Hypoxia-specific ultrasensitive detection of tumours and cancer cells in vivo

In Vivo Imaging of Hypoxia Associated with Inflammatory Bowel Disease by a Cytoplasmic Protein-Powered Fluorescence Cascade Amplifier

Accurate and sensitive imaging of hypoxia associated with inflammatory bowel disease (IBD) is significant for the precise diagnosis and treatment of this disease, but it remains a challenge for traditional hypoxia-activatable fluorescence probes because of a more moderate hypoxic state during IBD than under other pathological conditions. To address this issue, herein, we designed a hypoxia-activatable and cytoplasmic protein-powered fluorescence cascade amplifier, named HCFA, to image hypoxia associated with IBD in vivo. In our design, a 4-aminobenzoic acid (azo)-modified mesoporous silica nanoparticle (MSN) was used as a container to load black hole quencher 2 (BHQ2) and cytoplasmic protein-binding squarylium dye (SQ); then, the β-cyclodextrin polymer (β-CDP) combined with azo through a host-guest interaction to form HCFA. Upon passive stagnation in the inflamed tissue of IBD, the azo band would be cleaved under a hypoxic microenvironment, and SQ was released to activate the fluorescence of HCFA. Moreover, the unconstrained SQ can bind with cytoplasmic protein to exhibit drastic fluorescence intensity enhancement, realizing the fluorescence signal amplification for imaging of hypoxia. When one takes advantage of the large load capacity of MSN and the unique property of SQ, HCFA can sense oxygen levels in the range of 0% to 10%. Meanwhile, the fluorescence imaging results demonstrate that HCFA can sensitively distinguish different levels of cellular hypoxia and monitor the variations of hypoxia in vivo, highlighting HCFA as a promising tool for the detection of hypoxia associated with IBD.

Overcoming the hypoxia-induced drug resistance in liver tumor by the concurrent use of apigenin and paclitaxel

The chemotherapeutic efficacy of paclitaxel against hypoxic tumors is usually unsatisfactory, which is partially due to the so-called hypoxia-induced drug resistance. The mechanism of hypoxia-induced resistance is primarily associated with hypoxia-inducible factor 1α (HIF-1α), which is an oxygen-sensitive transcriptional activator coordinating the cellular response to hypoxia. Apigenin is a natural occurring HIF-1α inhibitor that can suppress the expression of HIF-1α through multiple pathways and reverse the hypoxia-induced resistance found in cancer cells. Here we report that the use of apigenin can suppress the HIF-1α expression in hypoxic tumors through the simultaneous inhibition of the AKT/p-AKT pathway and HSP90, which is beneficial for enhancing the anticancer activity of the co-administered paclitaxel. The potential synergistic effect of apigenin and paclitaxel was further validated on HepG2 cell line and tumor-bearing mouse models.

Mechanochemical generation of singlet oxygen

Controlled generation of singlet oxygen is very important due to its involvement in scheduled cellular maintenance processes and therapeutic potential. As a consequence, precise manipulation of singlet oxygen release rates under mild conditions, is crucial. In this work, a cross-linked polyacrylate, and a polydimethylsiloxane elastomer incorporating anthracene-endoperoxide modules with chain extensions at the 9,10-positions were synthesized. We now report that on mechanical agitation in cryogenic ball mill, fluorescence emission due to anthracene units in the PMA (polymethacrylate) polymer is enhanced, with a concomitant generation of singlet oxygen as proved by detection with a selective probe. The PDMS (polydimethylsiloxane) elastomer with the anthracene endoperoxide mechanophore, is also similarly sensitive to mechanical force.

Luminescent ruthenium(II)-containing metallopolymers with different ligands: synthesis and application as oxygen nanosensor for hypoxia imaging

A series of Ru(II)-containing metallopolymers with different polypyridyl complexes, namely [Ru(N^N)₂(L)](PF₆)₂ (L = bipyridine-branched polymer; N^N = bpy: 2,2'-bipyridine (Ru 1); phen: 1,10-phenanthroline (Ru 2); dpp: 4,7-diphenyl-1,10-phenanthroline (Ru 3)), were synthesized with the motive that adjusting π-conjugation length of ligands might produce competent luminescent oxygen probes. The three hydrophobic metallopolymers were studied with ¹H NMR, UV-Vis absorption, and emission spectroscopy, and then were utilized to prepare biocompatible nanoparticles (NPs) via a nanoprecipitation method. Luminescent properties of the NPs were investigated against dissolved oxygen by steady-state and time-resolved spectroscopy respectively. Luminescence quenching of the three NPs all followed a linear behavior in the range of 0-43 ppm (oxygen concentration), but Ru 3-NPs exhibited the highest oxygen sensitivity (82%) and longest emission wavelength (λ_ex = 460 nm; λ_em = 617 nm). In addition, external interferons from cellular environments (e.g., pH, temperature, and proteins) had been studied on Ru 3-NPs. Finally, dissolved oxygen in monolayer cells under normoxic/hypoxic conditions was clearly differentiated by using Ru 3-NPs as the luminescent sensor, and, more importantly, hypoxia within multicellular tumor spheroids was vividly imaged. These results suggest that such Ru(II)-containing metallopolymers are strong candidates for luminescent nanosensors towards hypoxia. Graphical abstract.

