Gold-silica Nanoshells Research Articles

Gold nanoshells for prostate cancer treatment: evidence for deposition in abdominal organs.

Gold-silica nanoshell therapy [AuroShells with subsequent focal laser therapy (AuroLase)] is an emerging targeted treatment modality for prostate cancer. We reviewed pre- and post-treatment unenhanced CT imaging to assess for retained gold-silica nanoshells in the abdomen and pelvis. This single-institution retrospective study identified patients in the AuroLase pilot who underwent pre- and post-treatment unenhanced abdominopelvic CT. The attenuation, before and after gold-silica nanoshell administration, of the liver, spleen, pancreas, kidneys, prostate, blood pool, paraspinal musculature, and abnormal lymph nodes were manually measured by two readers. After inter-reader agreement was calculated using intraclass correlation (ICC), a permutation test was used to assess pre- and post-therapy attenuation differences. Four patients met the inclusion criteria. Mean age was 72.3 ± 5.9years. Median time interval between pre-treatment CT and treatment, and between treatment and post-treatment CT, was 232days and 236.5days, respectively. The two readers' attenuation measurements had very high agreement (ICC = 0.99, p < 0.001). The highest differences in organ attenuation between pre- and post-therapy scans were seen in all four patients in the liver and spleen (liver increased by an average of 28.9 HU, p = 0.010; spleen increased by an average of 63.7 HU, p = 0.012). A single measured lymph node increased by an average of 58.9 HU. In the remainder of the measured sites, the change in attenuation from pre- to post-therapy scans ranged from -0.1 to 3.8 HU (p > 0.05). Increased attenuation of liver and spleen at CT can be an expected finding in patients who have received gold-silica nanoshell therapy.

Recent advances in combinatorial cancer therapy via multifunctionalized gold nanoparticles.

The diverse behavior of nanogold in the therapeutic field is related to its unique size and shape. Nanogold offers improvements in modern diagnostic and therapeutic implications, increases disease specificity and targeted drug delivery, and is relatively economical compared with other chemotherapeutic protocols. The diagnosis of cancer and photothermal therapy improve drastically with the implementation of nanotechnology. Different types of nanoparticles, that is, gold silica nanoshells, nanorods and nanospheres of diverse shapes and geometries, are used widely in the photothermal therapy of cancerous cells and nodules. Numerous reviews have been published on the therapeutic applications of gold nanoparticles, but studies on combinatorial applications of nanogold in cancer therapy are limited. This review focuses on the combinatorial cancer therapy using optical properties of nanogold with different shapes and geometries, and their therapeutic applications in cancer diagnosis, photothermal therapy, cancer imaging and targeted drug delivery.

Potentials and pitfalls of gold-silica nanoshell as the exogenous contrast agent for optical diagnosis of cancers: a numerical parametric study.

For nanoshell-assisted optical detection of cancers, gold shell, silica core (gold-silica) nanoshells are engineered to be the exogenous contrast agent. This work has performed systematic numerical parametric study to investigate the nonlinear dependences of the hemisphere diffuse reflectance on gold-silica nanoshells, laser irradiance, and hosting biology tissue. Planar phantom based tissue models have been constructed as platforms for study. The radiant transport equation (RTE) has been applied to mathematically describe the interactions among laser lights, hosting tissues, and hosted nanoshells. The diffuse reflectance signal under various combinations of parametric conditions has been computed and analyzed. Parametric parameters whose effects on the diffuse reflectance signal have been investigated are: (1) optical properties of a nanoshell generic, (2) nanoshell volume fraction, which is an indicator of nanoshell accumulation in the target tissue site, (3) the width of irradiating laser beam, and (4) thickness of the tissue slab. Seven nanoshell generics have been tested as the exogenous contrast agent including the R[50, 10] (radius of silica core is 50 nm and thickness of gold shell is 10 nm), R[55, 25], R[40, 15], R[40, 40], R[104, 23], R[75, 40] and R[154, 24] nanoshells. It has been found the R[55, 25] nanoshell works best as the exogenous contrast agent, the R[75, 40] and R[104, 23] nanoshells show good potentials as well while the R[50, 10] and R[40, 15] nanoshells should be avoided for diagnostic usage. The practice of neglecting the absorption characteristic of the exogenous contrast agent, which is quite common among the bio-nano community, has been proven to end up with an over-prediction of the effectiveness of the exogenous contrast agent. Such practice therefore is not well justified and should be avoided in future research. Interactions among laser lights, the tissue and nanoshells are highly nonlinear, demonstrated by that nanoshell generics with totally different optical properties might have similar effects on the diffuse reflectance signal and vice versa. Prior to any bench experiment, preliminary numerical investigation as this work has showcased is highly recommended.

