Liposomal Texaphyrin Theranostics for Metastatic Liver Cancer

Responsive Trimodal Probes for In Vivo Imaging of Liver Inflammation by Coassembly and GSH-Driven Disassembly

Noninvasive in vivo imaging of hepatic glutathione (GSH) levels is essential to early diagnosis and prognosis of acute hepatitis. Although GSH-responsive fluorescence imaging probes have been reported for evaluation of hepatitis conditions, the low penetration depth of light in liver tissue has impeded reliable GSH visualization in the human liver. We present a liver-targeted and GSH-responsive trimodal probe (GdNPs-Gal) for rapid evaluation of lipopolysaccharide- (LPS-) induced acute liver inflammation via noninvasive, real-time in vivo imaging of hepatic GSH depletion. GdNPs-Gal are formed by molecular coassembly of a GSH-responsive Gd(III)-based MRI probe (1-Gd) and a liver-targeted probe (1-Gal) at a mole ratio of 5/1 (1-Gd/1-Gal), which shows high r ₁ relaxivity with low fluorescence and fluorine magnetic resonance spectroscopic (¹⁹F-MRS) signals. Upon interaction with GSH, 1-Gd and 1-Gal are cleaved and GdNPs-Gal rapidly disassemble into small molecules 2-Gd, 2-Gal, and 3, producing a substantial decline in r ₁ relaxivity with compensatory enhancements in fluorescence and ¹⁹F-MRS. By combining in vivo magnetic resonance imaging (¹H-MRI) with ex vivo fluorescence imaging and ¹⁹F-MRS analysis, GdNPs-Gal efficiently detect hepatic GSH using three independent modalities. We noninvasively visualized LPS-induced liver inflammation and longitudinally monitored its remediation in mice after treatment with an anti-inflammatory drug, dexamethasone (DEX). Findings highlight the potential of GdNPs-Gal for in vivo imaging of liver inflammation by integrating molecular coassembly with GSH-driven disassembly, which can be applied to other responsive molecular probes for improved in vivo imaging.

Rational design of a "dual lock-and-key" supramolecular photosensitizer based on aromatic nucleophilic substitution for specific and enhanced photodynamic therapy

Photosensitizing agents are essential for precise and efficient photodynamic therapy (PDT). However, most of the conventional photosensitizers still suffer from limitations such as aggregation-caused quenching (ACQ) in physiological environments and toxic side-effects on normal tissues during treatment, leading to reduced therapeutic efficacy. Thus, integrating excellent photophysical properties and accurate carcinoma selectivity in a photosensitizer system remains highly desired. Herein, a “dual lock-and-key” supramolecular photosensitizer BIBCl–PAE NPs for specific and enhanced cancer therapy is reported. BIBCl–PAE NPs are constructed by encapsulating a rationally designed glutathione (GSH)-activatable photosensitizer BIBCl in a pH-responsive diblock copolymer. In normal tissues, BIBCl is “locked” in the hydrophobic core of the polymeric micelles due to ACQ. Under the “dual key” activation of low pH and high levels of GSH in a tumor microenvironment, the disassembly of micelles facilitates the reaction of BIBCl with GSH to release water-soluble BIBSG with ideal biocompatibility, enabling the highly efficient PDT. Moreover, benefiting from the Förster resonance energy transfer effect of BIBSG, improved light harvesting ability and ¹O₂ production are achieved. In vitro and vivo experiments have demonstrated that BIBCl–PAE NPs are effective in targeting and inhibiting carcinoma. BIBCl–PAE NPs show superior anticancer efficiency relative to non-activatable controls.

The “dual lock-and-key” supramolecular photosensitizers enable specific and enhanced photodynamic therapy (PDT).

Pro-organic radical contrast agents ("pro-ORCAs") for real-time MRI of pro-drug activation in biological systems

Nitroxide-based organic-radical contrast agents (ORCAs) are promising as safe, next-generation magnetic resonance imaging (MRI) tools. Nevertheless, stimuli-responsive ORCAs that enable MRI monitoring of prodrug activation have not been reported; such systems could open new avenues for prodrug validation and image-guided drug delivery. Here, we introduce a novel "pro-ORCA" concept that addresses this challenge. By covalent conjugation of nitroxides and drug molecules (doxorubicin, DOX) to the same brush-arm star polymer (BASP) through chemically identical cleavable linkers, we demonstrate that pro-ORCA and prodrug activation, i.e., ORCA and DOX release, leads to significant changes in MRI contrast that correlate with cytotoxicity. This approach is shown to be general for a range of commonly used linker cleavage mechanisms (e.g., photolysis and hydrolysis) and release rates. Pro-ORCAs could find applications as research tools or clinically viable "reporter theranostics" for in vitro and in vivo MRI-correlated prodrug activation.

AIE based GSH activatable photosensitizer for imaging-guided photodynamic therapy

A novel ferrocene decorated vinyl pyridinium-substituted tetraphenylethylene (TPEPY-S-Fc) linked by a disulfide bond was designed as a GSH activatable photosensitizer by aggregation-induced emission for imaging-guided photodynamic therapy of cancer cells.

Porphyrinoid Drug Conjugates

Drawing inspiration from nature today remains a time-honored means of discovering the therapies of tomorrow. Porphyrins, the so-called "pigments of life" have played a key role in this effort due to their diverse and unique properties. They have seen use in a number of medically relevant applications, including the development of so-called drug conjugates wherein functionalization with other entities is used to improve efficacy while minimizing dose limiting side effects. In this Perspective, we highlight opportunities associated with newer, completely synthetic analogs of porphyrins, commonly referred to as porphyrinoids, as the basis for preparing drug conjugates. Many of the resulting systems show improved medicinal or site-localizing properties. As befits a Perspective of this type, our efforts to develop cancer-targeting, platinum-containing conjugates based on texaphyrins (a class of so-called "expanded porphyrins") will receive particular emphasis; however, the promise inherent in this readily generalizable approach will also be illustrated briefly using two other common porphyrin analogs, namely the corroles (a "contracted porphyrin") and porphycene (an "isomeric porphyrin").

