Concentration Of Gold Nanorods Research Articles

Gold Nanorod-Mediated Photothermal Modulation for Localized Ablation of Cancer Cells

We estimated the photothermal transduction efficiency of gold nanorod (GNR) solutions for different GNR concentrations and irradiation laser power. In particular, we verified that the degree of cell death area could be modulated by GNR concentration and irradiation laser power. The efficacy of GNR-produced photothermal ablation of cancer cells was evaluated by irradiating GNRs in the presence of MDA-MB-231 breast cancer cells with a near-infrared (NIR) laser at different laser power densities and irradiation times. GNR-induced photothermal ablation was applied successfully to cancer cells at various NIR laser power densities and irradiation times and was characterized with live-dead cell staining. Through these techniques, we established the system for not only verification of induced photothermal effect using NIR laser and thermocouple, but also identification of uptake efficiency for GNRs and cell viability using dark field and fluorescence imaging, respectively.

Echographic detectability of optoacoustic signals from low-concentration PEG-coated gold nanorods

Purpose:To evaluate the diagnostic performance of gold nanorod (GNR)-enhanced optoacoustic imaging employing a conventional echographic device and to determine the most effective operative configuration in order to assure optoacoustic effectiveness, nanoparticle stability, and imaging procedure safety.Methods:The most suitable laser parameters were experimentally determined in order to assure nanoparticle stability during the optoacoustic imaging procedures. The selected configuration was then applied to a novel tissue-mimicking phantom, in which GNR solutions covering a wide range of low concentrations (25–200 pM) and different sample volumes (50–200 μL) were exposed to pulsed laser irradiation. GNR-emitted optoacoustic signals were acquired either by a couple of single-element ultrasound probes or by an echographic transducer. Off-line analysis included: (a) quantitative evaluation of the relationships between GNR concentration, sample volume, phantom geometry, and amplitude of optoacoustic signals propagating along different directions; (b) echographic detection of “optoacoustic spots,” analyzing their intensity, spatial distribution, and clinical exploitability. MTT measurements performed on two different cell lines were also used to quantify biocompatibility of the synthesized GNRs in the adopted doses.Results:Laser irradiation at 30 mJ/cm2 for 20 seconds resulted in the best compromise among the requirements of effectiveness, safety, and nanoparticle stability. Amplitude of GNR-emitted optoacoustic pulses was proportional to both sample volume and concentration along each considered propagation direction for all the tested boundary conditions, providing an experimental confirmation of isotropic optoacoustic emission. Average intensity of echographically detected spots showed similar behavior, emphasizing the presence of an “ideal” GNR concentration (100 pM) that optimized optoacoustic effectiveness. The tested GNRs also exhibited high biocompatibility over the entire considered concentration range.Conclusion:An optimal configuration for GNR-enhanced optoacoustic imaging was experimentally determined, demonstrating in particular its feasibility with a conventional echographic device. The proposed approach can be easily extended to quantitative performance evaluation of different contrast agents for optoacoustic imaging.

Long-Range Alignment of Gold Nanorods in Electrospun Polymer Nano/Microfibers

In this study, a scalable fabrication technique for controlling and maintaining the nanoscale orientation of gold nanorods (GNRs) with long-range macroscale order has been achieved through electrospinning. The volume fraction of GNRs with an average aspect ratio of 3.1 is varied from 0.006 to 0.045 in aqueous poly(ethylene oxide) solutions to generate electrospun fibers possessing different GNR concentrations and measuring 40-3000 nm in diameter. The GNRs within these fibers exhibit excellent alignment with their longitudinal axis parallel to the fiber axis n. According to microscopy analysis, the average deviant angle between the GNR axis and n increases modestly from 3.8 to 13.3° as the fiber diameter increases. Complementary electron diffraction measurements confirm preferred orientation of the {100} GNR planes. Optical absorbance spectroscopy measurements reveal that the longitudinal surface plasmon resonance bands of the aligned GNRs depend on the polarization angle and that maximum extinction occurs when the polarization is parallel to n.

Three-dimensional high-resolution imaging of gold nanorods uptake in sentinel lymph nodes.

In this paper, we demonstrate an application of a noninvasive imaging modality, photothermal optical coherence tomography (PT-OCT), for imaging gold nanorods (GNRs) uptake in sentinel lymph node (SLN) of mice in situ. This application enables us to obtain higher quality images of SLN structures due to the photothermal contrast properties of the GNRs. It is also demonstrated that GNRs accumulate differently within several SLN structures, and this uptake is time dependent. Finally, we determine the average concentration of GNRs within the whole SLN which is used to demonstrate uptake kinetics of the nanoparticles.

