The Experts below are selected from a list of 9312 Experts worldwide ranked by ideXlab platform
Naomi J Halas - One of the best experts on this subject based on the ideXlab platform.
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Electrical conductivity of cationized ferritin decorated gold Nanoshells
Journal of Applied Physics, 2012Co-Authors: Rebecca Cortez, Naomi J Halas, Joseph M. Slocik, Joseph E. Van Nostrand, Rajesh R. NaikAbstract:We report on a novel method of controlling the resistance of nanodimensional, gold-coated SiO2 nanoparticles by utilizing biomolecules chemisorbed to the Nanoshell surface. Local electronic transport properties of gold-coated Nanoshells were measured using scanning conductance microscopy. These results were compared to transport properties of identical gold Nanoshells biofunctionalized with cationized ferritin protein both with and without an iron oxide core (apoferritin). Measured resistances were on the order of mega-ohms. White light irradiation effects on transport properties were also explored. The results suggest that the light energy influences the Nanoshells’ conductivity. A mechanism for assembly of gold Nanoshells with cationized ferritin or cationized apoferritin is proposed to explain the resistivity dependence on irradiation.
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Temperature measurements of optically trapped gold Nanoshells
Optics in the Life Sciences, 2011Co-Authors: Brooke C. Hester, Gretchen K. Campbell, Kristian Helmerson, Ryan Huschka, Naomi J HalasAbstract:We measure the temperature of an optically trapped gold Nanoshell by tracking its Brownian motion. Single Nanoshells are found to heat significantly, and this heating varies with trap wavelength and particle number.
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Self-assembled plasmonic nanoparticle clusters
CLEO QELS: 2010 Laser Science to Photonic Applications, 2010Co-Authors: Chihhui Wu, Naomi J Halas, Rizia Bardhan, Vinothan N. Manoharan, Peter Nordlander, Gennady Shvets, Federico CapassoAbstract:Polymer-coated gold Nanoshells are assembled, using capillary forces, into packed clusters with tailored surface plasmon resonances. Separation between Nanoshells is engineered to be ~2 nm. Strongly coupled resonances in Nanoshell dimers and trimers are observed.
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Nanoshell based substrates for surface enhanced spectroscopic detection of biomolecules
Analyst, 2009Co-Authors: Carly S Levin, Janardan Kundu, Aoune Barhoumi, Naomi J HalasAbstract:Nanoshells are optically tunable core–shell nanostructures with demonstrated uses in surface enhanced spectroscopies. Based on their ability to support surface plasmons, which give rise to strongly enhanced electromagnetic fields at their surface, Nanoshells provide simple, scalable, high-quality substrates. In this article, we outline the development and use of Nanoshell-based substrates for direct, spectroscopic detection of biomolecules. Recent advances in the use of these nanostructures lead to improved spectroscopic quality, selectivity, and reproducibility.
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Nanoshells for Integrated Cancer Imaging and Therapy
Clinical Cancer Research, 2006Co-Authors: Andre M. Gobin, Rebekah A Drezek, Naomi J Halas, Jennifer L. WestAbstract:A104 This purpose of this study was to investigate the use of Nanoshells for a combined imaging application and cancer therapy using commercially available optical coherence tomography (OCT). Gold Nanoshells are a new class of nanoparticles with tunable optical absorption that can be designed in the near infrared where penetration of light through tissue is maximal. Nanoshells consist of a dielectric core of silica with an ultrathin shell of gold. It has been previously shown that gold Nanoshells can sufficiently accumulate in tumors due to the enhanced permeability and retention (EPR) effect thus allowing ablation of tumors using an external NIR laser source. This led to complete tumor regression. In the current studies, we have designed Nanoshells to both provide optical contrast for OCT to enhance diagnostic capabilities and also to then to generate localized heating under the appropriate illumination conditions to allow for ablation of the tumor.Murine colon carcinoma cells, CT-26, were grown subcutaneously in BALB/c mice. Tumors were allowed to grow to ~5 mm diameter. The surfaces of the Nanoshells were modified with polyethylene glycol (PEG-SH) to enhance circulation. For the treatment group PEGylated Nanoshells were injected into the tail vein of the animals 20 hours prior to imaging and treatment. PBS injected animals and untreated controls were also used in the study. The tumors were imaged using the Niris Imaging System OCT by applying glycerol for index matching and placing the probe directly on the skin. Images were captured at several locations on each tumor. After imaging the tumors were exposed to a NIR laser. Tumor size and animal survival following treatment was monitored for 8 weeks after treatment.OCT images of the tumors prior to irradiation shows substantially higher contrast, indicative of higher scattering, in the tumors of mice that received systemic Nanoshell injections compared to the mice receiving saline injections. Silver stained images show the presence of Nanoshells in the tumors of mice injected with Nanoshells compared to PBS injected mice. There was a greater than 80% survival rate of the Nanoshell therapy mice after 8 weeks, compared to 14% for the Saline + laser group and zero for the control group. Kaplan-Meier statistical analysis on the survival data showed a median survival of 14 days for the PBS + laser treatment group and 10 days for the Untreated Control group. At 21 days and to the end of the 8 week study period, the Nanoshell therapy group survival rate was significantly higher than either control group, p
Jennifer L. West - One of the best experts on this subject based on the ideXlab platform.
