Analytical Porous Media Model of Light Penetration in Photodynamic Therapy

2007 ◽  
Author(s):  
Amaranath Premasiri ◽  
Gemunu Happawana ◽  
Arye Rosen
Keyword(s):  
Photodynamic Therapy ◽  
Therapeutic Modality ◽  
Light Penetration ◽  
Liquid Content ◽  
Microvascular Damage ◽  
Essential Components ◽  
Porous Media Model ◽  
Different Types ◽  
Two Factors ◽  
Photosensitizing Agent

Photodynamic therapy (PDT) is currently being developed as a new therapeutic modality with minimal side effects in the treatment of many different types of cancers [1]. PDT requires three essential components, which includes a photosensitizing agent, activation light, and molecular oxygen [2, 3]. Light is one of the governing components for PDT, and the only component that can be controlled externally [4]. The understanding of light penetration in a tumor is critical for an efficient PDT protocol. A well-designed PDT protocol provides minimal microvascular damage and efficient killing of malignant tumor cells [5–7]. The depth of light penetration in a tumor depends on the microvascular nature of the tumor, amount of solid and liquid contents present, and the wavelength of the light source. The first two factors depend on the nature of the tumor tissue and therefore the optimal light dose is not standard for all tumors. Furthermore the liquid content of a tumor changes with the tumor temperature due to vasodilatation, and this in turn affects the depth of light penetration.

scholarly journals On the Concepts of Imported Language and Newspeakerism in the Sociolinguistic Context of Lithuania

2020 ◽  
Vol 65 (2) ◽  
pp. 116-130
Author(s):  
Alla Likhachiova
Keyword(s):  
Host Country ◽  
Statistical Data ◽  
Russian Language ◽  
Accurate Description ◽  
Linguistic Landscape ◽  
Essential Components ◽  
The Everyday ◽  
Different Types ◽  
Two Factors ◽  
External Migration

This article outlines the advantages of introducing some new terms to describe the current sociolinguistic situation in Lithuania. Its essential components are the heterogeneity of the country’s ethno-linguistic landscape, intensive internal and external migration and the different types of language practices within the country, which are the result of the first two factors. The term “imported language” proposed by the author of the article and the term “newspeakerism”, which has recently become established in European sociolinguistics, have not yet been used in the works of Lithuanian sociolinguists. However, these terms can be important for describing the linguistic specifics of some regions of Lithuania. The first term seems appropriate to denote the language of immigrants, which is used relatively widely in the host country, not only in family, but also in the everyday and official communication, and the second – for the sociolinguistic categorization of such immigrants. Most immigrants are residents of post-Soviet countries with native or well-mastered Russian language, therefore, in the article, it is Russian that is defined as an imported language. The paper examines the theoretical prerequisites for the introduction of new terms for a more accurate description of the current linguistic situation in Lithuania and the designation of its participants. Statistical data on migration processes in Lithuania and fragments of interviews with immigrants of chronologically different arrival streams are used.

Radiation Therapy Combined with Photofrin or 5-Ala: Effect on Lewis Sarcoma Tumor Lines Implanted in Mice. Preliminary Results

2002 ◽  
Vol 88 (5) ◽  
pp. 407-410 ◽  
Author(s):  
Moshe Schaffer ◽  
Pamela M Schaffer ◽  
Giulio Jori ◽  
Luigi Corti ◽  
Guido Sotti ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
Normal Tissue ◽  
Tumor Volume ◽  
Tissue Reaction ◽  
Therapeutic Modality ◽  
Chemical Modifier ◽  
Ionizing Irradiation ◽  
Normal Tissue Reaction ◽  
Tumor Types ◽  
Photosensitizing Agent

Aims and background Ionizing irradiation is a well-established therapeutic modality for cancer. Photodynamic therapy (PDT), especially with 5-ALA and Photofrin, is highly effective in some tumor types. Chemical modifiers, so-called radiosensitizers, are used in order to increase the efficacy of radiotherapy. Most of the known and routinely used radiosensitizers are not tumor selective, so that the normal tissue reaction toxicity is also increased. In the present study we investigated whether a porphyrin derivative that is currently used as a tumor-photosensitizing agent in photodynamic therapy (PDT) may also act as a tumor-specific radiosensitizer. Materials and methods For our investigation we used Balb/c mice implanted with Lewis sarcoma and irradiated with 3 Gy combined with injection of 5-ALA or Photofrin at various concentrations before irradiation. Results 5-ALA had no effect as a radiosensitizer at any of the concentrations examined. Photofrin at a concentration of 5 mg/kg proved to be a chemical modifier of ionizing radiation, delaying tumor growth and reducing the overall tumor volume by about 50% after six days. Conclusion Photofrin has marked efficacy as a radiosensitizer and can be used in the future as a selective tumor radiosensitizer.

