Frizzled-7-targeting antibody (SHH002-hu1) potently suppresses non-small-cell lung cancer via Wnt/ß-catenin signaling.

Non-small-cell lung cancer (NSCLC) is one of the deadliest cancers worldwide, and metastasis is considered one of the leading causes of treatment failure in NSCLC. Wnt/ß-catenin signaling is crucially involved in epithelial-mesenchymal transition (EMT), a crucial factor in promoting metastasis, and also contributes to resistance developed by NSCLC to targeted agents. Frizzled-7 (Fzd7), a critical receptor of Wnt/ß-catenin signaling, is aberrantly expressed in NSCLC and has been confirmed to be positively correlated with poor clinical outcomes. SHH002-hu1, a humanized antibody targeting Fzd7, was previously successfully generated by our group. Here, we studied the anti-tumor effects of SHH002-hu1 against NSCLC and revealed the underlying mechanism. First, immunofluorescence (IF) and near-infrared (NIR) imaging assays showed that SHH002-hu1 specifically binds Fzd7+ NSCLC cells and targets NSCLC tissues. Wound healing and transwell invasion assays indicated that SHH002-hu1 significantly inhibits the migration and invasion of NSCLC cells. Subsequently, TOP-FLASH/FOP-FLASH luciferase reporter, IF, and western blot assays validated that SHH002-hu1 effectively suppresses the activation of Wnt/ß-catenin signaling, and further attenuates the EMT of NSCLC cells. Finally, the subcutaneous xenotransplanted tumor model of A549/H1975, as well as the popliteal lymph node (LN) metastasis model, was established, and SHH002-hu1 was demonstrated to inhibit the growth of NSCLC xenografts and suppress LN metastasis of NSCLC. Above all, SHH002-hu1 with selectivity toward Fzd7+ NSCLC and the potential of inhibiting invasion and metastasis of NSCLC via disrupting Wnt/ß-catenin signaling, is indicated as a good candidate for the targeted therapy of NSCLC.

TNFα-induced IDH1 hyperacetylation reprograms redox homeostasis and promotes the chemotherapeutic sensitivity.

The heterogeneity and drug resistance of colorectal cancer (CRC) often lead to treatment failure. Isocitrate dehydrogenase 1 (IDH1), a rate-limiting enzyme in the tricarboxylic acid cycle, regulates the intracellular redox environment and mediates tumor cell resistance to chemotherapeutic drugs. The aim of this study was to elucidate the mechanism underlying the involvement of IDH1 acetylation in the development of CRC drug resistance under induction of TNFα. We found TNFα disrupted the interaction between SIRT1 and IDH1 and increased the level of acetylation at K115 of IDH1. Hyperacetylation of K115 was accompanied by protein ubiquitination, which increased its susceptibility to degradation compared to IDH1 K115R. TNFα-mediated hyperacetylation of K115 sensitized the CRC cells to 5FU and reduced the NADPH/NADP ratio to that of intracellular ROS. Furthermore, TNFα and 5FU inhibited CRC tumor growth in vivo, while the K115R-expressing tumor tissues developed 5FU resistance. In human CRC tissues, K115 acetylation was positively correlated with TNFα infiltration, and K115 hyperacetylation was associated with favorable prognosis compared to chemotherapy-induced deacetylation. Therefore, TNFα-induced hyperacetylation at the K115 site of IDH1 promotes antitumor redox homeostasis in CRC cells, and can be used as a marker to predict the response of CRC patients to chemotherapy.

Aptamer-functionalized targeted siRNA delivery system for tumor immunotherapy.

Programmed death ligand 1 (PD-L1) overexpressed on the surface of tumor cells is one of the reasons for tumor immune escape. Reducing PD-L1 expression has been proved to be an effective strategy to facilitate immune system activation and inhibit tumor progression. RNA interference (RNAi) is a promising technology for gene regulation in tumor therapy. In this study, we constructed a targeted siRNA delivery system NPs@apt to transfect PD-L1 siRNA into human non-small-cell lung carcinoma cell line (A549) for inhibiting tumor immune evasion. NPs@apt was prepared by compressing PD-L1 siRNA with cationic Lipofectamine 2000, fusing with erythrocyte membrane-derived nanovesicles, and further modifying with targeting AS1411 aptamer. The introduction of erythrocyte membrane endowed the siRNA delivery system with lower cytotoxicity and the ability to escape from the phagocytosis of macrophages. The stability of NPs@apt and the protection to loaded siRNA were confirmed.In vitrostudies after NPs@apt treatment demonstrated that PD-L1 siRNA was selectively delivered into A549 cells, and further resulted in PD-L1 gene knockdown, T cell activation and tumor cell growth inhibition. This study offered an alternative strategy for specific siRNA transfection for improving anti-tumor immunity.

