Mitochondrial dynamics as a novel treatment strategy for triple-negative breast cancer.

INTRODUCTION: Triple-negative breast cancer (TNBC), recognized as the most heterogeneous type of breast cancer (BC), exhibits a worse prognosis than other subtypes. Mitochondria dynamics play a vital role as mediators in tumorigenesis by adjusting to the cell microenvironments. However, the relationship between mitochondrial dynamics and metabophenotype exhibits discrepancies and divergence across various research and BC models. Therefore, this study aims to explore the role of mitochondrial dynamics in TNBC drug resistance and tumorigenesis. METHODS: The Wst-8 test was conducted to assess doxorubicin sensitivity in HCC38, MDA-MB-231 (TNBC), and MCF-7 (luminal). Confocal microscopy and FACS were used to quantify the mitochondrial membrane potential (ΔφM), mitophagy, and reactive oxygen species (ROS) production. Agilent Seahorse XF Analyzer was utilized to measure metabolic characteristics. Dynamin-related protein-1 (DRP1), Parkin, and p62 immunohistochemistry staining were performed using samples from 107 primary patients with BC before and after neoadjuvant chemotherapy (NAC). RESULTS: MDA-MB-231, a TNBC cell line with reduced sensitivity to doxorubicin, reduced ΔφM, and enhanced mitophagy to maintain ROS production through oxidative phosphorylation (OXPHOS)-based metabolism. HCC38, a doxorubicin-sensitive cell line, exhibited no alterations in ΔφM or mitophagy. However, it demonstrated an increase in ROS production and glycolysis. Clinicopathological studies revealed that pretreatment (before NAC) expression of DRP1 was significant in TNBC, as was pretreatment expression of Parkin in the hormone receptor-negative group. Furthermore, low p62 levels seem to be a risk factor for recurrence-free survival. CONCLUSION: Our findings indicated that the interplay between mitophagy, linked to a worse clinical prognosis, and OXPHOS metabolism promoted chemotherapy resistance in TNBC. Mitochondrial fission is prevalent in TNBC. These findings suggest that targeting the unique mitochondrial metabolism and dynamics in TNBC may offer a novel therapeutic strategy for patients with TNBC.

Clinical Significance of ABCG2/BCRP Quantified by Fluorescent Nanoparticles in Breast Cancer Patients Undergoing Neoadjuvant Chemotherapy.

Breast cancer resistance protein (BCRP), also known as ATP-binding cassette transporter G2 (ABCG2), is associated with chemotherapy resistance. BCRP is also implicated in breast cancer stem cells, and is reported as a poor prognostic factor. However, the relationship of BCRP levels in breast cancer tissues with chemotherapy resistance and prognosis has not been clarified. We aimed to evaluate the correlation between BCRP expression and prognosis in breast cancer using immunohistochemistry with fluorescent phosphor-integrated dots (IHC-PIDs). A total of 37 breast cancer patients with residual cancer in the primary tumor and axillary lymph nodes were evaluated. BCRP levels in breast cancer tissue and metastatic lymph nodes were quantitatively detected after neoadjuvant chemotherapy (NAC). Among these 37 patients, 24 had corresponding core needle biopsies obtained before NAC. Biomarker assay with IHC-PIDs showed high accuracy for the quantitative assessment of BCRP with low expression. High BCRP expression in the primary tumor and metastatic lymph nodes after preoperative chemotherapy was associated with worse overall survival. In conclusion, high BCRP levels may be associated with poor prognosis in patients with breast cancer, having residual tumors within the primary tumor and lymph nodes after preoperative chemotherapy. These findings provide a basis for further appropriate adjuvant therapy in these patients.

X-ray irradiation negatively affects immune responses in the lymphatic network.

