Gold Nanomaterials at Work in Biomedicine *
Valerio Voliani in Nanomaterials and Neoplasms, 2021
PTT relies on the use of hyperthermia to kill tumor cells. Hyperthermia is a condition under which cells are subject to a temperature in the range of 41–47°C for tens of minutes. Such a condition will cause irreversible damage to the cells due to denaturing of proteins and/or destruction of cell membranes [622]. A variety of heating methods, including those based on lasers [623, 624], microwaves [625, 626], and ultrasound [627], have been applied to achieve PTT. Compared to healthy cells, tumor cells are more prone to destruction at an elevated temperature due to their poor blood supply. A critical issue that hampers the clinical application of PTT lies in nonspecific heating, which will destroy malignant tissues as well as healthy ones. Nanomaterials can be used to address this issue. Specifically, Au nanostructures can absorb electromagnetic energy and convert it into heat through the photothermal effect, making them suitable agents for PTT [231, 628]. With their ability to accumulate at the tumor site through passive targeting [629] and/or active targeting enabled by ligands [16], Au nanostructures have much higher tumor specificity for PTT compared to the traditional heating methods. The accumulation of Au nanostructures at the desired site will lead to selective heating of target cells upon laser irradiation, minimizing potential damage to the surrounding, healthy tissue during a treatment. Compared to organic dyes, which have also been explored as photothermal agents for PTT [630, 631], Au nanostructures offer a number of distinctive advantages:(i) higher stability against photobleaching,
Dehydration and hyperthermia
Shaun Phillips in Fatigue in Sport and Exercise, 2015
Hyperthermia is an abnormally high core body temperature. Normal core body temperature is between 36.5–37.5°C, however the specific value will differ very slightly (approximately 0.1°C) dependent on the location of measurement (rectal, oesophageal, tympanic, etc). Technically, hyperthermia is therefore a body temperature greater than 37.5°C. However, there are different severities of hyperthermia, depending on the core temperature reached. Hyperthermia and fever (as part of an illness) both involve an elevated core temperature, but they are not the same thing as they have different causes and are regulated in different ways. A fever occurs when specific immune cells produced in response to infection release substances that stimulate the hypothamalus to raise core temperature. Essentially, normal core temperature is now considered too cold, and the hypothalamus raises core temperature to a new, higher set point. This process is analogous to raising the temperature setting on a thermostat. Conversely, hyperthermia occurs when core body temperature rises without a direct prior stimulation of the temperature control regions in the brain, usually as a result of an imbalance between heat production and heat dissipation (see Section 4.5.2).
Transpupillary thermotherapy of choroidal neovascularization
A Peyman MD Gholam, A Meffert MD Stephen, D Conway MD FACS Mandi, Chiasson Trisha in Vitreoretinal Surgical Techniques, 2019
TTT is a technique based on the principle of hyperthermia – defined as temperature elevation above normal temperature. Three ranges of temperature can be used for tumor destruction. The low range of 42–44°C does not have a direct destructive effect on cells. This level of hyperthermia potentiates the effects of radiotherapy on choroidal melanoma. In the high range at 60°C and above, hyperthermia results in coagulative necrosis. The intermediate range between 45°C and 60°C induces tumor necrosis without the need for concomitant radiotherapy. In the intermediate range, the coagulative effect seen with higher doses is absent and heat penetration is optimized. Hyperthermia treatment can be applied as either systemic hyperthermia or localized heating. In TTT, the difficulty of delivering hyperthermia to the target tissue is obviated, as the anatomy of the eye allows direct access to the posterior segment structures. Thermometry measurements in ocular hyperthermia are invasive and impractical and are not performed. In contrast to cancer treatments, in which complete tumor destruction to the last viable cell is required for treatment success, the success in TTT for CNV requires only the occlusion of neovascular vessels, making thermometry readings less important. For the treatment of CNV, heat energy is delivered slowly to the choroid and retinal pigment epithelium (RPE) through the pupil using an 810-nm diode laser. The laser is modified for a large spot size of 1.2, 2.0, or 3.0 mm (Iris Medical Instruments, Mountain View, CA). Typical laser parameters used are a duration of 60–70 s at power settings of 250–1000 mW. In general, for a 3-mm spot size, the initial power setting is 800 mW and is appropriately reduced for smaller spot sizes by keeping the power density at approximately 10 W/cm. Typically, no visible color change is seen at the end of the treatment. Near-infrared irradiation is ideal for use in TTT, as its tissue penetration is high and absorption by the ocular media is minimized. The large diameter of the irradiation beam allows homogeneous treatment of large lesions.