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Nanoshell mediated photothermal therapy improves survival in a murine glioma model
Journal of Neuro-oncology, 2011Co-Authors: Patrick A Thompson, Rebekah A Drezek, Linna Zhang, Nastassja A Lewinski, Nabil Ahmed, Susan M Blaney, Jennifer L. WestAbstract:We are developing a novel treatment for high-grade gliomas using near infrared-absorbing silica–gold Nanoshells that are thermally activated upon exposure to a near infrared laser, thereby irreversibly damaging cancerous cells. The goal of this work was to determine the efficacy of Nanoshell-mediated photothermal therapy in vivo in murine xenograft models. Tumors were induced in male IcrTac:ICR-PrkdcSCID mice by subcutaneous implantation of Firefly Luciferase-labeled U373 human glioma cells and biodistribution and survival studies were performed. To evaluate nanoparticle biodistribution, Nanoshells were delivered intravenously to tumor-bearing mice and after 6, 24, or 48 h the tumor, liver, spleen, brain, muscle, and blood were assessed for gold content by inductively coupled plasma-mass spectrometry (ICP-MS) and histology. Nanoshell concentrations in the tumor increased for the first 24 h and stabilized thereafter. Treatment efficacy was evaluated by delivering saline or Nanoshells intravenously and externally irradiating tumors with a near infrared laser 24 h post-injection. Success of treatment was assessed by monitoring tumor size, tumor luminescence, and survival time of the mice following laser irradiation. There was a significant improvement in survival for the Nanoshell treatment group versus the control (P < 0.02) and 57% of the mice in the Nanoshell treatment group remained tumor free at the end of the 90-day study period. By comparison, none of the mice in the control group survived beyond 24 days and mean survival was only 13.3 days. The results of these studies suggest that Nanoshell-mediated photothermal therapy represents a promising novel treatment strategy for malignant glioma.
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Diagnostic and Therapeutic Applications of Nanotechnology.
Cancer Research, 2009Co-Authors: Jennifer L. WestAbstract:The increasing capability to manipulate matter at the nanoscale is generating new materials with unique properties that promise to address unmet medical needs for future generations. As an example, metal Nanoshells are a relatively new class of nanoparticles with highly tunable optical properties. Metal Nanoshells consist of a dielectric core nanoparticle such as silica surrounded by an ultrathin metal shell, usually composed of gold for biomedical applications. Depending on the size and composition of each layer of the Nanoshell, particles can be designed to either absorb or scatter light over much of the visible and infrared regions of the electromagnetic spectrum, including the near infrared region where penetration of light through tissue is maximal. These particles are also easily conjugated to antibodies and other biomolecules for specific targeting. Further, the biocompatibility of these particles is excellent. One can envision a myriad of potential applications of such tunable particles. Several potential biomedical applications are under development, including immunoassays, modulated drug delivery, photothermal cancer therapy, and imaging contrast agents. For example, in photothermal cancer therapy, Nanoshells can be injected intravenously, accumulate at tumor sites due to the enhanced permeability and retention (EPR) effect and/or molecular targeting, then generate heat upon illumination with near infrared light, leading to destruction of the tumor. This has shown very promising results in several animal models. For example, in a mouse colon carcinoma model, we demonstrated 100% survival of Nanoshell treated mice at 1 year. These materials are now in phase I human clinical trials. For use in diagnostics and imaging, Nanoshells can be designed to strongly scatter near infrared light. Molecularly targeted Nanoshells have been used as optical contrast agents for cancer imaging with sub-cellular resolution. For example, anti-HER2 conjugated Nanoshells allow near infrared imaging of HER2+ breast carcinoma cells. Furthermore, integrated imaging and therapy applications have been accomplished with Nanoshells designed to provide both absorption and scattering, potentially enabling “see-and-treat” approaches to cancer therapy. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr MS1-1.