Evaluation of theranostic perspective of gold-silica nanoshell for cancer nano-medicine: a numerical parametric study.

Using gold-silica nanoshell as a reference nano-agent, this work has performed preliminary numerical parametric study to investigate the feasibility and if feasible the efficiency of using a single nano-agent to achieve theranostic goals. In total, seven generics of gold-silica nanoshells have been tested including the R[50,10] (radius of the silica core is 50 nm and thickness of the gold shell is 10 nm), R[40,15], R[55,25], R[40,40], R[75,40], R[104,23], and R[154,24] nanoshells. A planar tissue model has been constructed as the platform for parametric study. For mathematical modeling, radiant transport equation (RTE) has been applied to describe the interactions among laser lights, the hosting tissue, and the hosted nanoshells and Penne's bio-heat equation has been applied to describe the hyperthermia induced by such interactions. Effects of different nanoshell generics on the diffuse reflectance signal and hyperthermia temperature transition have been simulated, basing on which the potential of a certain nanoshell generic as theranostic nano-agent has been evaluated. It has been found that it is highly feasible for gold-silica nanoshells to be engineered for theranostic purpose and nanoshell generics that are preferentially scattering should be explored for good theranostic candidates. On the condition that nanoshell generic with the right optical properties has been located, a moderate nanoshell retention in the target tissue site is already sufficient to induce effective theranostic effects, which indicates that theranostic nano-medicine might not have a stringent requirement for the delivery technique. Among nanoshells that have been tested, the R[55,25] nanoshell seems to be a promising candidate as theranostic nano-agent. Further testing on it is highly recommended. Nanoshells that are preferentially absorbing such as the R[50,10] and R[40,15] nanoshells are efficient photothermal agent and could be used for therapeutic purpose only. However, it is not recommended that preferentially absorbing nanoshells being used for theranostic purpose due to possible negative effects such nanoshells might bring to the diffuse reflectance signal.

Enzyme-Linked Immunosorbent Assay to Quantify Targeting Molecules on Nanoparticles.

Molecular targeting presents a promising means of improving the specificity of cancer therapeutics, increasing accumulation at the cancer site and limiting off-target effects. These targeting schemes can be applied to nanoparticle-based treatments to further enhance their anticancer efficacy. Here, we describe methods to conjugate antibodies to silica-gold nanoshells and to quantify the resulting antibody content on the nanoparticles using a solution-based enzyme-linked immunosorbent assay (ELISA). Although we will be using anti-EGFR (epidermal growth factor receptor) antibodies conjugated to gold-silica nanoshells as a model system, this method is adaptable to quantify a range of targeting antibodies and proteins on various types of nanoparticles.

A Novel Nanoparticle Mediated Selective Inner Retinal Photocoagulation for Diseases of the Inner Retina.