Immune checkpoint inhibitor therapy has been attracting attention as a new cancer treatment and is likely to be widely used in combination with radiotherapy. Therefore, examination of the effects of X-ray irradiation on sentinel lymph nodes and lymphatic vessels, which are involved in antigen presentation, is important for therapy. The hindlimbs of mice were irradiated with X-rays (total radiation doses: 2, 10, and 30 Gy), and X-ray computed tomography (CT) imaging was performed using 15-nm or 2-nm gold nanoparticles (AuNPs) as contrast agents on days 7, 14, and 28 after irradiation to evaluate the diameter of the collecting lymph vessels and lymph flow within the irradiated area. X-ray CT imaging data using 15-nm AuNPs on day 28 after irradiation showed that the diameter of the collecting lymph vessels was significantly larger in all irradiated groups compared to the control group (p ≤ 0.01). CT imaging with 2-nm AuNPs showed that lymphatic drainage was significantly reduced in the lymph nodes irradiated with 10 Gy and 30 Gy compared to the lymph nodes irradiated with 2 Gy (p ≤ 0.05). Additionally, immunohistochemical analyses were conducted to evaluate the area density and morphology of high endothelial venules (HEVs) in the lymph nodes, which are important vessels for naive T cells to enter the lymph nodes. The expression level of MECA-79, which specifically localized to HEVs, was significantly decreased in the 10 Gy and 30 Gy irradiation groups compared to the control group (p ≤ 0.05). There was a significant decrease in normal HEV morphology (p ≤ 0.05) and a significant increase in abnormal HEV morphology (p ≤ 0.05) in all irradiated groups. These results also showed that X-ray irradiation induced a time- and radiation dose-dependent increase in the diameter of the collecting lymph vessels, stagnation of intralymphatic lymph flow, and a reduction in the area density of HEVs and their abnormal morphology, demonstrating that X-ray irradiation affected the immune responses. Therefore, these findings suggest that X-ray irradiation to lymph nodes may impair the opportunity for antigen presentation in the lymph nodes, which is the key to cancer immunity, and that for this reason, it is important to carefully plan irradiation of sentinel lymph nodes and develop treatment strategies according to future treatment options.

Development of X-ray contrast agents using single nanometer-sized gold nanoparticles and lactoferrin complex and their application in vascular imaging.

The technology to accurately image the morphology of tumor vessels with X-ray contrast agents is important to clarify mechanisms underlying tumor progression and evaluate the efficacy of chemotherapy. However, in clinical practice, iodine-based contrast agents present problems such as short blood retention owing to a high clearance ability and insufficient X-ray absorption capacity when compared with other high atomic number elements. To resolve these issues, gold nanoparticles (AuNPs), with a high atomic number, have attracted a great deal of attention as contrast agents for angiography, and have been employed in small animal models. Herein, we developed novel contrast agents using AuNPs and captured changes in tumor vessel morphology with time using X-ray computed tomography (CT). First, glutathione-supported single nanometer-sized AuNPs (sAu/GSH) (diameter, 2.2 nm) were fabricated using tetrakis(hydroxymethyl)phosphonium chloride as a reducing agent. The sAu/GSH particles were intravenously injected into mice, remained in vessels for a few minutes, and were then excreted by the kidneys after 24 h, similar to the commercial contrast agent iopamidol. Next, the Au/GSH and lactoferrin (sAu/GSH-LF) (long axis size, 17.3 nm) complex was produced by adding lactoferrin to the sAu/GSH solution under the influence of a condensing agent. On intravenously administering sAu/GSH-LF to mice, the blood retention time was 1-3 h, which was considerably longer than that observed with iopamidol and sAu/GSH. Moreover, we succeeded in imaging morphological changes in identical tumor vessels for several days using X-ray CT with sAu/GSH-LF.

The anti-angiogenic agent lenvatinib induces tumor vessel normalization and enhances radiosensitivity in hepatocellular tumors.