Optical and Optoacoustic Imaging

The spatiotemporal determination of molecular events and cells is important for understanding disease processes, especially in oncology, and thus for the development of novel treatments. Equally important is the knowledge of the biodistribution, localization, and targeted accumulation of novel therapies as well as monitoring of tumor growth and therapeutic response. Optical imaging provides an ideal versatile platform for imaging of all these problems and questions.

Mastering bioactive coatings of metal oxide nanoparticles and surfaces through phosphonate dendrons

Dendritic phosphonates are versatile coatings of several nanomaterials for health applications ranging from implants to nanoparticles and microbubbles.

A biocompatible phosphorescent Ir(iii) oxygen sensor functionalized with oligo(ethylene glycol) groups: synthesis, photophysics and application in PLIM experiments

NIR emitting Ir(iii) complexes decorated with oligo(ethylene glycol) were used to assess the degree of hypoxia in biosamples.

Efficient near-infrared luminescence from bis-cyclometalated iridium(iii) complexes with rigid quinoline-derived ancillary ligands

Rigid bis-cyclometalated iridium complexes with quinoline-based chelating ancillary ligands phosphoresce in the near-infrared region with high efficiency.

Glucose Oxidase-Instructed Traceable Self-Oxygenation/Hyperthermia Dually Enhanced Cancer Starvation Therapy

Cancer theranostics based on glucose oxidase (GOx)-induced starvation therapy has got more and more attention in cancer management. Herein, GOx armed manganese dioxide nanosheets (denoted as MNS-GOx) were developed as cancer nanotheranostic agent for magnetic resonance (MR)/photoacoustic (PA) dual-modal imaging guided self-oxygenation/hyperthermia dually enhanced starvation cancer therapy. The manganese dioxide nanomaterials with different morphologies (such as nanoflowers, nanosheets and nanowires) were synthesized by a biomimetic approach using melanin as a biotemplate. Afterwards, the manganese dioxide nanosheets (MNS) with two sides and large surface area were selected as the vehicle to carry and deliver GOx. The as-prepared MNS-GOx can perform the circular reaction of glucose oxidation and H2O2 decomposition for enhanced starvation therapy. Moreover, the catalytic activity of GOx could be further improved by the hyperthermia of MNS-GOx upon near-infrared laser irradiation. Most intriguingly, MNS-GOx could achieve "turn-on" MR imaging and "turn-off" PA imaging simultaneously. The theranostic capability of MNS-GOx was evaluated on A375 tumor-bearing mice with all tumor elimination. Our findings integrated molecular imaging and starvation-based synergistic cancer therapy, which provided a new platform for cancer nanotheranostics.

A Theranostic Nanoprobe for Hypoxia Imaging and Photodynamic Tumor Therapy

Hypoxia is a common feature for most malignant tumors, which was also closely related to the oxygen-dependent photodynamic therapy. Based on Förster resonance energy transfer (FRET), a smart nanoprobe (designated as H-Probe) was designed in this paper for hypoxia imaging and photodynamic tumor therapy. Due to the FRET process, H-Probe could respond to hypoxia with a significant fluorescence recovery. Moreover, abundant in vitro investigations demonstrated that the photosensitizer of PpIX in H-Probe could generate large amounts of singlet oxygen to kill cancer cells in the presence of oxygen and light with appropriate wavelength. Also, intravenously injected H-Probe with light irradiation achieved an effective tumor inhibition in vivo with a reduced side effect. This original strategy of integrating hypoxia imaging and tumor therapy in one nanoplatform would promote the development of theranostic nanoplatform for tumor precision therapy.

RNA imaging in living mice enabled by an in vivo hybridization chain reaction circuit with a tripartite DNA probe

RNA imaging in living animals helps decipher biology and creates new theranostics for disease treatment. Due to their low delivery efficiency and high background, however, fluorescence probes for in situ RNA imaging in living mice have not been reported. We develop a new cell-targeting fluorescent probe that enables RNA imaging in living mice via an in vivo hybridization chain reaction (HCR). The minimalistic Y-shaped design of the tripartite DNA probe improves its performance in live animal studies and serves as a modular scaffold for three DNA motifs for cell-targeting and the HCR circuit. The tripartite DNA probe allows facile synthesis with a high yield and demonstrates ultrasensitive RNA detection in vitro. The probe also exhibits selective and efficient internalization into folate (FA) receptor-overexpressed cells via a caveolar-mediated endocytosis mechanism and produces fluorescence signals dynamically correlated with intracellular target expressions. Furthermore, the probe exhibits specific delivery into tumor cells and allows high-contrast imaging of miR-21 in living mice. The tripartite DNA design may open the door for intracellular RNA imaging in living animals using DNA-minimal structures and its design strategy can help future development of DNA-based multi-functional molecular probes.