Transport of 527, 577, and 810 nm laser, heat deposition, and eventual thermal damage in vitreous, retina, RPE, choroid, and sclera were modeled using Bouguer-Beer-Lambert law of absorption and solved numerically using the finite volume method. Nanoparticles were designed using Mie theory of scattering. Performance of the new photocoagulation strategy using gold nanospheres and gold-silica nanoshells was compared with that of conventional methods without nanoparticles. For experimental validation, vitreous cavity of ex vivo porcine eyes was infused with gold nanospheres. After ~6 h of nanoparticle diffusion, the porcine retina was irradiated with a green laser and imaged simultaneously using a spectral domain optical coherence tomography (Spectralis SD-OCT, Heidelberg Engineering). Our computational model predicted a significant spatial shift in the peak temperature from RPE to the inner retinal region when infused with nanoparticles. Arrhenius thermal damage in the mid-retinal location was achieved in ~14 ms for 527 nm laser thereby reducing the irradiation duration by ~30 ms compared with the treatment without nanoparticles. In ex vivo porcine eyes infused with gold nanospheres, SD-OCT retinal images revealed a lower thermal damage and expansion at RPE due to laser photocoagulation. Nanoparticle infused laser photocoagulation strategy provided a selective inner retinal thermal damage with significant decrease in laser power and laser exposure time. The proposed treatment strategy shows possibilities for an efficient and highly selective inner retinal laser treatment.

Multifunctionalization of Gold Nanoshells.

Gold silica nanoshells have found many applications within the field of molecular biology, including as nanoscale sensors, the detection of biomarkers, and in the treatment of solid tumors using photothermal ablation. In order for them to be targeted to specific biomarkers while also remaining stable in biological media, it is often necessary to modify their surfaces with more than one functional group. Here, we describe how to create multifunctional gold nanoshells that can be used to either target specific tumor types in vivo or for the detection of biomarkers using biological specimen.

Spectral shift between the near-field and far-field optoplasmonic response in gold nanospheres, nanoshells, homo- and hetero-dimers

We investigate the shift between near- and far-field spectral properties in a set of different gold nanostructures using the multipole expansion of the electromagnetic fields. The optical behavior of isolated spheres, gold-silica nanoshells, homo- and hetero-di7mers is studied computationally as a function of the particle size. We show that in isolated nanospheres, both homogeneous and shell-like, the red-shift between near- and far-field peak intensities increases with nanoparticle dimension and has a universal character that can be attributed to the different spectral behavior of the radial component of the enhanced field, dominating in the near-field, with respect to its transverse part, which determines the far-field properties. Calculations on dimers of closely separated nanospheres, instead, highlight that the spectral shift between the maximum field intensity, calculated at the dimer nanocavity center, and the maximum extinction or scattering, computed in the far-field, strongly depends on both the radius of the monomers and the gap distance. The shift can turn from positive (i.e. red-shift) to negative (i.e.blue-shift) depending on the values of the nanostructure parameters. Our results call into question the universality of the energy red-shift, with relevant implications for the optimization of the efficiency in surface enhanced spectroscopies.

Nanoparticle Mediated Transmittance Signals From Pulsed Laser Irradiated Cancerous Lung as a Function of Respiration

Physiological optical signals in the form of transmittance and reflectance provide useful insight in the characterization of biological systems. In the present article, thermo-optical response of a lung tissue subjected to a short-pulse laser is reported. Consideration is given to a 2-D axisymmetric cylindrical lung tissue with a solid cancerous tumor. Tumor characteristics in the form of temporal transmittance and reflectance signals are analyzed. The radiative transfer equation, comprising both collimated and diffuse radiation, is solved using the discrete ordinate method. Effects of volume fraction of gold–silica nanoshells (i.e. Au/silica core–shell nanoparticles) infused in lung–tumor tissue, and also effect of respiratory lung volume on transmittance and reflectance signals are studied. Based on absorption and scattering abilities for different stages of lung volume, studies are made with a single and a train of laser pulses. Temporal transmittance signals are distinct for different stages of the respiratory lung volumes.

Hydrogel-Coated Near Infrared Absorbing Nanoshells as Light-Responsive Drug Delivery Vehicles.

