Dendrimer-based Nanoparticle for Dye Sensitized Solar Cells with Improved Efficiency

Dye sensitized solar cells were fabricated with DyLight680 (DL680) dye and its corresponding europium conjugated dendrimer, DL680-Eu-G5PAMAM, to study the effect of europium on the current and voltage characteristics of the DL680 dye sensitized solar cell. The dye samples were characterized by using Absorption Spectroscopy, Emission Spectroscopy, Fluorescence lifetime and Fourier Transform Infrared measurements. Transmission electron microscopy imaging was carried out on the DL680-Eu-G5PAMAM dye and DL680-Eu-G5PAMAM dye sensitized titanium dioxide nanoparticles to analyze the size of the dye molecules and examine the interaction of the dye with titanium dioxide nanoparticles. The DL680-Eu-G5PAMAM dye sensitized solar cells demonstrated an enhanced solar-to-electric energy conversion of 0.32% under full light illumination (100 mWcm−2, AM 1.5 Global) in comparison with that of DL680 dye sensitized cells which recorded an average solar-to-electric energy conversion of only 0.19%. The improvement of the efficiency could be due to the presence of the europium that enhances the propensity of dye to absorb sunlight

MRI to assess chemoprevention in transgenic adenocarcinoma of mouse prostate (TRAMP)

<p>Abstract</p> <p>Background</p> <p>The current method to determine the efficacy of chemoprevention in TRAMP mouse model of carcinoma of prostate (CaP) is by extracting and weighing the prostate at different time points or by immunohistochemistry analysis. Non-invasive determination of volumes of prostate glands and seminal vesicles before, during and after treatment would be valuable in investigating the efficacy of newer chemopreventive agents in CaP. The purpose of this study was to determine whether <it>in vivo </it>magnetic resonance imaging (MRI) using a 3 tesla clinical MRI system can be used to follow the effect of chemoprevention in TRAMP model of mouse CaP.</p> <p>Methods</p> <p>Mice were randomized into control and treated groups. The animals in treated group received 10 µmol/kg of CDDO, 5 days a week for 20 weeks. Animals underwent <it>in vivo </it>MRI of prostate gland and seminal vesicles by a clinical 3 Tesla MRI system just before (at 5 weeks), during and at the end of treatment, at 25 weeks. T1-weighted and fat saturation (FATSAT) multiecho fast spin echo T2- weighted images (T2WI) were acquired. Volume of the prostate glands and seminal vesicles was determined from MR images. T2 signal intensity changes in the seminal vesicles were determined by subtracting higher echo time (TE) from lower TE T2WI. Following treatments all animals were sacrificed, prostate and seminal vesicles collected, and the tissues prepared for histological staining. All data were expressed as mean ± 1 standard deviation. Two-way or multivariate analysis of variance followed by post-hoc test was applied to determine the significant differences. A p-value of <0.05 was considered significant.</p> <p>Results</p> <p>Histological analysis indicated tumor in 100% of control mice, whereas 10% of the treated mice showed tumor in prostate gland. Both MRI and measured prostate weights showed higher volume/weight in control mouse group. MRI showed significantly higher volume of seminal vesicles in control animals and T2 signal intensity changes in seminal vesicles of control mice indicating higher number of tumor foci, which was also proven by histology.</p> <p>Conclusions</p> <p><it>In vivo </it>MRI is helpful in determining the efficacy of chemoprevention of prostate cancer in TRAMP mice.</p

Enhancing the Performance of Dye Sensitized Solar Cells Using Silver Nanoparticles Modified Photoanode.

In this study, silver nanoparticles were synthesized, characterized, and applied to a dye-sensitized solar cell (DSSC) to enhance the efficiency of solar cells. The synthesized silver nanoparticles were characterized with UV-Vis spectroscopy, dynamic light scattering, transmission electron microscopy, and field emission scanning electron microscopy. The silver nanoparticles infused titanium dioxide film was also characterized by Fourier transform infrared and Raman spectroscopy. The performance of DSSC fabricated with silver nanoparticle-modified photoanode was compared with that of a control group. The current and voltage characteristics of the devices as well as the electrochemical impedance measurements were also carried out to assess the performance of the fabricated solar cells. The solar-to-electric efficiency of silver nanoparticles based DSSC was 1.76%, which is quite remarkable compared to the 0.98% realized for DSSC fabricated without silver nanoparticles

pH-Responsive Liposomes of Dioleoyl Phosphatidylethanolamine and Cholesteryl Hemisuccinate for the Enhanced Anticancer Efficacy of Cisplatin