Tumor Targeting Strategies of Smart Fluorescent Nanoparticles and Their Applications in Cancer Diagnosis and Treatment

Advantages such as strong signal strength, resistance to photobleaching, tunable fluorescence emissions, high sensitivity, and biocompatibility are the driving forces for the application of fluorescent nanoparticles (FNPs) in cancer diagnosis and therapy. In addition, the large surface area and easy modification of FNPs provide a platform for the design of multifunctional nanoparticles (MFNPs) for tumor targeting, diagnosis, and treatment. In order to obtain better targeting and therapeutic effects, it is necessary to understand the properties and targeting mechanisms of FNPs, which are the foundation and play a key role in the targeting design of nanoparticles (NPs). Widely accepted and applied targeting mechanisms such as enhanced permeability and retention (EPR) effect, active targeting, and tumor microenvironment (TME) targeting are summarized here. Additionally, a freshly discovered targeting mechanism is introduced, termed cell membrane permeability targeting (CMPT), which improves the tumor-targeting rate from less than 5% of the EPR effect to more than 50%. A new design strategy is also summarized, which is promising for future clinical targeting NPs/nanomedicines design. The targeting mechanism and design strategy will inspire new insights and thoughts on targeting design and will speed up precision medicine and contribute to cancer therapy and early diagnosis.

Metastatic renal cell carcinoma cells growing in 3D on poly‑D‑lysine or laminin present a stem‑like phenotype and drug resistance

3D spheroids are built by heterogeneous cell types in different proliferative and metabolic states and are enriched in cancer stem cells. The main aim of the study was to investigate the usefulness of a novel metastatic renal cell carcinoma (RCC) 3D spheroid culture for in vitro cancer stem cell physiology research and drug toxicity screening. RCC cell lines, Caki-1 (skin metastasis derived) and ACHN (pleural effusion derived), were efficiently cultured in growth-factor/serum deprived, defined, StemXvivo and Nutristem medium on laminin-coated or poly-D-lysine-coated plates. In optimal 3D culture conditions, ACHN cells (StemXVivo/poly-D-lysine) formed small spheroids with remaining adherent cells of an epithelial phenotype, while Caki-1 cells (StemXVivo/laminin) formed large dark spheroids with significantly reduced cell viability in the center. In the 3D structures, expression levels of genes encoding stem transcription factors (OCT4, SOX2, NES) and RCC stem cell markers (CD105, CD133) were deregulated in comparison to these expression levels in traditional 2D culture. Sunitinib, epirubicin and doxycycline were more toxic to cells cultured in monolayers than for cells in 3D spheroids. High numbers of cells arrested in the G0/G1 phase of the cell cycle were found in spheroids under sunitinib treatment. We showed that metastatic RCC 3D spheroids supported with ECM are a useful model to determine the cancer cell growth characteristics that are not found in adherent 2D cultures. Due to the more complex architecture, spheroids may mimic in vivo micrometastases and may be more appropriate to investigate novel drug candidate responses, including the direct effects of tyrosine kinase inhibitor activity against RCC cells.

Near infra-red polymeric nanoparticle based optical imaging in Cancer diagnosis

Cancer disease is a foremost health concern and top basis of death in comparison with many diseases including cardiovascular disorders. During initial diagnosis (usually late diagnosis), a majority of cancer patients suffer from metastatic and advanced cancer stages which resulted in limited therapeutic modalities based interventions and effectiveness. Though considerable advancement has been made in combating the disease, continuous and intense efforts are ongoing for early diagnosis and development of therapies. Generally applied treatment options for cancer are surgery, chemotherapy and radiotherapy, which are restricted by failure to early diagnose, insufficient on-targeted drug delivery, systemic toxicity, and lack of real-time monitoring of therapeutic responses in cancer. Noninvasive imaging or minimally invasive imaging methodology is valuable in clinical diagnostic settings. Specifically, noninvasive optical imaging integrated with polymeric nanomaterial have been extensively investigated in the field of cancer diagnostics and therapy. Currently, optical imaging methods go together with polymer-based fluorescent nanoparticles in accomplishing the molecular level detection of tumor boundaries. NIR probe tagged polymeric nanoparticles have potential to provide an advantage in the early cancer detection, therapeutic monitoring and image guided surgery procedures. This article review the recent progress in state-of-the-art NIRF polymeric nanoparticles used for optical imaging particularly on cancer diagnosis.

Rational Design of Nanoparticles to Overcome Poor Tumor Penetration and Hypoxia-Induced Chemotherapy Resistance: Combination of Optimizing Size and Self-Inducing High Level of Reactive Oxygen Species

One tough question induced by the hypoxia in cancer tissue is resistance to anticancer drugs basing on the reactive oxygen species (ROS) mechanism. Furthermore, the hypoxic regions locate in the center of tumor where tumor cells are easily residual and survival due to the poor drug-delivery efficiency even with nanocarriers. In this paper, these problems were well addressed through the rational combination of the enhanced penetration, self-inducing high level of intracellular ROS, and synchronously pH-sensitive drug release, realized by a simple structural and accessible copolymer, poly(poly(ethylene glycol) methyl ether methacrylate-co-(2-methylpropenoic acid-glycerol-cinnamaldehyde)) (PgEMC). For one thing, PgEMC could self-assemble into stable nanoparticles with PEG shell and optimizing diameters of 60 nm to simultaneously facilitate long blood circulation and deep tumor penetration. Second, cinnamylaldehyde moieties could detach from PgEMC NPs in intracellular acidic environment and trigger high level of ROS to allay the doxorubicin (DOX) resistance induced by hypoxia in solid malignancies. Furthermore, the DOX payload in PgEMC NPs could be synchronously released with the intracellular disassembly of PgEMC NPs due to the detaching of cinnamylaldehyde moieties. In 4T1 cells treated with PgEMC/DOX NPs, remarkable elevation of ROS level and enhanced DOX sensitivity in hypoxia environment were observed in in vitro studies. The results of tumor spheroid penetration indicated that 60 nm sized DOX-loaded PgEMC NPs (PgEMC₆₀/DOX) could distribute into deep site of tumor at a high intensity. In vivo studies using a 4T1 breast tumor model, PgEMC₆₀/DOX NPs, showed significant inhibition over 95.4% of the tumor growth. These results reveal that integrating optimizing size, self-inducing ROS, and pH-sensitive drug release into one small-sized nanoparticle can efficiently overcome the poor tumor penetration and hypoxia-induced chemotherapy resistance.