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Near Infrared Absorbing Nanoparticles for Photothermal Cancer Therapy
ASME 2008 Summer Bioengineering Conference Parts A and B, 2008Co-Authors: Jennifer L. WestAbstract:Advances in nanotechnology are expected to lead to the development of new and improved therapeutic strategies, amenable to targeting, that may ultimately revolutionize cancer treatment. For example, we have developed a nanoparticle-based photothermal cancer therapy that has shown high efficacy with virtually no damage to normal tissues (Hirsch et al., 2003, O’Neal et al., 2004, Lowery et al., 2006). This therapeutic strategy employs nanoparticles called Nanoshells that are designed to strongly absorb near infrared (NIR) light. Metal Nanoshells are a new type of nanoparticle composed of a dielectric (for instance, silica) core coated with an ultrathin metallic (for instance, gold) layer. Gold Nanoshells possess physical properties similar to gold colloid, in particular, a strong optical absorption due to the collective electronic response of the metal to light. The optical absorption of gold colloid yields a brilliant red color that has been of considerable utility in consumer-related medical products, such as home pregnancy tests. In contrast, the optical response of gold Nanoshells depends dramatically on the relative size of the nanoparticle core and the thickness of the gold shell. By varying the relative core and shell thicknesses, the color of gold Nanoshells can be varied across a broad range of the optical spectrum that spans the visible and the near infrared spectral regions (Oldenburg et al., 1999). Gold Nanoshells can be made to either preferentially absorb or scatter light at their plasmon resonance by varying the size of the particle relative to the wavelength of the light at their optical resonance. For cancer therapy, Nanoshells are injected intravenously and allowed to accumulate in tumor sites due to the leakiness of the vasculature (EPR) and/or molecular targeting. Accumulation in the tumor sites peaks after several hours, at which time the tissue region is illuminated with NIR light for several minutes. NIR light is not absorbed to a significant extent by tissue components, but is strongly absorbed by Nanoshells within the tumor. This leads to rapid heating of the tumor tissue without damage to adjacent normal tissues. In preliminary studies, complete tumor regression and 100% survival with no regrowth has been achieved. Mice with CT26 colon carcinoma tumors (4 mm diameter) were injected intravenously with NIR absorbing Nanoshells that were coated with PEG-SH. 6 hr following Nanoshell injection, the tumor sites were illuminated with light from a 820 nm diode laser (4 W/cm2) for 4 min. Animals in a sham group received a saline injection instead of Nanoshells prior to NIR treatment, while a control group was untreated. Tumor size and animal survival were then tracked. As shown in Figure 1, all tumors treated with Nanoshells had completely regressed within 10 days of treatment, while sham and control tumors had grown dramatically. Furthermore, all sham and control animals died within 20 days of treatment, while all Nanoshell-treated mice continue to live (+12 months) with no tumor regrowth (Figure 2, O’Neal et al., 2004). Excellent Nanoshell biocompatibility has been observed.Copyright © 2008 by ASME
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Nanoshells for Integrated Cancer Imaging and Therapy
Clinical Cancer Research, 2006Co-Authors: Andre M. Gobin, Rebekah A Drezek, Naomi J Halas, Jennifer L. WestAbstract:A104 This purpose of this study was to investigate the use of Nanoshells for a combined imaging application and cancer therapy using commercially available optical coherence tomography (OCT). Gold Nanoshells are a new class of nanoparticles with tunable optical absorption that can be designed in the near infrared where penetration of light through tissue is maximal. Nanoshells consist of a dielectric core of silica with an ultrathin shell of gold. It has been previously shown that gold Nanoshells can sufficiently accumulate in tumors due to the enhanced permeability and retention (EPR) effect thus allowing ablation of tumors using an external NIR laser source. This led to complete tumor regression. In the current studies, we have designed Nanoshells to both provide optical contrast for OCT to enhance diagnostic capabilities and also to then to generate localized heating under the appropriate illumination conditions to allow for ablation of the tumor.Murine colon carcinoma cells, CT-26, were grown subcutaneously in BALB/c mice. Tumors were allowed to grow to ~5 mm diameter. The surfaces of the Nanoshells were modified