Dual-modal MRI contrast agent with aggregation-induced emission characteristic for liver specific imaging with long circulation lifetime

Dual/Multi-Modal Image-Guided Diagnosis and Therapy Based on Luminogens with Aggregation-Induced Emission

The combination of multiple imaging methods has made an indelible contribution to the diagnosis, surgical navigation, treatment, and prognostic evaluation of various diseases. Due to the unique advantages of luminogens with aggregation-induced emission (AIE), their progress has been significant in the field of organic fluorescent contrast agents. Herein, this manuscript summarizes the recent advancements in AIE molecules as contrast agents for optical image-based dual/multi-modal imaging. We particularly focus on the exceptional properties of each material and the corresponding application in the diagnosis and treatment of diseases.

Self-Assembled Nano-CT Contrast Agent Leveraging Size Aggregation for Improved In Vivo Tumor CT Imaging

Computed tomography (CT) is a widely utilized noninvasive diagnostic tool in clinical practice. However, the commonly employed small molecular iodinated contrast agents (ICAs) in clinical CT imaging have limitations such as nonspecific distribution in body, rapid clearance through kidneys, etc., leading to a narrow imaging time window. In contrast, existing nano-sized ICAs face challenges like structural uncertainty, poor reproducibility, low iodine content, and uniformity issues. In this study, a novel approach is presented utilizing the aggregation-induced emission luminogen (AIEgen) to design and fabricate a kind of monocomponent nano-sized ICA (namely, BioDHU-CT NPs) that exhibits a unique aggregation effect upon activation. The small sized BioDHU-CT nanoparticles exhibit excellent tumor targeting capabilities and can release ICA modified with AIEgen with a high release efficiency up to 88.45%, under the activation of reactive oxygen species highly expressed in tumor regions. The released ICA performs in situ aggregation capability in the tumor region, which can enhance the retention efficiency of CT contrast agents, extending the imaging time window and improving the imaging quality in tumor regions.

Alkyl Chain Appended Fe(III) Catecholate Complex as a Dual-Modal T1 MRI-NIR Fluorescence Imaging Agent via Second Sphere Water Interactions

The C₁₂-alkyl chain-conjugated Fe(III) catecholate complex [Fe(C₁₂CAT)₃]^3-, Fe(C₁₂CAT)₃ [C₁₂CAT = N-(3,4-dihydroxyphenethyl)dodecanamide], was synthesized and characterized, reported as a dual-modal T₁-MRI and an optical imaging probe. The DFT-optimized structure of Fe(C₁₂CAT)₃ reveals a distorted octahedral coordination geometry around the high spin Fe(III) center. The formation constant (-log K) of Fe(C₁₂CAT)₃ was calculated as 45.4. The complex exhibited r₁-relaxivity values of 2.31 ± 0.12 and 1.52 ± 0.06 mM^-1 s^-1 at 25 and 37 °C, respectively, on 1.41 T at pH 7.3 via second-sphere water interactions. The interaction of Fe(C₁₂CAT)₃ with human serum albumin showed concomitant enhancement of r₁-relaxivity to 6.44 ± 0.15 mM^-1 s^-1. The MR phantom images are significantly brighter and directly correlate to the concentration of Fe(C₁₂CAT)₃. Adding an external fluorescent marker IR780 dye to Fe(C₁₂CAT)₃ leads to the formation of self-assembly by C₁₂-alkyl chains. It resulted in the fluorescence quenching of the dye, and its critical aggregation concentration was calculated as 70 μM. The aggregated matrix of Fe(C₁₂CAT)₃ and IR780 dye is spherical, with an average hydrodynamic diameter of 189.5 nm. This self-assembled supramolecular system is found to be non-fluorescent and was "turn-on" under acidic pH via dissociation of aggregates. The r₁-relaxivity is found to be unchanged during the matrix aggregation and disaggregation. The probe showed MRI ON and fluorescent OFF under physiological conditions and MRI ON and fluorescent ON under acidic pH. The cell viability experiments showed that the cells are 80% viable at 1 mM probe concentration. Fluorescence experiments and MR phantom images showed that Fe(C₁₂CAT)₃ is a potential dual model imaging probe to visualize the acidic pH environment of the cells.

Aggregation-induced emission-active micelles: synthesis, characterization, and applications

Aggregation-induced emission (AIE)-active micelles are a type of fluorescent functional materials that exhibit enhanced emissions in the aggregated surfactant state. They have received significant interest due to their excellent fluorescence efficiency in the aggregated state, remarkable processability, and solubility. AIE-active micelles can be designed through the self-assembly of amphipathic AIE luminogens (AIEgens) and the encapsulation of non-emissive amphipathic molecules in AIEgens. Currently, a wide range of AIE-active micelles have been constructed, with a significant increase in research interest in this area. A series of advanced techniques has been used to characterize AIE-active micelles, such as cryogenic-electron microscopy (Cryo-EM) and confocal laser scanning microscopy (CLSM). This review provides an overview of the synthesis, characterization, and applications of AIE-active micelles, especially their applications in cell and in vivo imaging, biological and organic compound sensors, anticancer drugs, gene delivery, chemotherapy, photodynamic therapy, and photocatalytic reactions, with a focus on the most recent developments. Based on the synergistic effect of micelles and AIE, it is anticipated that this review will guide the development of innovative and fascinating AIE-active micelle materials with exciting architectures and functions in the future.