Stimuli-responsive prodrug-based cancer nanomedicine

The rapid development of nanotechnology results in the emergence of nanomedicines, but the effective delivery of drugs to tumor sites remains a great challenge. Prodrug-based cancer nanomedicines thus emerged due to their unique advantages, including high drug load efficiency, reduced side effects, efficient targeting, and real-time controllability. A distinctive characteristic of prodrug-based nanomedicines is that they need to be activated by a stimulus or multi-stimulus to produce an anti-tumor effect. A better understanding of various responsive approaches could allow researchers to perceive the mechanism of prodrug-based nanomedicines effectively and further optimize their design strategy. In this review, we highlight the stimuli-responsive pathway of prodrug-based nanomedicines and their anticancer applications. Furthermore, various types of prodrug-based nanomedicines, recent progress and prospects of stimuli-responsive prodrug-based nanomedicines and patient data in the clinical application are also summarized. Additionally, the current development and future challenges of prodrug-based nanomedicines are discussed. We expect that this review will be valuable for readers to gain a deeper understanding of the structure and development of prodrug-based cancer nanomedicines to design rational and effective drugs for clinical use.

Biologically Responsive Plasmonic Assemblies for Second Near-Infrared Window Photoacoustic Imaging-Guided Concurrent Chemo-Immunotherapy

We developed dual biologically responsive nanogapped gold nanoparticle vesicles loaded with immune inhibitor and carrying an anticancer polymeric prodrug for synergistic concurrent chemo-immunotherapy against primary and metastatic tumors, along with guided cargo release by photoacoustic (PA) imaging in the second near-infrared (NIR-II) window. The responsive vesicle was prepared by self-assembly of nanogapped gold nanoparticles (AuNNPs) grafted with poly(ethylene glycol) (PEG) and dual pH/GSH-responsive polyprodug poly(SN₃₈-co-4-vinylpyridine) (termed AuNNP@PEG/PSN₃₈VP), showing intense PA signal in the NIR-II window. The effect of the rigidity of hydrophobic polymer PSN₃₈VP on the assembled structures and the formation mechanism of AuNNP@SN₃₈ Ve were elucidated by computational simulations. The immune inhibitor BLZ-945 was encapsulated into the vesicles, resulting in pH-responsive release of BLZ-945 for targeted immunotherapy, followed by the dissociation of the vesicles into single AuNNP@PEG/PSN₃₈VP. The hydrophilic AuNNP@PEG/PSN₃₈VP nanoparticles could penetrate deep into the tumor tissues and release the anticancer drug SN₃₈ under the reductive environment. A PA signal in the NIR-II window in the deep tumor region was obtained. The BLZ-945-loaded vesicle enabled enhanced PA imaging-guided concurrent chemo-immunotherapy efficacy, inhibiting the growth of both primary tumors and metastatic tumors.

Oxaliplatin Pt(IV) prodrugs conjugated to gadolinium-texaphyrin as potential antitumor agents

Described here is the development of gadolinium(III) texaphyrin-platinum(IV) conjugates capable of overcoming platinum resistance by 1) localizing to solid tumors, 2) promoting enhanced cancer cell uptake, and 3) reactivating p53 in platinum-resistant models. Side by side comparative studies of these Pt(IV) conjugates to clinically approved platinum(II) agents and previously reported platinum(II)-texaphyrin conjugates demonstrate that the present Pt(IV) conjugates are more stable against hydrolysis and nucleophilic attack. Moreover, they display high potent antiproliferative activity in vitro against human and mouse cell cancer lines. Relative to the current platinum clinical standard of care (SOC), a lead Gd(III) texaphyrin-Pt(IV) prodrug conjugate emerging from this development effort was found to be more efficacious in subcutaneous (s.c.) mouse models involving both cell-derived xenografts and platinum-resistant patient-derived xenografts. Comparative pathology studies in mice treated with equimolar doses of the lead Gd texaphyrin-Pt(IV) conjugate or the US Food and Drug Administration (FDA)-approved agent oxaliplatin revealed that the conjugate was better tolerated. Specifically, the lead could be dosed at more than three times (i.e., 70 mg/kg per dose) the tolerable dose of oxaliplatin (i.e., 4 to 6 mg/kg per dose depending on the animal model) with little to no observable adverse effects. A combination of tumor localization, redox cycling, and reversible protein binding is invoked to explain the relatively increased tolerability and enhanced anticancer activity seen in vivo. On the basis of the present studies, we conclude that metallotexaphyrin-Pt conjugates may have substantial clinical potential as antitumor agents.

Combination of chemotherapy and oxidative stress to enhance cancer cell apoptosis

Cancer cells are vulnerable to reactive oxygen species (ROS) due to their abnormal redox environment. Accordingly, combination of chemotherapy and oxidative stress has gained increasing interest for the treatment of cancer. We report a novel seleno-prodrug of gemcitabine (Gem), Se-Gem, and evaluated its activation and biological effects in cancer cells. Se-Gem was prepared by introducing a 1,2-diselenolane (a five-membered cyclic diselenide) moiety into the parent drug Gem via a carbamate linker. Se-Gem is preferably activated by glutathione (GSH) and displays a remarkably higher potency than Gem (up to a 6-fold increase) to a panel of cancer cell lines. The activation of Se-Gem by GSH releases Gem and a seleno-intermediate nearly quantitatively. Unlike the most ignored side products in prodrug activation, the seleno-intermediate further catalyzes a conversion of GSH and oxygen to GSSG (oxidized GSH) and ROS via redox cycling reactions. Thus Se-Gem may be considered as a suicide agent to deplete GSH and works by a combination of chemotherapy and oxidative stress. This is the first case that employs a cyclic diselenide in prodrug design, and the success of Se-Gem as well as its well-defined action mechanism demonstrates that the 1,2-diselenolane moiety may serve as a general scaffold to advance constructing novel therapeutic molecules with improved potency via a combination of chemotherapy and oxidative stress.

