Kilogram-Scale Synthesis of Extremely Small Gadolinium Oxide Nanoparticles as a T1-Weighted Contrast Agent for Magnetic Resonance Imaging.

Magnetic resonance imaging contrast agents are frequently used in clinics to enhance the contrast between diseased and normal tissues. The previously reported poly(acrylic acid) stabilized exceedingly small gadolinium oxide nanoparticles (ES-GdON-PAA) overcame the problems of commercial Gd chelates, but limitations still exist, i.e., high r2/r1 ratio, long blood circulation half-life, and no data for large scale synthesis and formulation optimization. In this study, polymaleic acid (PMA) is found to be an ideal stabilizer to synthesize ES-GdONs. Compared with ES-GdON-PAA, the PMA-stabilized ES-GdON (ES-GdON-PMA) has a lower r2/r1 ratio (2.05, 7.0 T) and a lower blood circulation half-life (37.51 min). The optimized ES-GdON-PMA-9 has an exceedingly small particle size (2.1 nm), excellent water dispersibility, and stability. A facile, efficient, and environmental friendly synthetic method is developed for large-scale synthesis of the ES-GdONs-PMA. The weight of the optimized freeze-dried ES-GdON-PMA-26 synthesized in a 20 L of reactor reaches the kilogram level. The formulation optimization is also finished, and the concentrated ES-GdON-PMA-26 formulation (CGd = 100 mm) after high-pressure steam sterilization possesses eligible physicochemical properties (i.e., pH value, osmolality, viscosity, and density) for investigational new drug application.

MRI-Guided Tumor Therapy Based on Synergy of Ferroptosis, Immunosuppression Reversal and Disulfidptosis.

Triple negative breast cancer (TNBC) cells have a high demand for oxygen and glucose to fuel their growth and spread, shaping the tumor microenvironment (TME) that can lead to a weakened immune system by hypoxia and increased risk of metastasis. To disrupt this vicious circle and improve cancer therapeutic efficacy, a strategy is proposed with the synergy of ferroptosis, immunosuppression reversal and disulfidptosis. An intelligent nanomedicine GOx-IA@HMON@IO is successfully developed to realize this strategy. The Fe release behaviors indicate the glutathione (GSH)-responsive degradation of HMON. The results of titanium sulfate assay, electron spin resonance (ESR) spectra, 5,5'-Dithiobis-(2-nitrobenzoic acid (DTNB) assay and T1-weighted magnetic resonance imaging (MRI) demonstrate the mechanism of the intelligent iron atom (IA)-based cascade reactions for GOx-IA@HMON@IO, generating robust reactive oxygen species (ROS). The results on cells and mice reinforce the synergistic mechanisms of ferroptosis, immunosuppression reversal and disulfidptosis triggered by the GOx-IA@HMON@IO with the following steps: 1) GSH peroxidase 4 (GPX4) depletion by disulfidptosis; 2) IA-based cascade reactions; 3) tumor hypoxia reversal; 4) immunosuppression reversal; 5) GPX4 depletion by immunotherapy. Based on the synergistic mechanisms of ferroptosis, immunosuppression reversal and disulfidptosis, the intelligent nanomedicine GOx-IA@HMON@IO can be used for MRI-guided tumor therapy with excellent biocompatibility and safety.

Kilogram scale facile synthesis and systematic characterization of a Gd-macrochelate as T1-weighted magnetic resonance imaging contrast agent.

To overcome the problems of commercial magnetic resonance imaging (MRI) contrast agents (CAs) (i.e., small molecule Gd chelates), we have proposed a new concept of Gd macrochelates based on the coordination of Gd3+ and macromolecules, e.g., poly(acrylic acid) (PAA). To further decrease the r2/r1 ratio of the reported Gd macrochelates that is an important factor for T1 imaging, in this study, a superior macromolecule hydrolyzed polymaleic anhydride (HPMA) was found to coordinate Gd3+. The synthesis conditions were optimized and the generated Gd-HPMA macrochelate was systematically characterized. The obtained Gd-HPMA29 synthesized in a 100 L of reactor has a r1 value of 16.35 mM-1 s-1 and r2/r1 ratio of 2.05 at 7.0 T, a high Gd yield of 92.7% and a high product weight (1074 g), which demonstrates the feasibility of kilogram scale facile synthesis. After optimization of excipients and sterilization at a high temperature, the obtained Gd-HPMA30 formulation has a pH value of 7.97, osmolality of 691 mOsmol/kg water, density of 1.145 g/mL, and viscosity of 2.2 cP at 20 â„ƒ or 1.8 cP at 37 â„ƒ, which meet all specifications and physicochemical criteria for clinical injections indicating the immense potential for clinical applications.