One-Pot Synthesis of Customized Metal-Phenolic-Network-Coated AIE Dots for In Vivo Bioimaging

The integration of aggregation-induced emission luminogens (AIEgens) and inorganic constituents to generate multifunctional nanocomposites has attracted much attention because it couples the bright aggregate-state fluorescence of AIEgens with the diverse imaging modalities of inorganic constituents. Herein, a facile and universal strategy to prepare metal-phenolic-network (MPN)-coated AIE dots in a high encapsulation efficiency is reported. Through precise control on the nucleation of AIEgens and deposition of MPNs in tetrahydrofuran/water mixtures, termed as coacervation, core-shell MPN-coated AIE dots with bright emission are assembled in a one-pot fashion. The optical properties of MPN-coated AIE dots can be readily tuned by varying the incorporated AIEgens. Different metal ions, such as Fe³⁺ , Ti⁴⁺ , Cu²⁺ , Ni²⁺ , can be introduced to the nanoparticles. The MPN-coated AIE dots with a red-emissive AIEgen core are successfully used to perform magnetic resonance/fluorescence dual-modality imaging in a tumor-bearing mouse model and blood flow visualization in a zebrafish larva. It is believed that the present study provides a tailor-made nanoplatform to meet the individual needs of in vivo bioimaging.

Multiple Light-Activated Photodynamic Therapy of Tetraphenylethylene Derivative with AIE Characteristics for Hepatocellular Carcinoma via Dual-Organelles Targeting

Photodynamic therapy (PDT) has emerged as a promising locoregional therapy of hepatocellular carcinoma (HCC). The utilization of luminogens with aggregation-induced emission (AIE) characteristics provides a new opportunity to design functional photosensitizers (PS). PSs targeting the critical organelles that are susceptible to reactive oxygen species damage is a promising strategy to enhance the effectiveness of PDT. In this paper, a new PS, 1-[2-hydroxyethyl]-4-[4-(1,2,2-triphenylvinyl)styryl]pyridinium bromide (TPE-Py-OH) of tetraphenylethylene derivative with AIE feature was designed and synthesized for PDT. The TPE-Py-OH can not only simultaneously target lipid droplets and mitochondria, but also stay in cells for a long period (more than 7 days). Taking advantage of the long retention ability of TPE-Py-OH in tumor, the PDT effect of TPE-Py-OH can be activated through multiple irradiations after one injection, which provides a specific multiple light-activated PDT effect. We believe that this AIE-active PS will be promising for the tracking and photodynamic ablation of HCC with sustained effectiveness.

AIE materials for cancer cell detection, bioimaging and theranostics

AIE materials exhibit weakly emissive or non-emissive properties in dilute solutions while emit powerful fluorescence in the aggregated/solid state. Recently, AIE based materials have gained immense attention due to their multifunctional role in cancer cell detection, bioimaging and cancer theranostics. In this present book chapter, we will highlight recent advancements of AIE materials for different cancer theranostics applications.

Synthesis of a Thermal-Responsive Dual-Modal Supramolecular Probe for Magnetic Resonance Imaging and Fluorescence Imaging

Dual-modal imaging can integrate the advantages of different imaging technologies, which could improve the accuracy and efficiency of clinical diagnosis. Herein, a novel amphiphilic thermal-responsive copolymer obtained from three types of monomers, N-isopropyl acrylamide, 2-(acetoacetoxy) ethyl methacrylate, and propargyl methacrylate, by RAFT copolymerization, is reported. It can be grafted with β-cyclodextrin and aggregation-induced emission (AIE) luminogens tetraphenylethylene by click chemistry and Biginelli reaction. The multifunctional supramolecular polymer (P4) can be constructed by host-guest inclusion between the copolymer and the Gd-based contrast agent (CA) modified by adamantane [Ad-(DOTA-Gd)]. And it can form vesicles with a bilayer structure in aqueous which will enhance the AIE and magnetic resonance imaging effects. As fluorescent thermometer, P4 can enter HeLa cells for intracellular fluorescence imaging (FI) and is sensitive to temperature with detection limit value of 1.5 °C. As magnetic resonance CA, P4 exhibits higher relaxation compared to Magnevist, which can prolong the circulation time in vivo. In addition, Gd³⁺ in the polymer can be quickly released from the body by disassembly that reduced the biological toxicity. This work introduces new synthetic ideas for dual-modal probe, which has great potential for clinical diagnostic applications in bioimaging.