In vivo CT imaging of gold nanoparticle-labeled exosomes in a myocardial infarction mouse model.

BACKGROUND: Acute myocardial infarction (MI) is the primary factor leading to cardiovascular diseases, which are the main causes of morbidity and mortality in developed countries. Mesenchymal stem cell (MSC)-derived exosomes have been reported to improve heart function after MI; however, the molecular mechanisms responsible for this are unknown. In vivo imaging can reveal the trafficking process and in vivo biodistribution of exosomes, which may provide an insight into the communication mechanisms and pharmacokinetics of exosomes. METHODS: Glucose modified gold nanoparticles were used to label MSC-derived exosomes, aimed at minimizing membrane damage and maintaining the integrity of the exosomes. After labeling, the exosomes were visualized by in vivo computed tomography (CT) imaging to determine the biodistribution at 4 and 24 h after injection into a MI mouse model. RESULTS: MSC-derived exosomes were successfully labeled by glucose modified gold nanoparticles and CT imaging of these labeled exosomes indicated that MSC-Exo remained in the MI area for up to 24 h after intramyocardial injection. Additionally, few MSC-Exo were observed in some other organs, particularly the liver, spleen, and kidney. CONCLUSIONS: A gentle method was used for loading GNPs into exosomes, and their successful labeling without causing aggregation was verified. In vivo CT imaging revealed the retention of MSC-Exo in the MI area, indicating their usefulness for improving heart function after infarction.

A novel humanized Frizzled-7-targeting antibody enhances antitumor effects of Bevacizumab against triple-negative breast cancer via blocking Wnt/ß-catenin signaling pathway.

BACKGROUND: Anti-angiogenic therapy has been widely applied to the clinical treatment of malignant tumors. However, the efficacy of such treatments has been called into question, especially in triple-negative breast cancer (TNBC). Bevacizumab, the first anti-angiogenic agent approved by FDA, actually increases invasive and metastatic properties of TNBC cells, resulting from the activation of Wnt/ß-catenin signaling in response to hypoxia. As a critical receptor of Wnt/ß-catenin signaling, Frizzled-7 (Fzd7) is aberrantly expressed in TNBC, indicating Fzd7 a potential target for developing drugs to be combined with anti-angiogenic agents. METHODS: Hybridoma technique and antibody humanization technique were utilized to generate a Fzd7-targeting antibody (SHH002-hu1). Biolayer interferometry (BLI) assay and near infrared (NIR) imaging were conducted to detect the affinity and targeting ability of SHH002-hu1. Next, whether SHH002-hu1 could suppress the invasion and migration of TNBC cells induced by Bevacizumab were validated, and the underlying molecular mechanisms were elucidated by luciferase reporter and western blot assays. The nude-mice transplanted TNBC models were established to assess the anti-TNBC activities of SHH002-hu1 when combined with Bevacizumab. Then, the effects on putative TNBC stem-like cells and Wnt/ß-catenin signaling were evaluated by immunofluorescence (IF). Further, the tumor-initiating and self-renew capacity of TNBC cells were studied by secondary nude mouse xenograft model and sphere formation assay. In addition, the effects of SHH002-hu1 on the adaptation of TNBC cells to hypoxia were evaluated by the detection of vasculogenic mimicry (VM) and hypoxia-inducible factor-1α (HIF-1α) transcriptional activity. RESULTS: The novel humanized antibody targeting Fzd7 (SHH002-hu1) exhibited extremely high affinity with Fzd7, and specifically targeted to Fzd7+ cells and tumor tissues. SHH002-hu1 repressed invasion, migration and epithelial-mesenchymal cell transformation (EMT) of TNBC cells induced by Bevacizumab through abating Wnt/ß-catenin signaling. SHH002-hu1 significantly enhanced the capacity of Bevacizumab to inhibit the growth of TNBC via reducing the subpopulation of putative TNBC stem-like cells, further attenuating Bevacizumab-enhanced tumor-initiating and self-renew capacity of TNBC cells. Moreover, SHH002-hu1 effectively restrained the adaptation of TNBC cells to hypoxia via disrupting Wnt/ß-catenin signaling. CONCLUSION: SHH002-hu1 significantly enhances the anti-TNBC capacity of Bevacizumab, and shows the potential of preventing TNBC recurrence, suggesting SHH002-hu1 a good candidate for the synergistic therapy together with Bevacizumab.