A mesoporous superparamagnetic iron oxide nanoparticle as a generic drug delivery system for tumor ferroptosis therapy.

As a famous drug delivery system (DDS), mesoporous organosilica nanoparticles (MON) are degraded slowly in vivo and the degraded components are not useful for cell nutrition or cancer theranostics, and superparamagnetic iron oxide nanoparticles (SPION) are not mesoporous with low drug loading content (DLC). To overcome the problems of MON and SPION, we developed mesoporous SPIONs (MSPIONs) with an average diameter of 70 nm and pore size of 3.9 nm. Sorafenib (SFN) and/or brequinar (BQR) were loaded into the mesopores of MSPION, generating SFN@MSPION, BQR@MSPION and SFN/BQR@MSPION with high DLC of 11.5% (SFN), 10.1% (BQR) and 10.0% (SNF + BQR), demonstrating that our MSPION is a generic DDS. SFN/BQR@MSPION can be used for high performance ferroptosis therapy of tumors because: (1) the released Fe2+/3+ in tumor microenvironment (TME) can produce •OH via Fenton reaction; (2) the released SFN in TME can inhibit the cystine/glutamate reverse transporter, decrease the intracellular glutathione (GSH) and GSH peroxidase 4 levels, and thus enhance reactive oxygen species and lipid peroxide levels; (3) the released BQR in TME can further enhance the intracellular oxidative stress via dihydroorotate dehydrogenase inhibition. The ferroptosis therapeutic mechanism, efficacy and biosafety of MSPION-based DDS were verified on tumor cells and tumor-bearing mice.

Synergistic Glutathione Depletion and STING Activation to Potentiate Dendritic Cell Maturation and Cancer Vaccine Efficacy.

Dendritic cell (DC) maturation and antigen presentation are key factors for successful vaccine-based cancer immunotherapy. This study developed manganese-based layered double hydroxide (Mn-LDH) nanoparticles as a self-adjuvanted vaccine carrier that not only promoted DC maturation through synergistically depleting endogenous glutathione (GSH) and activating STING signaling pathway, but also facilitated the delivery of model antigen ovalbumin (OVA) into lymph nodes and subsequent antigen presentation in DCs. Significant therapeutic-prophylactic efficacy of the OVA-loaded Mn-LDH (OVA/Mn-LDH) nanovaccine was determined by the tumor growth inhibition in the mice bearing B16-OVA tumor. Our results showed that the OVA/Mn-LDH nanoparticles could be a potent delivery system for cancer vaccine development without the need of adjuvant. Therefore, the combination of GSH exhaustion and STING pathway activation might be an advisable approach for promoting DC maturation and antigen presentation, finally improving cancer vaccine efficacy.

Exceedingly Small Magnetic Iron Oxide Nanoparticles for T1 -Weighted Magnetic Resonance Imaging and Imaging-Guided Therapy of Tumors.

Magnetic iron oxide nanoparticles (MIONs) based T2 -weighted magnetic resonance imaging (MRI) contrast agents (CAs) are liver-specific with good biocompatibility, but have been withdrawn from the market and replaced with Eovist (Gd-EOB-DTPA) due to their inherent limitations (e.g., susceptibility to artifacts, high magnetic moment, dark signals, long processing time of T2 imaging, and long waiting time for patients after administration). Without the disadvantages of Gd-chelates and MIONs, the recently emerging exceedingly small MIONs (ES-MIONs) (<5 nm) are promising T1 CAs for MRI. However, there are rare review articles focusing on ES-MIONs for T1 -weighted MRI. Herein, the recent progress of ES-MIONs, including synthesis methods (the current basic synthesis methods and improved methods), surface modifications (artificial polymers, natural polymers, zwitterions, and functional protein), T1 -MRI visual strategies (structural remodeling, reversible self-assemblies, metal ions doped, T1 /T2 dual imaging modes, and PET/MRI strategy), and imaging-guided cancer therapy (chemotherapy, gene therapy, ferroptosis therapy, photothermal therapy, photodymatic therapy, radiotherapy, immuotherapy, sonodynamic therapy, and multimode therapy), is summarized. The detailed description of synthesis methods and applications of ES-MIONs in this review is anticipated to attract extensive interest from researchers in different fields and promote their participation in the establishment of ES-MIONs based nanoplatforms for tumor theranostics.