with polyethylene glycol (PEG-SH) to enhance circulation. For the treatment group PEGylated Nanoshells were injected into the tail vein of the animals 20 hours prior to imaging and treatment. PBS injected animals and untreated controls were also used in the study. The tumors were imaged using the Niris Imaging System OCT by applying glycerol for index matching and placing the probe directly on the skin. Images were captured at several locations on each tumor. After imaging the tumors were exposed to a NIR laser. Tumor size and animal survival following treatment was monitored for 8 weeks after treatment.OCT images of the tumors prior to irradiation shows substantially higher contrast, indicative of higher scattering, in the tumors of mice that received systemic Nanoshell injections compared to the mice receiving saline injections. Silver stained images show the presence of Nanoshells in the tumors of mice injected with Nanoshells compared to PBS injected mice. There was a greater than 80% survival rate of the Nanoshell therapy mice after 8 weeks, compared to 14% for the Saline + laser group and zero for the control group. Kaplan-Meier statistical analysis on the survival data showed a median survival of 14 days for the PBS + laser treatment group and 10 days for the Untreated Control group. At 21 days and to the end of the 8 week study period, the Nanoshell therapy group survival rate was significantly higher than either control group, p
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Vascular targeting of Nanoshells for photothermal cancer therapy.
Clinical Cancer Research, 2006Co-Authors: Amanda R Lowery, Naomi J Halas, Andre M. Gobin, Jennifer L. WestAbstract:B83 Photothermal cancer therapy using targeted Nanoshells may enable the preferential destruction of cancer cells while minimizing damage to healthy tissue. Nanoshells possess an optical tunability that spans the near infrared (NIR) - a region where light penetrates tissues deeply. Conjugated with tumor-targeting molecules, NIR absorbing Nanoshells could be systemically injected and preferentially bound to tumor sites. NIR light heats the tumor-bound Nanoshells, thus destroying the tumor. In vitro and in vivo studies confirmed the ability to selectively induce cell death with the photothermal interaction of Nanoshells and NIR light. Previous studies demonstrated the ability of PEG-coated Nanoshells to passively accumulate at a tumor site. Complete regression of tumors was observed in animals receiving systemic injections of Nanoshells prior to NIR laser treatment. Furthermore, the tissue damage from the NIR laser therapy was confined to the tissue region receiving both Nanoshells and laser irradiation. Nanoshells can be targeted to cancer cells or tumor vasculature by the conjugation of tumor specific antibodies to the gold surface. These targeted Nanoshells may increase the cellular specificity of Nanoshell binding and improve the therapeutic results.Gold Nanoshells were manufactured as previously described. Briefly, silica cores were fabricated by the reduction of tetraethoxysilane in ethanol. Following amine functionalization, gold colloid was adsorbed to silica surface. Reduction of additional gold completes the shell. The Nanoshells used in the following study had a 110 nm core diameter with a 10 nm thick gold shell and a peak extinction at ~820 nm. Soluble vascular endothelial growth factor (VEGF) was conjugated to the gold Nanoshells through a bifunctional PEG linker, containing N-hydroxy succihimide for coupling and an orthopyridyl-disulfide for attachment to the gold surface. In vitro , targeted Nanoshells were incubated with murine endothelial cells at 2.9x10 9 particles/mL. Unbound Nanoshells were rinsed from the surface with PBS and replaced with fresh medium. Control cells were incubated with PEG-coated Nanoshells without targeting molecules. After exposure to NIR light (820 nm, 1.55 W, 1.5 mm diameter spot, for 7 min), the cells were incubated overnight at 37 o C. Cell viability was assessed by staining with calcein AM. Nanoshells were visualized by silver staining.Cell death was confined within the laser spot for cells incubated with properly targeted Nanoshells. Silver staining verified the presences of Nanoshells. Control Nanoshells did not bind to the cells, as indicated by silver staining, and control cells continued to be viable after irradiation. Nanoshells show promise as a minimally invasive cancer therapy. The Nanoshells are biocompatible and display selective photothermal destruction of tissue by absorption of NIR light. Targeting may improve the cellular specificity of the Nanoshell therapy.
Rebekah A Drezek - One of the best experts on this subject based on the ideXlab platform.