The current study aimed to develop pH-responsive cisplatin-loaded liposomes (CDDP@PLs) via the thin film hydration method. Formulations with varied ratios of dioleoyl phosphatidylethanolamine (DOPE) to cholesteryl hemisuccinate (CHEMS) were investigated to obtain the optimal particle size, zeta potential, entrapment efficiency, in vitro release profile, and stability. The particle size of the CDDP@PLs was in the range of 153.2 ± 3.08-206.4 ± 2.26 nm, zeta potential was -17.8 ± 1.26 to -24.6 ± 1.72, and PDI displayed an acceptable size distribution. Transmission electron microscopy revealed a spherical shape with ~200 nm size. Fourier transform infrared spectroscopic analysis showed the physicochemical stability of CDDP@PLs, and differential scanning calorimetry analysis showed the loss of the crystalline nature of cisplatin in liposomes. In vitro release study of CDDP@PLs at pH 7.4 depicted the lower release rate of cisplatin (less than 40%), and at a pH of 6.5, an almost 65% release rate was achieved compared to the release rate at pH 5.5 (more than 80%) showing the tumor-specific drug release. The cytotoxicity study showed the improved cytotoxicity of CDDP@PLs compared to cisplatin solution in MDA-MB-231 and SK-OV-3 cell lines, and fluorescence microscopy also showed enhanced cellular internalization. The acute toxicity study showed the safety and biocompatibility of the developed carrier system for the potential delivery of chemotherapeutic agents. These studies suggest that CDDP@PLs could be utilized as an efficient delivery system for the enhancement of therapeutic efficacy and to minimize the side effects of chemotherapy by releasing cisplatin at the tumor site

Endothelial Progenitor Cells (EPCs) as Gene Carrier System for Rat Model of Human Glioma

Due to their unique property to migrate to pathological lesions, stem cells are used as a delivery vehicle for therapeutic genes to tumors, especially for glioma. It is critically important to track the movement, localization, engraftment efficiency and functional capability or expression of transgenes of selected cell populations following transplantation. The purposes of this study were to investigate whether 1) intravenously administered, genetically transformed cord blood derived EPCs can carry human sodium iodide symporter (hNIS) to the sites of tumors in rat orthotopic model of human glioma and express transgene products, and 2) whether accumulation of these administered EPCs can be tracked by different in vivo imaging modalities.Collected EPCs were cultured and transduced to carry hNIS. Cellular viability, differential capacity and Tc-99m uptake were determined. Five to ten million EPCs were intravenously administered and Tc-99-SPECT images were acquired on day 8, to determine the accumulation of EPCs and expression of transgenes (increase activity of Tc-99m) in the tumors. Immunohistochemistry was performed to determine endothelial cell markers and hNIS positive cells in the tumors. Transduced EPCs were also magnetically labeled and accumulation of cells was confirmed by MRI and histochemistry. SPECT analysis showed increased activity of Tc-99m in the tumors that received transduced EPCs, indicative of the expression of transgene (hNIS). Activity of Tc-99m in the tumors was also dependent on the number of administered transduced EPCs. MRI showed the accumulation of magnetically labeled EPCs. Immunohistochemical analysis showed iron and hNIS positive and, human CD31 and vWF positive cells in the tumors.EPC was able to carry and express hNIS in glioma following IV administration. SPECT detected migration of EPCs and expression of the hNIS gene. EPCs can be used as gene carrier/delivery system for glioma therapy as well as imaging probes

MRI Tracking of FePro Labeled Fresh and Cryopreserved Long Term In Vitro Expanded Human Cord Blood AC133+ Endothelial Progenitor Cells in Rat Glioma

Background: Endothelial progenitors cells (EPCs) are important for the development of cell therapies for various diseases. However, the major obstacles in developing such therapies are low quantities of EPCs that can be generated from the patient and the lack of adequate non-invasive imaging approach for in vivo monitoring of transplanted cells. The objective of this project was to determine the ability of cord blood (CB) AC133+ EPCs to differentiate, in vitro and in vivo, toward mature endothelial cells (ECs) after long term in vitro expansion and cryopreservation and to use magnetic resonance imaging (MRI) to assess the in vivo migratory potential of ex vivo expanded and cryopreserved CB AC133+ EPCs in an orthotopic glioma rat model. Materials, Methods and Results: The primary CB AC133+ EPC culture contained mainly EPCs and long term in vitro conditions facilitated the maintenance of these cells in a state of commitment toward endothelial lineage. At days 15–20 and 25–30 of the primary culture, the cells were labeled with FePro and cryopreserved for a few weeks. Cryopreserved cells were thawed and in vitro differentiated or IV administered to glioma bearing rats. Different groups of rats also received long-term cultured, magnetically labeled fresh EPCs and both groups of animals underwent MRI 7 days after IV administration of EPCs. Fluorescent microscopy showed that in vitro differentiation of EPCs was not affected by FePro labeling and cryopreservation. MRI analysis demonstrated that in vivo accumulation of previously cryopreserved transplanted cells resulted in significantly higher R2 and R2* values indicating a higher rate of migration and incorporation into tumor neovascularization of previously cryopreserved CB AC133+ EPCs to glioma sites, compared to non-cryopreserved cells. Conclusion: Magnetically labeled CB EPCs can be in vitro expanded and cryopreserved for future use as MRI probes for monitoring the migration and incorporation to the sites of neovascularization