Nanoclustered Cascaded Enzymes for Targeted Tumor Starvation and Deoxygenation-Activated Chemotherapy without Systemic Toxicity

Intratumoral glucose depletion-induced cancer starvation represents an important strategy for anticancer therapy, but it is often limited by systemic toxicity, nonspecificity, and adaptive development of parallel energy supplies. Herein, we introduce a concept of cascaded catalytic nanomedicine by combining targeted tumor starvation and deoxygenation-activated chemotherapy for an efficient cancer treatment with reduced systemic toxicity. Briefly, nanoclustered cascaded enzymes were synthesized by covalently cross-linking glucose oxidase (GOx) and catalase (CAT) via a pH-responsive polymer. The release of the enzymes can be first triggered by the mildly acidic tumor microenvironment and then be self-accelerated by the subsequent generation of gluconic acid. Once released, GOx can rapidly deplete glucose and molecular oxygen in tumor cells while the toxic side product, i.e., H₂O₂, can be readily decomposed by CAT for site-specific and low-toxicity tumor starvation. Furthermore, the enzymatic cascades also created a local hypoxia with the oxygen consumption and reductase-activated prodrugs for an additional chemotherapy. The current report represents a promising combinatorial approach using cascaded catalytic nanomedicine to reach concurrent selectivity and efficiency of cancer therapeutics.

Intelligent protein-coated bismuth sulfide and manganese oxide nanocomposites obtained by biomineralization for multimodal imaging-guided enhanced tumor therapy

Radiotherapy (RT) has been used clinically to overcome cancer in recent decades. However, the abnormal tumor microenvironment (TME), involving hypoxia, acidosis and a dense extracellular matrix, is found to be related to the resistance of tumors to RT. Herein, intelligent bovine serum albumin (BSA)-coated Bi₂S₃ and MnO₂ (Bi₂S₃-MnO₂) nanocomposites synthesized via biomineralization are capable of modulating the hypoxic TME effectively to enhance the efficacy of RT. After intravenous injection, the BSA-Bi₂S₃-MnO₂ nanocomposites show efficient accumulation in tumors, where endogenous H₂O₂ can react with MnO₂ to generate oxygen in situ, leading to increased tumor oxygenation to overcome the hypoxia-associated resistance to RT. Moreover, the photothermal effect induced by the BSA-Bi₂S₃-MnO₂ nanocomposites further relieves hypoxia in the TME and, finally, synergistically improves the effects of RT. In this work, we present a simple strategy to fabricate intelligent therapeutic nanoparticles to improve therapeutic efficiency towards cervical cancer.

Simultaneous photoacoustic imaging of intravascular and tissue oxygenation

Hypoxia, a low tissue oxygenation condition caused by insufficient oxygen supply, leads to potentially irreversible tissue damage, such as brain infarction during stroke. Intravascular oxygenation has long been used by photoacoustic imaging, among other imaging modalities, to study hypoxia. However, intravascular oxygenation describes only the oxygen supply via microcirculation, which does not directly reflect the amount of free oxygen available for metabolism in the interstitial fluid. Therefore, to fully understand hypoxia, it is highly desirable to monitor blood oxygenation as well as tissue oxygenation during the same biological process. In this work, by combining high-resolution photoacoustic microscopy (PAM) and a novel bioreducible N-oxide-based hypoxia-sensitive probe HyP-650, we have demonstrated simultaneous imaging of intravascular oxygenation and tissue hypoxia. We have established detailed chemical, optical, and photoacoustic properties of HyP-650 for hypoxic activation in vitro and in living cells. We have also performed PAM on hindlimb ischemia models and tumor-bearing mice to study the correlation between intravascular oxygenation and tissue oxygenation at various hypoxic levels. We expect that Hyp-650 enhanced photoacoustic imaging will find a variety of applications in brain and cancer research.

