More than a decade into the development of gold nanoparticles for cancer therapies, with multiple clinical trials underway, ongoing pre-clinical research continues towards better understanding in vivo interactions with the goal of treatment optimization through improved best practices. In an effort to collect information for healthcare providers, enabling informed decisions in a relevant time frame, instrumentation for real-time plasma concentration (multi-wavelength pulse photometry) and protocols for rapid elemental analysis (energy dispersive X-Ray fluorescence) of biopsied tumor tissue have been developed in a murine model. An initial analysis, designed to demonstrate the robust nature and utility of the techniques, revealed that area under the bioavailability curve (AUC) alone does not currently inform tumor accumulation with a high degree of accuracy (R<sup>2</sup>=0.32), This finding suggests that the control of additional experimental and physiological variables may yield more predictable tumor accumulation. Subject core temperature are blood pressure were monitored, but did not demonstrate clear trends. An effort to modulate AUC has produced an adjuvant therapy which is employed to enhance circulation parameters, including the AUC, of nanorods and gold nanoshells. Preliminary studies demonstrated a greater than 300% increase in average AUC through the use of a reticuloendothelial blockade agent versus control groups. Given a better understanding of the relative importance of the physiological factors which impact rates of tumor accumulation, a proposed set of experimental best practices is presented.
Researchers employ increasingly complex sub-micron particles for oncological applications to deliver bioactive
therapeutic or imaging compounds to known and unknown in vivo tumor targets. These particles are often
manufactured using a vast array of compounds and techniques resulting in a complex architecture, which can be
quantified ex vivo by conventional metrology and chemical assays. In practice however, experimental homogeneity
using nanoparticles can be difficult to achieve. While several imaging techniques have been previously shown to
follow the accumulation of nanoparticles into tumor targets, a more rapid sensor that provides a quantifiable estimate
of dose delivery and short-term systemic response could increase the clinical efficacy and greatly reduce the
variability of these treatments. We have developed an optical device, the pulse photometer, that when placed on an
accessible location will estimate the vascular concentration of near-infrared extinguishing nanoparticles in murine
subjects. Using a technique called multi-wavelength photoplethysmography, the same technique used in pulse
oximetry, our pulse photometer requires no baseline for each estimate allowing it to be taken on and off of the
subject several times during experiments employing long circulating nanoparticles. We present a formal study of
our prototype instrument in which circulation half-life and nanoparticle concentration of gold nanorods is
determined in murine subjects with the aid of light anesthesia. In this study, we show good agreement between
vascular nanorod concentrations (given in optical density) as determined by our device and with UV-VIS
spectrophotometry using low volume blood samples.
There is an urgent clinical need to monitor the intravenous delivery and bioavailability of circulating nanoparticles used in cancer therapy. This work presents the use of photoplethysmography for the noninvasive real-time estimation of vascular gold nanoshell concentration in a murine subject. We develop a pulse photometer capable of accurately measuring the photoplethysmogram in mice and determining the ratio of pulsatile changes in optical extinction between 805 and 940 nm, commonly referred to as R. These wavelengths are selected to correspond to the extinction properties of gold nanoshells. Six 30-s measurements (5 min, 2, 4, 6, 8, 10 h) are taken under light anesthesia to observe the change in R as the nanoparticles clear from the circulation. Our model describes the linear fit (R2=0.85) between R and the concentration of nanoparticles measured via ex vivo spectrophotometric and instrumental neutron activation analysis. This demonstrates the utility of this technique in support of clinical nanoparticle therapies.