Synergistic Enhancement of Fluorescence and Magnetic Resonance Signals Assisted by Albumin Aggregate for Dual-Modal Imaging

Dual-modal fluorescence and magnetic resonance imaging (FLI/MRI) is important for the early diagnosis of malignant tumors. However, facile and opportune strategies to synergistically enhance fluorescence intensity and magnetic resonance (MR) contrast have rarely been reported. Herein, we present a facile strategy using albumin aggregates (AAs) to synergistically enhance the fluorescence intensity by aggregation-induced emission (AIE) and MR contrast with prolonged rotational correlation time (τ_R) of Gd(III) chelates and the diffusion correlation time (τ_D) of surrounding water molecules. The amphiphilic dual-modal FLI/MRI probe of NGd was facilely loaded into albumin pockets and then formed AAs to generate a supramolecular structure of NGd-albumin aggregates (NGd-AAs), which show excellent biocompatibility and biosafety, and exhibit superior fluorescence quantum yield and r₁ over NGd with 6- and 8-fold enhancement, respectively. Moreover, compared with the clinical MRI contrast agent Gd-DOTA, r₁ of NGd-AAs showed a 17-fold enhancement. Therefore, NGd-AAs successfully elicited high-performance dual-modal FLI/MRI in vitro and in vivo and high contrast MR signals were observed in the liver and tumor after intravenous injection of NGd-AAs at a dosage of 6 μmol Gd(III)/kg body weight. This generic and feasible strategy successfully realized a synergistic effect for dual-modal FLI/MRI.

Tetraphenylethylene-conjugated polycation covered iron oxide nanoparticles for magnetic resonance/optical dual-mode imaging

Magnetic resonance (MR)/optical dual-mode imaging with high sensitivity and high tissue resolution have attracted many attentions in biomedical applications. To avert aggregation-caused quenching of conventional fluorescence chromophores, an aggregation-induced emission molecule tetraphenylethylene (TPE)-conjugated amphiphilic polyethylenimine (PEI) covered superparamagnetic iron oxide (Alkyl-PEI-LAC-TPE/SPIO nanocomposites) was prepared as an MR/optical dual-mode probe. Alkyl-PEI-LAC-TPE/SPIO nanocomposites exhibited good fluorescence property and presented higher T ₂ relaxivity (352 Fe mM^-1s^-1) than a commercial contrast agent Feridex (120 Fe mM^-1s^-1) at 1.5 T. The alkylation degree of Alkyl-PEI-LAC-TPE effects the restriction of intramolecular rotation process of TPE. Reducing alkane chain grafting ratio aggravated the stack of TPE, increasing the fluorescence lifetime of Alkyl-PEI-LAC-TPE/SPIO nanocomposites. Alkyl-PEI-LAC-TPE/SPIO nanocomposites can effectively labelled HeLa cells and resulted in high fluorescence intensity and excellent MR imaging sensitivity. As an MR/optical imaging probe, Alkyl-PEI-LAC-TPE/SPIO nanocomposites may be used in biomedical imaging for certain applications.

Emerging trends in aggregation induced emissive luminogens as bacterial theranostics

The emergence and spread of pathogenic bacteria, particularly antibiotic-resistant strains pose grave global concerns worldwide, which demand for the rapid development of highly selective and sensitive strategies for specific bacterial detection, identification, imaging and therapy. The fascinating feature of aggregation-induced emissive molecules (AIEgens) to display fluorescence in aggregate form can be suitably coupled with nanotechnology for developing theranostic AIE dots that can offer convenient and customised functions such as sensing, imaging, detection, discrimination and cell kill of different bacterial types. The initial section of the article reveals the necessity for incorporating diagnostic imaging with antibacterial therapy, while the latter part delivers mechanistic insights on the benefits of AIE fluorophores in theranostic applications. Further, the review illustrates the recent advancements of AIEgens as theranostic nanolights in bacterial detection, identification and eradication. The review is organised according to the different classes of AIE-active bacterial theranostics such as carrier-free nanoprodrugs, nanomachines for synergistic imaging-guided cancer treatment and bacterial kill, AIE polymers, bioconjugates and nanoparticle carriers. By elucidating their design principles and applications, as well as highlighting the recent trends and perspectives that can be further explored, we hope to instill more research interest in AIE bacterial theranostics for future translational research.HighlightsCombination of aggregation induced emissive fluorophores and nanotechnology for developing bacterial theranostics.AIE theranostics with customised functions for bacterial imaging, detection, discrimination and cell kill.

