1. By integrating the quenching effect of Hg(2+) to reduce the background signal and target recycling for signal amplification, this proposed ECL aptasensor was successfully used to detect Hg(2+) and MUC1 sensitively with a wide linear response.