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

Highly Sensitive Early Diagnosis of Kidney Damage Using Renal Clearable Zwitterion-Coated Ferrite Nanoprobe via Magnetic Resonance Imaging In Vivo

Iron oxide nanoprobes exhibit substantial potential in magnetic resonance imaging (MRI) of kidney diseases and can eliminate the nephrotoxicity of gadolinium-based contrast agents (GBCAs). Nevertheless, there is an extreme shortage of highly sensitive and renal clearable iron oxide nanoprobes suitable for early kidney damage detection through MRI. Herein, a renal clearable ultra-small ferrite nanoprobe (UMFNPs@ZDS) is proposed for highly sensitive early diagnosis of kidney damage via structural and functional MRI in vivo for the first time. The nanoprobe comprises a ferrite core coated with a zwitterionic layer, and possesses a high T1 relaxivity (12.52 mm-1s-1), a small hydrodynamic size (6.43 nm), remarkable water solubility, excellent biocompatibility, and impressive renal clearable ability. In a rat model of unilateral ureteral obstruction (UUO), the nanoprobe-based MRI can not only accurately visualize the locations of renal injury, but also provide comprehensive functional data including peak value, peak time, relative renal function (RRF), and clearance percentage via MRI. The findings prove the immense potential of ferrite nanoprobes as a superior alternative to GBCAs for the early diagnosis of kidney damage.

A near infrared fluorescent probe for rapid sensing of peroxynitrite in living cells and breast cancer mice

Peroxynitrite (ONOO^-) plays an essential role in numerous physiological and pathological processes owing to its strong oxidation and nitrification. Many studies have shown that ONOO^- abnormalities are associated with inflammatory diseases, even cancer, such as arthritis, hepatitis, pneumonia, and breast cancer. Thus, developing a trustworthy technology to monitor ONOO^- levels is critical in inflammatory or cancer illnesses. Herein, an ultrafast near-infrared (NIR) fluorescent probe (Cy-OH-ONOO) is proposed to detect ONOO^- within 30 s. The probe's borate moiety is oxidized and separated from Cy-OH-ONOO, releasing a NIR fluorescence signal after interacting with ONOO^- under physiological circumstances. In addition, the probe displays good selectivity and sensitivity towards ONOO^- compared to other related biological species. Moreover, it is applied to the image and detects the level fluctuation of ONOO^- in living cells and breast cancer mice based on excellent features with high biocompatibility and low toxicity of the developed probe. Therefore, Cy-OH-ONOO could serve as a powerful imaging tool to understand the correlation of ONOO^- with inflammatory or breast cancer pathophysiological processes and to assess ONOO^- levels in cellular oxidative stress.

Sorafenib/2800Z Co-Loaded into Cholesterol and PEG Grafted Polylysine NPs for Liver Cancer Treatment

The treatment of liver cancer remains challenging due to the low responsiveness of advanced cancer to therapeutic options. Sorafenib is the first line chemotherapeutic drug for advanced liver cancer but is frequently associated with severe side effects lead to discontinuation of chemotherapy. We previously developed a specific SIRT7 inhibitor 2800Z, which suppressed tumor growth and enhanced the chemosensitivity of sorafenib. In this study, we constructed polylysine polymer nanoparticles modified with cholesterol and GSH-sensitive PEG (mPssPC) to load sorafenib (SOR) and the SIRT7 inhibitor 2800Z to form dual-loaded NPs (S2@PsPCs) to reduce the toxicity and increase efficacy of sorafenib in liver cancer. The average size of S2@PsPC NPs was approximately 370 nm and the zeta potential was approximately 50-53 mV. We found that the release of the drugs exhibited pH sensitivity and was significantly accelerated in an acid release medium simulating the tumor environment. In addition, S2@PsPC NPs inhibited the proliferation and induced apoptosis of liver cancer cells in vitro. An in vivo study further revealed that S2@PsPCs showed high specificity to the liver cancer but low affinity and toxicity to the main organs including the heart, kidneys, lungs, and liver. Our data thus further approved the combination of a SIRT7 inhibitor and sorafenib for the treatment of liver cancer and provided new drug delivery system for targeted therapy.

