Oxidative Stress-Based Photodynamic Therapy with Synthetic Sensitizers and/or Natural Antioxidants
Photodynamic therapy (also called PDT, photoirradiation therapy, phototherapy, or photochemotherapy) as a new modality for cancer treatment involves the combination of light with a photosensitizing drug in an oxygen-rich environment. PDT consists in the systemic administration of a photosensitizer (PS), which is selectively retained by tumor cells and the subsequent irradiation with visible light of the affected area. Basically two types of reactions can occur after photoactivation of the photosensitizer: the first involves the generation of free radicals (type-I photochemical reaction) and the other the production of singlet molecular oxygen, (type II) as the main species responsible for cell inactivation. The mechanism of PDT effects may involve a direct tumor cell injury and also an indirect cell killing via microcirculatory changes resulting in reduced blood flow in the tumor. Also, PDT may be considered an oxidative stress that induces cellular death in different types of cancerous cells both in vitro and in vivo. Oxidation or oxidative stress leads to the production of free radicals. Generated reactive oxygen species (ROS) cause oxidative stress in the cells targeting mainly at cellular macromolecules, such as lipids, nucleic acids and proteins. These oxidizing agents can damage cells by starting chain reactions such as lipid peroxidation, or oxidation of proteins or DNA, causing mutations and even major diseases, while protein oxidation can lead to distortion and degradation. To evaluate the presence of oxidative stress in PDT, some methods could be used: detection of malondialdehyde (MDA), the carbonylated proteins (CP), the hydrogen donating capacity (HDA), detection pf the -SH groups. By reducing basal levels of ROS in cells may facilitate the therapeutic effects of oxidative stress-based therapies. Natural antioxidants may also protect healthy tissues and lower the incidence of treatment-related side effects, and the chapter shows some results about hesperidin, hesperitine, diosmin and also, some tea rxtracts based on tea leaves and fruits. The Green tea polyphenols have been shown to have a protective effect in different forms of cancer in a variety of pre-clinical animal models. Green tea is composed of several catechins, including (-)-Epigallocatechin-3-gallate (EGCG), epicatechin (EC), epicatechin-3-gallate (ECG), and epigallocatechin (EGC). Among them, (-)-Epigallocatechin-3- gallate (EGCG), the major catechin found in green tea, has been recognized as a potential therapeutic agent. In the context where many clinical studies with respect to the application of antioxidants as sensitizers are lacking, this chapter shows a systematic review by putting into evidence the antioxidant action in photochemotherapy and their comparison with synthetic sensitizers (porphyrins and phthalocyanines). Some up-to-date results of photodynamic therapy with synthetic sensitizers and/or coupled with some natural antioxidants are shown and discussed.
Part of the book: Basic Principles and Clinical Significance of Oxidative Stress
Ceramic Materials Based on Clay Minerals in Cultural Heritage Study
The artifacts belonging to the ceramic heritage are mostly based on all clay types used by humans over the ages, because the sources of clays were easily available and people were interested to produce ceramics and pottery. This is the reason why the conservation of cultural heritage is of great concern. Ceramics (Greek κεράμιον Keramion) is a material obtained by shaping and firing clay. In the Romanian history, many ceramic pieces, of great diversity, have been discovered, and most of them are used in traditional households. Ceramic materials based on clay minerals in cultural heritage (ceramic heritage) involve techniques of characterization of raw materials and ceramic objects based on clays, discovered in different archaeological sites, leading to some results about the production technology, provenance, authentication, and historical appartenance on Romanian territory. The chemical composition of ancient ceramics and pigments decorating them, excavated from different Romanian archaeological sites, suggested a chemical composition of ceramic based on clay minerals (kaolinite, illite, and smectite), while the pigments belonging to them contained red pigments (hematite or ocher), manganese oxides (brown pigments), and magnetite or carbon of vegetable origin (black-pigmented layers).
Part of the book: Clays, Clay Minerals and Ceramic Materials Based on Clay Minerals
Porphyrins and Phthalocyanines: Photosensitizers and Photocatalysts
The porphyrins and phthalocyanines are among the most representative macrocycles in synthetic chemistry, characterized by specific molecular structures, responsible and associated with their particular properties. They have high versatility and an adequate variability introduced either by macrocycle metallation or by different substituents at its periphery called meso-substituents. The porphyrins could find, together with the synthetic phthalocyanines, various scientific and technological applications in chemical and photochemical areas. They can serve as catalysts and photocatalysts in different reactions, or as photosensitizers in photodynamic therapy of cancer, due to their high efficiency to generate free radicals and excited state species. The aim of this chapter is to achieve a better understanding of the complex and various properties of the porphyrins and phthalocyanines in different solvents or in heterogeneous media, trying to draw the relationships between these topics with their possible applications in catalytic, photocatalytic area (photodegradation of Kraft-lignin, photooxidation of different unsaturated hydrocarbons, photodegradation of different organic aquatic pollutants, oxirans polymerization) and some preliminary results about the heterogeneous porphyrin sensitizers in the photodynamic therapy area. Their photobleaching mechanisms in different conditions are also discussed.