De novo strategy with engineering anti-Kasha/Kasha fluorophores enables reliable ratiometric quantification of biomolecules

Fluorescence-based technologies have revolutionized in vivo monitoring of biomolecules. However, significant technical hurdles in both probe chemistry and complex cellular environments have limited the accuracy of quantifying these biomolecules. Herein, we report a generalizable engineering strategy for dual-emission anti-Kasha-active fluorophores, which combine an integrated fluorescein with chromene (IFC) building block with donor-π-acceptor structural modification. These fluorophores exhibit an invariant near-infrared Kasha emission from the S1 state, while their anti-Kasha emission from the S2 state at around 520 nm can be finely regulated via a spirolactone open/closed switch. We introduce bio-recognition moieties to IFC structures, and demonstrate ratiometric quantification of cysteine and glutathione in living cells and animals, using the ratio (S2/S1) with the S1 emission as a reliable internal reference signal. This de novo strategy of tuning anti-Kasha-active properties expands the in vivo ratiometric quantification toolbox for highly accurate analysis in both basic life science research and clinical applications.

Anti-Metastatic Effects on Melanoma via Intravenous Administration of Anti-NF-κB siRNA Complexed with Functional Peptide-Modified Nano-Micelles

Controlling metastasis is an important strategy in cancer treatment. Nanotechnology and nucleic acids with novel modalities are promising regulators of cancer metastasis. We aimed to develop a small interfering RNA (siRNA) systemic delivery and anti-metastasis system using nanotechnology. We previously reported that polyethylene glycol-polycaprolactone (PEG-PCL) and functional peptide CH2R4H2C nano-micelle (MPEG-PCL-CH2R4H2C) has high siRNA silencing effects, indicated by increased drug accumulation in tumor-bearing mice, and has an anti-tumor effect on solid tumors upon systemic injection. In this study, we aimed to apply our micelles to inhibit metastasis and evaluated the inhibitory effect of anti-RelA siRNA (siRelA), which is a subunit of NF-κB conjugated with MPEG-PCL-CH2R4H2C, via systemic administration. We report that siRelA/MPEG-PCL-CH2R4H2C had a high cellular uptake and suppressed the migration/invasion of cells in B16F10 cells without toxicity. In addition, in a lung metastasis mouse model using intravenous administration of B16F10 cells treated with siRelA/MPEG-PCL-CH2R4H2C, the number of lung nodules in lung tissue significantly decreased compared to naked siRelA and siControl/MPEG-PCL-CH2R4H2C micelle treatments. Hence, we show that RelA expression can reduce cancer metastasis, and MPEG-PCL-CH2R4H2C is an effective siRNA carrier for anti-metastasis cancer therapies.

Overexpression of long non-coding RNA cancer susceptibility 11 is involved in the development of chemoresistance to carboplatin in hepatocellular carcinoma

The long non-coding (lnc)RNA cancer susceptibility 11 (CASC11) promotes gastric cancer, however its role in other diseases is unknown. The present study demonstrated upregulation of lncRNA CASC11 and microRNA (miR)-21 in hepatocellular carcinoma (HCC). Furthermore, the expression of CASC11 was positively correlated with that of miR-21 in HCC tumors. Moreover, overexpression of lncRNA CASC11 led to upregulation of miR-21 in HCC cells, whereas overexpression of miR-21 had no effect on CASC11 levels. The levels of lncRNA CASC11 and miR-21 were found to be upregulated in the plasma of patients with HCC during chemotherapy. In vitro cell experiments demonstrated upregulation of lncRNA CASC11 in HCC cells treated with carboplatin. Additionally, overexpression of lncRNA CASC11 promoted, whereas its knockdown inhibited the viability of HCC cells following carboplatin treatment. Finally, overexpression of miR-21 ameliorated the effects of lncRNA CASC11 knockdown on cell viability. Thus, these findings suggest that upregulation of lncRNA CASC11 is involved in the development of chemoresistance to carboplatin in patients with HCC, via the upregulation of miR-21.

Disulfide chemistry in responsive aggregation of amphiphilic systems

The dynamic nature of the disulfide bond has enhanced the potential for disulfide based amphiphiles in the emerging biomedical field. Disulfide containing amphiphiles have extensively been used for constructing wide ranging soft nanostructures as potential candidates for delivery of drugs, proteins and genes owing to their degradable nature in the presence of intracellular glutathione (present in a many fold excess compared to the extracellular milieu). This degradable nature of amphiphiles is not only useful to deliver therapeutics but it also eliminates the toxicity issues associated with the carrier after delivery of such therapeutics. Therefore, these bioreducible and biocompatible nano-aggregates inspired researchers to use them as vehicles for therapeutic delivery and as a result the literature of disulfide containing amphiphiles has been intensified. This review article highlights the structural diversity in disulfide containing amphiphilic small molecule and polymeric systems, structural effects on their aqueous aggregation, redox-responsive disassembly and biological applications. Furthermore, the use of disulfide chemistry towards the design of cell penetrating polymers has also been discussed. Finally a brief perspective on some future opportunities of these systems is provided.

Protein encapsulation: a new approach for improving the capability of small-molecule fluorogenic probes

Herein, we report a protein-based hybridization strategy that exploits the host-guest chemistry of HSA (human serum albumin) to solubilize the otherwise cell impermeable ONOO^- fluorescent probe Pinkment-OAc. Formation of a HSA/Pinkment-OAc supramolecular hybrid was confirmed by SAXS and solution-state analyses. This HSA/Pinkment-OAc hybrid provided an enhanced fluorescence response towards ONOO^- versus Pinkment-OAc alone, as determined by in vitro experiments. The HSA/Pinkment-OAc hybrid was also evaluated in RAW 264.7 macrophages and HeLa cancer cell lines, which displayed an enhanced cell permeability enabling the detection of SIN-1 and LPS generated ONOO^- and the in vivo imaging of acute inflammation in LPS-treated mice. A remarkable 5.6 fold (RAW 264.7), 8.7-fold (HeLa) and 2.7-fold increased response was seen relative to Pinkment-OAc alone at the cellular level and in vivo, respectively. We anticipate that HSA/fluorescent probe hybrids will soon become ubiquitous and routinely applied to overcome solubility issues associated with hydrophobic fluorescent imaging agents designed to detect disease related biomarkers.

