Ultrasmall superparamagnetic iron oxide nanoparticles (USPIONs) are a novel T1 contrast agent with good biocompatibility and switchable imaging signal that have not been widely applied for magnetic resonance imaging (MRI) because it is difficult to induce their relatively close ideal agglomeration. Here, by combining the microemulsion method with the biomineralization principle, a pH-responsive T2-T1 switchable MRI nanoprobe was constructed via the microemulsion-confined biomineralization of PEGylated USPIONs (PEG-USPIONs). The size of the formed CaCO 3 -coated PEG-USPION conjugates (PEG-USPIONs@CaCO 3 nanoprobe) was uniform and controllable, and the preparation method was simple. The PEG-USPIONs inside the nanoconjugates agglomerate more tightly, and the T1-MRI signal of the nanoprobe is converted to the T2-MRI signal. When exposed to the acidic environment of the tumor tissue or internal organelles, the CaCO 3 -coating of the nanoprobes is dissolved, and free PEG-USPIONs are released, thus realizing the T1-weighted imaging of the tumors. The suitability of the PEG-USPIONs@CaCO 3 nanoprobe for tumor MRI detection was successfully demonstrated using a mouse model bearing a subcutaneous 4T1 xenograft.

In this work, a T 2 −T 1 switchable superparamagnetic iron oxide nanoprobe with a pH/H 2 O 2 dual response was obtained using a microemulsion method. This novel method for the controllable assembly of small iron clusters followed by their independent modification was reported, which could not be prepared by common synthetic methods. The size of the assembled nanoprobe was uniform and controllable, with a stable T 2 magnetic resonance imaging (MRI) signal under a single condition. When the nanoprobe was exposed to the tumor environment, the higher H + and H 2 O 2 concentrations at the tumor site could dissociate the nanoprobe and redisperse into small iron clusters. When this occurred, the T 2 MRI signal was converted into a T 1 MRI signal, achieving specific detection of tumors by a pH/H 2 O 2 dualresponse T 2 −T 1 MRI.

Due to both the requirements of repeated complex organic synthesis and tedious biochemical verification experiments for the screening of new photosensitizers, the development of a satisfactory photosensitizer with excellent photosensitivity and highly specific response ability is still a great challenge for the accurate imaging localization and the precise photodynamic therapy (PDT) of tumors. Herein, under the help of theoretical calculations, a high‐efficient target‐activatable aggregation‐induced emission (AIE) molecular photosensitizer, TPE‐TThPy, is rationally designed and synthesized by the conjugation of tetraphenylethylene (TPE, which is used as the electron donor) and tetrahydropyridine (ThPy, which can be converted to methylpyridine salts as the electron acceptor) using thiophene (T) as the π‐bridge. This TPE‐TThPy molecule exhibits not only good cellular uptake and mitochondrial targeting ability but also ultra‐high monoamine oxidase A (MAO‐A) response specificity and excellent photosensitivity when oxidized under the action of MAO‐A. The specifically imaging ability and cellular PDT performance of the MOA‐A‐activatable AIE photosensitizer of TPE‐TThPy is demonstrated by using different cell lines and mouse tumor models. The successful development of this MOA‐A‐activatable AIE photosensitizer also provides insight for the development of single‐molecule PDT therapeutic drugs with excellent photosensitivity and highly specific targeting‐response ability.

Unlike the aggregation caused quenching (ACQ) and reduced singlet oxygen (1O2) production of traditional photosensitizers at high concentrations, AIEgen photosensitizers show enhanced fluorescence emission and photosensitization ability in the aggregated...

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Here, we have developed a novel photoactivatable red chemiluminescent AIEgen probe (ACL), based on the combination of the red-emission AIEgen fluorophore (TPEDC) that shows excellent singlet oxygen ( 1 O 2 )-generation ability and the precursor of Schaap's dioxetane (the linker connected to adamantane is the CC bond) that can be modified to target various analytes, for in vitro and in vivo measurement of hydrazine. Prior to applying for sensing detection, the CC bond connected to adamantane in ACL was first converted into dioxetane by irradiation to form the activated chemiluminescent AIEgen probe (ACLD). Then, the self-immolative reaction was triggered upon the deprotection of the acylated phenolic hydroxyl group in ACLD in the presence of hydrazine, resulting in the release of the high energy held in the 1,2-dioxetanes, and then, the chemiexcitation was triggered, thereby producing red chemiluminescence through the intramolecular chemiluminescence resonance energy transfer from Schaap's dioxetane to TPEDC. This chemiluminescent AIEgen probe was evaluated in a clean buffer environment as well as using living cells and mouse models.

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