The evaluation of angiogenesis inhibitors requires the analysis of the precise structure and function of tumor vessels. The anti-angiogenic agents lenvatinib and sorafenib are multi-target tyrosine kinase inhibitors that have been approved for the treatment of hepatocellular carcinoma (HCC). However, the different effects on tumor vasculature between lenvatinib and sorafenib are not well understood. In this study, we analyzed the effects of both drugs on vascular structure and function, including vascular normalization, and investigated whether the normalization had a positive effect on a combination therapy with the drugs and radiation using micro X-ray computed tomography with gold nanoparticles as a contrast agent, as well as immunohistochemical analysis and interstitial fluid pressure (IFP) measurement. In mice subcutaneously transplanted with mouse HCC cells, treatment with lenvatinib or sorafenib for 14 days inhibited tumor growth and reduced the tumor vessel volume density. However, analysis of integrated data on vessel density, rates of pericyte-covering and perfused vessels, tumor hypoxia, and IFP measured 4 days after drug treatment showed that treatment with 3 mg/kg of lenvatinib significantly reduced the microvessel density and normalized tumor vessels compared to treatment with 50 mg/kg of sorafenib. These results showed that lenvatinib induced vascular normalization and improved the intratumoral microenvironment in HCC tumors earlier and more effectively than sorafenib. Moreover, such changes increased the radiosensitivity of tumors and enhanced the effect of lenvatinib and radiation combination therapy, suggesting that this combination therapy is a powerful potential application against HCC.

[Supporting Technology for Development of Antibody Drug and Diagnostic Method to Predict Response to the Drug, by Using Fluorescence Imaging].

Fluorescence imaging is a very useful method for visualizing molecules and cells, but when tissues are measured", decrease in resolution due to increased scattering and absorption of light in proportion to tissue thickness (problem 1)" and "decrease in signal to noise(S/N)ratio of positive signal due to tissue autofluorescence(problem 2)"are problems to be solved. In this paper, to develop a technology to improve the analysis accuracy of drug efficacy mechanisms in preclinical trial of drug discovery, we performed development of a supporting technology for drug discovery of antibody drug conjugates by imaging living tumor tissues, while solving problem 1. This technology is expected to lead to an improvement in the success rate of clinical trials. Next, to develop a diagnostic method to predict the response to neoadjuvant chemotherapy with antibody drugs for breast cancer, we performed development of fluorescence imaging of pathological tissues using fluorescent nanoparticles with ultra-high brightness, while solving problem 2. This diagnostic technology makes it possible to evaluate the expression level of the target protein of antibody drug with high quantitative and wide range sensitivity. This improved the accuracy of drug efficacy prediction. Therefore, patients who are expected to have a low drug efficacy will be able to select anticancer drugs with different mechanisms of action. These results of this study showed the reduction of drug discovery costs and improvement of individualized medicine. Thus, this study will greatly contribute to the development of precision medicine.

Heterogeneous Drug Efficacy of an Antibody-Drug Conjugate Visualized Using Simultaneous Imaging of Its Delivery and Intracellular Damage in Living Tumor Tissues.

Anticancer drug efficacy varies because the delivery of drugs within tumors and tumor responses are heterogeneous; however, these features are often more homogenous in vitro. This difference makes it difficult to accurately determine drug efficacy. Therefore, it is important to use living tumor tissues in preclinical trials to observe the heterogeneity in drug distribution and cell characteristics in tumors. In the present study, to accurately evaluate the efficacy of an antibody-drug conjugate (ADC) containing a microtubule inhibitor, we established a cell line that expresses a fusion of end-binding protein 1 and enhanced green fluorescent protein that serves as a microtubule plus-end-tracking protein allowing the visualization of microtubule dynamics. This cell line was xenografted into mice to create a model of living tumor tissue. The tumor cells possessed a greater number of microtubules with plus-ends, a greater number of meandering microtubules, and a slower rate of microtubule polymerization than the in vitro cells. In tumor tissues treated with fluorescent dye-labeled ADCs, heterogeneity was observed in the delivery of the drug to tumor cells, and microtubule dynamics were inhibited in a concentration-dependent manner. Moreover, a difference in drug sensitivity was observed between in vitro cells and tumor cells; compared with in vitro cells, tumor cells were more sensitive to changes in the concentration of the ADC. This study is the first to simultaneously evaluate the delivery and intracellular efficacy of ADCs in living tumor tissue. Accurate evaluation of the efficacy of ADCs is important for the development of effective anticancer drugs.