Integration of gadolinium in nanostructure for contrast enhanced-magnetic resonance imaging

Magnetic resonance imaging (MRI) is a routinely used imaging technique in medical diagnostics, which is further enhanced with the use of contrast agents (CAs). The most commonly used CAs are gadolinium-based contrast agents (GBCAs), in which gadolinium (Gd) is chelated with organic chelating agents (linear or cyclic). However, the use of GBCA is related to toxic side effect due to the release of free Gd³⁺ ions from the chelating agents. The repeated use of GBCAs has led to Gd deposition in various major organs including bone, brain, and kidneys. As a result, the use of GBCA has been linked to the development of nephrogenic systemic fibrosis (NSF). Due to the GBCA associated toxicities, some clinically approved GBCAs have been limited or revoked recently. Therefore, there is an urgent need for the development of new strategies to chelate and stabilize Gd³⁺ ions for contrast enhancement, safety profile, and selective imaging of a pathological site. Toward this endeavor, GBCAs have been engineered using different nanoparticulate systems to improve their stability, biocompatibility, and pharmacokinetics. Throughout this review, some of the important strategies for engineering small molecular Gd³⁺ chelates into a nanoconstruct is discussed. We focus on the development of GBCAs as liposomes, mesoporous silica nanoparticles (MSNs), polymeric nanocarriers, and plasmonic nanoparticles-based design strategies to improve safety and contrast enhancement for contrast enhanced-magnetic resonance imaging (Ce-MRI). We also discuss the in-vitro/in-vivo properties of strategically designed nanoscale MRI CAs, its potentials, and limitations. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging Diagnostic Tools > Diagnostic Nanodevices Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

A light-responsive, self-immolative linker for controlled drug delivery via peptide- and protein-drug conjugates

Photoirradiation of the PC4AP linker generates an active intermediate that reacts intramolecularly with a primary amine on the carrier peptide/protein, leading to rapid release of the drug without generating any toxic side products.

When designing prodrugs, choosing an appropriate linker is the key to achieving efficient, controlled drug delivery. Herein, we report the use of a photocaged C4′-oxidized abasic site (PC4AP) as a light-responsive, self-immolative linker. Any amine- or hydroxyl-bearing drug can be loaded onto the linker via a carbamate or carbonate bond, and the linker is then conjugated to a carrier peptide or protein via an alkyl chain. The PC4AP linker is stable under physiologically relevant conditions. However, photodecaging of the linker generates an active intermediate that reacts intramolecularly with a primary amine (the ε-amine of a lysine residue and the N-terminal amine) on the carrier, leading to rapid and efficient release of the drug via an addition–elimination cascade, without generating any toxic side products. We demonstrated that the use of this self-immolative linker to conjugate the anticancer drug doxorubicin to a cell-penetrating peptide or an antibody enabled targeted, controlled delivery of the drug to cells. Our results suggest that the linker can be used with a broad range of carriers, such as cell-penetrating peptides, proteins, antibodies, and amine-functionalized polymers, and thus will find a wide range of practical applications.

LINC01638 lncRNA promotes cancer cell proliferation in hepatocellular carcinoma by increasing cancer cell glucose uptake

The aim of the present study was to examine the function of long intergenic non-protein coding RNA 1638 (LINC01638) long non-coding RNA (lncRNA) in hepatocellular carcinoma (HCC). In the present study, gene expression was analyzed using qPCR and western blotting. Glucose uptake was analyzed using a glucose uptake assay and cell proliferation was analyzed using a cell counting kit-8 assay. LINC01638 lncRNA and glucose transporter 1 (GLUT1) were upregulated in tumor tissues compared with adjacent healthy tissues of patients with HCC. Expression levels of LINC01638 lncRNA and GLUT1 were positively correlated only in tumor tissues; however, there was no correlation in adjacent healthy tissues. Overexpression of LINC01638 lncRNA and GLUT1 promoted glucose uptake, while LINC01638 lncRNA and GLUT1-knockdown led to inhibited glucose uptake of cells of HCC cell lines. Overexpression of LINC01638 lncRNA mediated the upregulation of GLUT1 expression and accelerated cell proliferation. GLUT1 overexpression failed to significantly affect LINC01638 lncRNA expression, however also promoted cancer cell proliferation. In addition, GLUT1-knockdown attenuated the effects of LINC01638 overexpression on cancer cell proliferation. Therefore, LINC01638 lncRNA promoted cancer cell proliferation in HCC, potentially by increasing cancer cell glucose uptake.

Recent Advances and Challenges in Luminescent Imaging: Bright Outlook for Chemiluminescence of Dioxetanes in Water

Chemiluminescence is gradually being recognized as a powerful tool for sensing and imaging. Most known light-emitting compounds undergo chemiexcitation through spontaneous decomposition of cyclic peroxide moieties. A ground-breaking milestone in the chemistry of such compounds was achieved 30 years ago with the discovery of triggerable dioxetanes by Schaap's group. Our group has recently developed a distinct methodology to significantly improve the light emission efficiency of such phenoxy-dioxetane luminophores under physiological conditions. Introduction of an electron-withdrawing substituent at the ortho position of the phenoxy-dioxetane resulted in an approximately 3000-fold increase of the chemiluminescence quantum yield in aqueous media. Furthermore, we discovered that the emission wavelength and the kinetics of the chemiexcitation could be determined by the electronic nature of the substituent incorporated on the dioxetane luminophore. This recent development has provided scientists with new powerful chemiluminophores that can act as single-component probes for in vivo and in vitro detection and imaging of various analytes and enzymes. This outlook describes the recent progress toward applications of synthetic chemiluminescence luminophores suitable for sensing and imaging in aqueous environments.