Nanoparticle drug delivery carriers that can modulate drug release based on an exogenous signal, such as light, are of great interest, especially for improving cancer therapy. A light-activated delivery vehicle was fabricated by synthesizing a thin, thermally responsive poly(N-isopropylacrylamide-co-acrylamide) hydrogel coating directly onto the surfaces of individual near-infrared (NIR) absorbing gold-silica nanoshells. This hydrogel was designed to be in a swollen state under physiological conditions and expel large amounts of water, along with any entrapped drug, at elevated temperatures. The required temperature change can be achieved via NIR absorption by the nanoshell, allowing the hydrogel phase change to be triggered by light, which was observed by monitoring changes in particle sizes as water was expelled from the hydrogel network. The phase change was reversible and repeatable. As a model drug, the chemotherapeutic doxorubicin was loaded into this delivery vehicle, and rapid release of doxorubicin occurred upon NIR exposure. Further, colon carcinoma cells exposed to the irradiated platform displayed nearly 3 times as much doxorubicin uptake as cells exposed to nonirradiated particles or free drug, which in turn resulted in a higher loss of cell viability. We hypothesize these effects are because the NIR-mediated heating results in a transient increase in cell membrane permeability, thus aiding in cellular uptake of the drug.

Nanoparticle-loaded macrophage-mediated photothermal therapy: potential for glioma treatment.

Gold-based nanoparticles have been used in a number of therapeutic and diagnostic applications. The purpose of this study was to investigate the efficacy of gold-silica nanoshells (AuNS) in photothermal therapy (PTT) of rat gliomas. Rat alveolar macrophages (Ma) were used as nanoparticle delivery vectors. Uptake of AuNS (bare and PEGylated) was investigated in Ma. AuNS were incubated with Ma for 24 h. Phase contrast microscopy was used to visualize the distribution of loaded Ma in three-dimensional glioma spheroids. PTT efficacy was evaluated for both empty (Ma) and AuNS-loaded Ma (Ma(NS)) in both monolayers and spheroids consisting of C6 rat glioma cells and Ma. Monolayers/spheroids were irradiated for 5 min with light from an 810-nm diode laser at irradiances ranging from 7 to 28 W cm(-2). Monolayer survival was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay while PTT efficacy in spheroids was determined from growth kinetics and live/dead fluorescence microscopy. PTT efficacy was investigated in vivo using a Sprague-Dawley rat glioma model. Five rats received direct intracranial injection of a mixture of 10(4) C6 glioma cells and, 2 days later, an equal number of Ma(NS). Three rats received laser treatment (810 nm; 10 min; 1 W) while the remaining two served as controls (no laser treatment). The uptake ratio of bare to PEGylated AuNS by Ma was 4:1. A significant photothermal effect was observed in vitro, albeit at relatively high radiant exposures (2.1-4.2 kJ cm(-2)). PTT proved effective in vivo in preventing or delaying tumor development in the PTT-treated animals.

Optical coherence tomography guided microinjections in live mouse embryos: high-resolution targeted manipulation for mouse embryonic research.

The ability to conduct highly localized delivery of contrast agents, viral vectors, therapeutic or pharmacological agents, and signaling molecules or dyes to live mammalian embryos is greatly desired to enable a variety of studies in the field of developmental biology, such as investigating the molecular regulation of cardiovascular morphogenesis. To meet such a demand, we introduce, for the first time, the concept of employing optical coherence tomography (OCT)-guide microinjections in live mouse embryos, which provides precisely targeted manipulation with spatial resolution at the micrometer scale. The feasibility demonstration is performed with experimental studies on cultured live mouse embryos at E8.5 and E9.5. Additionally, we investigate the OCT-guided microinjection of gold–silica nanoshells to the yolk sac vasculature of live cultured mouse embryos at the stage when the heart just starts to beat, as a potential approach for dynamic assessment of cardiovascular form and function before the onset of blood cell circulation. Also, the capability of OCT to quantitatively monitor and measure injection volume is presented. Our results indicate that OCT-guided microinjection could be a useful tool for mouse embryonic research.

Laser-induced hyperthermia of nanoshell mediated vascularized tissue – A numerical study

Laser-induced hyperthermia treatment of tumor in a 2-D axisymmetric tissue embedded with moderate size (100–150µm) blood vessels is studied. Laser absorption is enhanced by embedding gold–silica nanoshells in the tumor. Heat transfer in the tissue is modeled using Weinbaum–Jiji bioheat transfer equation. With laser irradiation, the volumetric radiation is accounted in the governing bioheat equation. Radiative information needed in the bioheat equation is calculated using the discrete ordinate method, and the coupled bioheat-radiation equation is solved using the finite volume method. Effects of power density, laser exposure time, beam radius, diameter of blood vessel and volume fractions of nanoshells on temperature spread in the tissue are analyzed.