Cisplatin-resistant NSCLC cells induced by hypoxia transmit resistance to sensitive cells through exosomal PKM2.

Hypoxia is commonly observed in solid tumors and contributes to the resistance of DNA damage drugs. However, the mechanisms behind this resistance are still unclear. In this study, we aimed to explore the effects of hypoxia-induced exosomes on non-small cell lung cancer (NSCLC). Methods: NSCLC cells were subjected to either normoxic or hypoxic conditions to assess cell survival and changes in the expression levels of key proteins. Comparative proteomics were performed to identify exosomal PKM2 in normoxic or hypoxic cisplatin-resistant NSCLC cells-derived exosomes. Functions of hypoxia induced-exosomal PKM2 in promoting cisplatin resistance to NSCLC cells were evaluated both in vitro and in vivo experiments and the molecular mechanisms of hypoxia induced-exosomal PKM2 were demonstrated using flow cytometry, immunoblotting, oxidative stress detection and histological examination. A series of in vitro experiments were performed to evaluate the function of hypoxia-induced exosomes on cancer-associated fibroblasts (CAFs). Results: Hypoxia exacerbated the cisplatin resistance in lung cancer cells due to the increased expression of PKM2 that was observed in the exosomes secreted by hypoxic cisplatin-resistance cells. We identified that hypoxia-induced exosomal PKM2 transmitted cisplatin-resistance to sensitive NSCLC cells in vitro and in vivo. Mechanistically, hypoxia-induced exosomal PKM2 promoted glycolysis in NSCLC cells to produce reductive metabolites, which may neutralize reactive oxygen species (ROS) induced by cisplatin. Additionally, hypoxia-induced exosomal PKM2 inhibited apoptosis in a PKM2-BCL2-dependent manner. Moreover, hypoxia-induced exosomal PKM2 reprogrammed CAFs to create an acidic microenvironment promoting NSCLC cells proliferation and cisplatin resistance. Conclusions: Our findings revealed that hypoxia-induced exosomes transmit cisplatin resistance to sensitive NSCLC cells by delivering PKM2. Exosomal PKM2 may serve as a promising biomarker and therapeutic target for cisplatin resistance in NSCLC.

Oxymatrine enhanced anti-tumor effects of Bevacizumab against triple-negative breast cancer via abating Wnt/ß-Catenin signaling pathway.

Bevacizumab, a monoclonal antibody targeting vascular endothelial growth factor A (VEGF-A), was used in combination with traditional chemotherapy as the first line treatment for metastatic colorectal cancer (mCRC), non-small cell lung cancer (NSCLC) and advanced ovarian cancer. However, it shows limited efficacy for human triple-negative breast cancer (TNBC). Bevacizumab shows potent anti-angiogenesis activity, meanwhile, it also increases invasive and metastatic properties of TNBC cells by activiting Wnt/ß-Catenin pathway. To overcome this problem, and fully utilize its potency against cancer, further synergistic strategy is recommended to be developed, especially the concurrent use with those Wnt-targeting agents. Here, by screening a small library of traditional Chinese medicine, we identified a Chinese herb derived Oxymatrine, which could target Wnt/ß-Catenin signaling and compromise the oncogenic effects of Bevacizumab. Bevacizumab was validated to induce epithelial-mesenchymal cell transformation (EMT) and cancer stem-like properties of TNBC cells in hypoxia/nutritional stress environment. On the contrary, Oxymatrine reversed the EMT phenotype and depleted the subpopulation of TNBC stem cells induced by Bevacizumab. Oxymatrine enhanced the anti-tumor effects of Bevacizumab in vivo, and holded the potential of reducing the risk of relapse and metastasis by impairing the self-renewal ability of TNBC stem cells. The underlying mechanism was elucidated: Bevacizumab stimulated Wnt/ß-Catenin signaling pathway, and Oxymatrine could compromise this effect. On this foundation, factoring into the satisfactory anti-angiogenic activity and low toxicity, Oxymatrine is a good candidate for the synergistic therapy together with Bevacizumab for the treatment of TNBC.

A novel recombinant human Frizzled-7 protein exhibits anti-tumor activity against triple negative breast cancer via abating Wnt/ß-catenin pathway.