Three-in-One Functional Silica Nanocarrier with Singlet Oxygen Generation, Storage/Release, and Self-Monitoring for Enhanced Fractional Photodynamic Therapy

At present, the intermittent photodynamic therapy (fractional PDT) for overcoming tumor hypoxia still have their own defects, such as irradiation-dependence and rapid metabolism of organic photosensitizers. Therefore, it is still a really formidable challenge to achieve efficient fractional PDT. Herein, a three-in-one functional silica nanocarrier (FSNC) with singlet oxygen (¹O₂) generating unit (protoporphyrin IX derivative), ¹O₂ storage/release unit (2-pyridone derivative), and ¹O₂ self-monitoring unit (cyanine derivative) was prepared by reverse microemulsion method. Also, it could be efficiently internalized in the HeLa cells because of an appropriate particle size (∼44.8 nm). In the presence of light, the endoperoxide is formed to achieve ¹O₂ storage together with ¹O₂ generated by ¹O₂ generating unit for traditional PDT. In the absence of light, the endoperoxide produces ¹O₂ through cycloreversion for continuous PDT. As a result, the fractional PDT process of the FSNC on the HeLa cells performed a higher phototoxicity than traditional photosensitizer protoporphyrin IX. Furthermore, this real-time release behavior of ¹O₂ can be visually captured by confocal laser scanning microscope via monitoring fluorescent bleaching of ¹O₂ self-monitoring unit. Therefore, this fluorescent imaging-guided fractional PDT process could effectively enhance the PDT effect compared with traditional PDT.

A Near-Infrared Phosphorescent Nanoprobe Enables Quantitative, Longitudinal Imaging of Tumor Hypoxia Dynamics during Radiotherapy

Hypoxia plays a key role in tumor resistance to radiotherapy. It is important to study hypoxia dynamics during radiotherapy to improve treatment planning and prognosis. Here, we describe a luminescent nanoprobe, composed of a fluorescent semiconducting polymer and palladium complex, for quantitative longitudinal imaging of tumor hypoxia dynamics during radiotherapy. The nanoprobe was designed to provide high sensitivity and reversible response for the subtle change in hypoxia over a narrow range (0-30 mmHg O₂), which spans the oxygen range where tumors have limited radiosensitivity. Following intravenous administration, the nanoprobe efficiently accumulated in and distributed across the tumor, including the hypoxic region. The ratio between emissions at 700 and 800 nm provided quantitative mapping of hypoxia across the entire tumor. The nanoprobe was used to image tumor hypoxia dynamics over 7 days during fractionated radiotherapy and revealed that high fractional dose (10 Gy) was more effective in improving tumor reoxygenation than low dose (2 Gy), and the effect tended to persist longer in smaller or more radiosensitive tumors. Our results also indicated the importance of the reoxygenation efficiency of the first fraction in the prediction of the radiation treatment outcome. In summary, this work has established a new nanoprobe for highly sensitive, quantitative, and longitudinal imaging of tumor hypoxia dynamics following radiotherapy, and demonstrated its value for assessing the efficacy of radiotherapy and radiation treatment planning. SIGNIFICANCE: This study presents a novel nanoagent for the visualization and quantification of tumor hypoxia.

Multifunctional Magnetic Nanoplatform Eliminates Cancer Stem Cells via Inhibiting the Secretion of Extracellular Heat Shock Protein 90

Cancer stem cells (CSCs) are responsible for malignant tumor initiation, recurrences, and metastasis. Therefore, targeting CSCs is a promising strategy for the development of cancer therapies. A big challenge for CSC-based cancer therapy is the overexpression of therapeutic stress protein, heat shock protein 90 (Hsp90), which protects CSCs from further therapeutic-induced damage, leading to the failure of treatment. Thus, efficient strategies to target CSCs are urgently needed for cancer therapy. To this end, a multifunctional nanoparticle (MNP) for CSC-based combined thermotherapy and chemotherapy is reported. This strategy dramatically suppresses tumor growth in breast CSC xenograft-bearing mice. Furthermore, a new mechanism is present that the MNP exerts its striking effects on CSCs by inhibiting the secretion of extracellular Hsp90 (eHsp90), resulting in the interruption of several key signaling pathways. These findings open new perspectives on the use of an MNP for effective CSC-based cancer treatment by inhibiting the function of eHsp90.

In situ estimation of optical properties of rat and monkey brains using femtosecond time-resolved measurements

An accurate knowledge of tissue optical properties (absorption coefficients, μa, and reduced scattering coefficients, μs') is critical for precise modeling of light propagation in biological tissue, essential for developing diagnostic and therapeutic optical techniques that utilize diffusive photons. A great number of studies have explored the optical properties of various tissue, and these values are not known in detail due to difficulties in the experimental determination and significant variations in tissue constitution. Especially, in situ estimates of the optical properties of brain tissue, a common measurement target in optical imaging, is a challenge because of its layer structure (where the thin gray matter covers the white matter). Here, we report an approach to in situ estimates of the μa and μs' of the gray and white matter in living rat and monkey brains by using femtosecond time-resolved measurements and Monte Carlo simulation. The results demonstrate that the μa of the gray matter is larger than that of the white matter, while there was no significant difference in the μs' between the gray and white matter. The optical properties of the rat brain were very similar to those of the monkey brain except for the μa of the gray matter here.