Synthesis and preliminary evaluation of a PET-FI bimodal imaging agent targeting estrogen receptor

Estrogen receptor is an attractive target for the diagnosis and treatment of breast cancer. This article reports for the first time a dual-modality imaging agent targeting estrogen receptor that can use PET imaging to diagnose breast cancer and utilize fluorescence imaging to achieve intraoperative navigation. Fluorescence experiments show that [^natGa] 1 has typical aggregate induced emission characteristics. Above the critical concentration, [^natGa] 1 can form biocompatible nanomicelles. [^natGa] 1 can quickly light up estrogen receptor positive MCF-7 cells. Cell uptake experiments show that [⁶⁸Ga] 1 is mediated by estrogen receptor. Therefore, [^nat/68Ga] 1 shows the characteristics of highly sensitive diagnosis and visualization of breast cancer, and can be used as a lead compound for the development of a novel PET-FI bimodal imaging agent targeting the estrogen receptor.

Theranostic Nanoparticles with Aggregation-Induced Emission and MRI Contrast Enhancement Characteristics as a Dual-Modal Imaging Platform for Image-Guided Tumor Photodynamic Therapy

Introduction

Advanced tumor-targeted theranostic nanoparticles play a key role in tumor diagnosis and treatment research. In this study, we developed a multifunctional theranostic platform based on an amphiphilic hyaluronan/poly-(N-ε-carbobenzyloxy-L-lysine) derivative (HA-g-PZLL), superparamagnetic iron oxide (SPIO) and aggregation-induced emission (AIE) nanoparticles for tumor-targeted magnetic resonance (MR) and fluorescence (FL) dual-modal image-guided photodynamic therapy (PDT).

Materials and Methods

The amphiphilic hyaluronan acid (HA) derivative HA-g-PZLL was synthesized by grafting hydrophobic poly-(N-ε-carbobenzyloxy-L-lysine) (PZLL) blocks onto hyaluronic acid by a click conjugation reaction. The obtained HA-g-PZLLs self-assembled into nanoparticles in the presence of AIE molecules and SPIO nanoparticles to produce tumor-targeted theranostic nanoparticles (SPIO/AIE@HA-g-PZLLs) with MR/FL dual-modal imaging ability. Cellular uptake of the theranostic nanoparticles was traced by confocal laser scanning microscopy (CLSM), flow cytometry and Prussian blue staining. The intracellular reactive oxygen species (ROS) generation characteristics of the theranostic nanoparticles were evaluated with CLSM and flow cytometry. The effect of PDT was evaluated by cytotoxicity assay. The dual-mode imaging ability of the nanoparticles was evaluated by a real-time near-infrared fluorescence imaging system and magnetic resonance imaging scanning.

Results

The resulting theranostic nanoparticles not only emit red fluorescence for high-quality intracellular tracing but also effectively produce singlet oxygen for photodynamic tumor therapy. In vitro cytotoxicity experiments showed that these theranostic nanoparticles can be efficiently taken up and are mainly present in the cytoplasm of HepG2 cells. After internalization, these theranostic nanoparticles showed serious cytotoxicity to the growth of HepG2 cells after white light irradiation.

Discussion

This work provides a simple method for the preparation of theranostic nanoparticles with AIE characteristics and MR contrast enhancement, and serves as a dual-modal imaging platform for image-guided tumor PDT.

Application and mechanism of manganese-coated caramelization nanospheres for active targeting in hepatobiliary tumors

Aim: To elucidate the MRI mechanisms of manganese oxide-coated carbohydration nanosphere (Mn@CNS) for active targeting in hepatobiliary tumors. Materials & methods: The cytotoxicity, internalization pathway, metabolism and excretion pathway of Mn@CNS were assessed by several cell types. The MRI of Mn@CNS was verified via rat models bearing hepatobiliary tumors. Results: Mn@CNS showed no obvious cytotoxicity. Mice macrophage and hepatocellular Mn content significantly differed between pre- and post-uptake levels (p < 0.01). The animal experiment revealed fine T1 imaging of hepatobiliary tumors with peak enhancement at 3 h. Mn@CNS was metabolized within the cells and excreted mainly via feces. Conclusion: Mn@CNS is safe, biodegradable, and may serve as a new strategy for active target imaging and treatment applications.