Estimating nanoparticle optical absorption with magnetic resonance temperature imaging and bioheat transfer simulation

Purpose: Optically activated nanoparticle-mediated heating for thermal therapy applications is an area of intense research. The ability to characterise the spatio-temporal heating potential of these particles for use in modelling under various exposure conditions can aid in the exploration of new approaches for therapy as well as more quantitative prospective approaches to treatment planning. The purpose of this research was to investigate an inverse solution to the heat equation using magnetic resonance temperature imaging (MRTI) feedback, for providing optical characterisation of two types of nanoparticles (gold–silica nanoshells and gold nanorods).Methods: The optical absorption of homogeneous nanoparticle–agar mixtures was measured during exposure to an 808 nm laser using real-time MRTI. A coupled finite element solution of heat transfer was registered with the data and used to solve the inverse problem. The L2 norm of the difference between the temperature increase in the model and MRTI was minimised using a pattern search algorithm by varying the absorption coefficient of the mixture.Results: Absorption fractions were within 10% of literature values for similar nanoparticles. Comparison of temporal and spatial profiles demonstrated good qualitative agreement between the model and the MRTI. The weighted root mean square error was <1.5 σMRTI and the average Dice similarity coefficient for ΔT = 5 °C isotherms was >0.9 over the measured time interval.Conclusion: This research demonstrates the feasibility of using an indirect method for making minimally invasive estimates of nanoparticle absorption that might be expanded to analyse a variety of geometries and particles of interest.

Evaluation of the Toxicity of Intravenous Delivery of Auroshell Particles (Gold–Silica Nanoshells)

Gold nanoshells (155 nm in diameter with a coating of polyethylene glycol 5000) were evaluated for preclinical biocompatibility, toxicity, and biodistribution as part of a program to develop an injectable device for use in the photothermal ablation of tumors. The evaluation started with a complete good laboratory practice (GLP) compliant International Organization for Standardization (ISO)-10993 biocompatibility program, including cytotoxicity, pyrogenicity (US Pharmacopeia [USP] method in the rabbit), genotoxicity (bacterial mutagenicity, chromosomal aberration assay in Chinese hamster ovary cells, and in vivo mouse micronucleus), in vitro hemolysis, intracutaneous reactivity in the rabbit, sensitization (in the guinea pig maximization assay), and USP/ISO acute systemic toxicity in the mouse. There was no indication of toxicity in any of the studies. Subsequently, nanoshells were evaluated in vivo by intravenous (iv) infusion using a trehalose/water solution in a series of studies in mice, Sprague-Dawley rats, and Beagle dogs to assess toxicity for time durations of up to 404 days. Over the course of 14 GLP studies, the gold nanoshells were well tolerated and, when injected iv, no toxicities or bioincompatibilities were identified.

Feasibility of selective nanoparticle-assisted photothermal treatment for an embedded liver tumor

Using the finite volume method, the present work numerically explored the feasibility of extending nanoparticle-assisted photothermal therapy (PPTT) from treating subcutaneous tumors to treating organ tumors, particularly tumors growing in the clearance organ liver. To serve this purpose, a superficially embedded liver tumor and its immediate surrounding medium were selected as the study object. A 633-nm laser beam of 1- W/cm(2) intensity externally irradiated the tumor. The matching gold-silica nanoshell with a 16-nm silica core and a 5-nm-thick gold shell was used as the photothermal agent. The nanoshell retention ratio was varied to simulate different levels of nanoshell tumor discriminations. Laser light distributions, conversions from photon energy to heat, and tissues' thermal responses to the generated heat within the study object were analyzed. It was found that although nanoshells have enhanced the thermal transportation, they also restricted the optical transportation of PPTT. This indicates that laser delivery is more demanding for PPTT than for the conventional laser therapy. For the investigated case, when the nanoshell retention ratio was in the range of 2/1-4/1, the therapeutic effects were optimal: a confined medium temperature hyperthermia (47-55°C) was achieved in the liver tumor while impacts on the surrounding health liver tissues were only marginal. When then nanoshell retention ratio was 8/1 or higher, about half of the liver tumor was ablated. However, some of the surrounding healthy liver tissues were sacrificed as well. The therapeutic effects of PPTT depend nonlinearly on the nanoshell tumor discriminations. Better tumor discriminations do not necessarily result in better PPTT therapeutic effects.