Positive feedback nanoamplifier responded to tumor microenvironments for self-enhanced tumor imaging and therapy

Targeted activation or enhancement is an attractive strategy in the design of nano-theranostics. However, the responsiveness of the nanoagents is restricted by the limited levels of intra-tumor stimuli. Herein, we constructed a positive feedback nanoamplifier by encapsulating glucose oxidase (GOx) in the ferric ions contained metal organic framework (MIL-100), and coating the nanoparticles with polydopamine modified hyaluronic acid (HA-PDA). The mechanism of action of the ensuing nanoamplifiers was three pronged: 1) the high intra-tumor acidity accelerated the release of GOx, which consumed endogenous glucose and "starved" the tumors, in addition to aggravating the local acidity and H₂O₂ levels; 2) the hydroxyl radicals (·OH) generated from the Fenton-like reaction between MIL-100 with H₂O₂ contributed to the chemodynamic tumor therapy and augmented the O₂ microenvironment, which could be speeded up under acid condition; 3) the oxygen (O₂) produced in the Fenton-like reaction relieved the intra-tumor hypoxia and ensured the enzymatic reaction of GOx, along with augmenting the photoacoustic signal of nanoamplifier. Preliminary experiments in tumor bearing mice showed that the nanoamplifier not only boosted the local acidity/H₂O₂/O₂ levels in tumor site to successfully suppress the growth of tumors through the self-enhanced chemodynamic/starving therapy, but also achieved the photoacoustic imaging of tumors. Taken together, this novel nanoamplifier with the abilities of self-enhanced tumor imaging and therapy is a promising entrant in the field of anti-tumor theranostics.

Au@SiO2@CuInS2-ZnS/Anti-AFP fluorescent probe improves HCC cell labeling

BACKGROUND

Clear tumor imaging is essential to the resection of hepatocellular carcinoma (HCC). This study aimed to create a novel biological probe to improve the HCC imaging.

METHODS

Au nano-flower particles and CuInS₂-ZnS core-shell quantum dots were synthesized by hydrothermal method. Au was coated with porous SiO₂ and combined with anti-AFP antibody. HCC cell line HepG2 was used to evaluate the targeting efficacy of the probe, while flow cytometry and MTT assay were used to detect the cytotoxicity and bio-compatibility of the probe. Probes were subcutaneously injected to nude mice to explore light intensity and tissue penetration.

RESULTS

The fluorescence stability of the probe was maintained 100% for 24 h, and the brightness value was 4 times stronger than that of the corresponding CuInS₂-ZnS quantum dot. In the targeting experiment, the labeled HepG2 emitted yellow fluorescence. In the cytotoxicity experiments, MTT and flow cytometry results showed that the bio-compatibility of the probe was fine, the inhibition rate of HepG2 cell with 60% Cu-QDs/Anti-AFP probe and Au-QDs/Anti-AFP probe solution for 48 h were significantly different (86.3%±7.0% vs. 4.9%±1.3%, t = 19.745, P<0.05), and the apoptosis rates were 83.3%±5.1% vs. 4.4%±0.8% (P<0.001). In the animal experiment, the luminescence of the novel probe can penetrate the abdominal tissues of a mouse, stronger than that of CuInS₂-ZnS quantum dot.

CONCLUSIONS

The Au@SiO₂@CuInS₂-ZnS/Anti-AFP probe can targetedly recognize and label HepG2 cells with good bio-compatibility and no toxicity, and the strong tissue penetrability of luminescence may be helpful to surgeons.

GSH Activated Biotin-tagged Near-Infrared Probe for Efficient Cancer Imaging

Tumor imaging tools with high specificity and sensitivity are needed to aid the boundary recognition in solid tumor diagnosis and surgical resection. In this study, we developed a near infra-red (NIR) probe (P6) for in vitro/in vivo tumor imaging on the basis of the dual strategy of cancer cell targeting and stimulus-dependent activation. The selective imaging capacity towards cancer cells of P6 was thoroughly investigated, and the potential mechanisms of endocytosis were preliminary explored. Methods: GSH-activated biotin labelled NIR probe (P6) was designed, synthesized and characterized. The GSH responsive properties were systematically illustrated through UV-vis, fluorescent tests and LC-MS analysis. In vitro fluorescent imaging of probe P6 was collected in various living cancer cell lines (i.e. SW480, HGC-27, H460, BxPC-3, KHOS) and normal cell lines (i.e. BEAS-2B, HLF-1, THP1) under confocal laser scanning microscopy. Probe P6 was further applied to image primary human cancer cells which were freshly isolated from the peritoneal carcinoma and rectal cancer patients. Serial sections of human tumor tissues were collected and sent for H&E (hematoxylin-eosin) staining and P6 imaging. Live fluorescent and photoacoustic imaging were used to investigate the in vivo imaging of P6 in both tumor and normal tissues in HGC-27 and KHOS xenograft model. Results: Probe P6 could be recognized and transported into cancer cells by tumor specific biotin receptors and efficiently be triggered by GSH to release fluorophore 4. In fact, the cellular uptake of P6 could be partially blocked by the addition of free biotin. Furthermore, probe P6 could image various cancer cell lines, as well as primary cancer cells, exhibiting a ten-fold increase in fluorescence intensity over normal cells. In freshly dissected cancer tissues, P6 fluorescent imaging distinguished the cancerous area under confocal laser scanning microscopy, which was exact the same area as indicated by H&E staining. We also found that P6 exhibited superior selectivity against cancer tissues by local injection. Conclusion: In this study, we developed a dual-modal NIR probe P6 with enhanced cellular uptake into cancer cells and environmental stimulus triggered fluorescence. Our strategy provided a novel insight into the development of imaging tools that could be potentially used for fluorescent image-guided cancer boundary recognition and possibly cancer diagnosis.

