A Gold Nanocage/Cluster Hybrid Structure for Whole-Body Multispectral Optoacoustic Tomography Imaging, EGFR Inhibitor Delivery, and Photothermal Therapy.

Gold nanocages (AuNCs) and gold nanoclusters (AuClusters) are two classes of advantageous nanostructures with special optical properties, and many other attractive properties. Integrating them into one nanosystem may achieve greater and smarter performance. Herein, a hybrid gold nanostructure for fluorescent and optoacoustic tomography imaging, controlled release of drugs, and photothermal therapy (PTT) is demonstrated. For this nanodrug (EA-AB), an epidermal growth factor receptor (EGFR) inhibitor erlotinib (EB) is loaded into AuNCs, which are then capped and functionalized by biocompatible AuCluster@BSA (BSA = bovine serum albumin) conjugates via electrostatic interaction. Upon cell internalization, the lysosomal proteases and low pH cause the release of EB from EA-AB, and also induce fluorescence restoration of the AuCluster for imaging. Irradiation with near-infrared light further promotes the drug release and affords a PTT effect as well. The AuNC-based nanodrug is optoacoustically active, and its biodistribution and metabolic process have been successfully monitored by whole-body and 3D multispectral optoacoustic tomography imaging. Owing to the combined actions of PTT and EGFR pathway blockage, EA-AB exhibits marked tumor inhibition efficacy in vivo.

Activatable probes for diagnosing and positioning liver injury and metastatic tumors by multispectral optoacoustic tomography.

Optoacoustic tomography (photoacoustic tomography) is an emerging imaging technology displaying great potential for medical diagnosis and preclinical research. Rationally designing activatable optoacoustic probes capable of diagnosing diseases and locating their foci can bring into full play the role of optoacoustic tomography (OAT) as a promising noninvasive imaging modality. Here we report two xanthene-based optoacoustic probes (C1X-OR1 and C2X-OR2) for temporospatial imaging of hepatic alkaline phosphatase (or ß-galactosidase) for evaluating and locating drug-induced liver injury (or metastatic tumor). The probes rapidly respond to the disease-specific biomarkers by displaying red-shifted NIR absorption bands and generate prominent optoacoustic signals. Using multispectral optoacoustic tomography (MSOT), we can precisely localize the focus of drug-induced liver injury in mice using C1X-OR1, and the metastatic tumors using C2X-OR2. This work suggests that the activatable optoacoustic chromophores may potentially be applied for diagnosing and localizing disease foci, especially smaller and deeper ones.

A turn-on fluorescence probe based on aggregation-induced emission for leucine aminopeptidase in living cells and tumor tissue.

Abnormally-expressed leucine aminopeptidase (LAP) is associated with diverse physiological and pathological disorders; hence developing a highly selective and sensitive detection system for LAP is of great significance. Herein, a fluorescent light-up system with aggregation-induced emission (AIE) characteristic, (DPA-TPE-Leu) has been developed for detecting LAP, in which the recognition unit l-leucine amide group also acts as the hydrophilic moiety. Upon LAP-triggered enzymatic reaction, l-leucine amide moiety is cleaved from the probe molecule, resulting in the formation and aggregation of the hydrophobic reaction product (DPE-TPE-OH) with AIE effect and thus giving out the turn-on green fluorescence. The system features excellent photostability, large Stokes shift (194 nm), good water solubility, high sensitivity with the detection limit of 0.16 U L-1, favorable specificity and low cytotoxicity. It has been effectively utilized in fluorescent imaging of endogenous LAP in living cells, and also successfully applied for fluorescent imaging of HepG2 xenograft tumor. Such a fluorescent assay could provide a convenient and sensitive method for detecting LAP activity and might aid in the auxiliary diagnosis of hepatocellular carcinoma and related pathological analysis in biopsy.

A Fluorescent Probe for Early Detection of Melanoma and Its Metastasis by Specifically Imaging Tyrosinase Activity in a Mouse Model.

Melanoma is a type of highly malignant and metastatic skin cancer, and early detection of melanoma by analyzing the level of its biomarker may decrease the likelihood of mortality. In this study, a fluorescent probe called NBR-AP for detecting tyrosinase (a biomarker of melanoma) has been created by incorporating a hydroxyphenylurea group (as a substrate for the enzyme) onto a fluorescent dye phenoxazine derivative (as an activatable signal reporter). This probe can be activated to generate fluorescence through a tyrosinase-mediated oxidation followed by hydrolysis of the urea linkage. The probe is able to detect the endogenous tyrosinase level in live cells and in zebrafish sensitively and selectively. Moreover, by imaging the tyrosinase activity, NBR-AP has been successfully applied to diagnose the melanoma and its metastasis in xenogeneic mouse models established via subcutaneous injection of B16F10 cells.

AIE fluorophore with enhanced cellular uptake for tracking esterase-activated release of taurine and ROS scavenging.

Fluorophores with aggregation-induced emission (AIE) characteristics are attractive and versatile tools for both chemical sensing and biological imaging. Herein, we designed and synthesized a fluorescent light-up system CTPE-Tau with enhanced cellular uptake ability. The system possesses several advantages, such as a large Stokes shift, low cytotoxicity, and good photostability. Also, it has been successfully utilized to track esterase-activated release of taurine and to scavenge intracellular ROS, and shows great potential for trackable visualized therapy.

Pyrene Derivative Emitting Red or near-Infrared Light with Monomer/Excimer Conversion and Its Application to Ratiometric Detection of Hypochlorite.

Fluorescent sensors are attractive and versatile tools for both chemical sensing and biological imaging. Herein, a novel pyrene derivative fluorophore, Py-Cy, possessing the monomer/excimer conversion feature, was synthesized; and the design rationale for this fluorophore is combination of extending conjugation length and incorporating donor-π-acceptor structure. The positively charged Py-Cy shows quite good water solubility and exhibits absorption in the visible-light range, and its monomer and excimer emit red light and near-infrared light respectively, which is extremely beneficial for biosensing or bioimaging. To explore the potential utilization of this new fluorophore, we choose hypochlorite as a model analyte, which can break the double bond in the molecular structure, thereby generating the water-insoluble pyrenecarboxaldehyde; this process correspondingly leads to fluorescence changes and thus affords the ratiometric fluorescent detection of hypochlorite in real samples and cell imaging. The approach offers new insights for designing other fluorophores which emit red or near-infrared light and for devising technically simple ratiometric fluorescent sensors.

A ratiometric fluorescent system for carboxylesterase detection with AIE dots as FRET donors.

A ratiometric fluorescent system for CaE detection with AIE dots as the FRET donors was designed. Upon enzymatic reaction, electrostatic interaction between the cationic TPE-N(+) dots and the enzymatic reaction product - the negatively charged fluorescein molecules - allows the FRET process to proceed, thus affording the ratiometric fluorescence CaE assay.