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Nanoshell mediated photothermal therapy improves survival in a murine glioma model
Journal of Neuro-oncology, 2011Co-Authors: Patrick A Thompson, Rebekah A Drezek, Linna Zhang, Nastassja A Lewinski, Nabil Ahmed, Susan M Blaney, Jennifer L. WestAbstract:We are developing a novel treatment for high-grade gliomas using near infrared-absorbing silica–gold Nanoshells that are thermally activated upon exposure to a near infrared laser, thereby irreversibly damaging cancerous cells. The goal of this work was to determine the efficacy of Nanoshell-mediated photothermal therapy in vivo in murine xenograft models. Tumors were induced in male IcrTac:ICR-PrkdcSCID mice by subcutaneous implantation of Firefly Luciferase-labeled U373 human glioma cells and biodistribution and survival studies were performed. To evaluate nanoparticle biodistribution, Nanoshells were delivered intravenously to tumor-bearing mice and after 6, 24, or 48 h the tumor, liver, spleen, brain, muscle, and blood were assessed for gold content by inductively coupled plasma-mass spectrometry (ICP-MS) and histology. Nanoshell concentrations in the tumor increased for the first 24 h and stabilized thereafter. Treatment efficacy was evaluated by delivering saline or Nanoshells intravenously and externally irradiating tumors with a near infrared laser 24 h post-injection. Success of treatment was assessed by monitoring tumor size, tumor luminescence, and survival time of the mice following laser irradiation. There was a significant improvement in survival for the Nanoshell treatment group versus the control (P < 0.02) and 57% of the mice in the Nanoshell treatment group remained tumor free at the end of the 90-day study period. By comparison, none of the mice in the control group survived beyond 24 days and mean survival was only 13.3 days. The results of these studies suggest that Nanoshell-mediated photothermal therapy represents a promising novel treatment strategy for malignant glioma.
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immunoconjugated gold Nanoshell mediated photothermal ablation of trastuzumab resistant breast cancer cells
Breast Cancer Research and Treatment, 2011Co-Authors: Laura B Carpin, Lissett R Bickford, Germaine Agollah, Tsekuan Yu, Rachel Schiff, Yi Li, Rebekah A DrezekAbstract:Trastuzumab is a FDA-approved drug that has shown clinical efficacy against HER2+ breast cancers and is commonly used in combination with other chemotherapeutics. However, many patients are innately resistant to trastuzumab, or will develop resistance during treatment. Alternative treatments are needed for trastuzumab-resistant patients. Here, we investigate gold nanoparticle-mediated photothermal therapies as a potential alternative treatment for chemotherapy-resistant cancers. Gold Nanoshell photothermal therapy destroys the tumor cells using heat, a physical mechanism, which is able to overcome the cellular adaptations that bestow trastuzumab resistance. By adding anti-HER2 to the gold surface of the Nanoshells as a targeting modality, we increase the specificity of the Nanoshells for HER2+ breast cancer. Silica–gold Nanoshells conjugated with anti-HER2 were incubated with both trastuzumab-sensitive and trastuzumab-resistant breast cancer cells. Nanoshell binding was confirmed using two-photon laser scanning microscopy, and the cells were then ablated using a near-infrared laser. We demonstrate the successful targeting and ablation of trastuzumab-resistant cells using anti-HER2-conjugated silica–gold Nanoshells and a near-infrared laser. This study suggests potential for applying gold Nanoshell-mediated therapy to trastuzumab-resistant breast cancers in vivo.
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Optical properties of gold-silica-gold multilayer Nanoshells
Optics Express, 2008Co-Authors: Ying Hu, Ryan C. Fleming, Rebekah A DrezekAbstract:The spectral and angular radiation properties of gold-silica-gold multilayer Nanoshells are investigated using Mie theory for concentric multilayer spheres. The spectral tunability of multilayer Nanoshells is explained and characterized by a plasmon hybridization model and a universal scaling principle. A thinner intermediate silica layer, scaled by particle size, red shifts the plasmon resonance. This shift is relatively insensitive to the overall particle size and follows the universal scaling principle with respect to the resonant wavelength of a conventional silica-gold core-shell Nanoshell. The extra tunability provided by the inner core further shifts the extinction peak to longer wavelengths, which is difficult to achieve on conventional sub-100 nm Nanoshells due to limitations in synthesizing ultrathin gold coatings. We found multilayer Nanoshells to be more absorbing with a larger gold core, a thinner silica layer, and a thinner outer gold shell. Both scattering intensity and angular radiation pattern were found to differ from conventional Nanoshells due to spectral modulation from the inner core. Multilayer Nanoshells may provide more backscattering at wavelengths where silica-gold core-shell Nanoshells predominantly forward scatter.