Automated Quantification of Extranuclear ERα using Phosphor-integrated Dots for Predicting Endocrine Therapy Resistance in HR+/HER2- Breast Cancer.

In addition to genomic signaling, Estrogen receptor alpha (ERα) is associated with cell proliferation and survival through extranuclear signaling contributing to endocrine therapy (ET) resistance. However, the relationship between extranuclear ERα and ET resistance has not been extensively studied. We sought to measure extranuclear ERα expression by immunohistochemistry using phosphor-integrated dots (IHC-PIDs) and to assess its predictive value for ET resistance. After quantitative detection of ERα by IHC-PIDs in vitro, we developed "the nearest-neighbor method" to calculate the extranuclear ERα. Furthermore, tissue sections from 65 patients with HR+/HER2- BC were examined by IHC-PIDs, and the total ERα, nuclear ERα, extranuclear ERα PIDs score, and ratio of extranuclear-to-nuclear ERα (ENR) were measured using the novel method. We demonstrate that quantification of ERα using IHC-PIDs exhibited strong correlations to real-time qRT-PCR (r2 = 0.94) and flow cytometry (r2 = 0.98). High ERα ENR was significantly associated with poor overall survival (p = 0.048) and disease-free survival (DFS) (p = 0.007). Multivariate analysis revealed that the ERα ENR was an independent prognostic factor for DFS [hazard ratio, 3.8; 95% CI, 1.4-11.8; p = 0.006]. Our automated measurement has high accuracy to localize and assess extranuclear ERα. A high ERα ENR in HR+/HER2- BC indicates decreased likelihood of benefiting from ET.

Quantitative analyses of amount and localization of radiosensitizer gold nanoparticles interacting with cancer cells to optimize radiation therapy.

Previous studies showed that gold nanoparticles (AuNPs) are useful radiosensitizers which optimize radiation therapy under low-dose radiation. However, the mechanisms of AuNP radiosensitization, including the amount and localization of the AuNPs interacting with cancer cells, has not yet been quantified. To answer these questions, we prepared AuNPs conjugated with anti-human epidermal growth factor receptor type 2 (HER2) antibody via polyethylene glycol (PEG) chains (AuNP-PEG-HER2ab). AuNP-PEG-HER2ab specifically bound to the HER2-expressing cancer cells and entered the cells via endocytosis. Whether endocytosis of AuNP-PEG-HER2ab occurred had no effect on radiosensitization efficacy by AuNP-PEG-HER2ab in vitro. The radiosensitization efficacy in vitro depended on dose of AuNP-PEG-HER2ab or dose of X-ray. Moreover, AuNP-PEG-HER2ab administrated into tumor-bearing mice was localized to both the periphery of the tumor tissue and near the nuclei in cancer cells in tumor deep tissue. The localization of AuNP-PEG-HER2ab in tumor tissues was important factors for in vivo powerful radiosensitization efficacy.

X-ray computed tomography imaging of a tumor with high sensitivity using gold nanoparticles conjugated to a cancer-specific antibody via polyethylene glycol chains on their surface.