Magnetic liposomal emodin composite with enhanced killing efficiency against breast cancer

As an active natural ingredient extracted from the plant Rheum palmatum, emodin exhibits various pharmacological activities, especially the inhibition of tumor growth and migration. However, the anticancer activity of emodin is limited mainly due to its poor solubility and the lack of specific targeting. Herein, we employed liposome to load emodin into the lipid bilayer, and high-performance ferromagnetic iron oxide nanocubes were simultaneously encapsulated in the hydrophilic bilayer. The optimized magnetic liposomal emodin nanocomposite (MLE) exhibited a 24.1% increase in the efficiency of killing MCF-7 cancer cells at a low concentration of 16 μg mL-1 compared with that of the hydrophobic free emodin. A further 8.67% enhancement of the killing efficiency was obtained by magnetic targeting. Benefitting from the high ferromagnetism, the transverse relaxivity (r2) of MLE was measured to be as high as 392.9 mM-1 s-1. With guidance from the external magnetic field, the effective accumulation of this magnetic liposome in the tumor region of a 4T1 breast tumor bearing mouse was observed by both MR tracking and fluorescence imaging, which should be beneficial for decreasing the required therapeutic dose of emodin. Hemolysis, cytotoxicity and biochemistry assays confirmed the excellent biocompatibility of this magnetic liposomal carrier. The anti-tumor therapeutic effect of MLE was further investigated in vivo, and the tumor in the therapeutic group was almost eliminated, indicating that this magnetic liposomal emodin could serve as a novel magnetically guided theranostic nanoagent.

Light-Controlled Generation of Singlet Oxygen within a Discrete Dual-Stage Metallacycle for Cancer Therapy

Noninvasive control over the reversible generation of singlet oxygen (¹O₂) has found the practical significance in benefiting photodynamic therapy. In this study, we developed a new dual-stage metallacycle (M) by using a photosensitizer and photochromic switch as the functional building blocks, which enables the noninvasive "off-on" switching of ¹O₂ generation through the efficient intramolecular energy transfer. Due to the proximal placement of the functional entities within the well-defined metallacyclic scaffold, ¹O₂ generation in the ring-closed form state of the photochromic switch (C-M) is quenched by photoinduced energy transfer, whereas the generation of ¹O₂ in the ring-open form state (O-M) is activated upon light irradiation. More interestingly, the metallacycle-loaded nanoparticles with relatively high stability and water solubility were prepared, which allow for the delivery of metallacycles to cancer cells via endocytosis. Their theranostic potential has been systematically investigated both in vitro and in vivo. Under the light irradiation, the designed ring-open form nanoparticles (O-NPs) show remarkable higher cytotoxicity against cancer cells compared to the ring-closed form nanoparticles (C-NPs). In vivo experiments also revealed that tumors can be very efficiently eliminated by the designed nanoparticles under light irradiation with the ability to regulate in vivo generation of singlet oxygen. All these results demonstrated that the supramolecular coordination complexes with a dual-stage state provide a highly efficient nanoplatform for noninvasive control over the reversible generation of ¹O₂, thus allowing for their promising applications in tumor treatment and beyond.

Gadolinium Metallofullerene-Based Activatable Contrast Agent for Tumor Signal Amplification and Monitoring of Drug Release

Activatable imaging probes are promising to achieve increased signal-to-noise ratio for accurate tumor diagnosis and treatment monitoring. Magnetic resonance imaging (MRI) is a noninvasive imaging technique with excellent anatomic spatial resolution and unlimited tissue penetration depth. However, most of the activatable MRI contrast agents suffer from metal ion-associated potential long-term toxicity, which may limit their bioapplications and clinical translation. Herein, an activatable MRI agent with efficient MRI performance and high safety is developed for drug (doxorubicin) loading and tumor signal amplification. The agent is based on pH-responsive polymer and gadolinium metallofullerene (GMF). This GMF-based contrast agent shows high relaxivity and low risk of gadolinium ion release. At physiological pH, both GMF and drug molecules are encapsulated into the hydrophobic core of nanoparticles formed by the pH-responsive polymer and shielded from the aqueous environment, resulting in relatively low longitudinal relativity and slow drug release. However, in acidic tumor microenvironment, the hydrophobic-to-hydrophilic conversion of the pH-responsive polymer leads to amplified MR signal and rapid drug release simultaneously. These results suggest that the prepared activatable MRI contrast agent holds great promise for tumor detection and monitoring of drug release.

Light emission enhancement by supramolecular complexation of chemiluminescence probes designed for bioimaging

Chemiluminescence offers advantages over fluorescence for bioimaging, since an external light source is unnecessary with chemiluminescent agents. This report demonstrates the first encapsulation of chemiluminescence phenoxy-adamantyl-1,2-dioxetane probes with trimethyl β-cyclodextrin. Clear proof for the formation of a 1 : 1 host-guest complex between the adamantyl-1,2-dioxetane probe and trimethyl β-cyclodextrin was provided by mass spectroscopy and NMR experiments. The calculated association constant of this host-guest system, 253 M-1, indicates the formation of a stable inclusion complex. The inclusion complex significantly amplified the light emission intensity relative to the noncomplexed probe under physiological conditions. Complexation of adamantyl-dioxetane with fluorogenic dye-tethered cyclodextrin resulted in light emission through energy transfer to a wavelength that corresponds to the fluorescent emission of the conjugated dye. Remarkably, the light emission intensity of this inclusion complex was approximately 1500-fold higher than that of the non-complexed adamantyl-dioxetane guest. We present the first demonstration of microscopic cell images obtained using a chemiluminescence supramolecular dioxetane probe and demonstrate the utility of these supramolecular complexes by imaging of enzymatic activity and bio-analytes in vitro and in vivo. We anticipate that the described chemiluminescence supramolecular dioxetane probes will find use in various biological applications.

Hypoxia-targeted drug delivery

Hypoxia is a state of low oxygen tension found in numerous solid tumours. It is typically associated with abnormal vasculature, which results in a reduced supply of oxygen and nutrients, as well as impaired delivery of drugs. The hypoxic nature of tumours often leads to the development of localized heterogeneous environments characterized by variable oxygen concentrations, relatively low pH, and increased levels of reactive oxygen species (ROS). The hypoxic heterogeneity promotes tumour invasiveness, metastasis, angiogenesis, and an increase in multidrug-resistant proteins. These factors decrease the therapeutic efficacy of anticancer drugs and can provide a barrier to advancing drug leads beyond the early stages of preclinical development. This review highlights various hypoxia-targeted and activated design strategies for the formulation of drugs or prodrugs and their mechanism of action for tumour diagnosis and treatment.