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Nanoshells for Integrated Cancer Imaging and Therapy
Clinical Cancer Research, 2006Co-Authors: Andre M. Gobin, Rebekah A Drezek, Naomi J Halas, Jennifer L. WestAbstract:A104 This purpose of this study was to investigate the use of Nanoshells for a combined imaging application and cancer therapy using commercially available optical coherence tomography (OCT). Gold Nanoshells are a new class of nanoparticles with tunable optical absorption that can be designed in the near infrared where penetration of light through tissue is maximal. Nanoshells consist of a dielectric core of silica with an ultrathin shell of gold. It has been previously shown that gold Nanoshells can sufficiently accumulate in tumors due to the enhanced permeability and retention (EPR) effect thus allowing ablation of tumors using an external NIR laser source. This led to complete tumor regression. In the current studies, we have designed Nanoshells to both provide optical contrast for OCT to enhance diagnostic capabilities and also to then to generate localized heating under the appropriate illumination conditions to allow for ablation of the tumor.Murine colon carcinoma cells, CT-26, were grown subcutaneously in BALB/c mice. Tumors were allowed to grow to ~5 mm diameter. The surfaces of the Nanoshells were modified with polyethylene glycol (PEG-SH) to enhance circulation. For the treatment group PEGylated Nanoshells were injected into the tail vein of the animals 20 hours prior to imaging and treatment. PBS injected animals and untreated controls were also used in the study. The tumors were imaged using the Niris Imaging System OCT by applying glycerol for index matching and placing the probe directly on the skin. Images were captured at several locations on each tumor. After imaging the tumors were exposed to a NIR laser. Tumor size and animal survival following treatment was monitored for 8 weeks after treatment.OCT images of the tumors prior to irradiation shows substantially higher contrast, indicative of higher scattering, in the tumors of mice that received systemic Nanoshell injections compared to the mice receiving saline injections. Silver stained images show the presence of Nanoshells in the tumors of mice injected with Nanoshells compared to PBS injected mice. There was a greater than 80% survival rate of the Nanoshell therapy mice after 8 weeks, compared to 14% for the Saline + laser group and zero for the control group. Kaplan-Meier statistical analysis on the survival data showed a median survival of 14 days for the PBS + laser treatment group and 10 days for the Untreated Control group. At 21 days and to the end of the 8 week study period, the Nanoshell therapy group survival rate was significantly higher than either control group, p
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Reflectance spectroscopy of gold Nanoshells: computational predictions and experimental measurements
Journal of Nanoparticle Research, 2006Co-Authors: Nastassja A Lewinski, Rebekah A DrezekAbstract:Gold Nanoshells are concentric spherical constructs that possess highly desirable optical responses in the near infrared. Gold Nanoshells consist of a thin outer gold shell and a silica core and can be used for both diagnostic and therapeutic purposes by tuning the optical response through changing the core–shell ratio as well as the overall size. Although optical properties of gold Nanoshells have already been well documented, the reflectance characteristics are not well understood and have not yet been elucidated by experimental measurements. Yet, in order to use gold Nanoshells as an optical contrast agent for scattering-based optical methods such as reflectance spectroscopy, it is critical to characterize the reflectance behavior. With this in mind, we used a fiber-optic-based spectrometer to measure diffuse reflectance of gold Nanoshell suspensions from 500 nm to 900 nm. Experimental results show that gold Nanoshells cause a significant increase in the measured reflectance. Spectral features associated with scattering from large angles (~180°) were observed at low Nanoshell concentrations. Monte Carlo modeling of gold Nanoshells reflectance demonstrated the efficacy of using such methods to predict diffuse reflectance. Our studies suggest that gold Nanoshells are an excellent candidate as optical contrast agents and that Monte Carlo methods are a useful tool for optimizing Nanoshells best suited for scattering-based optical methods.
Ben Q. Li - One of the best experts on this subject based on the ideXlab platform.