Contrast agents are often used to enhance the contrast of X-ray computed tomography (CT) imaging of tumors to improve diagnostic accuracy. However, because the iodine-based contrast agents currently used in hospitals are of low molecular weight, the agent is rapidly excreted from the kidney or moves to extravascular tissues through the capillary vessels, depending on its concentration gradient. This leads to nonspecific enhancement of contrast images for tissues. Here, we created gold (Au) nanoparticles as a new contrast agent to specifically image tumors with CT using an enhanced permeability and retention (EPR) effect. Au has a higher X-ray absorption coefficient than does iodine. Au nanoparticles were supported with polyethylene glycol (PEG) chains on their surface to increase the blood retention and were conjugated with a cancer-specific antibody via terminal PEG chains. The developed Au nanoparticles were injected into tumor-bearing mice, and the distribution of Au was examined with CT imaging, transmission electron microscopy, and elemental analysis using inductively coupled plasma optical emission spectrometry. The results show that specific localization of the developed Au nanoparticles in the tumor is affected by a slight difference in particle size and enhanced by the conjugation of a specific antibody against the tumor.

Quantitative diagnosis of HER2 protein expressing breast cancer by single-particle quantum dot imaging.

Overexpression of HER2 is one of the major causes of breast cancer, and therefore precise diagnosis of its protein expression level is important. However, current methods estimating the HER2-expression level are insufficient due to problem with the lack of quantification. This might result in a gap between diagnostics and therapeutics targeting HER2. Therefore, a new effective diagnostic method is needed. We developed a new immunohistochemical (IHC) technique with quantum dots (QD)-conjugated trastuzumab using single-particle imaging to quantitatively measure the HER2 expression level. Tissues from 37 breast cancer patients with available detailed clinical information were tested by IHC with QDs (IHC-QD) and the correlation with IHC with 3,3'-diaminobenzidine (DAB), fluorescence in situ hybridization (FISH), and IHC-QD was examined. The number of QD-conjugated trastuzumab particles binding specifically to a cancer cell was precisely calculated as the IHC-QD score. The IHC-QD score in 37 cases was correlated proportionally with the score of HER2 gene copy number as assessed by FISH (R = 0.83). When HER2 positivity was judged to be positive, the IHC-QD score with our cut-off level was exactly concordant with the FISH score with a cut-off value of 2.0. Furthermore, IHC-QDs score and time to progression (TTP) of trastuzumab therapy were well correlated in HER2-positive cases (R = 0.69). Conversely, the correlation between FISH score and TTP was not observed. We developed a precisely quantitative IHC method using trastuzumab-conjugated QDs and single-particle imaging analysis and propose the possibility of using IHC-QDs score as a predictive factor for trastuzumab therapy.

Interaction between cells and poly(ethylene glycol)-lipid conjugates.

Eight types of poly(ethylene glycol)-lipid(PEG-lipids) carrying different lipid tails were synthesized. These PEG-lipids were labeled with fluorescein isothiocyanate (FITC-PEG-lipids) to examine their interaction with cells and to quantitatively determine amounts of PEG-lipids bound on the cell surface. FITC-PEG-lipids spontaneously anchored to the cell membrane within 15 min without loss of cell viability. The type of lipid had very little effect on the anchoring rates, while an increase in the hydrophobicity of the lipid portion of the PEG-lipids slowed their dissociation rates. Densities of FITC-PEG-lipids on the cell surface ranged from 1 × 10(-3) to 1 × 10(-2)molecules/nm(2), depending on the kinds of lipids employed. The relationship between the stability of the lipids on the cell membrane and the hydrophobicity of the lipid moieties will give a basis for the selection of a hydrophobic moiety in PEG-lipid conjugates for use in specific applications.

A DNA hybridization system for labeling of neural stem cells with SPIO nanoparticles for MRI monitoring post-transplantation.