Antigens reversibly conjugated to a polymeric glyco-adjuvant induce protective humoral and cellular immunity

Fully effective vaccines for complex infections must elicit a diverse repertoire of antibodies (humoral immunity) and CD8⁺ T-cell responses (cellular immunity). Here, we present a synthetic glyco-adjuvant named p(Man-TLR7), which, when conjugated to antigens, elicits robust humoral and cellular immunity. p(Man-TLR7) is a random copolymer composed of monomers that either target dendritic cells (DCs) via mannose-binding receptors or activate DCs via Toll-like receptor 7 (TLR7). Protein antigens are conjugated to p(Man-TLR7) via a self-immolative linkage that releases chemically unmodified antigen after endocytosis, thus amplifying antigen presentation to T cells. Studies with ovalbumin (OVA)-p(Man-TLR7) conjugates demonstrate that OVA-p(Man-TLR7) generates greater humoral and cellular immunity than OVA conjugated to polymers lacking either mannose targeting or TLR7 ligand. We show significant enhancement of Plasmodium falciparum-derived circumsporozoite protein (CSP)-specific T-cell responses, expansion in the breadth of the αCSP IgG response and increased inhibition of sporozoite invasion into hepatocytes with CSP-p(Man-TLR7) when compared with CSP formulated with MPLA/QS-21-loaded liposomes-the adjuvant used in the most clinically advanced malaria vaccine. We conclude that our antigen-p(Man-TLR7) platform offers a strategy to enhance the immunogenicity of protein subunit vaccines.

Metalloporphyrin Nanoparticles: Coordinating Diverse Theranostic Functions

Metalloporphyrins serve key roles in natural biological processes and also have demonstrated utility for biomedical applications. They can be encapsulated or grafted in conventional nanoparticles or can self-assemble themselves at the nanoscale. A wide range of metals can be stably chelated either before or after porphyrin nanoparticle formation, without the necessity of any additional chelator chemistry. The addition of metals can substantially alter a range of behaviors such as modulating phototherapeutic efficacy; conferring responsiveness to biological stimuli; or providing contrast for magnetic resonance, positron emission or surface enhanced Raman imaging. Chelated metals can also provide a convenient handle for bioconjugation with other molecules via axial coordination. This review provides an overview of some recent biomedical, nanoparticulate approaches involving gain-of-function metalloporphyrins and related molecules.

Engineered Paramagnetic Graphene Quantum Dots with Enhanced Relaxivity for Tumor Imaging

Nano contrast agents (Nano CA) are nanomaterials used to increase contrast in the medical magnetic resonance imaging (MRI). However, the related relaxation mechanism of the Nano CA is not clear yet and little significant breakthrough in relaxivity enhancement has been achieved. Herein, a new hydrophilic Gd-DOTA complex functionalized with different chain length of PEG was synthesized and incorporated into graphene quantum dots (GQD) to obtain paramagnetic graphene quantum dots (PGQD). We performed a variable-temperature and variable-field intensity NMR study in aqueous solution on the water exchange and rotational dynamics of three different chain lengths of PGQD. The optimal GQD with paramagnetic chain length shows a great improvement in performance on ¹H NMR relaxometric studies. In vitro results demonstrated that the relaxivity of the designed PGQD could be controlled by regulating the PEG length, and its relaxivity was ∼16 times higher than that of current commercial MRI contrast agents (e.g., Gd-DTPA), on a "per Gd" basis. The relaxivity of the Nano CA can be rationally tuned to obtain unmatched potentials in MR imaging, exemplified by preparation of the paramagnetic GQD with the enhanced T₁ relaxivity. The fabricated PGQDs with suitable PEG length got the best relaxivity at 1.5 T. After intravenous injection, its feeding process by solid tumor could even be monitored by clinically used 1.5 T MRI scanners. This research will also provide an excellent platform for the design and synthesis of highly effective MR contrast agents.

Current Trends in Cancer Nanotheranostics: Metallic, Polymeric, and Lipid-Based Systems

Theranostics has emerged in recent years to provide an efficient and safer alternative in cancer management. This review presents an updated description of nanotheranostic formulations under development for skin cancer (including melanoma), head and neck, thyroid, breast, gynecologic, prostate, and colon cancers, brain-related cancer, and hepatocellular carcinoma. With this focus, we appraised the clinical advantages and drawbacks of metallic, polymeric, and lipid-based nanosystems, such as low invasiveness, low toxicity to the surrounding healthy tissues, high precision, deeper tissue penetration, and dosage adjustment in a real-time setting. Particularly recognizing the increased complexity and multimodality in this area, multifunctional hybrid nanoparticles, comprising different nanomaterials and functionalized with targeting moieties and/or anticancer drugs, present the best characteristics for theranostics. Several examples, focusing on their design, composition, imaging and treatment modalities, and in vitro and in vivo characterization, are detailed herein. Briefly, all studies followed a common trend in the design of these theranostics modalities, such as the use of materials and/or drugs that share both inherent imaging (e.g., contrast agents) and therapeutic properties (e.g., heating or production reactive oxygen species). This rationale allows one to apparently overcome the heterogeneity, complexity, and harsh conditions of tumor microenvironments, leading to the development of successful targeted therapies.

Redox Dual-Responsive and O2‑Evolving Theranostic Nanosystem for Highly Selective Chemotherapy against Hypoxic Tumors

Activatable theranostic agents, which combine fluorescent reporters with masked chemotherapeutic agents that are activated by tumor-associated stimuli, would be attractive candidates to improve the tumor selectivity of chemotherapy. This work reports a ROS/GSH dual-activatable and O2‑evolving theranostic nanosystem (RA-S-S-Cy@PLGA NPs) for highly selective therapy against hypoxic tumors and in situ fluorescence-tracking of cancer chemotherapy. Methods: In this system, the newly designed theranostic agent (RA-S-S-Cy) is composed of a disulfide bond as a cleavable linker, a near infrared (NIR) active fluorophore as a fluorescent tracker, and a natural cyclopeptide RA-V as the active anti-cancer agent. Upon reaction with the high level of intracellular glutathione (GSH), disulfide cleavage occurs, resulting in concomitant active drug RA-V release and significant NIR fluorescence increase. To further improve the tumor targeting of RA-S-S-Cy and achieve redox dual-responsiveness, RA-S-S-Cy was incorporated into the c(RGDfK)-targeted PLGA nanoparticles together with an O2-generating agent (catalase) to produce RA-S-S-Cy@PLGA NPs. Results: The cell-specific and redox dual-activatable release of RA-V lead to enhanced therapeutic outcomes in vivo and in vitro. More significantly, the RA-S-S-Cy@PLGA NPs were successfully applied for monitoring of drug release and chemotherapeutic efficacy in situ by "turn-on" NIR fluorescence. Conclusions: RA-S-S-Cy@PLGA NPs would be efficient theranostic nanosystems for more precise therapy against hypoxic tumors and provides a potential tool for deeper understanding of drug release mechanisms.