A highly effective "naked eye" colorimetric and fluorimetric curcumin-based fluorescent sensor for specific and sensitive detection of H2O2in vivo and in vitro.

Hydrogen peroxide (H2O2) is involved in many important tasks in normal cell metabolism and signaling. However, abnormal levels of H2O2 are associated with the occurrence of several diseases. Therefore, it is important to develop a new method for the detection of H2O2in vivo and in vitro. A turn-off sensor, 2,2-difluoro-4,6-bis(3-methoxy-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)oxy)styryl)-2H-1,3,2-dioxaborine (DFCB), based on curcumin was developed for the detection of H2O2. The DFCB, an orange-emitting sensor, was constructed by employing 2,2-difluoro-4,6-bis(4-hydroxy-3-methoxystyryl)-2H-1,3,2-dioxaborine (DFC) as the main carrier, and 2-(4-bromomethylphenyl)-4,4,5,5-tetramethyl-1,3,2-doxaborolane as the recognition site. The recognition group on the DFCB sensor could be completely cleaved by H2O2 to generate the intermediate DFC, which would lead to a colorimetric change from bright orange to light blue accompanying by a significantly quenched fluorescence, which could be seen by the naked eye. This sensor exhibited a highly specific fluorescence response to H2O2, in preference to other relevant species, with an excellent anti-interference performance. The sensor DFCB also possessed some advantages including a wide pH response range (6-11), a broad linear range (0-300 µM), and a low detection limit (1.31 µM). The sensing mechanism of the DFCB sensor for H2O2 was verified by HRMS analysis, 1H-NMR titration and DFT calculations. In addition, the use of the DFCB sensor was compatible with the fluorescence imaging of H2O2 in living cells and zebrafish.

Cycloacceleration of Reactive Oxygen Species Generation Based on Exceedingly Small Magnetic Iron Oxide Nanoparticles for Tumor Ferroptosis Therapy.

Because of the insufficiency of hydrogen peroxide, the relatively low rate of Fenton reaction, and the active glutathione (GSH) peroxidase 4 (GPX4) in tumor cells, it is difficult to achieve a desirable efficacy of ferroptosis therapy (FT) for tumors based on nanomaterials. Inspired by the concept of "cyclotron" in physics, in this study, a new concept of cycloacceleration of reactive oxygen species (ROS) generation in tumor cells to realize high-performance FT of tumors is proposed. Typically, a magnetic resonance imaging (MRI) contrast agent of dotted core-shell Fe3 O4 /Gd2 O3 hybrid nanoparticles (FGNPs) is prepared based on exceedingly small magnetic iron oxide nanoparticles (ES-MIONs). Sorafenib (SFN) is loaded and poly(ethylene glycol) methyl ether-poly(propylene sulfide)-NH2 (mPEG-PPS-NH2 ) is grafted on the surface of FGNP to generate SA-SFN-FGNP via self-assembly. The results of in vitro and in vivo demonstrate SA-SFN-FGNP can work with the acidic tumor microenvironment and endosomal conditions, Fenton reaction and system XC - , and generate cyclic reactions in tumor cells, resulting in specific cycloacceleration of ROS generation for high-performance FT of tumors. The very high longitudinal relaxivity (r1 , 33.43 mM-1 s-1 , 3.0 T) makes sure that the SA-SFN-FGNP can be used for MRI-guided FT of tumors.

Biodegradable and biocompatible exceedingly small magnetic iron oxide nanoparticles for T1-weighted magnetic resonance imaging of tumors.