Neural stem cells (NSCs) demonstrate encouraging results in cell replacement therapy for neurodegenerative disorders and traumatic injury in the central nervous system. Monitor the survival and migration of transplanted cells would provide us important information concerning the performance and integration of the graft during the therapy time course. Magnetic resonance imaging (MRI) allow us to monitor the transplanted cells in a non-invasive way. The only requirement is to use an appropriate contrast agent to label the transplanted cells. Superparamagnetic iron oxide (SPIO) nanoparticles are one of the most commonly used contrast agent for MRI detection of transplanted cells. SPIO nanoparticles demonstrated to be suitable for labeling several types of cells including NSCs. However, the current methods for SPIO labeling are non-specific, depending mostly on electrostatic interactions, demanding relatively high SPIO concentration, and long incubation time, which can affect the viability of cells. In this study, we propose a specific and relatively fast method to label NSCs with SPIO nanoparticles via DNA hybridization. Two short single stranded DNAs (ssDNAs), oligo[dT]20 and oligo[dA]20 were conjugated with a lipid molecule and SPIO nanoparticle respectively. The labeling process comprises two simple steps; first the cells are modified to present oligo[dT]20 ssDNA on the cell surface, then the oligo[dA]20 ssDNA conjugated with SPIO nanoparticles are presented to the modified cells to allow the oligo[dT]20-oligo[dA]20 hybridization. The method showed to be non-toxic at concentrations up to 50 µg/mL oligo[dA]20-SPIO nanoparticles. Presence of SPIO nanoparticles at cell surface and cell cytoplasm was verified by transmission electron microscopy (TEM). SPIO labeling via DNA hybridization demonstrated to not interfere on NSCs proliferation, aggregates formation, and differentiation. NSCs labeled with SPIO nanoparticles via DNA hybridization system were successfully detected by MRI in vitro as well in vivo. Cells transplanted into the rat brain striatum could be detected by MRI scanning up to 1 month post-transplantation.

Labeling of islet cells with iron oxide nanoparticles through DNA hybridization for highly sensitive detection by MRI.

A labeling method for islet cells with superparamagnetic iron oxide nanoparticles (SPIOs) based on DNA hybridization is proposed for monitoring of transplanted islets by magnetic resonance imaging (MRI). The surfaces of SPIOs were modified by via Michael reaction by reacting oligo-(deoxyadenylic acid)-bearing a terminal thiol group at the 5'-end ((dA)20-SH) with maleic acid functional groups on the SPIOs. The SPIOs were immobilized on islet cells which had been pretreated with oligo-(thymidylic acid)-poly(ethylene glycol)-phospholipid conjugates ((dT)20-PEG-DPPE) through DNA hybridization. Transmission electron microscopy observations revealed that SPIOs were initially anchored on the islet cell surfaces and subsequently transferred to endosomes or exfoliated with time. The SPIO-labeled islet cells could be clearly detected as dark spots by T2(*)-weighted MR image, whereas non-labeled islet cells could not be detected.

Heat-initiated detection for reduced glutathione with ¹9F NMR probes based on modified gold nanoparticles.

For detecting reduced glutathione (GSH) with a (19)F NMR spectroscopy with time-specificity, we developed the probes based on gold nanoparticles modified with the fluorinated groups via the thermally-cleavable linkers. Before the heating treatment with the probe, the maleimide moiety as a binding site with GSH in the probe is inactivated by cycloaddition of furan. At this silent state, the magnitude of (19)F NMR signals from the fluorinated groups was suppressed. By heating for the activation of the probe, the maleimide moiety was produced via retro Diels-Alder reaction, and (19)F NMR signals were observed. From this moment, GSH started the reaction with the probe via Michael addition to the maleimide moiety, leading to the observation of the new peak in (19)F NMR spectra. Finally, the amounts of GSH were determined from the increase of the magnitude of (19)F NMR signals.

Reduced glutathione-resisting ¹9F NMR sensors for detecting HNO.

The (19)F NMR probes for the HNO detection are reported. We synthesized the probe molecules with the paramagnetic Cu(II) complex and fluorine atoms using a cubic silsesquioxane. By using the magnetism changes of the Cu(II) to Cu(I) in the complex by the reduction with HNO, the (19)F NMR signal intensities of the probe increased. Noteworthily, our probes have superior resistance to reduced glutathione which is the major intracellular molecule to maintain the reductive environment and the competitor in the reduction of Cu(II) against HNO.