Erratum to: Tunable Nanostructures as Photothermal Theranostic Agents

Figure captions 1 through 17 and 19 point to the wrong references. The corrected references and author permissions are listed below. Figure 1. Near-infrared light (650–900 nm) is of particular interest in biological applications as it is minimally absorbed by biological chromophores and water. Reprinted by permission from Macmillan Publishers Ltd, Weissleder et al. Copyright 2001. Figure 2. (a) UV–Vis–NIR absorption spectra of nine HGN samples with varying diameters and wall thicknesses. (b) Image showing the color range of HGN solutions. The vial on the far left contains solid gold nanoparticles, the rest are HNGs with varying diameters and wall thicknesses. Reprinted with permission from Schwartzberg et al. Copyright 2006 American Chemical Society. Figure 3. Calcein AM staining indicated that cancerous cells remained viable (evidenced by green fluorescent signal) when exposed to 1 mW laser power, regardless of nanoparticle presence. At 50 mW laser output a red fluorescent EthD-1 signal indicative of membrane damage was observed in cells exposed to anti-HER2 functionalized GGS NPs only where the laser was applied. Laser exposure alone was harmless to cells, as was laser exposure combined with nonspecifically targeted nanoparticles. Scale bar = 250 lm. Reprinted with permission from Day et al. Figure 4. Kaplan–Meier survival of mice following treatment with GGS NPs and laser irradiation. There is a statistically significant increase in survival with 48 h accumulation compared to 24 h accumulation for the GGS NP treated mice and no difference for 48 h GGS NP treated mice as compared to gold silica nanoshell treated mice. Reprinted by permission from Gobin et al. Figure 5. (a) The extinction (Cext), absorption (Cabs), and scattering (Csca) cross-sections (note that Cext = Cabs + Csca) calculated using the DDA method for a gold nanocage of 45 nm in edge length and 3.5 nm in wall thickness, and with the geometry depicted in the inset in (d). The alloy composition of the nanocages is Au3Ag. (b) SEM images of Ag nanocubes prepared by sulfide-mediated polyol synthesis. The inset shows TEM image of the Ag nanocubes. (c) Normalized Vis–NIR extinction spectra recorded from aqueous suspensions of nanostructures after titrating Ag nanocubes with different amounts of a HAuCl4 aqueous solution. Note that the spectrum in red is corresponding to the Au nanocages shown in (d). (d) SEM image of Au nanocages prepared by refluxing an aqueous solution containing both silver nanocubes and HAuCl4. The inset shows a TEM image of the Au nanocages. Reprinted with permission from Chen et al. Copyright 2007 American Chemical Society. Figure 6. SK-BR-3 breast cancer cells that were treated with immuno gold nanocages and then irradiated by 810-nm laser at a power density of 1.5 W/cm for 5 min showed a well-defined circular zone of dead cells as revealed by: (a) calcein AM assay (where green fluorescence indicates the cells were live), and (b) EthD-1 assay (where red fluorescence indicates the cells were dead). In the control experiment, cells irradiated under the same conditions but without immuno gold nanocage treatment maintained viability, as indicated by (c) calcein fluorescence assay, and (d) the lack of intracellular EthD-1 uptake. Modified with permission from Chen et al. Copyright 2007 American Chemical Society. Figure 7. (a) Photograph of a tumor-bearing mouse under the photothermal treatment. 100 lL of PEGylated nanocages at a concentration of 9 9 10 particles/mL or saline was administrated intravenously through the tail vein as indicated by an arrow. After the nanocages had been cleared from the circulation (72 h after injection), the tumor on the right frank was irradiated by the diode laser at 0.7 W/cm with a beam Address correspondence to Rebekah A. Drezek, Department of Bioengineering, Rice University, 6100 Main Street, Houston, TX 77005, USA. Electronic mail: jky1@rice.edu, joekyoung@gmail. com, lizfig@rice.edu, drezek@rice.edu The online version of the original article can be found under doi: 10.1007/s10439-011-0472-5. Annals of Biomedical Engineering, Vol. 40, No. 5, May 2012 ( 2012) pp. 1206–1208 DOI: 10.1007/s10439-012-0535-2