Magnetic resonance imaging (MRI) has been widely using in clinical diagnosis, and contrast agents (CAs) can improve the sensitivity MRI. To overcome the problems of commercial Gd chelates-based T1 CAs, commercial magnetic iron oxide nanoparticles (MIONs)-based T2 CAs, and reported exceedingly small MIONs (ES-MIONs)-based T1 CAs, in this study, a facile co-precipitation method was developed to synthesize biodegradable and biocompatible ES-MIONs with excellent water-dispersibility using poly (aspartic acid) (PASP) as a stabilizer for T1-weighted MRI of tumors. After optimization of the synthesis conditions, the final obtained ES-MION9 with 3.7 nm of diameter has a high r1 value (7.0 ± 0.4 mM-1 s-1) and a low r2/r1 ratio (4.9 ± 0.6) at 3.0 T. The ES-MION9 has excellent water dispersibility because of the excessive -COOH from the stabilizer PASP. The pharmacokinetics and biodistribution of ES-MION9 in vivo demonstrate the better tumor targetability and MRI time window of ES-MION9 than commercial Gd chelates. T1-weighted MR images of aqueous solutions, cells and tumor-bearing mice at 3.0 T or 7.0 T demonstrate that our ES-MION9 has a stronger capability of enhancing the MRI contrast comparing with the commercial Gd chelates. The MTT assay, live/dead staining of cells, and H&E-staining indicate the non-toxicity and biosafety of our ES-MION9. Consequently, the biodegradable and biocompatible ES-MION9 with excellent water-dispersibility is an ideal T1-weighted CAs with promising translational possibility to compete with the commercial Gd chelates.

Intelligent Pore Switch of Hollow Mesoporous Organosilica Nanoparticles for High Contrast Magnetic Resonance Imaging and Tumor-Specific Chemotherapy.

Hollow mesoporous organosilica nanoparticles (HMONs) are widely considered as a promising drug nanocarrier, but the loaded drugs can easily leak from HMONs, resulting in the considerably decreased drug loading capacity and increased biosafety risk. This study reports the smart use of core/shell Fe3O4/Gd2O3 (FG) hybrid nanoparticles as a gatekeeper to block the pores of HMONs, which can yield an unreported large loading content (up to 20.4%) of DOX. The conjugation of RGD dimer (R2) onto the DOX-loaded HMON with FG capping (D@HMON@FG@R2) allowed for active tumor-targeted delivery. The aggregated FG in D@HMON@FG@R2 could darken the normal tissue surrounding the tumor due to the high r2 value (253.7 mM-1 s-1) and high r2/r1 ratio (19.13), and the intratumorally released FG as a result of reducibility-triggered HMON degradation could brighten the tumor because of the high r1 value (20.1 mM-1 s-1) and low r2/r1 ratio (7.01), which contributed to high contrast magnetic resonance imaging (MRI) for guiding highly efficient tumor-specific DOX release and chemotherapy.

Ten-Gram-Scale Facile Synthesis of Organogadolinium Complex Nanoparticles for Tumor Diagnosis.

The market of available contrast agents for clinical magnetic resonance imaging (MRI) has been dominated by gadolinium (Gd) chelates based T1 contrast agents for decades. However, there are growing concerns about their safety because they are retained in the body and are nephrotoxic, which necessitated a warning by the U.S. Food and Drug Administration against the use of such contrast agents. To ameliorate these problems, it is necessary to improve the MRI efficiency of such contrast agents to allow the administration of much reduced dosages. In this study, a ten-gram-scale facile method is developed to synthesize organogadolinium complex nanoparticles (i.e., reductive bovine serum albumin stabilized Gd-salicylate nanoparticles, GdSalNPs-rBSA) with high r1 value of 19.51 mm-1 s-1 and very low r2 /r1 ratio of 1.21 (B0 = 1.5 T) for high-contrast T1 -weighted MRI of tumors. The GdSalNPs-rBSA nanoparticles possess more advantages including low synthesis cost (≈0.54 USD per g), long in vivo circulation time (t1/2 = 6.13 h), almost no Gd3+ release, and excellent biosafety. Moreover, the GdSalNPs-rBSA nanoparticles demonstrate excellent in vivo MRI contrast enhancement (signal-to-noise ratio (ΔSNR) ≈ 220%) for tumor diagnosis.

Boron-Containing Lipids and Liposomes: New Conjugates of Cholesterol with Polyhedral Boron Hydrides.

A series of boron-containing lipids were prepared by reactions of cyclic oxonium derivatives of polyhedron boranes and metallacarboranes (closo-dodecaborate anion, cobalt and iron bis(dicarbollides)) with amine and carboxylic acids which are derived from cholesterol. Stable liposomal formulations, on the basis of synthesized boron-containing lipids, hydrogenated soybean l-α-phosphatidylcholine and (HSPC) 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG) as excipients, were prepared and then characterized by dynamic light scattering (DLS) that revealed the formation of particles to be smaller than 200 nm in diameter. The resulting liposomal formulations showed moderate to excellent loading and entrapment efficiency, thus justifying the design of the compounds to fit in the lipid bilayer and ensuring ease of in vivo use for future application. The liposomal formulations based on cobalt and iron bis(dicarbollide)-based lipids were found to be nontoxic against both human breast normal epithelial cells MCF-10A and human breast cancer cells MCF-7.

