Date of Award

8-2023

Document Type

Campus Access Thesis

Degree Name

Master of Science (MS)

Department

Physics, Applied

First Advisor

Jonathan Celli

Second Advisor

Chandra Yelleswarapu

Third Advisor

Mohamed Amine Gharbi

Abstract

Photodynamic therapy is a drug-light based treatment method that involves administration of photosensitizing drug which is a light-sensitive compound, after some hours which is known as drug-light interval, light of specific wavelength is then delivered to the targeted cell to kill the cancerous cell. ALA-PpIX based PDT uses drug (5-aminolevulinic acid) that are photosensitizing agent to accumulate more Photosensitizer (Protoporphyrin IX) on the cancerous cell, followed by light activation. ALA-PpIX based PDT is commonly used for the treatment of oral cancer, various skin conditions like actinic keratosis, basal cell carcinoma, and acne. For successful PDT treatment of any condition an essential consideration is the selection of a light source with appropriate spectral properties, power, and physical form factor for the target tissue. Many light source like LEDs of different wavelength, laser of different wavelength, and fluorescent Lamp have been used for the treatment of oral cancer and found effective in clinical settings. Due to limited access to suitable conventional treatment of oral cancer in rural clinical settings, we are specifically working on light sources that are reasonably compact, portable and low-cost for use in global health settings where oral cancer incidence is extremely high. It is important to note that the choice of light source in PDT of oral cancer depends on the photosensitizing agent. For the light to activate and excite the photosensitizer, the light emission spectrum has to match the absorption spectrum of the photosensitizer. This research compares and contrasts a red diode laser coupled to a fiber optic with peak emission wavelength of 638nm, powered with high input current of 300mA and input voltage of 2.8V versus a red LED light source with a broader emission spectrum centered at 631nm, powered without heat sink and runs with a low input current of 70mA and input voltage of 3V. The light emitting diode, intended to be used at the lesion site (without fiber coupling) produces a relatively low output power of 11mW (irradiance of 16mW/cm2) compared to the laser source with output power of 100mW and irradiance of 141mW/cm2. Both light source were evaluated for PDT treatment of oral cancer cell (TR146) using 5-aminolevulinic acid (ALA) as the photosensitizing agent. The result revealed that both LED and diode laser are effective for PDT treatment though the laser achieved better PDT cytotoxic response. Overall, our results suggest that the constraints of LED operation inside the oral cavity without active heat dissipation render it less effective in comparison to the fiber-coupled laser with relatively high driving current enabled by external heat dissipation.

Comments

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