Bimodal Fluorescence-Magnetic Resonance Contrast Agent for Apoptosis Imaging

Effective cancer therapy largely depends on inducing apoptosis in cancer cells via chemotherapy and/or radiation. Monitoring apoptosis in real-time provides invaluable information for evaluating cancer therapy response and screening preclinical anticancer drugs. In this work, we describe the design, synthesis, characterization, and in vitro evaluation of caspase probe 1 (CP1), a bimodal fluorescence-magnetic resonance (FL-MR) probe that exhibits simultaneous FL-MR turn-on response to caspase-3/7. Both caspases exist as inactive zymogens in normal cells but are activated during apoptosis and are unique biomarkers for this process. CP1 has three distinct components: a DOTA-Gd(III) chelate that provides the MR signal enhancement, tetraphenylethylene as the aggregation induced emission luminogen (AIEgen), and DEVD peptide which is a substrate for caspase-3/7. In response to caspase-3/7, the water-soluble peptide DEVD is cleaved and the remaining Gd(III)-AIEgen (Gad-AIE) conjugate aggregates leading to increased FL-MR signals. CP1 exhibited sensitive and selective dual FL-MR turn-on response to caspase-3/7 in vitro and was successfully tested by fluorescence imaging of apoptotic cells. Remarkably, we were able to use the FL response of CP1 to quantify the exact concentrations of inactive and active agents and accurately predict the MR signal in vitro. We have demonstrated that the aggregation-driven FL-MR probe design is a unique method for MR signal quantification. This probe design platform can be adapted for a variety of different imaging targets, opening new and exciting avenues for multimodal molecular imaging.

Aggregation-induced emission (AIE) fluorophores as imaging tools to trace the biological fate of nano-based drug delivery systems

The vigorous development of nanotechnology has been accompanied by an equally strong interest and research efforts in nano-based drug delivery systems (NDDSs). However, only a few NDDSs have been translated into clinic thus far. One of the important hurdles is the lack of tools to comprehensively and directly trace the biological fate of NDDSs. Recently, aggregation-induced emission (AIE) fluorophores have emerged as attractive bioimaging tools due to flexible controllability, negligible toxicity and superior photostability. Herein, we recapitulate the current advances in the application of AIE fluorophores to monitor NDDSs both in vitro and in vivo. Particularly, we discuss the cellular fates of self-indicating and stimuli-responsive NDDSs with AIE fluorophores. Moreover, we highlight the in vivo application of AIE agents on the long-term tracking of therapeutics and the multi-modal monitoring of diagnostics in NDDSs. Challenges and opportunities in AIE-guided exploration of NDDSs are also discussed in detail.

Theranostic Nanodots with Aggregation-Induced Emission Characteristic for Targeted and Image-Guided Photodynamic Therapy of Hepatocellular Carcinoma

Photosensitizer (PS) serves as the central element of photodynamic therapy (PDT). The use of common nanoparticles (NPs) for PDT has typically been rendered less effective by the undesirable aggregation-caused quenching (ACQ) effect, resulting in quenched fluorescence and reduced reactive oxygen species (ROS) generation that diminish the imaging quality and PDT efficacy. To overcome the ACQ effect and to enhance the overall efficacy of PDT, herein, integrin ανβ3-targeted organic nanodots for image-guided PDT were designed and synthesized based on a red emissive aggregation-induced emission (AIE) PS. Methods: The TPETS nanodots were prepared by nano-precipitation method and further conjugated with thiolated cRGD (cRGD-SH) through a click reaction to yield the targeted TPETS nanodots (T-TPETS nanodots). Nanodots were characterized for encapsulation efficiency, conjugation rate, particle size, absorption and emission spectra and ROS production. The targeted fluorescence imaging and antitumor efficacy of T-TPETS nanodot were evaluated both in vitro and in vivo. The mechanism of cell apoptosis induced by T-TPETS nanodot mediated-PDT was explored. The biocompatibility and toxicity of the nanodots was examined using cytotoxicity test, hemolysis assay, blood biochemistry test and histological staining. Results: The obtained nanodots show bright red fluorescence and highly effective 1O2 generation in aggregate state. Both in vitro and in vivo experiments demonstrate that the nanodots exhibit excellent tumor-targeted imaging performance, which facilitates image-guided PDT for tumor ablation in a hepatocellular carcinoma model. Detailed analysis reveals that the nanodot-mediated PDT is able to induce time- and concentration-dependent cell death. The use of PDT at a high PDT intensity leads to direct cell necrosis, while cell apoptosis via the mitochondria-mediated pathway is achieved under low PDT intensity. Conclusion: Our results suggest that well-designed AIE nanodots are promising for image-guided PDT applications.

Aggregation-Induced Emission for Visualization in Materials Science

Fluorescent imaging techniques have attracted much attention as a powerful tool to realize the visualization of structural and morphological evolution of various materials. However, the traditional fluorescent dyes usually suffered from aggregation-caused quenching, which severely limits the visualization results. In contrast, aggregation-induced emission (AIE) molecules with high quantum yields in the condensed state showed great opportunities for imaging techniques. In this feature article, recent progresses in visualization with AIE molecules are discussed. Assembly processes including crystallization, gelation process, and dissipative assembly have been observed. To better study information obtained regarding the processes, visualization during reactions, phase transitions, and molecular motions are successfully presented. Based on these successes, AIE molecules were further applied for phase recognition, macro-dispersion evaluation, and damage detection. Finally, we also present the outlook and perspectives, in our opinion, for the development of visualization by AIE molecules.

