R. Edziah

Treatment efficacy of laser photothermal therapy using gold nanorods

In vivo experiments are performed to induce temperature elevations in implanted prostatic tumours in mice using 0.1 ml commercially available gold nanorod solution injected into the tumour. Tumour shrinkage studies and histological analyses of tumour cell death are conducted, and the equivalent minutes at 43°C (EM43) for inducing tissue thermal damage are estimated based on temperature elevations during the treatment. It has been shown that the laser heating of 15 minutes in the tumour tissue containing gold nanorods is effective to cause irreversible thermal damage to the tumours, with a low laser irradiance on the tumour surface (1.6 W/cm2). The effectiveness of the heating protocol is demonstrated by tumour shrinkage to 7% of its original volume on the 25th day after the laser treatment and tumour necrosis events observed by histological analyses. The results are consistent with the EM43 distribution estimated by possible temperature elevations during the treatment.

MicroCT Imaging and In Vivo Temperature Elevations in Implanted Prostatic Tumors in Laser Photothermal Therapy Using Gold Nanorods

In this study, in vivo animal experiments are performed on implanted xenograph prostatic tumors in nude mice to investigate enhanced laser energy absorption in the tumors by an intratumoral injection of gold nanorod solutions. in vivo temperature mapping of the tumors during laser photothermal therapy has shown the feasibility of elevating tumor temperatures higher than 50 C using only 0.1ml nanorod solution and a low laser irradiance of 1.6W/cm 2 incident on the tumor surface. The temperature profile suggests that normal tumor tissue still absorbs some amount of the laser energy without nanorod presence; however, the injected nanorods ensure that almost all the laser energy is absorbed and confined to the targeted tumors. The inverse relationship between the temperature elevations and the tumor size implies a relatively uniform spreading of the nanorods to the entire tumor, which is also shown by microcomputed tomography (microCT) imaging analyses. The feasibility of detecting 250 OD gold nanorod solution injected to the tumors is demonstrated via a high resolution microCT imaging system. Compared to other nanostructures, the gold nanorods used in this study do not accumulate surrounding the injection site. The relatively uniform deposition of the nanorods in the tumors observed by the microCT scans can be helpful in future study in simplifying theoretical simulation of temperature elevations in tumors during laser photothermal therapy. [DOI: 10.1115/1.4007161]

Visualization and quantification of gold nanorods distribution in prostatic tumors using microct imaging

One uncertainty in use of gold nanorods for laser photothermal therapy is the non-uniform spreading of gold nanorods in tissue after either systemic delivery or intratumoral injections. High concentration of gold nanorods in certain areas influences the resulted optical absorption of the laser and thermal damage to tumors. This also provides challenges in designing optimal heating protocols via modeling thermal transport in laser photothermal therapy. For successful cancer treatment, the tissue should be heated with minimum thermal dosage to induce tumor cell damage, while minimizing overheating in the surrounding healthy tissues. Thus, one of the main challenges for reliable cancer therapy is to precisely control loading and distribution of gold nanorods in the tumour tissue. The critical mass transport processes are the distribution of gold nanorods after injection to the tumor and the redistribution of gold nanorods during laser treatment. Since tumors are opaque, nanostructure distribution in tissue is often studied either by theoretical modeling approaches1, or via dye enhanced imaging on superficial layers of tumors.2 It is important to find a technique which can directly visualize and analyze three-dimensional nanostructure distribution of tumors. Three-dimensional reconstructions of tumors with the ability to trace gold nanorod spreading have the potential for precise theoretical simulation of temperature fields. Previous studies showed that computer tomography (CT) scan is a promising technique to be utilized to characterize the distribution of intratumorally injected magnetic nanoparticles in tumors 3.© 2012 ASME

Thermal effect of gold nanorods in implanted prostatic tumors during laser photothermal therapy

In recent years, nanotechnologies have emerged as promising therapies due to their ability to deliver adequate thermal dosage to irregular and/or deep-seated tumors. Gold nanorods can be tuned to a specific laser wavelength and serve as strong laser energy absorbers. Due to the powerful optical absorption, the laser energy is concentrated in an area congregating by nanorods, and then the energy absorbed can be transferred to the surrounding tumor tissue by heat conduction.1–4 Currently, there are wide variation ranges of treatment protocols using photothermal therapy. A systematic approach is lacking to analyze temperature elevation history in tumors during heating to design an optimized combination of laser parameters to maximize thermal damage to tumors.Copyright

Treatment efficacy of laser photothermal therapy using gold nanorods: Tumor shrinkage study

Gold nanorods can be tuned to a specific laser wavelength and serve as strong laser energy absorbers. Due to the powerful optical absorption, the laser energy is concentrated in an area congregating by nanorods, and then the energy absorbed can be transferred to the surrounding tumor tissue by heat conduction.1–4 Previous studies have shown a wide range of heating parameters with or without temperature measurements. Our previous experiment4 has demonstrated that using only 0.1 cc gold nanorod solution can lead to tumor temperature higher than 50°C when the laser irradiance is only 2 W/cm2. Based on the measured temperature elevation and heating duration, thermal damage to the tumor is highly likely. However, some researchers raised the question whether temperature sensors used in those experimental studies are truly reflecting the temperatures in the tumors. The objective of this study is to measure quantitatively tumor shrinkage after laser irradiation to evaluate efficacy of laser photothermal therapy.Copyright

Temperature elevations in prostatic tumors during laser photothermal therapy

In vivo experiments were performed to measure temperature elevations in prostatic tumors implanted in mice during laser photothermal therapy using nanorods. Ti:Sapphire laser tuned at 800 nm irradiating the surface of the tumor delivered an average laser power of 0.5 - 1.0 W, equivalent to a laser radiance of 1.3-2.6 W/cm2. The temperature elevations measured by two thermocouples located at the center and bottom of the tumor have shown non-uniform tumor temperature field, 10-30°C above the baseline temperature of 37°C. The experimental studies have demonstrated the capability of confining laser energy in tumors by a very small amount of nanorod solution.

Temperature Elevations in Implanted Prostatic Tumors During Laser Photothermal Therapy Using Nanorods

Gold nanoshells or nanorods are newly developed nanotechnology in laser photothermal therapy for cancer treatments in recent years [1–10]. Gold nanoshells consists of a solid dielectric nanoparticle core (∼100 nm) coated by a thin gold shell (∼10 nm). Gold nanorods have a diameter of 10 nm and an aspect ratio of approximately four. Nanorods may be taken up by tumors more readily than nanoshells due to nanorods’ smaller size. By varying the geometric ratio, both nanoshells and nanorods can be tuned to have strong absorption and scattering to a specific laser wavelength. Among a wide range of laser wavelengths, the near infrared (NIR) laser at ∼800 nm is most attractive to clinicians due to its deep optical penetration in tissue. Therefore, the tissue would appear almost “transparent” to the 800 nm laser light before the laser reaches the nanoshells or nanorods in tumors, with minimal laser energy wasted by the tissue without the nanostructures. The laser energy absorbed in an area congregating by the nanostructures is transferred to the surrounding tissue by heat conduction. This approach not only achieves targeted delivery of laser energy to the tumor, but also maximally concentrates a majority of the laser energy to the tumor region.Copyright

100X enhancement of the nonlinear refractive index of sulfur-doped CS2 over pure CS2

Preliminary Z-scan measurements of variable concentration sulfur-doped CS2 indicate a twoorder of magnitude enhancement of the nonlinear index (n2) over CS2. The laser repetition rate will be varied to determine any thermal contribution to n2.