Emerging blood-brain-barrier-crossing nanotechnology for brain cancer theranostics.

Brain cancer, especially the most common type of glioblastoma, is highly invasive and known as one of the most devastating and deadly neoplasms. Despite surgical and medical advances, the prognosis for most brain cancer patients remains dismal and the median survival rarely exceeds 16 months. Drug delivery to the brain is significantly hindered by the existence of the blood-brain barrier (BBB), which serves as a protective semi-permeable membrane for the central nervous system. Recent breakthroughs in nanotechnology have yielded multifunctional theranostic nanoplatforms with the ability to cross or bypass the BBB, enabling accurate diagnosis and effective treatment of brain tumours. Herein, we make our efforts to present a comprehensive review on the latest remarkable advances in BBB-crossing nanotechnology, with an emphasis on the judicious design of multifunctional nanoplatforms for effective BBB penetration, efficient tumour accumulation, precise tumour imaging, and significant tumour inhibition of brain cancer. The detailed elucidation of BBB-crossing nanotechnology in this review is anticipated to attract broad interest from researchers in diverse fields to participate in the establishment of powerful BBB-crossing nanoplatforms for highly efficient brain cancer theranostics.

Precision Cancer Theranostic Platform by In Situ Polymerization in Perylene Diimide-Hybridized Hollow Mesoporous Organosilica Nanoparticles.

Phototheranostics refers to advanced photonics-mediated theranostic methods for cancer and includes imaging-guided photothermal/chemotherapy, photothermal/photodynamic therapy, and photodynamic/chemotherapy, which are expected to provide a paradigm of modern precision medicine. In this regard, various phototheranostic drug delivery systems with excellent photonic performance, controlled drug delivery/release, and precise photoimaging guidance have been developed. In this study, we reported a special "in situ framework growth" method to synthesize novel phototheranostic hollow mesoporous nanoparticles by ingenious hybridization of perylene diimide (PDI) within the framework of small-sized hollow mesoporous organosilica (HMO). The marriage of PDI and HMO endowed the phototheranostic silica nanoparticles (HMPDINs) with largely amplified fluorescence and photoacoustic signals, which can be used for enhanced fluorescence and photoacoustic imaging. The organosilica shell can be chemically chelated with isotope 64Cu for positron emission tomography imaging. Moreover, in situ polymer growth was introduced in the hollow structure of the HMPDINs to produce thermosensitive polymer (TP) in the cavity of HMPDINs to increase the loading capacity and prevent unexpected leakage of the hydrophobic drug SN38. Furthermore, the framework-hybridized PDI generated heat under near-infrared laser irradiation to trigger the deformation of TP for controlled drug release in the tumor region. The fabricated hybrid nanomedicine with organic-inorganic characteristic not only increases the cancer theranostic efficacy but also offers an attractive solution for designing powerful theranostic platforms.

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.

Exceedingly Small Gadolinium Oxide Nanoparticles with Remarkable Relaxivities for Magnetic Resonance Imaging of Tumors.

Gd chelates have occupied most of the market of magnetic resonance imaging (MRI) contrast agents for decades. However, there have been some problems (nephrotoxicity, non-specificity, and low r1 ) that limit their applications. Herein, a wet-chemical method is proposed for facile synthesis of poly(acrylic acid) (PAA) stabilized exceedingly small gadolinium oxide nanoparticles (ES-GON-PAA) with an excellent water dispersibility and a size smaller than 2.0 nm, which is a powerful T1 -weighted MRI contrast agent for diagnosis of diseases due to its remarkable relaxivities (r1 = 70.2 ± 1.8 mM-1 s-1 , and r2 /r1 = 1.02 ± 0.03, at 1.5 T). The r1 is much higher and the r2 /r1 is lower than that of the commercial Gd chelates and reported gadolinium oxide nanoparticles (GONs). Further ES-GON-PAA is developed with conjugation of RGD2 (RGD dimer) (i.e., ES-GON-PAA@RGD2) for T1 -weighted MRI of tumors that overexpress RGD receptors (i.e., integrin αv ß3 ). The maximum signal enhancement (ΔSNR) for T1 -weighted MRI of tumors reaches up to 372 ± 56% at 2 h post-injection of ES-GON-PAA@RGD2, which is much higher than commercial Gd-chelates (<80%). Due to the high biocompatibility and high tumor accumulation, ES-GON-PAA@RGD2 with remarkable relaxivities is a promising and powerful T1 -weighted MRI contrast agent.

