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Recent Progress in Cancer Thermal Therapy Using Gold Nanoparticles *
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Nardine S. Abadeer, Catherine J. Murphy
Due to the great variation in methods of nanoparticle delivery, dosing, and irradiation conditions in photothermal treatment, the cellular responses to photothermal therapy seem to also vary. These particular studies demonstrated that photothermal treatment may result in cancer cell death via apoptosis or necrosis, but oncosis has also been observed. Higher laser powers and pulsed lasers appeared to trigger necrosis, while lower laser powers and continuous wave lasers resulted in apoptosis. Heating with continuous wave lasers, resulting in apoptosis, is the same mechanism observed in traditional hyperthermia. This may potentially be due to similar changes in temperature near cancer cells, which would be influenced by heating conditions. However, gold nanoparticle location on the surface, in the cytoplasm, or at the cell nucleus also influenced photothermal therapy. Further investigations into the effect of irradiation conditions are required to gain a more complete picture of what influences each pathway. One avenue not yet explored is the effects of cancer cell type on the mechanism of death. Differences between death mechanisms in cancer cell types may also be due to the elevation of heat shock proteins and may greatly affect the success of thermal therapy. If scientists are better able to understand the mechanisms and pathways that lead to cell death in a specific type of cancer, photothermal heating conditions can potentially be tailored to enhance the success of cancer treatment.
Lasers in Medicine: Healing with Light
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
In one method for achieving laser pulses, called Q-switching, a device called a Pockels cell is inserted inside the lasing medium. The Pockels cell acts like an electromagnetic switch that prevents lasing from occurring by blocking the passage of light while the population inversion accumulates to very high levels. When the switch is opened, lasing occurs, releasing an enormous amount of energy rapidly. This rapid release of laser energy is what creates the pulses of light in a pulsed laser.
Emerging Biomedical Imaging
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
Essentially, a pulse laser delivers a pulsed light onto the image target through a living tissue. The pulsed light results in generation of a heat (temperature change), which is then transformed to a pressure change. Lastly this changing pressure is converted to an acoustic (sound) wave that will be picked up by an ultrasound transducer or probe. In short, it is a “light goes in sound comes out” process (Fig. 1).
Blue light filtering ophthalmic lenses: A systematic review
Published in Seminars in Ophthalmology, 2021
Aldo Vagge, Lorenzo Ferro Desideri, Chiara Del Noce, Ilaria Di Mola, Daniele Sindaco, Carlo E. Traverso
There are three putative mechanisms of retinal damage exerted by blue-light: photothermal, photomechanical, and photochemical. The photothermal damage is due to the transfer of radiant energy into the retinal tissues; photothermal energy is thought to be absorbed by melanin located in the RPE, xanthophyll situated mainly in Muller cells and neurosensory retina and by hemoglobin contained in the blood vessels.11The photomechanical damage is due to compressive forces, created by the introduction of energy into the melanosomes of the RPE and it is directly related to the amount of energy absorbed.12This is only applicable to exposure to high-power pulsed lasers. Finally, the photochemical damage is thought to be caused by a dose-dependent generation of free radicals directly damaging the retinal tissue. This damage is thought to be associated with both long-duration and lower-wavelength, which is related to higher energy and light exposure. In particular, chromophores are molecules located in the retina (including photoreceptors, flavoproteins, heme proteins, melanosomes and lipofuscin), which are responsible for mediating light-induced retinal damage.13 In this regard, retinal photoreceptors have a large number of biological membranes, which are highly susceptible to free radicals-related damage, causing protein and lipid oxidation and ultimately leading to a neurosensory retina and RPE damage.14
Assessing the impact of low level laser therapy (LLLT) on biological systems: a review
Published in International Journal of Radiation Biology, 2019
Ruwaidah A. Mussttaf, David F. L. Jenkins, Awadhesh N. Jha
However, there is some agreement on the best wavelengths of light and appropriate dosages to be used (irradiance and fluence), there is no agreement on the emission mode of laser light; whether continuous wave (CW) or pulsed light is more suitable for the various applications of PBM. However, pulsed lasers in PBM therapy are used widely in clinical research (Fonseca et al. 2010; da Silva Sergio et al. 2012); and for medical treatment (Vasheghani et al. 2009; Ahrari et al. 2014; de Meneses et al. 2015; Bayat et al. 2016). Two types of pulsed laser are used for PBM therapy: (a) super-pulsing gallium-arsenide (GaAs) diode laser, which has a wavelength in the region of 904 nm and pulse duration in the range of 100–200 ns, and (b) the semiconductor super-pulsing indium-gallium-arsenide (In-Ga-As) diode laser, which emits light at a similar wavelength (904–905 nm), producing very short pulses of light (200 ns) in the range of kilohertz (kHz) frequencies (Hashmi et al. 2010b). Therapeutically, the super-pulsed GaAs and In-Ga-As lasers are capable of deep penetration without the undesirable influences associated with continuous wave lasers (CW) (such as thermal damage), as well as allowing for shorter treatment periods. Pulsed lasers offer potential benefits, attributed to the pulse OFF times (pulse quench intervals) following the pulse ON times, so that pulsed lasers can deliver less tissue heating.
Progress on utilizing hyperthermia for mitigating bacterial infections
Published in International Journal of Hyperthermia, 2018
Taylor Ibelli, Sarah Templeton, Nicole Levi-Polyachenko
Similar to silver nanoparticles, gold nanoparticles are excellent photothermal absorbers because their plasmon resonance can be tuned to the near-infrared range [124]. The generation of heat is the major mechanism for ablation of the bacteria; however, as noted by a number of groups, application of intense laser pulses also induces the formation of cavitation bubbles, which may further improve the delivery of antibiotic agents [125–127]. This was demonstrated by Meeker et al. using gold nanocages conjugated to daptomycin for targeted photothermal and antibiotic eradication of S. aureus and S. epidermidis [128]. Similarly, Pissuwan et al. investigated the effects of antibody-conjugated gold nanorods against the pathogenic parasite Toxoplasma gondii using 100 mW of 650 nm laser irradiation, resulting in a death rate of 82.2% [129]. Both continuous wave and pulsed laser irradiation for PTT have been shown to be effective for killing bacteria; however, as noted by Millenbaugh et al. the use of pulsed lasers may be preferential for inducing cavitation [130]. Zharov et al. also investigated the effects on antibody-conjugated gold nanoparticles on bacteria, using anti-protein A antibody conjugated gold nanoparticles for selective photothermal ablation, using nanosecond laser pulses, of S. aureus leading to greater than 90% bacterial death [131].