Controlling Disassembly of Paramagnetic Prodrug and Photosensitizer Nanoassemblies for On-Demand Orthotopic Glioma Theranostics

Controlling delivery and release of therapeutic agents to accomplish on-demand synergistic therapy of orthotopic gliomas is desired but challenging. Here, we report a glioma targeting and redox activatable theranostic nanoprobe (Co-NP-RGD_1/1) for magnetic resonance (MR) and fluorescence (FL) bimodal imaging-guided on-demand synergistic chemotherapy/photodynamic therapy (Chemo-PDT) of orthotopic gliomas. Co-NP-RGD_1/1 is formed via molecular coassembly of two paramagnetic and fluorogenic small-molecule probes CPT-RGD and PPa-RGD at an optimized molar ratio of 1/1, which shows a high longitudinal relaxivity (r₁ = 17.0 ± 0.6 mM^-1 s^-1, 0.5 T) but weak FL emissions and low Chemo-PDT activity. Upon reduction by endogenous glutathione (GSH), Co-NP-RGD_1/1 disassemble and release small molecules 2-RGD, chemodrug camptothecin (CPT), and near-infrared (NIR) photosensitizer (PS) PPa-SH that further binds to endogenous albumin to form PPa-SH-albumin complex, allowing to turn on FL, chemotherapeutic efficacy, and PDT activity for synergistic Chemo-PDT of orthotopic U87MG or U251 gliomas in living mice. Moreover, Co-NP-RGD_1/1 can also allow noninvasive detection and monitoring of orthotopic brain tumor growth via FL and MR imaging. Findings suggest the potential of cascade coassembly and stimuli-controlled intracellular disassembly strategy for constructing targeted and activatable nanoagents for improving combinational cancer theranostics.

Fluorinated Ionic Liquid Based Multicolor 19 F MRI Nanoprobes for In Vivo Sensing of Multiple Biological Targets

Multicolor imaging, which maps the distribution of different targets, is important for in vivo molecular imaging and clinical diagnosis. Fluorine 19 magnetic resonance imaging (¹⁹ F MRI) is a promising technique because of unique insights without endogenous background or tissue penetration limit. Thus multicolor ¹⁹ F MRI probes, which can sense a wide variety of molecular species, are expected to help elucidate the biomolecular networks in complex biological systems. Here, a versatile model of activatable probes based on fluorinated ionic liquids (ILs) for multicolor ¹⁹ F MRI is reported. Three types of ILs at different chemical shifts are loaded in nanocarriers and sealed by three stimuli-sensitive copolymers, leading to "off" ¹⁹ F signals. The coating polymers specifically respond to their environmental stimuli, then degrade to release the loaded ILs, causing ¹⁹ F signals recovery. The nanoprobes are utilized for non-invasive detection of tumor hallmarks, which are distinguished by their individual colors in one living mouse, without interference between each other. This multicolor imaging strategy, which adopts modular construction of various ILs and stimuli-responsive polymers, will allow more comprehensive sensing of multiple biological targets, thus, opening a new realm in mechanistic understanding of complex pathophysiologic processes in vivo.

Recent research progress in galactose-based fluorescent probes for detection of biomarkers of liver diseases

This highlight illustrates the challenges and latest progress in galactose-based fluorescent probes for early diagnosis of liver diseases.

Redox-Activated Contrast-Enhanced T1-Weighted Imaging Visualizes Glutathione-Mediated Biotransformation Dynamics in the Liver

GSH-mediated liver biotransformation is a crucial physiological process demanding efficient research tools. Here, we report a type of amorphous Fe_xMn_yO nanoparticles (AFMO-ZDS NPs) as redox-activated probes for in vivo visualization of the dynamics of GSH-mediated biotransformation in liver with T₁-weighted magnetic resonance imaging (MRI). This imaging technique reveals the periodic variations in GSH concentration during the degradation of AFMO-ZDS NPs due to the limited transportation capacity of GSH carriers in the course of GSH efflux from hepatocytes to perisinusoidal space, providing direct imaging evidence for this important carrier-mediated process during GSH-mediated biotransformation. Therefore, this technique offers an effective method for in-depth investigations of GSH-related biological processes in liver under various conditions as well as a feasible means for the real-time assessment of liver functions, which is highly desirable for early diagnosis of liver diseases and prompt a toxicity evaluation of pharmaceuticals.

19 F MRI Probes for Multimodal Imaging*

Magnetic resonance imaging (MRI) is one of the most powerful imaging tools today, capable of displaying superior soft-tissue contrast. This review discusses developments in the field of ¹⁹ F MRI multimodal probes in combination with optical fluorescence imaging (OFI), ¹ H MRI, chemical exchange saturation transfer (CEST) MRI, ultrasonography (USG), X-ray computed tomography (CT), single photon emission tomography (SPECT), positron emission tomography (PET), and photoacoustic imaging (PAI). In each case, multimodal ¹⁹ F MRI probes compensate for the deficiency of individual techniques and offer improved sensitivity or accuracy of detection over unimodal counterparts. Strategies for designing ¹⁹ F MRI multimodal probes are described with respect to their structure, physicochemical properties, biocompatibility, and the quality of images.