The photothermal ablation of solid tumors using exogenous, near-infrared (NIR)-absorbing nanoparticles has been previously investigated using various preclinical models and is currently being evaluated in the clinic. Here, we evaluate the circulation kinetics, preliminary toxicity, and efficacy of photothermal ablation of solid tumors using gold nanorods systemically delivered and passively accumulated in a murine subcutaneous colon cancer model. Tumored animals were infused with nanorods followed by the percutaneous illumination of the tumor with an 808-nm laser. Control groups consisted of laser-only, nanorod-only, and untreated tumored animals. The survival of the treated and control groups were monitored for 60 days post-treatment. The survival of the photothermally treated group was statistically longer than the control groups, with approximately 44% tumor free through the evaluation period. Histopathology of the major organs of animals infused with nanorods did not indicate any significant toxicity at 60 days post-treatment. Particle biodistribution was evaluated by elemental analysis of the major organs of untumored mice at 1, 7, and 30 days after infusion with nanorods. Elemental analysis indicates nanorod clearance from the blood and retention by the reticuloendothelial system. This study indicates that gold nanorods are promising agents for photothermal ablation of solid tumors.
As the use of lasers proliferate in military and civilian applications, the importance of laser eye protection becomes increasingly significant. Of particular relevance is protection from non-visible laser sources operating in the near-infrared, as it is impossible to determine when the eye is being exposed to such harmful radiation. Current technologies for laser eye protection, such as dyes or reflective coatings of visors/glasses, are generally bulky, which presents a challenge for use and integration with oxygen masks, helmets and night vision apparatus. A contact-lens based laser eye protection system would offer the advantage of minimal modification of current equipment to provide protection against laser exposure.
A laser eye protection system has been developed based on the unique optical properties of gold nanoshells. Gold nanoshells consist of a dielectric silica core, surrounded by a thin (nm) shell of gold. By adjusting the core size and the shell thickness, these nanoparticles can provide high extinction levels throughout the near-infrared region of the spectrum. Unlike some organic dyes, the particles are photostable and non-toxic, increasing the practical life of the lens. The design and fabrication of a soft contact lens containing nanoshells is described. The optical and physiochemical properties are compared to a standard soft contact control. The results of preliminary toxicity studies are also presented
The use of near-infrared absorbing nanoparticles recently has been proposed for the minimally invasive photothermal
ablation of solid tumors, and this approach currently is being investigated in the clinic. One class of nanoparticles, gold
nanorods, has been investigated for the ablation of various cancer types using both direct injection and systemic delivery.
Here we investigate the photothermal ablation of colon cancer in an animal model using intravenously delivered gold
nanorods. Nanorods with an aspect ratio of ~3.2 and an extinction peak of 774 nm were PEGylated, suspended in an
isotonic solution, and infused into the tail vein of BALB/c mice bearing subcutaneous CT26.wt murine colon cancer
tumors. After 24 hrs, an isotropic laser fiber was inserted through a small incision in the skin to a point proximate to and
beneath the tumor. The area was illuminated with 3.5 W average power for 3 minutes. Control groups consisted of
laser-only, nanorod-only and untreated tumored animals. The survival of the animals receiving nanorod-based
photothermal ablation was statistically longer than the control groups with >44% complete response. This work
demonstrates the promise of systemically delivering nanoparticles to tumors for thermal ablation
In recent years there has been a great deal of interest in the measurement of DNA hybridization at surfaces. Surface-confined DNA hybridization has been used to monitor gene expression, to detect the presence of a particular DNA sequence and determine single nucleotide polymorphisms (SNPs). DNA microarrays, which can contain thousands of discrete DNA sequences on a single surface, have become widely used for hybridization studies. While a powerful technique, this technology is limited by the stability of the fluorescent dyes used to label the DNA, and the need to perform measurements ex-situ to reduce the fluorescence background. In this report, we describe the use of colloid-amplified surface plasmon resonance (SPR) to measure DNA hybridization at surfaces. SPR is a surface sensitive technique, which can be used to study hybridization in situ, and the use of colloidal metal tags provides excellent sensitivity. Angle-scanning SPR has been used to study oligonucleotide hybridization to surface confined probes, and work is underway to apply SPR imaging to study DNA hybridization in macro- and microarray formats.