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Measurement of Light Attenuation in Phantom Tissue Embedded with Gold Nanoshells
Advanced Materials Research, 2020Co-Authors: A. Yella, Ben Q. Li, Krisanu BandyopadhyayAbstract:Light attenuation in phantom tissue embedded with gold Nanoshells is measured using a photospectrometer with an integrated sphere system. Gold Nanoshells are synthesized and a paste is made by mixing them with agar (or phantom tissue); from which slab samples of different Nanoshell concentrations and thicknesses are prepared. Light attenuation is measured as a function of light exciting frequencies, Nanoshell concentrations and tissue thickness. The Nanoshell particle concentrations are determined by matching the Mie solution for a single Nanoshell with the measured attenuation coefficient at the local surface plasma resonance frequency. For the range of the concentrations studied, light attenuation is linearly dependent on the Nanoshell concentration, and thus the rule of independent scattering/absorption is observed. The frequency of exciting light strongly affects light attenuation in a Nanoshell-populated medium, with the largest attenuation occurring at the local surface plasma resonance frequency of the Nanoshells, which is consistent with theoretical predictions. For the measured samples of phantom tissue populated with Nanoshells, the optical thickness is about ~8 mm.
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Energy Absorption in Gold Nanoshells
Journal of Nano Research, 2013Co-Authors: Ben Q. LiAbstract:A modeling study on energy absorption and transport in an isolated Nanoshell and aggregates of Nanoshells under localized surface plasma resonance (SPR) conditions is presented. A comprehensive model for multi-scattering of electromagnetic waves by a cluster of multilayered Nanoshells is developed, which applies the Wigner-Eckart theorem for the calculation of the total scattering cross sessions of Nanoshell aggregates. Absorption by an isolated Nanoshell and by Nanoshell clusters is studied using the model. Results show that the inter-Nanoshell coupling results in strong field enhancement near the particle surface. Energy absorption in a Nanoshell can be tuned by varying the structural parameters of the Nanoshell. Smaller particles are more absorbing than the large ones, other conditions being equal. Because of the presence of a dielectric cavity, the radial distribution of the absorbed power in the metal shell may differ from the classical skin depth phenomena. The interaction among particles in close proximity causes the energy absorption efficiency and the resonance position of a Nanoshell cluster to differ from those of an isolated Nanoshell.
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Absorption and Scattering of the Aggregated Multi-Layered Nanoshells
ASME JSME 2011 8th Thermal Engineering Joint Conference, 2011Co-Authors: Ben Q. LiAbstract:A generalized mathematical formulation is presented for multi-scattering of electromagnetic fields by an ensemble consisting of arbitrarily-positioned multilayered Nanoshells. The model is developed by combining the addition theorem and the efficient recursive procedure for multilayered Nanoshells and general procedures for computing the multiple scattered fields and optical properties of the particle ensemble are presented. The enhancement of the electric field and the energy absorbed by the aggregated silica-gold Nanoshell and gold-silica-gold Nanoshells are analyzed to understand the physics governing the electromagnetic field interaction with aggregated multilayered Nanoshells. The mathematical model should be helpful in providing valuable information on optical and radative transfer characteristics needed for the Nanoshell-based applications in photothermal therapy, biomedical imaging, biosensing and waveguide for energy transport.Copyright © 2011 by ASME
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Energy Absorption of Gold Nanoshells in Hyperthermia Therapy
IEEE Transactions on NanoBioscience, 2008Co-Authors: Chunting Chris Mi*, Ben Q. LiAbstract:The unique optical characteristics of a gold Nanoshell motivate the application of Nanoshell-based hyperthermia in drug delivery and cancer treatment. However, most of our understanding on energy absorption and heat transfer is still focused on individual particles, which may not be accurate for Nanoshell aggregates in a real application due to the strong optical interaction of Nanoshells. This paper investigates the relationship between the optical interaction and the interparticle distance in the visible and near-infrared regions by means of a finite-difference time-domain (FDTD) method. The objective is to explore the energy transportation mechanism, which is critical for hyperthermia therapy. From the numerical simulation results of different forms of Nanoshell aggregates, including individual Nanoshells, 1-D chains, 2-D arrays, and 3-D clusters, it was found that the interparticle distance plays a crucial role from the maximal absorption point of view. The interparticle distance affects both field enhancement and surface plasmon resonance position. The accurate prediction of energy absorption also helps the way Nanoshells are populated in the tumor cell so as to prevent heat damage to healthy tissues in clinic applications. In the case of 3-D clusters, the laser energy decays exponentially along the wave propagation, and the penetration depth greatly depends on the interparticle distance. The closer the Nanoshells are placed, the shorter the penetration depth is. The maximal total length for the laser penetration through the shell of gold nanoparticles is about a few hundred to several nanometers. The actual penetration depth primarily depends not only on the interparticle distance, but also on the size of the Nanoshells as well as other factors. Since the absorption energy is concentrated on the surface clusters of nanoparticles, heat transfer mechanisms in metal-nanoparticles-based hyperthermia will differ from that in other hyperthermia. The information obtained from this paper will serve as a basis for further study of heat transfer in metal-nanoparticles-based hyperthermia.
