A facile and novel AIE vesicle as nanoprobe for simple and rapid detection of TNT in water

Trinitrotoluene (TNT) in water will damage biological tissues and organs of the human body due to its high toxicity and risk. However, the simple and rapid detection of TNT in water is always a challenging task. Herein, we reported a novel aggregation-induced emission-a vesicle (AIE-a-V) as fluorescent nanoprobe for the detection of TNT in water by π-π self-assembly of π-π stacking induced aggregation-emission. The AIE-a-V was spherical in shape with a hydrodynamic diameter of ∼106 nm and possessed robust stability. In addition, the AIE-a-V showed strong fluorescence and its fluorescence would quickly disappear after contact with TNT. Based on this, without any cumbersome operation, the AIE-a-V could detect the presence of TNT in water within 60 s, and its minimum detectable concentration was as low as 50 nM. Moreover, the AIE-a-V could selectively detect TNT in water and would not be affected by other components, including other aromatic compounds, toxic metals, and acid-base. Therefore, the new AIE-a-V with simplicity, rapidity, sensitivity and selectivity have great application potential in the detection of TNT in water.

Stimuli-responsive liposomal nanoformulations in cancer therapy: Pre-clinical & clinical approaches

The site-specific delivery of antitumor agents is of importance for providing effective cancer suppression. Poor bioavailability of anticancer compounds and the presence of biological barriers prevent their accumulation in tumor sites. These obstacles can be overcome using liposomal nanostructures. The challenges in cancer chemotherapy and stimuli-responsive nanocarriers are first described in the current review. Then, stimuli-responsive liposomes including pH-, redox-, enzyme-, light-, thermo- and magneto-sensitive nanoparticles are discussed and their potential for delivery of anticancer drugs is emphasized. The pH- or redox-sensitive liposomes are based on internal stimulus and release drug in response to a mildly acidic pH and GSH, respectively. The pH-sensitive liposomes can mediate endosomal escape via proton sponge. The multifunctional liposomes responsive to both redox and pH have more capacity in drug release at tumor site compared to pH- or redox-sensitive alone. The magnetic field and NIR irradiation can be exploited for external stimulation of liposomes. The light-responsive liposomes release drugs when they are exposed to irradiation; thermosensitive-liposomes release drugs at a temperature of >40 °C when there is hyperthermia; magneto-responsive liposomes release drugs in presence of magnetic field. These smart nanoliposomes also mediate co-delivery of drugs and genes in synergistic cancer therapy. Due to lack of long-term toxicity of liposomes, they can be utilized in near future for treatment of cancer patients.

AIE-Based Fluorescent Triblock Copolymer Micelles for Simultaneous Drug Delivery and Intracellular Imaging

Fluorescent drug delivery systems have received increasing attention in cancer therapy because they combine drug delivery and bioimaging into a single platform. For example, polymers with aggregation-induced emission (AIE) fluorophores, such as tetraphenylethylene (TPE), have emerged as an elegant choice for drug delivery/bioimaging applications. In this work, we report one-pot sequential organocatalytic ring-opening polymerization of ε-caprolactone (CL) and ethylene oxide (EO) using TPE-(OH)₂ as a difunctional initiator, in the presence of a t-BuP₂/TEB Lewis pair (catalyst), in THF at room temperature. Two well-defined triblock copolymers with inverse block sequences, TPE-(PCL-b-PEO)₂ and TPE-(PEO-b-PCL)₂, were synthesized by altering the sequential addition of CL and EO. The physicochemical properties, including hydrodynamic diameter, morphology, and AIE properties of the synthesized amphiphilic triblock copolymers were investigated in aqueous media. The block copolymer micelles were loaded with anticancer drugs doxorubicin and curcumin to serve as drug delivery vehicles. In vitro studies revealed the accelerated drug release at lower pH (5.5), which mimics the tumor microenvironment, different from the physiological pH (7.4). In vitro cytotoxicity studies demonstrated that the neat block copolymer micelles are biocompatible, while drug-loaded micelles exhibited a significant cytotoxic effect in cancer cells. Cellular uptake, examined by confocal laser scanning microscopy, showed that the block copolymer micelles were rapidly internalized by the cells with simultaneous emission of TPE fluorophore. These results suggest that these triblock copolymers can be utilized for intracellular bioimaging.

