A fluoro-substituted cyanine showing reliable in vivo labelling of Aβ oligomers and potent neuroprotective effect against Aβ-induced toxicities is reported as a novel theranostic agent for the early diagnosis and therapy of Alzheimer's disease.

Purpose : Exosomes (EXs) have been increasingly recognized as natural nanoscale vehicles for microRNA (miRNA)-based cell-cell communication and an ideal source of miRNA biomarkers in bodily fluids. Current methods allow bulk analysis of the miRNA contents of EXs, but these approaches are not suitable for the in situ stoichiometry of exosomal miRNAs and fail to reveal phenotypic heterogeneity at the single-vesicle level. This study aimed to develop a single vesicle-based, mild, precise, but versatile method for the in situ quantitative and stoichiometric analysis of exosomal miRNAs. Methods : A total internal reflection fluorescence (TIRF)-based single-vesicle imaging assay was developed for direct visualization and quantification of the single-vesicles of EXs and their miRNA contents in serum microsamples. The assay uses co-delivery of inactive split DNAzymes and fluorescence-quenched substrates into nanosized EXs treated with streptolysin O to produce a target miRNA-activated catalytic cleavage reaction that amplifies the readout of fluorescence signal. We perform the in situ quantitative and stoichiometric analysis of serum exosomal hsa-miRNA-21 (miR-21), a common cancer biomarker, by using the developed TIRF imaging assay. Results : The TIRF imaging assay for serum exosomal miR-21 can distinguish cancer patients from healthy subjects with better performance than conventional real-time polymerase chain reaction (PCR) assay. The exosomal miR-21 level in serum is also informative for monitoring tumor progression and responses to treatment. Moreover, the TIRF assays can readily determine the precise stoichiometry of target exosomal miRNA contents in situ by delivering molecular beacon (MB) probes into EXs. Conclusions : The created TIRF imaging platform shows high applicability to serve as a universal and useful tool for the single-vesicle in situ quantitative and stoichiometric analysis of other disease-associated exosomal miRNAs markers and provide valuable insight into the physiological relevance of EX-mediated miRNA communication.

No abstract

While the deposition of amyloid-β (Aβ) plaques is one of the main pathological hallmarks of incurable Alzheimer's disease (AD), Aβ oligomers have been identified as a more appealing AD biomarker due to their being more pathogenic and neurotoxic. Therefore, the development of a sensitive and effective technique for oligomeric Aβ detection and imaging is beneficial for the early detection of AD, monitoring disease progression, and assessing the efficacy of potential AD drugs. Herein, the development and investigation of the first Aβ oligomer-specific Gd 3+ -based nanoparticles (NPs), NP@SiO 2 @F-SLOH as a multimodal near-infrared imaging (NIRI)/T 1weighted magnetic resonance imaging (MRI) contrast agent for real-time visualization of Aβ contents in an AD mouse model is reported. Remarkably, the NP@SiO 2 @F-SLOH is successfully applied for in vivo and ex vivo NIRI with high sensitivity and selectivity for Aβ oligomers and for MRI with good spatial resolution in different age groups in an AD mouse model. Furthermore, the NP probe exhibits a noticeable inhibitory effect on Aβ fibrillation and neuroprotection against Aβ-induced toxicity indicating its desirable therapeutic potential for AD. All these results illustrate the tremendous potential of this versatile and sensitive nanomaterial as an effective theranostic MRI nanoprobe for practical use.