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In Vitro Alternative Methods for the Assessment of Dermal Irritation and Inflammation
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
David W. Hobson, James A. Blank
Photochemical reactions induced by UV rays may be enhanced as a result of chemical present in skin tissue from either dermal or systemic exposure. These reactions may also be classified as either phototoxic or photoallergic. Chemicals which enhance photochemical reactions are known as photosensitizers. Photochemical reactions may result in erythema, edema, papules, macules, epidermal thickening, proliferative changes in epidermal cells, suppression of T lymphocytes, or the development of precancerous and cancerous conditions.56 Examples of photosensitizers include select sulfonamides, tetracyclines, nalidixic acid, sulfonylureas, thiazides, phenothiazines, furocoumarins, and coal tars.57
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
Lasers can be employed in therapy by using them as agents for causing highly specific chemical changes. One such application, photodynamic therapy (PDT), uses light to target and destroy the cells in cancer therapy and other applications. In this technique, a light-activated chemical called a photosensitizer is introduced into the body. One such chemical is a naturally occurring blood component, called hematoporphyrin derivative (HpD), one member of a family of chemicals called porphyrins. This substance is introduced orally or injected in high concentrations into the bloodstream of a person with cancer. After the initial dose, the HpD accumulates in cells of the body. While it clears from normal, noncancerous cells in roughly 72 hours, malignant cells retain the HpD for longer (Figure 3.33).
Palliation of malignant lower gastrointestinal disease
Published in David Westaby, Martin Lombard, Therapeutic Gastrointestinal Endoscopy A problem-oriented approach, 2019
This technique makes it safe to treat deeper into the bowel wall, as even with full-thickness necrosis, preservation of collagen preserves the mechanical integrity. This can even be true in tumour areas as there is often more collagen in tumour tissue than in the adjacent normal areas, although of course tumours may perforate spontaneously. However, in the present context, there are major drawbacks to using PDT. It is suitable for treating only small volumes of diseased tissue, and administration of a photosensitizing drug leaves patients generally sensitive to bright lights for a period that may vary from a few days up to 2–3 months, depending on which photosensitizer is used (see Chapter 4).
Impact of Aluminium phthalocyanine nanoconjugate on melanoma stem cells
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2023
Bridgette Mkhobongo, Rahul Chandran, Heidi Abrahamse
Photodynamic therapy (PDT) has proven to be both a promising and effective cancer treatment. PDT has been listed and recognised by the US Food and Drug Administration in clinical trials as one of the more recent cancer treatment methods [20]. With its impressive results, PDT is being employed to treat cancer either alone or in combination with conventional treatment modalities like surgery and chemotherapy [21,22]. Systematic PDT strategies have been developed in some Western countries [23–25]. The mechanisms of action of photodynamic treatment involve two sorts of reactions. The first happens when the light stimulates the PS, forcing an electron to shift to a higher energy level [9]. Light stimulation of the photosensitizers (PS) activates an additional action mechanism. When the energy is transported to the molecular oxygen ground state, singlet oxygen species are stimulated, which disrupts cellular processes and causes tumour death [26].
Trial watch: an update of clinical advances in photodynamic therapy and its immunoadjuvant properties for cancer treatment
Published in OncoImmunology, 2023
Mafalda Penetra, Luís G. Arnaut, Lígia C. Gomes-da-Silva
PDT is a medical treatment that requires a molecule (named photosensitizer) that is activated by visible or near infrared light. When the photosensitizer is photoactivated in the presence of molecular oxygen (O2), reactive oxygen species (ROS) are promptly generated. The acute oxidative stress associated with PDT can be used to selectively kill cancer cells and other abnormal cells in the body3,4. In clinical practice, PDT is a two-step treatment modality that begins with the intravenous administration (iv) of the photosensitizer or its topical application to the skin. After a specific period of time, known as drug-to-light interval (DLI), the photosensitizer is activated at tumor sites using an external light source (e.g. laser or LED) at a wavelength that matches the lowest energy band of the photosensitizer. Ideally, this wavelength should be between 650 and 850 nm to allow deeper light penetration into the tumor tissues3. Clinically approved photosensitizers are typically administered for several hours (or even days) in advance of the light treatment. These protocols with a long DLI allow enough time for the photosensitizer to be internalized by the cancer cells, meaning that generated ROS can directly damage and kill the cancer cells (cellular-PDT). In contrast, PDT with a short DLI (e.g. 15 minutes) destroys the tumor vasculature (vascular-PDT), killing cancer cells indirectly by interrupting their supply of nutrients and oxygen3,5,6.
aMMP-8 point-of-care - diagnostic methods and treatment modalities in periodontitis and peri-implantitis
Published in Expert Opinion on Therapeutic Targets, 2023
Hanna Lähteenmäki, Tommi Pätilä, C Pirjo Pärnänen, Ismo Räisänen, Taina Tervahartiala, Shipra Gupta, Timo Sorsa
Biofilm can be removed with careful anti-infective treatment, but bacteria that have already penetrated the tissue defense somehow survive. This issue has led to further research into the possibilities of different light treatments to eliminate those pathogens [86–88]. Dental clinicians so far have almost no chance of destroying these pathogens so an alternative method to treat drug-resistant bacterial infections is needed [89]. Photodynamic therapy (PDT) is a method that is based on local application of a photosensitive compound (the photosensitizer). This accumulates in pathological tissues. The photosensitizer molecules absorb the light of the wavelength, initiating the activation processes that lead to the destruction of the cells. The photodynamic therapy is well tolerated. The ease of application allows for home use [89]. Several studies have also demonstrated that bacterial destruction in dental implant tissues can be achieved without any damage to the treated titanium surfaces [90].