Application of Dendrimer-based Nanoparticles in Glioma Imaging

Dendritic polymers or dendrimers present an alternate template for the development of nanoparticulate-based drug delivery and imaging systems. The smaller size (~7-12 nm) of dendrimers have the advantage over the other particles, because its smaller size can possibly improve tumor penetration and the inclusion of tumor specific drug release mechanisms. A Paramagnetic Chemical Exchange Saturation Transfer (PARACEST) MRI contrast agent, Eu-DOTA-Gly4 or a clinical relevant Gd-DOTA was conjugated on the surface of a G5 PAMAM dendrimer. To create a dual mode MRI-optical imaging nanoparticle, Dylight680 was also incorporated on the amines surface of a G5 dendrimer. The particle was detected with in vivo MRI in preclinical glioma animal model. Furthermore, noninvasive imaging results were validated with in vivo and ex-vivo optical imaging

Development and testing of nanoformulation of a vascular disrupting agent in rat glioma with MRI monitoring

Anti-angiogenesis therapy VEGF-VEGF receptors (VEGFRs) axis alone or in combination with other therapeutic agents have demonstrated mixed results, with the majority of reports indicating that glioblastoma multiform (GBM) developed resistance against anti-angiogenesis therapy as well as small molecular receptor tyrosine kinase inhibitors. This result is perhaps not unexpected, because angiogenesis is obviously complex, involving dozen of different growth factors that trigger a cascade of subsequent events. Even if a drug effectively blocks one angiogenic growth factor, such as VEGF, blood vessels may still develop via activating alternative pathways. Yet without a sufficient blood supply, cancerous tumors can\u27t grow larger than the head of a pin and are unlikely to become lethal. Therefore, tumor vascularization is a critical process that determines tumor growth, progression and metastasis. Thus, tumor vasculature has become an emerging target for new chemotherapeutic drugs Vascular disrupting agents (VDAs) for example, combretastatin (CA4), represent a new class of chemotherapeutic agent that targets the newly formed vasculature in solid tumors. Preclinical and early phase trials have demonstrated the promising therapeutic benefits of CA4. Nevertheless, the clinical translation of CA4 has been significantly hampered due to its poor systemic bioavailability and the non-specific distribution of CA4 throughout the body when administered intravenously. Thus, it is reasonable to explore novel formulations of CA4 that overcome the limitations mentioned above. To improve bioavailability combretastatin phosphate (CA4-P) has been synthesized. But, CA4-P showed short blood half life. We have engineered dendrimer-based nano-sized CA4 conjugate which demonstrates high water solubility. Preliminary intravenous (i.v.) delivery of nano-combretastatin in an orthotropic glioma model demonstrated a necrosis at the core of the tumor leaving a rim of viable tissue. The MRI-determined tissue parameters Ktrans, blood flow (CBF), DWI, ADC map, distribution volume and tumor size indicated the effectiveness of nano-combretastatin treatment

Targeting Glioma with a Dual Mode Optical and Paramagnetic Nanoprobe across the Blood-brain Tumor Barrier

In brain tumors, delivering nanoparticles across the blood-tumor barrier presents major hurdles. A clinically relevant MRI contrast agent, GdDOTA and a near-infrared (NIR) fluorescent dye, DL680 were conjugated to a G5 PAMAM dendrimer, thus producing a dual-mode MRI and NIR imaging agent. Systemic delivery of the subsequent nano-sized agent demonstrated glioma-specific accumulation, probably due to the enhanced permeability and retention effect

Targeted Theranostic Approach for Glioma Using Dendrimer-Based Curcumin Nanoparticle

The delivery of anti-cancer agents to brain tumors represent a challenge because the blood-brain tumor barrier (BBTB) effectively limits the delivery of many agents. A new generation 3 (G3) dendrimer-based curcumin (Curc) conjugate was synthesized. The synthesized G3-Curc conjugate demonstrated full solubility in aqueous media. The in vitro study revealed that G3-Curc nanoparticles were internalized into glioma U-251 cells. Systemic delivery of G3-Curc conjugate led to preferentially accumulation in an orthotopic preclinical glioma model minimizing systemic toxic effect. Multicolor microscopy images of the tumor tissue showed that G3-Curc particles were internalized inside tumor cells selectively and further localized within nuclei. Enhanced bioavailability of G3-Curc conjugate was also observed with improved therapeutic efficacy against different cancers cells