Mahi R Singh - One of the best experts on this subject based on the ideXlab platform.
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medical applications of hybrids made from quantum emitter and metallic Nanoshell
Journal of Applied Physics, 2017Co-Authors: Mahi R Singh, Chandra M Sekhar, Shankar Balakrishnan, Shahbaz MasoodAbstract:We have studied the photoluminescence emission in a quantum emitter and metallic Nanoshell hybrid system. The metallic Nanoshell is made of a dielectric core coated with a thin layer of metal and is surrounded by biological cells such as cancer cells. Surface plasmon polariton resonances in the metallic Nanoshell are calculated using Maxwell's equations in the quasi-static approximation. It is found that the metallic Nanoshell has two surface plasmon polariton resonances. Locations of surface plasmon polariton resonances can be manipulated by changing the size of the core and the metallic shell. We have compared our theory with the extinction coefficient of metallic Nanoshells. A good agreement between theory and experiment is found. A probe laser field is applied to study the photoluminescence spectrum in the hybrid system. Dipoles are induced in the metallic Nanoshell and quantum emitter due to the probe laser. Hence the quantum emitter and metallic Nanoshell interact via the dipole-dipole interaction. ...
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control of fluorescence in quantum emitter and metallic Nanoshell hybrids for medical applications
Journal of Applied Physics, 2017Co-Authors: Mahi R Singh, Jesus Enrique De Hoyos MartinezAbstract:We study the light emission from a quantum emitter and double metallic Nanoshell hybrid systems. Quantum emitters act as local sources which transmit their light efficiently due to a double Nanoshell near field. The double Nanoshell consists of a dielectric core and two outer Nanoshells. The first Nanoshell is made of a metal, and the second spacer Nanoshell is made of a dielectric material or human serum albumin. We have calculated the fluorescence emission for a quantum emitter-double Nanoshell hybrid when it is injected in an animal or a human body. Surface plasmon polariton resonances in the double Nanoshell are calculated using Maxwell's equations in the quasi-static approximation, and the fluorescence emission is evaluated using the density matrix method in the presence of dipole-dipole interactions. We have compared our theory with two fluorescence experiments in hybrid systems in which the quantum emitter is Indocyanine Green or infrared fluorescent molecules. The outer spacer Nanoshell of double metallic Nanoshells consists of silica and human serum albumin with variable thicknesses. Our theory explains the enhancement of fluorescence spectra in both experiments. We find that the thickness of the spacer Nanoshell layer increases the enhancement when the fluorescence decreases. The enhancement of the fluorescence depends on the type of quantum emitter, spacer layer, and double Nanoshell. We also found that the peak of the fluorescence spectrum can be shifted by changing the shape and the size of the Nanoshell. The fluorescence spectra can be switched from one peak to two peaks by removing the degeneracy of excitonic states in the quantum emitter. Hence, using these properties, one can use these hybrids as sensing and switching devices for applications in medicine.We study the light emission from a quantum emitter and double metallic Nanoshell hybrid systems. Quantum emitters act as local sources which transmit their light efficiently due to a double Nanoshell near field. The double Nanoshell consists of a dielectric core and two outer Nanoshells. The first Nanoshell is made of a metal, and the second spacer Nanoshell is made of a dielectric material or human serum albumin. We have calculated the fluorescence emission for a quantum emitter-double Nanoshell hybrid when it is injected in an animal or a human body. Surface plasmon polariton resonances in the double Nanoshell are calculated using Maxwell's equations in the quasi-static approximation, and the fluorescence emission is evaluated using the density matrix method in the presence of dipole-dipole interactions. We have compared our theory with two fluorescence experiments in hybrid systems in which the quantum emitter is Indocyanine Green or infrared fluorescent molecules. The outer spacer Nanoshell of double ...
