Jon A. Schwartz

Modulation of in Vivo Tumor Radiation Response via Gold Nanoshell-Mediated Vascular-Focused Hyperthermia: Characterizing an Integrated Antihypoxic and Localized Vascular Disrupting Targeting Strategy

We report noninvasive modulation of in vivo tumor radiation response using gold nanoshells. Mild-temperature hyperthermia generated by near-infrared illumination of gold nanoshell-laden tumors, noninvasively quantified by magnetic resonance temperature imaging, causes an early increase in tumor perfusion that reduces the hypoxic fraction of tumors. A subsequent radiation dose induces vascular disruption with extensive tumor necrosis. Gold nanoshells sequestered in the perivascular space mediate these two tumor vasculature-focused effects to improve radiation response of tumors. This novel integrated antihypoxic and localized vascular disrupting therapy can potentially be combined with other conventional antitumor therapies.

Anisotropy in the absorption and scattering spectra of chicken breast tissue.

Oblique incidence reflectometry is a simple and accurate method for measuring the absorption and the reduced-scattering coefficients of turbid media. We used this technique to deduce absorption and reduced-scattering spectra from wavelength-resolved measurements of the relative diffuse reflectance profile of white light as a function of source-detector distance. In this study, we measured the absorption and the reduced-scattering coefficients of chicken breast tissue in the visible range (400-800 nm) with the oblique incidence probe oriented at 0 degrees and 90 degrees relative to the muscle fibers. We found that the deduced optical properties varied with the probe orientation. Measurements on homogenized chicken breast tissue yielded an absorption spectrum comparable with the average of the absorption spectra for 0 degrees and 90 degrees probe orientations measured on the unhomogenized tissue. The reduced-scattering spectrum for homogeneous tissue was greater than that acquired for unhomogenized tissue taken at either probe orientation. This experiment demonstrated the application of oblique-incidence, fiber-optic reflectometry to measurements on biological tissues and the effect of tissue structural anisotropy on optical properties.

Feasibility Study of Particle-Assisted Laser Ablation of Brain Tumors in Orthotopic Canine Model

We report on a pilot study showing a proof of concept for the passive delivery of nanoshells to an orthotopic tumor where they induce a local, confined therapeutic response distinct from that of normal brain resulting in the photothermal ablation of canine transmissible venereal tumor (cTVT) in a canine brain model. cTVT fragments grown in severe combined immunodeficient mice were successfully inoculated in the parietal lobe of immunosuppressed, mixed-breed hound dogs. A single dose of near-IR (NIR)-absorbing, 150-nm nanoshells was infused i.v. and allowed time to passively accumulate in the intracranial tumors, which served as a proxy for an orthotopic brain metastasis. The nanoshells accumulated within the intracranial cTVT, suggesting that its neovasculature represented an interruption of the normal blood-brain barrier. Tumors were thermally ablated by percutaneous, optical fiber-delivered, NIR radiation using a 3.5-W average, 3-minute laser dose at 808 nm that selectively elevated the temperature of tumor tissue to 65.8 +/- 4.1 degrees C. Identical laser doses applied to normal white and gray matter on the contralateral side of the brain yielded sublethal temperatures of 48.6 +/- 1.1 degrees C. The laser dose was designed to minimize thermal damage to normal brain tissue in the absence of nanoshells and compensate for variability in the accumulation of nanoshells in tumor. Postmortem histopathology of treated brain sections showed the effectiveness and selectivity of the nanoshell-assisted thermal ablation.

A three-dimensional dielectrophoretic particle focusing channel for microcytometry applications

In this paper, we have designed and fabricated a microfluidic channel to focus biological cells using dielectrophoresis for cytometry applications. The device consists of an elliptic-like channel fabricated by isotropic etching of soda lime glass wafers and a subsequent wafer-bonding process. Microelectrodes are patterned on the circumference of the channel to generate ac fringing fields that result in negative dielectrophoretic forces directing cells from all directions to the center of the channel. An analysis using a thin shell model and experiments with microbeads and human leukemia HL60 cells indicate that biological cells can be focused using an ac voltage of an amplitude up to 15 V/sub p-p/ and a frequency below 100 kHz, respectively. This design eliminates the sheath flow and the fluid control system that makes conventional cytometers bulky, complicated, and difficult to operate, and offers the advantages of a portable module that could potentially be integrated with on-chip impedance or optical sensors into a micro total analysis system.

In-vivo photoacoustic microscopy of nanoshell extravasation from solid tumor vasculature

In this study, high resolution backward-mode photoacoustic microscopy (PAM) is used to noninvasively image progressive extravasation and accumulation of nanoshells within a solid tumor in vivo. PAM takes advantage of the strong near-infrared absorption of nanoshells and their extravasation tendency from leaky tumor vasculatures for imaging. Subcutaneous tumors are grown on immunocompetent BALB/c mice. Polyethylene glycol (PEGylated) nanoshells with a peak optical absorption at approximately 800 nm are intravenously administered. With an 800-nm laser source, a prescan prior to nanoshell injection is taken to determine the background that is free of nanoshell accumulation. After injection, the 3-D nanoshell distribution at the tumor foci is monitored by PAM for 6 h. Experimental results show that accumulated nanoshells delineate the tumor position. Nanoshell accumulation is heterogeneous in tumors: more concentrated within the tumor cortex and largely absent from the tumor core. Because nanoshells have been recently demonstrated to enhance thermal therapy of subcutaneous tumors, we anticipate that PAM will be an important aid before, during, and after nanoshell thermal therapy.