Macrophages as Cell-Based Delivery Systems for Nanoshells in Photothermal Therapy

Site-specific delivery of nanoparticles poses a significant challenge, especially in the brain where the blood-brain barrier prevents the entry of most therapeutic compounds including nanoparticle-based anti-cancer agents. In this context, the use of macrophages as vectors for the delivery of gold-silica nanoshells to infiltrating gliomas will be reviewed in this article. Gold-silica nanoshells are readily phagocytosed by macrophages without any apparent toxic effects, and the results of in vitro studies have demonstrated the migratory potential of nanoshell-loaded macrophages in human glioma spheroids. Of particular interest is the observation that, after near-infrared exposure of spheroids containing nanoshell-loaded macrophages, sufficient heat was generated to suppress spheroid growth. Collectively, these findings demonstrate the potential of macrophages as nanoshell delivery vectors for photothermal therapy of gliomas, and they certainly provide the basis for future animal studies.

SERS Biodetection Using Gold–Silica Nanoshells and Nitrocellulose Membranes

We have developed a rapid, reproducible, easy to execute, surface enhanced Raman scattering (SERS) method for detection of low volumes and total amounts of biological antigens using an analyte capture system derived from methods commonly used in Western blotting. Our method is a "half-sandwich" assay with an antigen detection scheme that employs a nitrocellulose (NC) membrane with 200 nm pore size to capture subnanograms of analyte and concentrate them in a small area from applied volumes as low as one microliter. The SERS probes used for detection consist of gold-silica nanoshells modified with a two-component mixed monolayer system. One component consists of a poly(ethylene glycol) (PEG)-modified Raman-active chromophore bound to the gold surface which allows for SERS detection and imparts particle stability. The second component uses (ortho-pyridyl) disulfide-PEG-succinimidyl ester to couple the recognition antibody to the particle surface. By controlling the reaction time and concentration of thiols, a mixed monolayer is prepared on the nanoshell surface with the ability to recognize low concentrations of analyte and generate reproducible SERS signals. Using this strategy, we have achieved SERS signals that are proportional to antigen present on the membrane allowing detection of total antigen amounts as low as 1.25 ng for some cases. The performance of this new SERS bioassay has been tested with a variety of potential antigens, demonstrating the potential for multiplexed detection of analytes.

Modeling the cellular impact of nanoshell-based biosensors using mouse alveolar macrophage cultures

In this study, the relative toxicity of native gold-silica nanoshells (NS) has been compared to nanoshells modified with poly(ethylene glycol)-thiol (PEG-SH) and a Raman-active PEG, p-mercaptoaniline-poly(ethylene glycol) (pMA-PEG), in mouse alveolar macrophage cell cultures (RAW 264.7). The results from toxicity profiling using an MTT assay demonstrate that cell viability post-particle exposure is a function of three factors: nanoshell concentration, surface functionalization, and incubation time. By minimizing particle concentrations and incubation times, cell cultures are able to recover within 24 h of nanoshell removal, indicative of nanoshells having more of a cytostatic versus cytotoxic effect on macrophage cells. The mechanism of the cytostatic effect has been investigated by imaging the presence of reactive oxygen species (ROS) using a fluorescence assay kit (Image-iT™ LIVE) after the introduction of NS to the cell cultures. Elevated ROS signals are seen in the cells containing higher concentration of NS, and indicate that the major reason of toxicity may due to the oxidative stress caused by excess NS particles. Raman imaging experiments with pMA-PEG coated nanoshells showed that cells exposed for even short exposure times (∼2 h) retained those particles up to 24 h after exposure, while migration experiments suggest that surviving cells retain their nanoshells and may reallocate them to progeny cells upon cell division.