Electrochemiluminescence (ECL), as a sensitive and controllable assay, offers a considerable opportunity for multiple types of biomarkers detection. However, constructing such a biosensor remains a significant challenge. Herein, an ultrasensitive and versatile ECL biosensor was constructed to detect multiple types of biomarkers from breast cancer by taking the strategies of nonenzymatic catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR) amplification, as well as aptamer-triggered emitter release. Concretely, with the appearance of target 1 microRNA-21 (miRNA-21), abundant double-stranded DNA (dsDNA) polymers were generated on this biosensing surface via amplification circuits of CHA and HCR, which could be intercalated into substantial ([Ru(bpy) 2 dppz]Cl 2 ) as ECL indicators to obtain an obvious enhancement of ECL signal for target 1 detection with a detection limit (0.1 fM). Furthermore, in the presence of target 2 human mucin 1 (MUC1) protein, the ECL signal had a distinct decrease, because aptamer recognition induced the release of [Ru(bpy) 2 dppz]Cl 2 from the sensing surface, thus, achieving a sensitive detection for MUC1 with a detection limit (2.4 fg•mL −1 ). Simultaneously, this sensing platform was applied to monitor the biomarkers from MDA-MB-231 breast cancer cells, suggesting that this method was applicable to detect real samples. Therefore, this platform is an applicable and versatile implement for the determination of multiple types of biomarkers to improve diagnostic accuracy and efficiency.

Real-time imaging of DNA damage in cancer cells could provide valuable information on the formation and development of cancer. Herein, a two-photon fluorescence probe was discovered. Through sequential ICT processes, it allows successful in vivo visualization of DNA damage in cancer cells by one/two-photon microscopic imaging or by the unaided eye and a hand-held ultraviolet lamp.

Detecting and imaging of ultratrace cyclooxygenase-2 in living biosystems could provide much important valuable information for the diagnosis and intervention of cancer. Molecular probes, whose fluorescent signals are generated by cyclooxygenase-2, hold great potential for identification and enumeration of cyclooxygenase-2 in living biosystems. Although quite a few fluorescent probes have been reported for cyclooxygenase-2, the use fluorogenic probe with the excellent two-photon properties for the determination of ultratrace cyclooxygenase-2 has been scarce. Herein, an "off-on" fluorescence probe (BTDAN-COX-2), able to report and image the presence of ultratrace cyclooxygenase-2 in living biosystems, has been designed and evaluated. In order to improve sensitivity and specific selectivity of probe for ultratrace cyclooxygenase-2, BTDAN-COX-2 employed cyclooxygenase-2's inhibitor as recognition group, because it is a classical and efficient recognition group for cyclooxygenase-2. A polarity-sensitive naphthalene derivative (BTDAN) as fluorophore was introduced into the molecule to enhance two-photon properties of BTDAN-COX-2. In the absent of cyclooxygenase-2, BTDAN-COX-2 mainly exists in a folded conformation where probe fluorescence is quenched through photoinduced electron transfer between the fluorophore and the recognition group. Under the condition of existence of cyclooxygenase-2, fluorescence of probe is turned on, because photoinduced electron transfer between the fluorophore and the recognition group is restrained. BTDAN-COX-2 provides high signal-to-background staining for the ultratrace cyclooxygenase-2 and has been successfully used to rapidly detect and image ultratrace cyclooxygenase-2 in living biosystems.

Ligand-protected gold nanoclusters (Au NCs) are promising electrochemiluminescence (ECL) emitters because of their striking optical properties and excellent biocompatibility, but free vibration and rotation of their ligand result in low ECL efficiency, dramatically limiting their applications. Herein, using the ligand of Au NCs as one of the building units, a Au NC-based metal–organic framework (Au NC-based MOF) was constructed by the coordination-assisted self-assembly strategy, which not only impedes the ligand rotation-induced energy dissipation but also diminishes the self-quenching effect due to the spatial distribution of Au NCs. As a proof of concept, the prepared GSH-Au NCs@ZIF-8 gives rise to a 10-fold enhanced anodic ECL efficiency compared to that of densely aggregated GSH-Au NCs with triethylamine as the coreactant. Based on high ECL efficiency of GSH-Au NCs@ZIF-8, a “signal off” sensing platform was proposed with rutin as a model analyte, achieving a low detection limit of 10 nM. Therefore, the strategy paves an effective and alternative methodology to enhance ECL efficiency of metal NCs, considerably broadening their potential applications in sensing analysis, clinical diagnosis, and light-emitting devices.