Porous Media Tumor Model for Light Penetration and Oxygen Diffusion During Photodynamic Therapy

2008 ◽  
Author(s):  
A. Premasiri ◽  
G. Happawana ◽  
A. Rosen
Keyword(s):  
Porous Media ◽  
Photodynamic Therapy ◽  
Molecular Oxygen ◽  
Oxygen Diffusion ◽  
Transport Model ◽  
Tumor Model ◽  
Analytical Equation ◽  
Light Penetration ◽  
Model Calculations ◽  
Porous Media Model

Photodynamic therapy (PDT) is an FDA approved, effective, and minimally invasive cancer treatment modality with few side effects. PDT requires three major components; photosensitizing agent, activation light, and molecular oxygen. Optimization of PDT for an individual patient requires good therapeutic selectivity and high efficacy, where the design of such an effective protocol is based on the understanding of the interaction of key therapeutic components with tumor tissue. Tumor models expressive of changes during the growth of tumor along with the behavior of PDT components facilitate the above requirement. In this study we have developed a mathematical model considering tumor as a porous medium of solid of and liquid that enables to express characteristics of a growing tumor. The characteristic lengths and the volumes that can be changed in the model represent the dynamic changes during the growth of the tumor. An energy based light transport model is superimposed with the porous media model to yield an analytical equation of light penetration in turbid media. In addition a molecular diffusion model combined with the porous media tumor model provides a second analytical equation yielding molecular oxygen diffusion during PDT. Experimentally available physiological and photophysical data are used to obtain the results from the developed models. The commonly used wavelength for PDT, 635nm and corresponding photophsical parameters for a healthy tissue are used for the calculations. The modeling results reveal an exponential decay of optical power along the direction of light penetration and the characteristic changes in oxygen diffusion during PDT. Further observations include the time dependent changes in photosensitizer photobleaching and the corresponding increase in oxygen diffusion length. The modeling results in both cases show a promising accordance with the available experimental results in literature. The model calculations also reveal the effect of light penetration on oxygen diffusion in PDT milieu adding to the expression of its usefulness.

scholarly journals Computational simulation of low energy x-ray source for photodynamic therapy: a preliminary study

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Leandro da Silva De Souza ◽  
Mirko Salomón Alva-Sánchez ◽  
Alexandre Bonatto
Keyword(s):  
Photodynamic Therapy ◽  
Computational Simulation ◽  
Energy Spectra ◽  
Therapeutic Modality ◽  
Light Penetration ◽  
Cytotoxic Effects ◽  
X Ray ◽  
Preliminary Study ◽  
A Minor ◽  
Tumoral Cells

Photodynamic therapy is a therapeutic modality capable of selectively inducing cytotoxic effects in malignant cells. Such effects are obtained by using a laser or a lamp as a light source to irradiate a previously-delivered photosensitizer into the tumoral cells. Since clinical application of photodynamic therapy depends on light penetration, lasers and lamps can only be used for shallow tissue treatment. To overcome this limitation, x-ray induced photodynamic therapy has been recently proposed. The goal of this work is to investigate the x-ray interactions in a medium containing a homogeneous concentration of distinct photosensitizers. This is achieved by evaluating the relative doses and energy spectra, obtained at distinct depths by means of Monte Carlo simulations. Preliminary results for the relative dose showed a minor dose increase, of approximately 0.15%, when photosensitizers are used. In addition, x-ray interactions with the investigated photosensitizers mostly occur from photons with energies below 60 keV.

Nanoparticles Functionalized with Venom-Derived Peptides and Toxins for Pharmaceutical Applications

2020 ◽  
Vol 21 (2) ◽  
pp. 97-109 ◽  
Author(s):  
Ana P. dos Santos ◽  
Tamara G. de Araújo ◽  
Gandhi Rádis-Baptista
Keyword(s):  
Oral Absorption ◽  
Current Data ◽  
Pharmacological Activities ◽  
Venom Peptides ◽  
Essential Components ◽  
Wide Range ◽  
Different Types ◽  
Direct Use ◽  
Animal Venoms ◽  
Pharmaceutical Biotechnology

Venom-derived peptides display diverse biological and pharmacological activities, making them useful in drug discovery platforms and for a wide range of applications in medicine and pharmaceutical biotechnology. Due to their target specificities, venom peptides have the potential to be developed into biopharmaceuticals to treat various health conditions such as diabetes mellitus, hypertension, and chronic pain. Despite the high potential for drug development, several limitations preclude the direct use of peptides as therapeutics and hamper the process of converting venom peptides into pharmaceuticals. These limitations include, for instance, chemical instability, poor oral absorption, short halflife, and off-target cytotoxicity. One strategy to overcome these disadvantages relies on the formulation of bioactive peptides with nanocarriers. A range of biocompatible materials are now available that can serve as nanocarriers and can improve the bioavailability of therapeutic and venom-derived peptides for clinical and diagnostic application. Examples of isolated venom peptides and crude animal venoms that have been encapsulated and formulated with different types of nanomaterials with promising results are increasingly reported. Based on the current data, a wealth of information can be collected regarding the utilization of nanocarriers to encapsulate venom peptides and render them bioavailable for pharmaceutical use. Overall, nanomaterials arise as essential components in the preparation of biopharmaceuticals that are based on biological and pharmacological active venom-derived peptides.