High-efficiency fluorescent and magnetic multimodal probe for long-term monitoring and deep penetration imaging of tumors

High-quality multimodal imaging requires exogenous contrast agents with high sensitivity, spatial–temporal resolution, and high penetration depth for the accurate diagnosis and surveillance of cancer.

Aggregation-induced emission based PET probe for liver function imaging

A novel aggregation-induced emission based PET probe for liver function imaging was developed.

AIEgen functionalized inorganic–organic hybrid nanomaterials for cancer diagnosis and therapy

AIEgen functionalized inorganic–organic hybrid nanomaterials with multifunctions can be used for cancer diagnosis and imaging-guided synergistic therapy.

Aggregation-Induced Emission Luminogens: Union Is Strength, Gathering Illuminates Healthcare

The rapid development of healthcare techniques encourages the emergence of new molecular imaging agents and modalities. Fluorescence imaging that enables precise monitoring and detection of biological processes/diseases is extensively investigated as this imaging technique has strengths in terms of high sensitivity, excellent temporal resolution, low cost, and good safety. Aggregation-induced emission luminogens (AIEgens) have recently emerged as a new class of emitters that possess several notable features, such as high brightness, large Stokes shift, marked photostability, good biocompatibility, and so on. So far, AIEgens are widely explored and exhibit superb performance in the area of biomedicine and life sciences. Herein, this review summarizes and discusses the recent investigations of AIEgens for in vivo diagnosis and therapy including long-term tracking, 3D angiography, multimodality imaging, disease theranostics, and activatable sensing. Collectively, these results reveal that AIEgens are of great promise for in vivo biomedical applications. It is hoped that this review will lead to new insights into the development of advanced healthcare materials.

Iron oxide nanoparticles for targeted imaging of liver tumors with ultralow hepatotoxicity

Even though iron oxide (Fe₃O₄) nanoparticles are promising materials for magnetic resonance imaging (MRI) contrast agents, their biocompatibility and targeting efficacy still need to be improved. Herein, we modified glycyrrhetinic acid (GA) groups on Fe₃O₄ nanoparticles (Fe₃O₄@cGlu-GA) for liver tumor-targeted imaging. To evaluate the biocompatibility of these nanoparticles, we studied their cytotoxicity, hemolysis, and hepatotoxicity. We measured the uptake of Fe₃O₄@cGlu-GA nanoparticles in normal and liver tumor cells, then we investigated the specificity of Fe₃O₄@cGlu-GA nanoparticles in mouse models bearing subcutaneous and orthotopic liver tumors. With good biocompatibility and targeting efficacy both in vitro and in vivo, the Fe₃O₄@cGlu-GA nanoparticles are promising MRI contrast agents with ultralow hepatotoxicity and show great improvement on existing Fe₃O₄-based nanoparticles.

Positively Charged Hyperbranched Polymers with Tunable Fluorescence and Cell Imaging Application

Fluorescence-tunable materials are becoming increasingly attractive because of their potential applications in optics, electronics, and biomedical technology. Herein, a multicolor molecular pixel system is realized using a simple copolymerization method. Bleeding of two complementary colors from blue and yellow fluorescence segments reproduced serious multicolor fluorescence materials. Interestingly, the emission colors of the polymers can be fine-tuned in the solid state, solution phase, and in hydrogel state. More importantly, the positive fluorescent polymers exhibited cell-membrane permeable ability and were found to accumulate on the cell nucleus, exhibiting remarkable selectivity to give bright fluorescence. The DNA/RNA selectivity experiments in vitro and in vivo verified that [tris(4-(pyridin-4-yl)phenyl)amine]-[1,8-dibromooctane] has prominent selectivity to DNA over RNA inside cells.

Progress and Trends in AIE-Based Bioprobes: A Brief Overview

Luminescent bioprobes are powerful analytical means for biosensing and optical imaging. Luminogens featured with aggregation-induced emission (AIE) attributes have emerged as ideal building blocks for high-performance bioprobes. Bioprobes constructed with AIE luminogens have been identified to be a novel class of FL light-up probing tools. In contrast to conventional bioprobes based on the luminophores with aggregation-caused quenching (ACQ) effect, the AIE-based bioprobes enjoy diverse superiorities, such as lower background, higher signal-to-noise ratio and sensitivity, better accuracy, and more outstanding resistance to photobleaching. AIE-based bioprobes have been tailored for a vast variety of purposes ranging from biospecies sensing to bioimaging to theranostics (i.e., image-guided therapies). In this review, recent five years' advances in AIE-based bioprobes are briefly overviewed in a perspective distinct from other reviews, focusing on the most appealing trends and progresses in this flourishing research field. There are altogether 11 trends outlined, which have been classified into four aspects: the probe composition and form (bioconjugtes, nanoprobes), the output signal of probe (far-red/near-infrared luminescence, two/three-photon excited fluorescence, phosphorescence), the modality and functionality of probing system (dual-modality, dual/multifunctionality), the probing object and application outlet (specific organelles, cancer cells, bacteria, real samples). Typical examples of each trend are presented and specifically demonstrated. Some important prospects and challenges are pointed out as well in the hope of intriguing more interests from researchers working in diverse areas into this exciting research field.