A Flexible Caterpillar-Like Gold Nanoparticle Assemblies with Ultrasmall Nanogaps for Enhanced Dual-Modal Imaging and Photothermal Therapy.

Gold nanoparticle (AuNP) assemblies (GNAs) have attracted attention since enhanced coupling plasmonic resonance (CPR) emerged in the nanogap between coupling AuNPs. For one dimensional GNAs (1D-GNAs), most CPR from the nanogaps could be easily activated by electromagnetic waves and generate drastically enhanced CPR because the nanogaps between coupling AuNPs are linearly distributed in the 1D-GNAs. The reported studies focus on the synthesis of 1D-GNAs and fundamental exploration of CPR. There are still problems which impede further applications in nanomedicine, such as big size (>500 nm), poor water solubility, and/or poor stability. In this study, a kind of 1D flexible caterpillar-like GNAs (CL-GNAs) with ultrasmall nanogaps, good water solubility, and good stability is developed. The CL-GNAs have a flexible structure that can randomly move to change their morphology, which is rarely reported. Numerous ultrasmall nanogaps (<1 nm) are linearly distributed along the structure of CL-GNAs and generate enhanced CPR. The toxicity assessments in vitro and vivo respectively demonstrate that CL-GNAs have a low cytotoxicity and good biocompatibility. The CL-GNAs can be used as an efficient photothermal agent for photothermal therapy, a probe for Raman imaging and photothermal imaging.

Current detection technologies for circulating tumor cells.

Circulating tumor cells (CTCs) are cancer cells that circulate in the blood stream after being naturally shed from original or metastatic tumors, and can lead to a new fatal metastasis. CTCs have become a hotspot research field during the last decade. Detection of CTCs, as a liquid biopsy of tumors, can be used for early diagnosis of cancers, earlier evaluation of cancer recurrence and chemotherapeutic efficacy, and choice of individual sensitive anti-cancer drugs. Therefore, CTC detection is a crucial tool to fight against cancer. Herein, we classify the currently reported CTC detection technologies, introduce some representative samples for each technology, conclude the advantages and limitations, and give a future perspective including the challenges and opportunities of CTC detection.

Simultaneous Fenton-like Ion Delivery and Glutathione Depletion by MnO2 -Based Nanoagent to Enhance Chemodynamic Therapy.

Chemodynamic therapy (CDT) utilizes iron-initiated Fenton chemistry to destroy tumor cells by converting endogenous H2 O2 into the highly toxic hydroxyl radical (. OH). There is a paucity of Fenton-like metal-based CDT agents. Intracellular glutathione (GSH) with . OH scavenging ability greatly reduces CDT efficacy. A self-reinforcing CDT nanoagent based on MnO2 is reported that has both Fenton-like Mn2+ delivery and GSH depletion properties. In the presence of HCO3- , which is abundant in the physiological medium, Mn2+ exerts Fenton-like activity to generate . OH from H2 O2 . Upon uptake of MnO2 -coated mesoporous silica nanoparticles (MS@MnO2 NPs) by cancer cells, the MnO2 shell undergoes a redox reaction with GSH to form glutathione disulfide and Mn2+ , resulting in GSH depletion-enhanced CDT. This, together with the GSH-activated MRI contrast effect and dissociation of MnO2 , allows MS@MnO2 NPs to achieve MRI-monitored chemo-chemodynamic combination therapy.

Synchronous Chemoradiation Nanovesicles by X-Ray Triggered Cascade of Drug Release.

The approach of concurrent-to-synchronous chemoradiation has now been advanced by well-designed nanovesicles that permit X-ray irradiation-triggered instant drug release. The nanovesicles consist of Au nanoparticles tethered with irradiation labile linoleic acid hydroperoxide (LAHP) molecules and oxidation-responsive poly(propylene sulfide)-poly(ethylene glycol) (PPS-PEG) polymers, where DOX were loaded in the inner core of the vesicles (Au-LAHP-vDOX). Upon irradiation, the in situ formation of hydroxyl radicals from LAHP molecules triggers the internal oxidation of PPS from being hydrophobic to hydrophilic, leading to degradation of the vesicles and burst release of cargo drugs. In this manner, synchronous chemoradiation showed impressive anticancer efficacy both in vitro and in a subcutaneous mouse tumor model by one-dose injection and one-time irradiation.