In Vivo Detection of Gold Nanoshells in Tumors Using Diffuse Optical Spectroscopy

This study demonstrates the use of diffuse optical spectroscopy (DOS) for the noninvasive measurement of gold nanoshell concentrations in tumors of live mice. We measured the diffuse optical spectra (500-800 nm) using an optical fiber probe placed in contact with the tissue surface. We performed in vitro studies on tissue phantoms illustrating an accurate measurement of gold-silica nanoshell concentration within 12.6% of the known concentration. In vivo studies were performed on a mouse xenograft tumor model. DOS spectra were measured at preinjection, immediately postinjection, 1 and 24 h postinjection times, and the nanoshell concentrations were verified using neutron activation analysis.

Internal absorption coefficient and threshold for pulsed laser disruption of melanosomes isolated from retinal pigment epithelium

This study determine the threshold radiant exposure from a 10-ns pulsed laser (532 nm) which caused bovine melanosomes to present various observable endpoints of disruption. The endpoints tested were (1) a visible region of clearing in a uniform field of melanosomes under a glass cover slip, (2) an audible sound, and (3) the increase in melanin photoreactivity due to photodisruption of melanosomes. The thresholds were tested for different starting temperatures by pre-equilibrating the melanosomes in aqueous solution at various temperatures. Lower temperatures required larger exposures to attain a given endpoint. The data suggest that bovine RPE melanosomes are about 4-fold denser in melanin content than cutaneous melanosomes.

Laser‐induced thermal response and characterization of nanoparticles for cancer treatment using magnetic resonance thermal imaging

Spherical nanoparticles with a gold outer shell and silica core can be tuned to absorb near-infrared light of a specific wavelength. These nanoparticles have the potential to enhance the treatment efficacy of laser-induced thermal therapy (LITT). In order to enhance both the potential efficacy and safety of such procedures, accurate methods of treatment planning are needed to predict the temperature distribution associated with treatment application. In this work, the standard diffusion approximation was used to model the laser fluence in phantoms containing different concentrations of nanoparticles, and the temperature distribution within the phantom was simulated in three-dimensions using the finite element technique. Magnetic resonance temperature imaging was used to visualize the spatiotemporal distribution of the temperature in the phantoms. In most cases, excellent correlation is demonstrated between the simulations and the experiment (<3.0% mean error observed). This has significant implications for the treatment planning of LITT treatments using gold-silica nanoshells.

Near-infrared narrow-band imaging of gold/silica nanoshells in tumors

Gold nanoshells (GNS) are a new class of nanoparticles that can be optically tuned to scatter or absorb light from the near-ultraviolet to near-infrared (NIR) region by varying the core (dielectric silica)/shell (gold) ratio. In addition to spectral tunability, GNS are inert and bioconjugatable, making them potential labels for in vivo imaging and therapy of tumors. We report the use of GNS as exogenous contrast agents for enhanced visualization of tumors using narrow-band imaging (NBI). NBI takes advantage of the strong NIR absorption of GNS to distinguish between blood and nanoshells in the tumor by imaging in narrow wavelength bands in the visible and NIR, respectively. Using tissue-simulating phantoms, we determined the optimum wavelengths to enhance contrast between blood and GNS. We then used the optimum wavelengths for ex vivo imaging of tumors extracted from human colon cancer xenograft bearing mice injected with GNS. Systemically delivered GNS accumulated passively in tumor xenografts by the enhanced permeability and retention (EPR) effect. Ex vivo NBI of tumor xenografts demonstrated heterogeneous distribution of GNS with a clear distinction from the tumor vasculature. The results of this study demonstrate the feasibility of using GNS as contrast agents to visualize tumors using NBI.

Initial Evaluation of the Safety of Nanoshell-Directed Photothermal Therapy in the Treatment of Prostate Disease

To evaluate the clinical safety profile for the use of gold nanoshells in patients with human prostate cancer. This follows on the nonclinical safety assessment of the AuroShell particles reported previously. Twenty-two patients, with biopsy diagnosed prostate cancer, underwent nanoshell infusion and subsequent radical prostatectomy (RRP). Fifteen of these patients had prostates that were additionally irradiated by a single-fiber laser ablation in each prostate hemisphere prior to RRP. Patients in the study were assessed at 9 time points through 6 months postinfusion. Adverse events were recorded as reported by the patients and from clinical observation. Blood and urine samples were collected at each patient visit and subjected to chemical (16 tests), hematological (23 tests), immunological (3 tests, including total PSA), and urinalysis (8 tests) evaluation. Temperature of the anterior rectal wall at the level of the prostate was measured. The study, recorded 2 adverse events that were judged attributable to the nanoparticle infusion: (1) an allergic reaction resulting in itching, which resolved with intravenous antihistamines, and (2) in a separate patient, a transient burning sensation in the epigastrium. blood/hematology/urinalysis assays indicated no device-related changes. No change in temperature of the anterior rectal wall was recorded in any of the patients. The clinical safety profile of AuroShell particles is excellent, matching nonclinical findings. A recent consensus statement suggested that the published literature does not support a preference for any ablation technique over another.1 Now that clinical safety has been confirmed, treatment efficacy of the combined infusion plus laser ablation in prostate will be evaluated in future studies using imaging modalities directing the laser against identified prostate tumors.