Nanocarriers for Photodynamic Therapy Intended to Cutaneous Tumors

2021 ◽  
Vol 22 ◽  
Author(s):  
Maria Bernadete Riemma Pierre
Keyword(s):  
Photodynamic Therapy ◽  
Drug Delivery Systems ◽  
Active Agent ◽  
Therapeutic Modality ◽  
Tissue Penetration ◽  
Promising Tool ◽  
Skin Cancers ◽  
Superficial Basal Cell Carcinoma ◽  
The Stability ◽  
Disor Ders

Abstract: Photodynamic Therapy (PDT) is a therapeutic modality used for several malignant and premalignant skin disor-ders, including Bowen's disease skin cancers and Superficial Basal Cell Carcinoma (BCC). Several photosensitizers (PSs) have been explored for tumor destruction of skin cancers, after their activation by a light source of appropriate wavelength. Topical release of PSs avoids prolonged photosensitization reactions associated with systemic administration; however, its clinical usefulness is influenced by its poor tissue penetration and the stability of the active agent. Nanotechnology-based drug delivery systems are promising tool to enhance the efficiency for PDT of cancer. This review focuses on PSs encap-sulated in nanocarriers explored for PDT of skin tumors.

Induction Heating Power Supplies

1988 ◽  
pp. 47-75
Keyword(s):  
Induction Heating ◽  
Maximum Output Power ◽  
Heating System ◽  
Power Supplies ◽  
Maximum Output ◽  
Frequency Multipliers ◽  
Ac Power ◽  
Different Types ◽  
Two Factors ◽  
Induction Heating System

Abstract Besides the induction coil and workpiece, the induction generator (source of ac power) is probably the most important component of an overall induction heating system. Such equipment is typically rated in terms of its frequency and maximum output power (in kilowatts). This chapter addresses the selection of power supplies in terms of these two factors as well as the operational features of different types of sources. The six different types of power supplies for induction heating applications covered in this chapter are line-frequency supplies, frequency multipliers, motor-generators, solid-state (static) inverters, spark-gap converters, and radio-frequency power supplies. The chapter discusses the design and characteristics of each of the various types of power supplies.

Topical Administration of Tetrasodium-Mesotetraphenyl-Porphinesulfonate (TPPS): Correlation between Drug Penetration and Depth of Necrosis in Skin of Nude Mice following Red Light Irradiation

1987 ◽  
Vol 73 (1) ◽  
pp. 11-17 ◽  
Author(s):  
Renato Marchesini ◽  
Elsa Melloni ◽  
Giovanni Bottiroli ◽  
Salvatore Andreola ◽  
Giannino Fava ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
Nude Mice ◽  
Red Light ◽  
Local Treatment ◽  
Topical Administration ◽  
Skin Lesions ◽  
Drug Penetration ◽  
Suitable Treatment ◽  
Epithelial Layers ◽  
Photosensitizing Agent

The main side effect in photodynamic therapy is photosensitization of the patient's skin following systemic administration of the photosensitizing agent. In the case of superficial lesions, this problem can be avoided by topically applying the drug: in this way a local treatment can be performed. We tested the photosensitizing properties of a 2 % solution of TPPS (tetrasodium-tetraphenylporphinesulfonate) in a vehicle containing a penetration enhancer, Azone, on skin of nude mice. An aliquot of 0.1 ml/cm2 of the solution was painted on the skin overlying an s.c. implanted NMU-1 tumor. Subsequently, animals were sacrificed at different times after application. Fluorescence microscopy revealed that TPPS penetration depth was related to time elapsed after application and to painting modalities. Solution penetration was enhanced by wiping with ether immediately before painting. Irradiation at 80 mW/cm2 for 20 min with a dye laser emitting at 640 am, 4 h after TPPS application, produced necrosis of the upper skin layers, up to 0.2 mm in depth. These findings suggest that topical TPPS administration, followed by laser irradiation, may be a suitable treatment modality for skin lesions involving epithelial layers, even though several aspects of this metodology need further investigation.

Sign in / Sign up

Export Citation Format

Share Document