Self-assembly of peptide nanofibers for imaging applications

Pathological stimuli-responsive self-assembly of peptide nanofibers enables selective accumulation of imaging agent cargos in the stimuli-rich regions of interest. It provides enhanced imaging signals, biocompatibility, and tumor/disease accessibility and retention, thereby promoting smart, precise, and sensitive tumor/disease imaging both in vitro and in vivo. Considering the remarkable significance and recent encouraging breakthroughs of self-assembled peptide nanofibers in tumor/disease diagnosis, this reivew is herein proposed. We emphasize the recent advances particularly in the past three years, and provide an outlook in this field.

A pH-Activatable MnCO3 Nanoparticle for Improved Magnetic Resonance Imaging of Tumor Malignancy and Metastasis

Engineered magnetic nanoparticles have been extensively explored for magnetic resonance imaging (MRI) diagnosis of a tumor to improve the visibility. However, most of these nanoparticles display "always-on" signals without tumor specificity, causing insufficient contrast and false positives. Here, we provide a new paradigm of MRI diagnosis using MnCO₃ nanorhombohedras (MnNRs) as an ultrasensitive T₁-weighted MRI contrast agent, which smartly enhances the MR signal in response to the tumor microenvironment. MnNRs would quickly decompose and release Mn²⁺ at mild acidity, one of the pathophysiological parameters associated with cancer malignancy, and then Mn²⁺ binds to surrounding proteins to achieve a remarkable amplification of T₁ relaxivity. In vivo MRI experiments demonstrate that MnNRs can selectively brighten subcutaneous tumors from the edge to the interior may be because of the upregulated vascular permeation at the tumor edge, where cancer cell proliferation and angiogenesis are more active. Specially, benefiting from the T₂ shortening effect in normal liver tissues, MnNRs can detect millimeter-sized liver metastases with an ultrahigh contrast of 294%. The results also indicate an effective hepatic excretion of MnNRs through the gallbladder. As such, this pH-activatable MRI strategy with facility, biocompatibility, and excellent efficiency may open new avenues for tumor malignancy and metastasis diagnosis and holds great promise for precision medicine.

Scratching the Surface of Unventured Possibilities with In Situ Self-Assembly: Protease-Activated Developments for Imaging and Therapy

In situ self-assembly has attracted increasing research interest for applications in imaging and therapy in recent years. Particularly for protease-activated developments, inspiration is drawn from the innate specificity of their catalytic activities, rapid discovery of the various roles they play in the proliferation of certain diseases, and inherent susceptibility of small molecule peptide conjugates to proteolytic digestion in vivo. The overexpression of a disease-related protease of interest can be exploited as an endogenous stimulus for site-specific self-assembly to largely amplify a molecular event happening at the cellular level. This holds great potential for applications in early stage disease detection, long-term disease monitoring, and sustained therapeutic effects. This review summarizes the recent developments in protease-activated self-assemblies for imaging and therapeutic applications toward the manifestation of tumors, bacterial infections, neurodegenerative disorders, and wound recovery.

Activatable Nanoparticles: Recent Advances in Redox-Sensitive Magnetic Resonance Contrast Agent Candidates Capable of Detecting Inflammation

The emergence of activatable magnetic resonance (MR) contrast agents has prompted significant interest in the detection of functional markers of diseases, resulting in the creation of a plethora of nanoprobes capable of detecting these biomarkers. These markers are commonly dysregulated in several chronic diseases, specifically select cancers and inflammatory diseases. Recently, the development of redox-sensitive nanoparticle-based contrast agents has gained momentum given advances in medicine linking several inflammatory diseases to redox imbalance. Researchers have pinpointed redox dysregulation as an opportunity to use activatable MR contrast agents to detect and stage several diseases as well as monitor the treatment of inflammatory diseases or conditions. These new classes of agents represent an advancement in the field of MR imaging as they elicit a response to stimuli, creating contrast while providing evidence of biomarker changes and commensurate disease state. Most redox-sensitive nanoparticle-based contrast agents are sensitive to reductive glutathione or oxidative reactive oxygen species. In this review, we will explore recent investigations into redox-activatable, nanoparticle-based MR contrast agent candidates.