Hyperthermia exposure impaired the early stage of face recognition: An ERP study
Published in International Journal of Hyperthermia, 2012
Gang Sun, Min Li, Zhen Yang, Li Li, Qingjun Jiang, Lun Zhao
We investigated the effect of hyperthermia exposure on the early stages of face processing by recording event-related potentials (ERPs) elicited by faces and non-face stimuli presented in upright and inverted orientations. Across all conditions, both the peak latencies of P1 and N170 components were earlier in the hyperthermia group than in the control participants. Although no effects of P1 amplitudes were influenced by hyperthermia, the face effect (larger amplitude for faces relative to other object categories) of the N170 was modulated by hyperthermia, whereas the face effect was significant in the control group, it was minimised in the hyperthermia group. The inversion effect of faces on N170 amplitudes, however, was not affected by hyperthermia. These data suggest that the detection of faces in the visual field and their initial streaming to face-specific structural encoding mechanisms are impaired by hyperthermia. However, subsequent face-specific configural processing revealed by the N170 inversion effect is not affected by hyperthermia. In addition, hyperthermia accelerates the early stage of visual perception, regardless of faces or non-face objects.
Effect of hyperthermia on improving neutrophil restoration after intraperitoneal chemotherapy
Published in International Journal of Hyperthermia, 2019
Wan-Chun Huang, Chao-Chih Wu, Yun-Ting Hsu, Chih-Long Chang
Purpose: Intraperitoneal (IP) chemotherapy has several benefits but also can have severe hematologic side effects. We compared the effects of hyperthermic intraperitoneal chemotherapy (HIPEC) and conventional IP chemotherapy on bone marrow suppression and evaluated whether HIPEC increased neutrophil recovery. Methods: HIPEC or IP chemotherapy was administered to ovarian cancer–bearing mice. Bone marrow progenitor cell colony-forming unit (CFU) count, serum cytokine levels, and peripheral leukocyte count after HIPEC and IP chemotherapy were compared. Results: Peripheral neutrophil count, cytokine (G-CSF and CXCL1/KC) levels, and bone marrow progenitor cell CFU count were significantly higher after HIPEC than after IP chemotherapy. Conclusions: Hyperthermia increased the serum neutrophil-recruiting cytokine levels and reduced the magnitude of chemotherapy-induced neutropenia. Thus, HIPEC improved neutrophil and bone marrow recovery compared with conventional IP chemotherapy.
Is intracellular hyperthermia superior to extracellular hyperthermia in the thermal sense?
Published in International Journal of Hyperthermia, 2002
More than 20 years ago, it was hypothesized that intracellular hyperthermia is superior to extracellular hyperthermia. It was further hypothesized that even a single biological cell containing magnetic nanoparticles can be treated for hyperthermia by an AC magnetic field, independent of its surrounding cells. Since experimental investigation of the thermal effects of intracellular hyperthermia is not feasible, these hypotheses have been studied theoretically. The current report shows that nano-scale heating effects are negligible. This study further shows that intracellular heat generation is sufficient to create the necessary conditions for hyperthermia only in a large group of cells loaded with nanoparticles, having an overall diameter of at least 1mm. It is argued in this report that there is no reason to believe that intracellular hyperthermia is superior to extracellular hyperthermia in the thermal sense.
Related Knowledge Centers
- Central Nervous System
- Heat Stroke
- Malignant Hyperthermia
- Thermoregulation
- Heat Stress Disorders
- Body Temperature Changes
- Medical Emergency