A Transformable Chimeric Peptide for Cell Encapsulation to Overcome Multidrug Resistance

Multidrug resistance (MDR) remains one of the biggest obstacles in chemotherapy of tumor mainly due to P-glycoprotein (P-gp)-mediated drug efflux. Here, a transformable chimeric peptide is designed to target and self-assemble on cell membrane for encapsulating cells and overcoming tumor MDR. This chimeric peptide (C₁₆ -K(TPE)-GGGH-GFLGK-PEG₈ , denoted as CTGP) with cathepsin B-responsive and cell membrane-targeting abilities can self-assemble into nanomicelles and further encapsulate the therapeutic agent doxorubicin (termed as CTGP@DOX). After the cleavage of the Gly-Phe-Leu-Gly (GFLG) sequence by pericellular overexpressed cathepsin B, CTGP@DOX is dissociated and transformed from spherical nanoparticles to nanofibers due to the hydrophilic-hydrophobic conversion and hydrogen bonding interactions. Thus obtained nanofibers with cell membrane-targeting 16-carbon alkyl chains can adhere firmly to the cell membrane for cell encapsulation and restricting DOX efflux. In comparison to free DOX, 45-time higher drug retention and 49-fold greater anti-MDR ability of CTGP@DOX to drug-resistant MCF-7R cells are achieved. This novel strategy to encapsulate cells and reverse tumor MDR via morphology transformation would open a new avenue towards chemotherapy of tumor.

AIEgen-Based Fluorescent Nanomaterials: Fabrication and Biological Applications

In recent years, luminogens with the feature of aggregation-induced emission (AIEgen) have emerged as advanced luminescent materials for fluorescent nanomaterial preparation. AIEgen-based nanomaterials show enhanced fluorescence efficiency and superior photostability, which thusly offer unique advantages in biological applications. In this review, we will summarize the fabrication methods of AIEgen-based nanomaterials and their applications in in vitro/in vivo imaging, cell tracing, photodynamic therapy and drug delivery, focusing on the recent progress.

‘Aggregation induced emission’ active iridium(iii) complexes with applications in mitochondrial staining

Synthesized two new bis-cyclometalated iridium(iii) complexes exhibiting strong AIE, studied their luminescence by spectroscopy and quantum chemical calculations and applied as a non-toxic bio-imaging probe for mitochondrial staining.

Multifunctional AIEgens for Future Theranostics

The combination of diagnosis and therapeutics into one theranostics system has attracted great interest in life science and biomedical fields. The current theranostic platform largely relies on the integration of multiple materials with different functionalities. The all-in-one approach has the risk of high complicity with reduced reproducibility. Smart design of simple molecules born with multifunctions should represent one of the future directions in theranostics. Fluorogens with aggregation-induced emission (AIEgens) are one type of such smart materials, which have attracted increasing attentions in recent years. In this concept, the key frontier developments of simple AIEgens with multifunctions for imaging and therapy are presented, which include fluorescence-photoacoustic imaging, fluorescence-magnetic resonance imaging, fluorescence image-guided photodynamic therapy, fluorescence image-guided chemotherapy and photoacoustic image-guided photothermal therapy. The smart molecular design to endow each AIEgen with strong capability to simultaneously offer two or more theranostic functions should attract more scientists into this exciting research direction.

Ligand-based targeted therapy: a novel strategy for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver cancer with high morbidity and mortality worldwide. Chemotherapy is recommended to patients with intermediate or advanced stage cancer. However, the conventional chemotherapy yields low desired response rates due to multidrug resistance, fast clearance rate, nonspecific delivery, severe side effects, low drug concentration in cancer cells, and so on. Nanoparticle-mediated targeted drug delivery system can surmount the aforementioned obstacles through enhanced permeability and retention effect and active targeting as a novel approach of therapeutics for HCC in recent years. The active targeting is triggered by ligands on the delivery system, which recognize with and internalize into hepatoma cells with high specificity and efficiency. This review focuses on the latest targeted delivery systems for HCC and summarizes the ligands that can enhance the capacity of active targeting, to provide some insight into future research in nanomedicine for HCC.

A four-fold interpenetrated metal-organic framework as a fluorescent sensor for volatile organic compounds

A four-fold interpenetrated three dimensional (3D) metal-organic framework, [Cd2(tppe)(bpdc)2(H2O)]·solvent (1), was synthesized with a tetraphenylethene (TPE)-based ligand, 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethene (TPPE). This complex exhibits intense blue luminescence and is sensitive to toxic volatile organic compounds (VOCs).