Part of the book: Phthalocyanines and Some Current Applications
316L Stainless Steel/Hydroxyapatite Composite Materials for Biomedical Applications
Hydroxyapatite (HAp) is known as one of the most important biomaterials used for orthopedic and dental applications due to chemical composition similar to that of bone and bioactive properties. However, due to its reduced resistance, HAp should be mixed with different components in order to create composite materials. A good example is austenitic stainless steel (AA 316L), as a class of metallic materials used for biomedical applications. The aim of this chapter is to show a series of our group studies for obtaining a hybrid metal-ceramic composite by powder metallurgy, the physicochemical, mechanical, and biological properties of these hybrid composites and the investigation of possible functional coating layers and adherent bioactive hydroxyapatite Ca10(PO4)6(OH)2 on the metal of 316L stainless steel, correlating our data with literature data. Hardness properties of the obtained composites are close to those of human bones. In biological systems, could be observed that after 6 months, the relevant metals (Fe, Mn, Cr, and Ni) concentration (ppb), that may be released from composite materials in simulated physiological fluids (SBF), is practically zero.
Part of the book: Hydroxyapatite
Nanotechnologies in Cultural Heritage - Materials and Instruments for Diagnosis and Treatment
This chapter aims to evaluate the nanomaterials that can be used to diagnostic, conservation and restoration of different artifacts and monuments and that can contribute to solving the problems which could appear during weathering processes of them. The nanotechnology, as a new and revolutionary area in science, can improve the traditional methods currently used for restoration and preservation in cultural heritage and can contribute to the creation of new highly specialized methods for diagnostic and treatment of different artifacts or even monuments. With a smaller size, a higher penetrability, viscosity, thermal and magnetic properties, in comparison with the traditional materials, the nanomaterials can contribute to solve the problems deriving from specific phenomena that could appear during the intervention and to identify the potential newly formed products in the treated materials. In this chapter, some aspects about the nanomaterials used for conservation and restoration of stone and paper artifacts are evidenced and discussed.
Part of the book: Novel Nanomaterials
Photochemical Degradation Processes of Painting Materials from Cultural Heritage
This chapter describes some recent studies and applications of photochemistry in the physical–chemical characterization of two acrylic paint materials based on phthalocyanines and the study of the photodegradation (photobleaching) processes which could occur, caused by exposure to artificial irradiation, similar as in the museum. The studies in this paper has been conducted on phthalocyanines, these compounds being known as organic colorants in painting. Their color depends not only on the chemical nature of the colorant, which play an important role in the kinetics and degree of aging, but also on the compounds added to the paints (TiO2, micas, arylamide yellow). The techniques used in such studies involve UV–Vis spectroscopy, gloss, and colorimetric measurements, comparing our results with similar ones from the literature.
Part of the book: Photochemistry and Photophysics
Pale-Green Kohlrabi, a Versatile Brassica Vegetable
This chapter describes recent research studies about kohlrabi, a versatile vegetable with important health benefits (e.g. reduces risk of breast and prostate cancer, improves body metabolism, helps in weight loss diets, etc.). The investigations are focused on pale-green kohlrabi giving an accurate and precise description, from a qualitative point of view, of the bioactive compounds found in different parts of the pale-green kohlrabi: core, peel, leaves and equal combinations between these parts. All the active principles from pale-green kohlrabi are extracted following a well-established method, in an aqueous medium at a constant temperature of 4°C for 24 h. The qualitative screening of phytochemicals gives details regarding the presence or absence of chemical compounds using different colour reactions.
Part of the book: Brassica Germplasm
Qualitative Analysis of Phytochemicals from Sea Buckthorn and Gooseberry
This chapter describes in detail recent research results obtained from the qualitative screening of different phytochemicals found in aqueous extracts of sea buckthorn and gooseberry, fruits with important pharmacological effects due to their high content in vitamin C. Phytochemical investigations reveal the presence of active principles (e.g., saponins, flavonoids, alkaloids, carbohydrates, terpenoids, etc.) in sea buckthorn and gooseberry and are accomplished by using well-established standard methods. All these qualitative determinations rely on the visual color change reaction as a basic response to the presence of a specific phytochemical compound. The active principles from sea buckthorn and gooseberry are extracted according to a well-settled extraction method, which involves infusing the fruits in an aqueous medium, for 24 h, at a constant temperature of 4°C.
Part of the book: Phytochemicals
Polymeric Micro- and Nanosystems for Wood Artifacts PreservationView all chapters
The complex methods of diagnosis investigation of the wood artifacts state and proper materials for their protection against decay are very important goals in cultural heritage. This chapter focuses on the recent trends in micro- and nanostructured polymer systems for application in cultural heritage and on wood preservation, especially. The synthesis, properties, and applications, as well as the relevant analysis techniques to reveal the structures and properties of polymer systems, are discussed, too. To overcome the specific problems that exist for wood artifacts, some aspects should be treated: effects of the environmental factors, as moisture and pollutant absorption into the wood fibers, over-exposure effect of sun or artificial light sources, biological attack of different microorganisms, and the effects of the protective and decorative coatings.
Part of the book: New Uses of Micro and Nanomaterials