Utilizing Stimuli Responsive Linkages to Engineer and Enhance Polymer Nanoparticle-Based Drug Delivery Platforms

The devastating nature of cancer continues to be one of the leading causes of death in the world. Chemotherapy is among the most common forms of cancer treatment but comes with a host of adverse effects caused by the therapeutic agents damaging healthy tissue and organs. To limit these side effects, scientists have been designing stimuli responsive drug delivery vessels for targeted release. This Review focuses on the incorporation of stimuli responsive linkages in targeted drug delivery systems to enhance therapeutic efficiency. These platforms are primarily employed to control the distribution of anticancer agents in the body to reduce the adverse side effects caused by their toxicities. We will outline how drug delivery vessels are constructed so that exposure to select environmental and external stimuli releases the enclosed drug only at the target site. Stimuli responsive components are integrated within drug delivery vessels in the form of cross-linkers, polymers, and surface modifications. The changes, these moieties undergo upon stimuli exposure, cascade into larger scale alterations to the platforms, resulting in complete disassembly, reversible morphological variations, and enhanced cellular uptake. The ability for these modes of delivery to be initiated exclusively under stimuli exposure allows for release of toxic therapeutic agents to be confined only to the affected area.

Fe3O4@Void@Microporous Organic Polymer-Based Multifunctional Drug Delivery Systems: Targeting, Imaging, and Magneto-Thermal Behaviors

Multifunctional drug delivery systems were designed and engineered by template synthesis of a microporous organic polymer (MOP) and by postsynthetic modification. Hollow MOP spheres bearing Fe₃O₄ yolks (Fe₃O₄@Void@MOP) were prepared by the synthesis of MOP on Fe₃O₄@SiO₂ nanoparticles and by successive silica etching. In addition to the magneto-thermal function of Fe₃O₄ yolks, an aggregation-induced emission (AIE) feature was incorporated into the Fe₃O₄@Void@MOP through a homocoupling of tetra(4-ethynylphenyl)ethylene to form Fe₃O₄@Void@MOP-TE. Folate groups were further introduced into Fe₃O₄@Void@MOP-TE through the postsynthetic modification based on the thiol-yne click reaction. The resultant Fe₃O₄@Void@MOP-TE-FA showed multifunctionality in antitumoral therapy via folate receptor targeting, doxorubicin delivery, AIE-based imaging, and the magneto-thermal feature.

Novel polymeric micelles as enzyme-sensitive nuclear-targeted dual-functional drug delivery vehicles for enhanced 9-nitro-20(S)-camptothecin delivery and antitumor efficacy

9-Nitro-20(S)-camptothecin (9-NC) is a broad-spectrum antitumor drug used in tumor treatments, but its clinical applications and antitumor efficacy are limited by its structural instability, poor solubility, and extremely low drug utilization in tumor tissues. In this study, enzyme-sensitive nuclear-targeted dual-functional polymeric micelles were developed for 9-NC delivery with a high drug loading content (12.93 ± 0.88%), steady-state circulation, and a rapid attack at the "heart" of tumor cells. Briefly, chrysin (CHR) as a π-conjugated moiety was immobilized on the PCL terminal in the TAT-PCL amphiphiles and combined with the ALAL peptide as a linker on HA chains to yield the ultimate CHR-PCL-TAT-ALAL-HA (HATPC) amphiphiles. Spherical 9-NC-loaded micelles were obtained from the self-assembly of the dual-functional amphiphiles comprising HATPC and 9-NC with uniform nanosize (121.6 ± 5.79 nm), well-distributed morphology (PDI: 0.256), and negative surface charge (-23.2 ± 0.5 mV), yielding high stability during blood circulation. In this drug delivery system, HA acts as an active tumor-targeting instrument via CD44-receptor-mediated endocytosis; further, the ALAL peptide could be cutoff in the lysosomes of the tumor cells due to the high expression of cathepsin B, leading to lysosomal escape, while the secondary polymeric micelles targeted the tumor cell nucleus via the exposed TAT peptide. The enzyme sensitivity and nuclei targetability of the 9-NC/HATPC micelles were confirmed by dynamic light scattering and confocal laser scanning microscopy analyses. As compared to free 9-NC and traditional mPEG2k-PCL2k polymeric micelles, 9-NC/HATPC micelles were the most concentrated in the tumor cell nucleus; therefore, they exhibited the highest cytotoxicity against SKOV3 tumor cells both in vitro (IC50 = 0.03 μg mL-1) and in vivo. This enzyme-sensitive nuclear-targeted dual-functional drug delivery system involving HATPC provided a new and promising strategy for enhanced 9-NC delivery and antitumor efficacy.