AS1411 aptamer-modified theranostic liposomes co-encapsulating manganese oxide nano-contrast agent and paclitaxel for MRI and therapy of cancer

With the advantages and development of MRI nano-contrast agents (CAs), increasing number of MRI-based theranostic nanoparticles have emerged. Liposome, as a biosafe nanocarrier has been used phase III trial for cancer treatment. In this study, liposome was employed as a nanocarrier to co-encapsulate MRI nano-contrast agent poly(ethylene glycol)-grafted manganese oxide (PEG-MnO) and anticancer drug paclitaxel (PTX) for the fabrication of a novel theranostic nanocomplex. After being further modified with AS1411 aptamer, the obtained nanoprobe AS1411-liposome-PEG-MnO-PTX displayed the potential of simultaneous MRI diagnosis and therapy of renal carcinoma in vitro and in vivo. It was found that compared with PEG-MnO nano-CA, liposome-PEG-MnO and AS1411-liposome-PEG-MnO presented a stronger MR contrast enhancement effect in the tumor and longer retention time in the tumor region. More importantly, the introduction of AS1411 aptamer further enhanced the MRI effect and the tumor growth inhibition effect, showing its potential use as a theranostic nanoprobe for renal carcinoma.

AS1411 aptamer modified theranostic liposomes co-encapsulating manganese oxide nano-contrast agent and paclitaxel for MRI and therapy of cancer was realized.

A gadolinium-complex-based theranostic prodrug for in vivo tumour-targeted magnetic resonance imaging and therapy

A molecular theranostic prodrug for treatment of tumour and real-time monitoring via MRI in vivo was reported.

Cancer-targeted design of bioresponsive prodrug with enhanced cellular uptake to achieve precise cancer therapy

Chemical drug design based on the biochemical characteristics of cancer cells has become an important strategy for discovery of novel anticancer drugs to enhance the cancer targeting effects and biocompatibility, and decrease toxic side effects. Camptothecin (CPT) demonstrated strong anticancer activity in clinical trials but also notorious adverse effects. In this study, we presented a smart targeted delivery system (Biotin-ss-CPT) that consists of cancer-targeted moiety (biotin), a cleavable disulfide linker (S-S bond) and the active drug CPT. Biotin-ss-CPT was found to exhibit potent effects on the migration of cancer cells and induced apoptosis by induction of ROS-mediated mitochondrial dysfunction and perturbation of GSH/GPXs system, as well as activation of caspases. In vivo tumor suppression investigation including toxicity evaluation and pathology analysis, accompanied by MR images showed that Biotin-ss-CPT can be recognized specifically and selectively and taken up preferentially by cancers cells, followed by localization and accumulation effectively in tumor site, then released CPT by biological response to achieve high therapeutic effect and remarkably reduced the side effects that free CPT caused, such as liver damage, renal injury, and weight loss to realize precise cancer therapy. Taken together, our results suggest that biotinylation and bioresponsive functionalization of anticancer drugs could be a good way for the discovery of next-generation cancer therapeutics.

Hypoxia-Activated Anticancer Prodrug for Bioimaging, Tracking Drug Release, and Anticancer Application

A novel anticancer theranostic prodrug, FDU-DB-NO₂, specifically activated by hypoxia for selective two-photon imaging hypoxia status, real-time tracking drug release, and solid tumor therapy was designed. The devised prodrug consists of an anticancer drug floxuridine (FDU), a fluorescence dye precursor 4'-(diethylamino)-1,1'-biphenyl-2-carboxylate (DB), and a hypoxic trigger 4-nitrobenzyl group. In normal cells, FDU-DB-NO₂ is "locked". Whereas in tumor cells, the prodrug is "unlocked" by hypoxia and results in fluorescent dye 7-(diethylamino)coumarin (CM) generation along with FDU release. The amounts and rates of CM formation and FDU release were controlled by hypoxic status and increased with the decreasing of the O₂ concentration. The hypoxic status, distribution of oxygen, and amount of FDU release in tumor cells, spheroids, and tumor tissue could be visualized by fluorescence. FDU-DB-NO₂ showed high cytotoxicity against hypoxic MCF-7 and MCG-803 cell lines and no cytotoxicity against normoxic BRL-3A cells and exhibited effective inhibition on tumor growth of MCF-7-cell-inoculated xenograft nude mice. This strategy may provide a promising platform for selective two-photon imaging hypoxia status, real-time tracking drug release, and personalized solid tumor treatment.

A sequence-activated AND logic dual-channel fluorescent probe for tracking programmable drug release

The translation of biomarker sensing into programmable diagnostics or therapeutic applications in vivo is greatly challenging, especially for eliminating the 'false positive' signals from OR logic gates. Herein we present a sense-of-logic dual-channel nanoprobe, operating through a sequence-activated AND logic gate by responding ultra-sensitively to pH changes and being subsequently triggered with biothiol for the controllable release of anti-cancer drugs. Specifically, programmable drug release is conducted in a multistage tumor microenvironment (acidic endocytic organelles followed by abnormal glutathione-overexpressing cell cytosol), which is synchronous with dual-channel near-infrared (NIR) fluorescence output. This approach represents the merging of sensing and release, including logically enabled molecular design, biomarker sensing, and controllable drug release. Impressively, the sequential AND logic feature within an unprecedented framework provides feedback on the diversity and complexity of biological milieu, along with remarkably enhancing the tumor therapeutic efficiency via its precise targeting ability and programmable drug release.