Effects of Gold Nanorod Concentration on the Depth‐Related Temperature Increase During Hyperthermic Ablation

The photothermal properties of gold nanorods (GNRs) provide an opportunity for the clinical application of highly efficient and tumor-specific photothermal therapy. For the effective hyperthermic ablation of tumor tissue using GNRs, it is essential to maintain a homogeneous therapeutic temperature in the target tissue during treatment. This study investigates whether the concentration of GNRs affects the distribution of the temperature increase during hyperthermal therapy. The investigation is conducted using polyacrylamide phantoms containing varying amounts of GNRs. In 0.1, 0.25, and 0.5 nM GNR-suspended phantoms, the change in temperature is relatively uniform along the depth of each phantom during laser irradiation at 2 W cm(-2) . In 1.0, 2.0, and 5.0 nM GNR-suspended phantoms, the rates of temperature increase in the deep regions of the phantoms decrease with increasing GNR concentration. At a laser irradiation of 5 W cm(-2) , the temperature of the GNR-suspended phantoms increases at a faster rate, whereas the range of GNR concentrations for maintaining the homogeneity of the temperature increase is not affected. This suggests that the concentration of GNRs is the major determinant of the depth-related temperature increase during hyperthermic ablation. Therefore, prior to the clinical application of hyperthermic ablation using GNRs, the concentration of GNRs has to be optimized to ensure a homogeneous distribution of therapeutic temperature in the targeted tissue.

Three-wavelength murine photoplethysmography for estimation of vascular gold nanorod concentration

Nanoparticle-assisted photo-thermal (NAPT) ablation has become a new and attractive modality for the treatment of cancerous tumors. This therapy exploits the passive accumulation of intravenously delivered optically resonant metal nanoparticles into tumors, however, the circulating bioavailability of these particles is often unknown. We present a non-invasive optical device capable of monitoring the circulation of optically resonant gold nanorods. The device, referred to as a pulse photometer, uses the technique of multi-wavelength photoplethysmography. We simultaneously report the circulation of gold nanorods and oximetry for six hours post-injection in mice with no anesthesia and remove the probe when not collecting data. The instrument shows good agreement (R(2) = 0.903, n = 30) with ex vivo spectrophotometric analysis of blood samples. The real-time feedback provided has a strong potential for reducing variability and thus improving the efficacy of similar clinical therapies.

Enhancement of anisotropic conductivity, elastic, and dielectric constants in a liquid crystal-gold nanorod system

We report electrical conductivity (σ), dielectric constant (ε) and the elastic constant measurements in a nematic liquid crystal (LC) doped with small concentrations of gold nanorods. This LC-nanoparticle complex, shows not only orders of magnitude higher σ, but also stabilizes its anisotropy. The ε data suggests an increased ordering in the nematic phase, and an improved antiparallel correlation of the molecules in the isotropic phase. Surprisingly, an anisotropic enhancement of the Frank elasticity is also seen. We suggest a possible electro/magnetomechanical conductivity switch and also provide explanations based on the aspect ratio of the nanoparticles vis-à-vis the LC molecules.

Anisotropic and enhanced absorptive nonlinearities in a macroscopic film induced by aligned gold nanorods

Anisotropic and enhanced nonlinear absorption (NLA) has been observed from aligned gold nanorods (GNRs) embedded in a poly(vinyl alcohol) film, which was realized by a stretched-film method. Open-aperture Z-scan experiments revealed that the stretch process enhanced the NLA coefficient by approximately nine times and increased the anisotropic factor of NLA to ∼20. The enhancement in the NLA coefficient reached as high as ∼91 times after increasing the concentration of GNRs by four times and this is attributed to the plasmonic interaction between densely packed GNRs.

SU‐FF‐J‐153: Photothermal Cancer Therapy Using Gold Nanorods

Purpose: Gold nanorods were used to investigate the effects of heat on PA‐1 ovarian cancer cells and their response to thermal treatment through laser irradiation. In addition, the question of how the combination of X‐ray radiation and nanoparticles affects cancer cell survival was also addressed. Method and Materials: Different concentrations of Gold nanorods of diameter 10 nm and length 40 nm coated in a dense layer of hydrophilic polymers were used and two configurations of laser light were employed. A picosecond laser pulse with 1000 Hz repetition rate yielding 1 Watt of average power, and a continuous wave delivery technique yielding 0.5 Watt of laser power. PA‐1 ovarian cancer cells were put into 96 well microtiter plate. Each well contained about 5000 cells plated in 100 μl of BME media. In addition, three wells containing cells and nanorods and three wells containing only cells were subjected to 1 Gy of photon dose. Results: Three different nanoparticle concentrations were used for the case of pulsed laser beam irradiating the cells. The highest concentration of 6×1012 nr/ml led to complete cell killing even without any laser irradiation. For nanorods concentration of 1.2×1011 nr/ml and 6×1010 nr/ml, the number of survived cells decreased as the laser irradiation time increased from 1 min to 20 min, reaching 59% at 20 min mark. For the case of continuous laser operation and nanoparticle concentration of 1.2×1012 nr/ml, the number of cancer cells surviving laser irradiation dropped to 0 at all time intervals from 2 min to 10 min. When cells were subjected to 1 Gy of photon dose, no visible advantage of using nanorods in conjunction with radiation was observed. Conclusions: Results of experimental studies show that nanorods are extremely effective agents in converting laser light into heat with promising thermal therapy applications for cancer treatment.