Triple negative breast cancer (TNBC) is one of the most difficult malignancy to treat due to a lack of targeted therapy. Studies have demonstrated that the activation of Wnt/ß-catenin signaling was preferentially found in TNBC. Frizzled-7 (Fzd7), one of the Wnt receptors, was significantly up-regulated in TNBC and modulated TNBC tumorigenesis through the Wnt signaling pathway, indicating Fzd7 is a biomarker and a potential therapeutic target for TNBC. Here, we designed a recombinant soluble peptide fragment (rhFzd7) to antagonize Fzd7 by competitively binding with Wnt ligands. We demonstrated the ability of rhFzd7 to bind to its ligand, Wnt3a, and monitored the kinetic process using a Biacore X100 system. In addition, the anti-tumor and anti-angiogenic activity of rhFzd7 were studied in vitro and in vivo. Results showed that the purified rhFzd7 pulled down Wnt3a from MDA-MB-231 cells and exhibited high affinity with Wnt3a (KD: 3.41 × 10-8 M). The data in vitro revealed that rhFzd7 inhibited proliferation and invasion of TNBC cells, and induced apoptosis of TNBC cells effectively. The anti-angiogenic assay indicated that rhFzd7 repressed TNBC angiogenesis in vitro and in vivo. Furthermore, the study in vivo showed that rhFzd7 could sensitize TNBC cells to the anti-tumor effect of Docetaxel. In conclusion, the generation of rhFzd7 lays foundation for the screening of anti-Fzd7 antibody, and this novel design provides an effective candidate for the clinical treatment of TNBC.

Aptamer-Targeted Magnetic Resonance Imaging Contrast Agents and Their Applications.

Magnetic resonance imaging is a powerful diagnostic technology with high spatial resolution and non-invasion. The contrast agents have significant effect on the resolution of the MR imaging. However, the commercial contrast agents (CAs) usually consist of individual Gd3+ chelated with a low molecular weight acyclic or cyclic ligand, and these small-molecule CAs are usually subjected to nonspecificity, thus leading to rapid renal clearance and modest contrast enhancement for tumor imaging. In recent years, the nanostructured materials conjugated with aptamers were widely used and opened a new door in biomedical imaging due to excellent specificity, non-immunogenicity, easily synthesis and chemical modification of aptamers. This review summarizes all kinds of aptamertargeted MRI CAs and their applications.

Hydrophobic IR-780 Dye Encapsulated in cRGD-Conjugated Solid Lipid Nanoparticles for NIR Imaging-Guided Photothermal Therapy.

This is high demand to enhance the accumulation of near-infrared theranostic agents in the tumor region, which is favorable to the effective phototherapy. Compared with indocyanine green (a clinically applied dye), IR-780 iodide possesses higher and more stable fluorescence intensity and can be utilized as an imaging-guided PTT agent with laser irradiation. However, lipophilicity and short circulation time limit its applications in cancer imaging and therapy. Moreover, solid lipid nanoparticles (SLNs) conjugated with c(RGDyK) was designed as efficient carriers to improve the targeted delivery of IR-780 to the tumors. The multifunctional cRGD-IR-780 SLNs exhibited a desirable monodispersity, preferable stability and significant targeting to cell lines overexpressing αvß3 integrin. Additionally, the in vitro assays such as cell viability and in vivo PTT treatment denoted that U87MG cells or U87MG transplantation tumors could be eradicated by applying cRGD-IR-780 SLNs under laser irradiation. Therefore, the resultant cRGD-IR-780 SLNs may serve as a promising NIR imaging-guided targeting PTT agent for cancer therapy.

Poly(glycerol) Used for Constructing Mixed Polymeric Micelles as T1 MRI Contrast Agent for Tumor-Targeted Imaging.

There was much interest in the development of nanoscale delivery vehicles based on polymeric micelles to realize the diagnostic and therapeutic applications in biomedicine. Here, with the purpose of constructing a micellar magnetic resonance imaging (MRI) contrast agent (CA) with well biocompatibility and targeting specificity, two types of amphiphilic diblock polymers, mPEG-PG(DOTA(Gd))-b-PCL and FA-PEG-b-PCL, were synthesized to form mixed micelles by coassembly. The nanostructure of the resulting micellar system consisted of poly(caprolactone) (PCL) as core and poly(glycerol) (PG) and poly(ethylene glycol) (PEG) as shell, simultaneously modified with DOTA(Gd) chelates and folic acid (FA), which afforded functions of MRI contrast enhancement and tumor targeting. The mixed micelles in aqueous solution presented a hydrodynamic diameter of about 85 nm. Additionally, this mixed micelles exhibited higher r1 relaxivity (14.01 mM-1 S1-) compared with commercial Magnevist (3.95 mM-1 S1-) and showed negligible cytotoxicity estimated by WST assay. In vitro and in vivo MRI experiments revealed excellent targeting specificity to tumor cells and tissue. Furthermore, considerably enhanced signal intensity and prominent positive contrast effect were achieved at tumor region after tumor-bearing mice were intravenously injected with the mixed micelles. These preliminary results indicated the potential of the mixed micelle as T1 MRI CA for tumor-targeted imaging.