Molecularly precise self-assembly of theranostic nanoprobes within a single-molecular framework for in vivo tracking of tumor-specific chemotherapy

Structural heterogeneity and the lack of in vivo real-time tracking of drug release are the utmost barriers for nanocarrier-mediated prodrugs in targeted therapy. Herein, we describe the strategy of molecularly precise self-assembly of monodisperse nanotheranostics for BP n -DCM-S-CPT (n = 0, 5 and 20) with fixed drug loadings (36%, 23% and 16%) and constant release capacities, permitting in vivo real-time targeted therapy. We focus on regulating the hydrophilic fragment length to construct stable, well-defined nanostructured assemblies. Taking the bis-condensed dicyanomethylene-4H-pyran (DCM) derivative as the activatable near-infrared (NIR) fluorophore, it makes full use of two terminal conjunctions: the hydrophobic disulfide-bridged anticancer prodrug camptothecin (CPT) and the hydrophilic oligomer-bridged biotin segment serving as an active targeting unit. From the rational design, only BP20-DCM-S-CPT forms uniform and highly stable self-assemblies (ca. 80 nm, critical micelle concentration = 1.52 μM) with several advantages, such as structural homogeneity, fixed drug loading efficiency, real-time drug release tracking and synergistic targeting (passive, active and activatable ability). More importantly, in vitro and in vivo experiments verify that the surface-grafted biotins of nanoassemblies are directly exposed to receptors on cancer cells, thus markedly facilitating cellular internalization. Notably, through synergistic targeting, BP20-DCM-S-CPT displays excellent tumor-specific drug release performance in HeLa tumor-bearing nude mice, which has significantly enhanced in vivo antitumor activity and nearly eradicates the tumor (IRT = 99.7%) with few side effects. For the first time, the specific molecularly precise self-assembly of BP20-DCM-S-CPT within a single-molecular framework has successfully achieved a single reproducible entity for real-time reporting of drug release and cancer therapeutic efficacy in living animals, providing a new insight into amphiphilic nanotheranostics for clinical translation.

Supramolecular glyco-poly-cyclodextrin functionalized thin-layer manganese dioxide for targeted stimulus-responsive bioimaging

We have developed a supramoleuclar imaging probe based on thin-layer manganese dioxide functionalized with a fluorescent, multivalent glyco-poly-cycolodextrin for the targeted, stimulus-responsive bioimaging of cancer cells.

Selective Activation of a Prodrug by Thioredoxin Reductase Providing a Strategy to Target Cancer Cells

Elevated reactive oxygen species and antioxidant defense systems have been recognized as one of the hallmarks of cancer cells. As a major regulator of the cellular redox homeostasis, the selenoprotein thioredoxin reductase (TrxR) is increasingly considered as a promising target for anticancer drug development. The current approach to inhibit TrxR predominantly relies on the modification of the selenocysteine residue in the C-terminal active site of the enzyme, in which it is hard to avoid the off-target effects. By conjugating the anticancer drug gemcitabine with a 1,2-dithiolane scaffold, an unprecedented prodrug strategy is disclosed that achieves a specific release of gemcitabine by TrxR in cells. As overexpression of TrxR is frequently found in different types of tumors, the TrxR-dependent prodrugs are promising for further development as cancer chemotherapeutic agents.

Gadolinium as an MRI contrast agent

MRI contrast is often enhanced using a contrast agent. Gd³⁺-complexes are the most widely used metallic MRI agents, and several types of Gd³⁺-based contrast agents (GBCAs) have been developed. Furthermore, recent advances in MRI technology have, in part, been driven by the development of new GBCAs. However, when designing new functional GBCAs in a small-molecular-weight or nanoparticle form for possible clinical applications, their functions are often compromised by poor pharmacokinetics and possible toxicity. Although great progress must be made in overcoming these limitations and many challenges remain, new functional GBCAs with either small-molecular-weight or nanoparticle forms offer an exciting opportunity for use in precision medicine.

Reduction Responsive Nanovesicles Derived from Novel α-Tocopheryl-Lipoic Acid Conjugates for Efficacious Drug Delivery to Sensitive and Drug Resistant Cancer Cells

Two novel α-tocopheryl-lipoic acid conjugates (TL1 and TL2) were synthesized for the anticancer drug, doxorubicin (DOX), delivery. Both conjugates were able to form stable nanovesicles. The critical aggregation concentration (CAC) was determined using 4-(N,N-dimethylamino)cinnamaldehyde (DMACA) as a fluorescence probe. Formation of highly packed nanovesicles was characterized by 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence anisotropy and microviscosity measurements. The morphologies of nanovesicles were visualized by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The response of nanovesicles to reducing environment of cells was probed by the addition of dithiothreitol (DTT), which was followed by the increase in the hydrodynamic diameter under dynamic light scattering (DLS) measurements. The encapsulation efficiency of a commonly used anticancer drug, doxorubicin (DOX), in nanovesicles was found to be ∼60% and ∼55% for TL1 and TL2, respectively (TL1-DOX and TL2-DOX). Also, the cumulative drug (DOX) release from DOX-encapsulated nanovesicles in response to biological reducing agent glutathione (GSH) was ∼50% and ∼40% for TL1-DOX and TL2-DOX, respectively, over a period of 10 h. Both TL1-DOX and TL2-DOX delivered the anticancer drug, doxorubicin (DOX), across the DOX-sensitive and DOX-resistant HeLa (HeLa-DOX^R) cells in an efficient manner and significantly more efficaciously than the drug alone treatments, especially in HeLa-DOX^R cells. The nanovesicle mediated DOX treatment also showed significantly higher cell death when compared to DOX alone treatment in HeLa-DOX^R cells. Blood compatibility of the nanovesicles was supported from clotting time, hemolysis, and red blood cell (RBC) aggregation experiments for their potential in vivo applications. Concisely, we present biocompatible and responsive nanovesicles for efficacious drug delivery to drug-sensitive and drug-resistant cancer cells.