Enhancing singlet oxygen generation in semiconducting polymer nanoparticles through fluorescence resonance energy transfer for tumor treatment

Photosensitizers (PSs) are of particular importance for efficient photodynamic therapy (PDT). Challenges for PSs simultaneously possessing strong light-absorbing ability, high 1O2 generation by effective intersystem crossing from the singlet to the triplet state, good water-solubility and excellent photostability still exist. Reported here are a new kind of dual-emissive semiconducting polymer nanoparticles (SPNs) containing fluorescent BODIPY derivatives and near-infrared (NIR) phosphorescent iridium(iii) complexes. In the SPNs, the BODIPY units serve as the energy donors in the fluorescence resonance energy transfer (FRET) process for enhancing the light absorption of the SPNs. The NIR emissive iridium(iii) complexes are chosen as the energy acceptors and efficient photosensitizers. The ionized semiconducting polymers can easily self-assemble to form hydrophilic nanoparticles and homogeneously disperse in aqueous solution. Meanwhile, the conjugated backbone of SPNs provides effective shielding for the two luminophores from photobleaching. Thus, an excellent overall performance of the SPN-based PSs has been realized and the high 1O2 yield (0.97) resulting from the synergistic effect of BODIPY units and iridium(iii) complexes through the FRET process is among the best reported for PSs. In addition, owing to the phosphorescence quenching of iridium(iii) complexes caused by 3O2, the SPNs can also be utilized for O2 mapping in vitro and in vivo, which assists in the evaluation of the PDT process and provides important instructions in early-stage cancer diagnosis.

The destructive spontaneous ingression of tunable silica nanosheets through cancer cell membranes

Beyond conventional therapies, the sharp edge ingress of ‘thin’ silica nanosheets treats cancer via mechanical scalpelling, albeit with limited oxidative stress.

Robust inorganic graphene analogues with atomic level sharp edges have seldom been investigated to decipher the interaction of two-dimensional materials with the cell membrane. Silica nanosheets (NSs) with four different thicknesses between 2.9 nm and 11.1 nm were synthesized by microwave irradiation and these colloidal NSs were able to spontaneously penetrate the cell membrane leaving membrane perforations at their sites of entry. The NS-ingression was most effective with the thinnest NSs, when studied in vitro. The atomistic details of the NS-membrane interaction were revealed by molecular dynamics (MD) simulations, which showed that the extraction of phospholipids was most favored when NSs were oriented vertically with respect to the membrane surface. While the folic acid modified NSs demonstrated a riveting tendency to penetrate the cancer cell membrane, co-modification with doxorubicin (DOX) unexpectedly reduced their capability. Migrating away from a conventional drug delivery approach, here we show that silica NSs can kill cancer cells primarily by mechanical scalpelling. Targeted ingress could be achieved through antibody conjugation on the NSs and thus only cancerous HeLa cells are affected by this treatment, leaving the normal HEK-293 cells intact. This destructive ingress through limited oxidative stress offers a previously unexplored route to treat fatal diseases without the necessity of transporting expensive drugs or radiation therapy, thereby bypassing deleterious side effects on healthy cells.

Highly sensitive electron paramagnetic resonance nanoradicals for quantitative intracellular tumor oxymetric images

Purpose: Tumor oxygenation is a critical parameter influencing the efficacy of cancer therapy. Low levels of oxygen in solid tumor have been recognized as an indicator of malignant progression and metastasis, as well as poor response to chemo- and radiation therapy. Being able to measure oxygenation for an individual's tumor would provide doctors with a valuable way of identifying optimal treatments for patients. Methods: Electron paramagnetic resonance imaging (EPRI) in combination with an oxygen-measuring paramagnetic probe was performed to measure tumor oxygenation in vivo. Triarylmethyl (trityl) radical exhibits high specificity, sensitivity, and resolution for quantitative measurement of O₂ concentration. However, its in vivo applications in previous studies have been limited by the required high dosage, its short half-life, and poor intracellular permeability. To address these limitations, we developed high-capacity nanoformulated radicals that employed fluorescein isothiocyanate-labeled mesoporous silica nanoparticles (FMSNs) as trityl radical carriers. The high surface area nanostructure and easy surface modification of physiochemical properties of FMSNs enable efficient targeted delivery of highly concentrated, nonself-quenched trityl radicals, protected from environmental degradation and dilution. Results: We successfully designed and synthesized a tumor-targeted nanoplatform as a carrier for trityl. In addition, the nanoformulated trityl does not affect oxygen-sensing capacity by a self-relaxation or broadening effect. The FMSN-trityl exhibited high sensitivity/response to oxygen in the partial oxygen pressure range from 0 to 155 mmHg. Furthermore, MSN-trityl displayed outstanding intracellular oxygen mapping in both in vitro and in vivo animal studies. Conclusion: The highly sensitive nanoformulated trityl spin probe can profile intracellular oxygen distributions of tumor in a real-time and quantitative manner using in vivo EPRI.