Gd2O3 and GH combined with red blood cells to improve the sensitivity of contrast agents for cancer targeting MR imaging.

Herein, we fabricated efficient MR imaging probes by incorporating gadolinium oxide nanoparticles (Gd2O3) and gadolinium hybrid nanoparticles (GH) within RBCs. The Gd2O3 and GH encapsulated in the RBCs exhibited high relaxation rates and revealed high sensitivity for T1 MR imaging.

915 nm Light-Triggered Photodynamic Therapy and MR/CT Dual-Modal Imaging of Tumor Based on the Nonstoichiometric Na0.52 YbF3.52 :Er Upconversion Nanoprobes.

Lanthanide (Ln(3+) )-doped upconversion nanoparticles (UCNPs) as a new generation of multimodal bioprobes have attracted great interest for theranostic purpose. Herein, red emitting nonstoichiometric Na0.52 YbF3.52 :Er UCNPs of high luminescence intensity and color purity are synthesized via a facile solvothermal method. The red UC emission from the present nanophosphors is three times more intense than the well-known green emission from the ≈30 nm sized hexagonal-phase NaYF4 :Yb,Er UCNPs. By utilizing Na0.52 YbF3.52 :Er@SrF2 UCNPs as multifunctional nanoplatforms, highly efficient in vitro and in vivo 915 nm light-triggered photodynamic therapies are realized for the first time, with dramatically diminished overheating yet similar therapeutic effects in comparison to those triggered by 980 nm light. Moreover, by virtue of the high transverse relaxivity (r 2 ) and the strong X-ray attenuation ability of Yb(3+) ions, these UCNPs also demonstrate good performances as contrast agents for high contrast magnetic resonance and X-ray computed tomography dual-modal imaging. Our research shows the great potential of the red emitting Na0.52 YbF3.52 :Er UCNPs for multimodal imaging-guided photodynamic therapy of tumors.

Functional Hyperbranched Polylysine as Potential Contrast Agent Probes for Magnetic Resonance Imaging.

Researchers have never stopped questing contrast agents with high resolution and safety to overcome the drawbacks of small-molecule contrast agents in clinic. Herein, we reported the synthesis of gadolinium-based hyperbranched polylysine (HBPLL-DTPA-Gd), which was prepared by thermal polymerization of l-lysine via one-step polycondensation. After conjugating with folic acid, its potential application as MRI contrast agent was then evaluated. This contrast agent had no obvious cytotoxicity as verified by WST assay and H&E analysis. Compared to Gd(III)-diethylenetriaminepentaacetic acid (Gd-DTPA) (r1 = 4.3 mM(-1) s(-1)), the FA-HBPLL-DTPA-Gd exhibited much higher longitudinal relaxivity value (r1 = 13.44 mM(-1) s(-1)), up to 3 times higher than Gd-DTPA. The FA-HBPLL-DTPA-Gd showed significant signal intensity enhancement in the tumor region at various time points and provided a long time window for MR examination. The results illustrate that FA-HBPLL-DTPA-Gd will be a potential candidate for tumor-targeted MRI.

Biocleavable Oligolysine-Grafted Poly(disulfide amine)s as Magnetic Resonance Imaging Probes.

To develop safe and effective macromolecular MRI contrast agents, a macromolecular contrast agent (mCA) containing biocleavable disulfide bonds in the main chain and oligolysine in the side chain is prepared, and its applicability as a MRI contrast agent is demonstrated both in vitro and in vivo. This brush-like mCA possesses a high T1 relaxivity (11.8 mM(-1) s(-1)), up to 3 times higher than the commercial Gd-DTPA (4.2 mM(-1) s(-1)), along with very low toxicity as determined by WST assay and histological analysis. Meanwhile, the disulfide bond can be broken under appropriate reducing conditions, followed by degradation into small fragments. Furthermore, the mCA is functionalized with folic acid to improve the target specificity. In vivo experiments show that FA-labeled mCA can efficiently enhance the resolution between the tumor and surrounding tissues compared to the mCA without FA. This study may provide helpful insights for the further development of sensitive and biocompatible MRI probes.