Heavy metal-free 19F NMR probes for quantitative measurements of glutathione reductase activity using silica nanoparticles as a signal quencher.

For the quantitative assessment of the glutathione reductase (GR) activity with a (19)F NMR spectroscopy, we developed the heavy metal-free probes based on silica nanoparticles modified with water-soluble perfluorinated dendrimers via the disulfide linkers. Before enzymatic reaction, the molecular rotation of the perfluorinated dendrimers is highly restricted, and the magnitude of (19)F NMR signals from the perfluorinated dendrimers can be suppressed. By the reductive cleavage of the disulfide linkers with the reduced glutathione-mediated enzymatic reaction of GR, perfluorinated dendrimers can be released from the surfaces of the nanoparticles. Consequently, the (19)F NMR signals of perfluorinated dendrimers were recovered. The enzymatic activity of GR was determined from the increase of the magnitude of (19)F NMR signals. Finally, to demonstrate the feasibility of the probe in the presence of miscellaneous molecules under bio-mimetic conditions, the comparison study was executed with the cancer cell lysate. The value determined from our method showed a good agreement with that from the conventional method.

Bimodal quantitative monitoring for enzymatic activity with simultaneous signal increases in 19F NMR and fluorescence using silica nanoparticle-based molecular probes.

We describe the bimodal quantitative assay for enzymatic activity in (19)F NMR spectroscopy and fluorescence spectroscopy using a nanoparticle-based molecular probe. Perfluorinated dendrimers were tethered on silica nanoparticles with a phosphate-caged fluorescein as a linker. Before enzymatic reaction, the molecular rotation of the perfluorinated dendrimers should be highly restricted, and the (19)F NMR signals from the perfluorinated dendrimers were too broad to be detected relative to the noise level. Fluorescence signals of fluorescein were suppressed by the presence of the diphosphate groups. Following the enzymatic reaction with an alkaline phosphatase, perfluorinated dendrimers and fluorescein were released, and the NMR signals of perfluorinated dendrimers and strong fluorescence from fluorescein were correspondingly observed. The enzymatic activity and reaction rates of the hydrolysis of alkaline phosphatase were detected from the increases of fluorescence and (19)F NMR signals. Finally, the feasibility of the probe in the presence of miscellaneous molecules under biomimetic conditions was demonstrated by determining of the enzymatic activity in cell lysate. Quantitative analysis using both (19)F NMR spectroscopy and fluorescence spectroscopy can be accomplished.

Preparation for highly sensitive MRI contrast agents using core/shell type nanoparticles consisting of multiple SPIO cores with thin silica coating.

We describe here the facile and robust preparation methods for the multiple-SPIO-containing silica-coated core/shell type nanoparticles which can serve as a highly sensitive MRI contrast agent. The imidazolium-tethered core/shell type particles were synthesized, and the centrifugal selection for the multiple-SPIO-containing particles and the etching process to fabricate thin silica layers were carried out to improve the proton relaxivity of water tissue. We found that the synthetic particles can provide approximately 7-fold clearer contrasts than that of the particles before treatments. In addition, the particles can show good dispersibility at least for 1 week in aqueous media.

Acceleration of guanine oxidation under visible light irradiation by photon upconversion based on triplet-triplet annihilation.

We report the fluorescent polymer complex which can show fluorescence emission at 380 nm with the excitation of 520 nm in aqueous media. This photon upconversion based on triplet-triplet annihilation can efficiently take place via inter-molecular energy transfers between the Ru complex as a sensitizer and anthracene molecules as an emitter captured into the water-soluble network polymers. We performed the oxidation reaction of 2'-deoxyguanosine by riboflavin in the presence of the polymer complex with the visible light irradiation. It was clearly indicated that oxidative decomposition can be accelerated by UV light generation via upconversion based on triplet-triplet annihilation.