Ms. Nisha Sharma Profile

Nisha Sharma

at Lawson Health Research Institute

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Proceedings Article | 16 September 2010 Paper

Depth and extent of gold nanorod photothermal conversion in tissue-mimicking phantoms

Nisha Sharma, Esther Kim, Michelle Belton, Jeffrey J. L. Carson

Proceedings Volume 7750, 775007 (2010) https://doi.org/10.1117/12.877186

KEYWORDS: Spherical lenses, Near infrared, Gold, Pulsed laser operation, Tissue optics, Tissues, Laser therapeutics, Absorbance, Absorption, Nanorods

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Gold nanorods (AuNRs) efficiently absorb pulsed near-infrared (NIR) light. If the fluence is sufficiently high, then the absorption of pulsed light results in photothermal conversion to spherical morphology and a decrease in NIR absorption. In aqueous media, photothermal conversion also produces localized microbubble formation, which has the potential to kill nearby cells. Our objective was to study the potential of AuNRs to elicit cell killing effects at depth within a tissue-like phantom material. The approach was to measure photothermal conversion in phantoms with embedded inclusions representative of breast tumors. Phantoms were prepared with a homogeneous mixture of 1% Intralipid™ and 1% agarose to simulate tissue optical properties. Gold nanorod-loaded spherical inclusions 6 mm in diameter were prepared at an optical density of 0.67 at 800 nm. Inclusions were cast into the phantom material at a depth of 0, 5, 10, or 15 mm. Phantoms were then exposed to pulsed laser (800 nm, 5 ns pulse duration) for a range of fluence (17-100 mJ/cm²) and pulse count (10-1000). Each phantom was then cut longitudinally and imaged with a NIR camera. The images were analyzed for changes in contrast representative of photothermal conversion. Preliminary results indicated that photothermal conversion occurred only in spherical AuNR-loaded inclusions at or within 10 mm of the phantom surface. Based on these results, we concluded that within ANSI limits of laser exposure photothermal therapy with AuNR-based agents will be limited to lesions at or near the surface and lesions accessible with needlebased light delivery.

Proceedings Article | 11 September 2010 Paper

Depth and extent of gold nanorod photothermal conversion in tissue-like phantoms that contain hemoglobin

Nisha Sharma, Astrid Chamson-Reig, Hazem Al-Aabed, Jeffrey J. Carson

Proceedings Volume 7754, 77541D (2010) https://doi.org/10.1117/12.860786

KEYWORDS: Spherical lenses, Tissue optics, Near infrared, Pulsed laser operation, Gold, Tissues, Optical properties, Cameras, Natural surfaces, Nanorods

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Gold nanorods (AuNRs) are of interest for many biomedical applications due to their tunable optical properties. AuNRs efficiently absorb light in the near-infrared (NIR) region, which induces effects such as hyperthermia and/or cell killing by localized microbubble formation through photothermal conversion. Our objective was to study the potential of AuNRs to elicit photothermal conversion effects due to pulsed laser exposure at depth within tissue-like phantoms. The approach was to measure photothermal conversion in inclusion-containing phantoms representative of breast cancer. Tissue-like phantoms were prepared with hemoglobin at 10 μM in a homogeneous mixture of 1% agarose and 1% Intralipid to mimic the optical properties of human breast tissue. Polyethylene glycol AuNR-loaded gel spheres (at an equivalent optical density of 0.67 at 800 nm) were prepared with hemoglobin at 20 μM in a homogeneous mixture of 1% agarose and 1% Intralipid. The spherical gel inclusions were cast into the phantom material at a depth of 0, 5, 10, or 15 mm. Phantoms were then exposed to nanosecond pulsed-NIR light (800 nm; 5 ns pulse duration; 17-100 mJ/cm²; 10- 1000 pulse count). Each phantom was then cut longitudinally and imaged with a NIR camera. The images were examined with image analysis software. Preliminary results indicated that the greatest extent of photothermal conversion occurred in spherical AuNR-loaded gels next to the phantom surface. Based on these results, we concluded that within ANSI limits of laser exposure photothermal therapy with AuNR-based agents will be limited to surface lesions and/or lesions accessible with needle-based light delivery.

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