Noninvasive quantification of oxygen saturation in the portal and hepatic veins in healthy mice and those with colorectal liver metastases using QSM MRI

PURPOSE

This preclinical study investigated the use of QSM MRI to noninvasively measure venous oxygen saturation (SvO2) in the hepatic and portal veins.

METHODS

QSM data were acquired from a cohort of healthy mice (n = 10) on a 9.4 Tesla MRI scanner under normoxic and hyperoxic conditions. Susceptibility was measured in the portal and hepatic veins and used to calculate SvO2 in each vessel under each condition. Blood was extracted from the inferior vena cava of 3 of the mice under each condition, and SvO2 was measured with a blood gas analyzer for comparison. QSM data were also acquired from a cohort of mice bearing liver tumors under normoxic conditions. Susceptibility was measured, and SvO2 calculated in the portal and hepatic veins and compared to the healthy mice. Statistical significance was assessed using a Wilcoxon matched-pairs signed rank test (normoxic vs. hyperoxic) or a Mann-Whitney test (healthy vs. tumor bearing).

RESULTS

SvO2 calculated from QSM measurements in healthy mice under hyperoxia showed significant increases of 15% in the portal vein (P < 0.05) and 21% in the hepatic vein (P < 0.01) versus normoxia. These values agreed with inferior vena cava measurements from the blood gas analyzer (26% increase). SvO2 in the hepatic vein was significantly lower in the colorectal liver metastases cohort (30% ± 11%) than the healthy mice (53% ± 17%) (P < 0.05); differences in the portal vein were not significant.

CONCLUSION

QSM is a feasible tool for noninvasively measuring SvO2 in the liver and can detect differences due to increased oxygen consumption in livers bearing colorectal metastases.

Cellular interface supported toehold strand displacement cascade for amplified dual-electrochemical signal and its application for tumor cell analysis

In this work, toehold strand displacement cascade (TSDC) has been delicately designed and carried out on the cellular interface for the amplification and output of dual-electrochemical signal. Specifically, antibody cross-linked T strand can recognize cell which is linked with immune-magnetic bead. Subsequently, T strand on the cellular interface can mediate the occurrence of TSDC, resulting the change of SN₃/S1-MB to SN₃/S2-Fc ratio in the supernatant after magnetic separation. The resultant SN₃/S1-MB and SN₃/S2-Fc can be immobilized on the electrode interface through click chemistry and give the amplified double electrochemical signal. So the tumor cell amount can closely correlate with the change of the double signal. Except for output of the double signal for improvement of analytical accuracy, the double magnetic separation not only eliminate the interference of the complicated substances in serum, but also remove the influence of cell on click reaction on the electrode interface. So based on cellular interface supported TSDC for amplified dual-electrochemical signal, the established method has been successfully applied to analyze the tumor cells in serum accurately and sensitively.

AIE Multinuclear Ir(III) Complexes for Biocompatible Organic Nanoparticles with Highly Enhanced Photodynamic Performance

The singlet oxygen (1O2) generation ability of a photosensitizer (PS) is pivotal for photodynamic therapy (PDT). Transition metal complexes are effective PSs, owing to their high 1O2 generation ability. However, non-negligible cellular toxicity, poor biocompatibility, and easy aggregation in water limit their biomedical applications. In this work, a series of red-emitting aggregation-induced emission (AIE) Ir(III) complexes containing different numbers of Ir centers (mono-, di-, and trinuclear) and the corresponding nanoparticles (NPs) AIE-NPs, are designed and synthesized. The increase of 1O2 generation ability is in line with the increasing number of Ir centers. Compared with the pure Ir(III) complexes, the corresponding NPs offer multiple advantages: (i) brighter emission; (ii) higher phosphorescence quantum yields; (iii) longer excited lifetime; (iv) higher 1O2 generation ability; (v) better biocompatibility; and (vi) superior cellular uptake. Both in vitro and in vivo experiments corroborate that AIE-NPs with three iridium centers possess potent cytotoxicity toward cancer cells and effective inhibition of tumor growth. To the best of knowledge, this work is the first example of NPs of multinuclear AIE Ir(III) complexes as PSs for enhanced PDT. This study offers a new method to improve the efficiency of PSs for clinical cancer treatments.

Stable radical anions generated from a porous perylenediimide metal-organic framework for boosting near-infrared photothermal conversion

Radical anions of electron-deficient systems are widely used, but are easily reoxidized upon exposure to air. Therefore, the stabilization of radical anions under ambient conditions is of great significance, but still remains a scientific challenge. Herein, perylenediimide is employed to prepare a crystalline metal-organic framework for stabilizing radical anions without extensive chemical modification. The porous, three-dimensional framework of perylenediimide can trap electron donors such as amine vapors and produce radical anions in-situ through photo-induced electron transfer. The radical anions are protected against quenching by shielding effect in air and remain unobstructed in air for at least a month. Because of the high yield and stability of the radical anions, which are the basis for near-infrared photothermal conversion, the framework shows high near-infrared photothermal conversion efficiency (η = 52.3%). The work provides an efficient and simple method towards ambient stable radical anions and affords a promising material for photothermal therapy.

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.