Oligoethylenimine-grafted chitosan as enhanced T1 contrast agent for in vivo targeted tumor MRI.

PURPOSE: To synthesize and characterize an effective macromolecular magnetic resonance imaging (MRI) contrast agent based on oligoethylenimine-grafted chitosan with targeting capability. MATERIALS AND METHODS: In this study we synthesized and characterized oligoethylenimine-grafted chitosan copolymers, followed by conjugating with Gd-DTPA and folic acid. The toxicity was evaluated by WST assay, and in vitro MRI studies were performed in comparison with Gd-DTPA. Finally, the contrast enhancement of the new macromolecular MRI contrast agent was then evaluated in the mice bearing KB xenografts. RESULTS: Compared to Gd-DTPA (4.3 mM(-1) s(-1) ), this macromolecular contrast agent (mCA) exhibited much higher T1 relaxivity (14.4 mM(-1) s(-1) ), up to 3.3 times higher. Meanwhile, the WST assay illustrated that the viability of KB cells remained at 90% even when the Gd concentration was 1 mM. During the in vivo study, the image contrast produced by FA-mCA was higher than one produced by mCA, up to 2.5 times higher. CONCLUSION: Our results showed this macromolecular contrast agent has potential for developing sensitive and biocompatible MRI probe with targeting capability. J. Magn. Reson. Imaging 2016;44:23-29.

Oligoethylenimine grafted PEGylated poly(aspartic acid) as a macromolecular contrast agent: properties and in vivo studies.

PEGylated poly(aspartate-g-OEI) was developed as a magnetic resonance imaging probe. The PEG-PBLA block copolymer was prepared by the ring-opening polymerization of ß-benzyl-l-aspartate N-carboxy-anhydride (BLA-NCA) initiated by the terminal primary amino group of mPEG-NH2, followed by grafting with oligoethylenimine (OEI, Mw = 800) and Gd-DTPA. Compared to Gd-DTPA (4.42 mM-1 s-1), PEG-p(Asp-OEI-DTPA-Gd) exhibited much higher T1 relaxivity (19.03 mM-1 s-1), up to 4.3 times higher than Gd-DTPA. No obvious cytotoxicity was observed from the WST assay and H&E analysis, which illustrated that this macromolecular contrast agent (mCA) exhibited excellent biocompatibility. Folic acid (FA) was further labeled onto the mCA to endow the mCA with targeting ability. During in vivo animal studies, the FA labeled MRI probes showed a significant signal intensity enhancement in the tumor during different time intervals and provided a long and efficient window time for MR examination. These results suggest that such mCAs are excellent candidates as magnetic resonance imaging (MRI) probes with high efficiency and safety.

Preparation of linear poly(glycerol) as a T1 contrast agent for tumor-targeted magnetic resonance imaging.

Macromolecular contrast agents (CAs) labeled with targeting molecules are gaining remarkable interest as promising materials overcoming the defects of small-molecule CAs. Designed on the basis of biocompatible poly(glycerol) (PG), a linear macromolecular contrast agent (CA) was synthesized with a composition of PG as a backbone and partial hydroxyl connected with gadolinium labeled poly(l-lysine) dendrons, where folic acid was also conjugated. This linear CA exhibited higher relaxivity (7.04 mM-1 S-1) relative to Magnevist® (3.98 mM-1 S-1), and showed negligible toxicity determined by WST assay and histological analysis. In vitro and in vivo magnetic resonance imaging (MRI) measurements presented obvious target specificity to KB cells and tumor. Moreover, high signal enhancement was observed in the tumor region at various time points after intravenous injection to ensure the long time window for imaging. All the findings make it an attractive candidate for tumor-targeted MRI CAs.

Label-free Detection of Zn(2+) Based on G-quadruplex.

Herein, we developed a sensing strategy for the label-free detection of Zn(2+) based on G-quadruplex. In the absence of Zn(2+), there was a fluorescence enhancement of thioflavin T by interaction with human telomere sequence. On the addition of Zn(2+), Zn(2+) induced a more compact G-quadruplex structure to release thioflavin T, resulting in a fluorescence decrease. This simple "mix-then-detect" method gave the detection limit of 0.91 µM with linear dynamic ranges from 0 to 10 µM. Because it does not require the use of expensive and unstable DNAzyme systems, or need synthesis and modification of nanomaterials, this label-free biosensor is simple, fast, cost-effective and applicable for real samples taken from lake water.