Harnessing the Cancer Radiation Therapy by Lanthanide-Doped Zinc Oxide Based Theranostic Nanoparticles

In this paper, doping of europium (Eu) and gadolinium (Gd) as high-Z elements into zinc oxide (ZnO) nanoparticles (NPs) was designed to optimize restricted energy absorption from a conventional radiation therapy by X-ray. Gd/Eu-doped ZnO NPs with a size of 9 nm were synthesized by a chemical precipitation method. The cytotoxic effects of Eu/Gd-doped ZnO NPs were determined using MTT assay in L929, HeLa, and PC3 cell lines under dark conditions as well as exposure to ultraviolet, X-ray, and γ radiation. Doped NPs at 20 μg/mL concentration under an X-ray dose of 2 Gy were as efficient as 6 Gy X-ray radiation on untreated cells. It is thus suggested that the doped NPs may be used as photoinducers to increase the efficacy of X-rays within the cells, consequently, cancer cell death. The doped NPs also could reduce the received dose by normal cells around the tumor. Additionally, we evaluated the diagnostic efficacy of doped NPs as CT/MRI nanoprobes. Results showed an efficient theranostic nanoparticulate system for simultaneous CT/MR imaging and cancer treatment.

MoS2-Gd Chelate Magnetic Nanomaterials with Core-Shell Structure Used as Contrast Agents in in Vivo Magnetic Resonance Imaging

Despite their frequent usages as contrast agents for in vivo MRI imaging, paramagnetic molecules continue to suffer from low resolution, physicochemical instability, and high toxicity. Herein, we present a molybdenum disulfide and gadolinium complex, as an alternative core-shell magnetic nanomaterial that exhibits enhanced paramagnetic property; 4.5-times longer water proton spin-lattice relaxation time (T1) when compared to commercial gadolinium contrast agents; as well as lowered toxicity, extended blood circulation time, increased stability, and desirable excretion characteristic. Transmission electron microscopy (TEM) revealed smooth core-shell nanoparticles 100 nm in size with a shell width of approximately 10 nm. These findings suggest that the synthesized nanomaterial possesses high potential as a positive contrast agent for the enhancement of MRI imaging.

Selective detection of nitrite ion by an AIE-active tetraphenylethene dye through a reduction step in aqueous media

We report selective and sensitive nitrite sensor in water based on AIE-active tetraphenylethene bearing amino functionality.

Multifunctional polymer nanoparticles: ultra bright near-infrared fluorescence and strong magnetization and their biological applications

Magnetic fluorescent multifunctional polymer NPs Fe₃O₄/DPPBPA@F-127 and their application in MRI and NIR imaging.

pH-responsive iron manganese silicate nanoparticles as T1-T2* dual-modal imaging probes for tumor diagnosis

Magnetic resonance imaging (MRI) probes can be concentrated in tumors through grafting targeting agents. However, the clinical application of such targeted MRI probes is largely limited because specific agents are only used to target specific characteristics of cancer cells. The development of the MRI probes that can be used regardless of tumor types or their developmental stages is highly appreciated. The acidic tumor microenvironments and acidic organelles (endosomes/lysosomes) in cancer cells are universal phenomena of solid tumors, and nanoparticles can also accumulate in tumor tissues by enhanced permeability and retention (EPR) effect. Here, we reported the synthesis of pH-responsive T1-T2* dual-modal contrast agents based on iron manganese silicate (FeMn(SiO4)) hollow nanospheres, which can release Mn(2+) ions in acidic environments, exhibiting excellent ability as agents for magnetic resonance and red fluorescence imaging. MRI for mouse models revealed that the nanoprobes could accumulate in tumors via EPR effect and then distinguish tumors from normal tissues with the synergistic effect of T1 and T2* signal only 10 min after intravenous injection. Fluorescence imaging demonstrated that the nanoprobes could be endocytosed into cancer cells and located at their lower pH compartments. Moreover, the hollow nanospheres showed no obvious toxicity and inflammation to the major organs of mice, which made them attractive diagnostic agents for different types of cancers.

Amine functionalized tetraphenylethylene: a novel aggregation-induced emission based fluorescent chemodosimeter for nitrite and nitrate ions

A novel AIE-based fluorescent probe for the detection of trace amounts of nitrite and nitrate ions in water has been developed, which spontaneously detects nitrites (or nitrates) by a fluorescence “turn-off” method.

An aggregation-induced emission based “turn-on” fluorescent chemodosimeter for the selective detection of Pb2+ ions

An aggregation-induced emission (AIE) based “turn-on” fluorescent chemodosimeter for selective detection of Pb²⁺ ions has been developed. The probe is a phosphate functionalized tetraphenylethylene derivative and the resulting lead–TPE complex has very low solubility in working solvent and triggers AIE and shows a low detection limit of 10 ppb.