Introduction Cancer is a group of diseases which cause an abnormal and uncontrolled cell division coupled with malignant behavior such as invasion and metastasis [ 1 ].
For the treatment of cancer various methods have already been discovered and many others are in the process of discovery e. But the anticancer drugs can fail to kill cancer cells for various reasons, the transport of the anticancer drug being governed by physiological and physicochemical properties of the target cell and of the drug itself [ 4 ].
These properties include pressure, charge, size, configuration, electrochemical properties, hydrophilicity, etc.
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Нет,-- ответил Хилвар.
И вслед за этим стремительным рассветом произошло возвращение к реальности.
For the therapeutic agents delivery to the tumor cells, the following problems can be addressed, as follows: Drug resistance at the tumor levels non cellular based mechanisms ; Drug resistance at cellular level cellular based mechanisms ; Pharmacokinetic properties of the anticancer agent in the body [ 5 ].
The gastric cancer new treatments of the nanoparticles which permits higher absorption of the drugs in a specific tissue, and this concept has been applied for hyperthermia, radiation therapy, photodynamic therapy, etc. Meanwhile, the nanoparticles opened new horizons for drug delivery and bringing the term nanomedicines.
Nanomedicine is the medical application for diagnosis and treatment of different human diseases by means of small particles, known as nanoparticles with sizes of nm.
The nanoparticles are known by their large surface area, high reactivity, high solubility, reduced side effects and gastric cancer new treatments toxicity [ 7 - 9 ].
The main nanoparticles applied in nanomedicine are: polymeric nanoparticles, liposomes and lipid gastric cancer new treatments, micelles, microcapsules, magnetic particles, and carbon nanoparticles fullerenes, carbon nanotubes, carbon nanofibers, etc and the nanoassemblies [ 10 - 12 ]. Photodynamic therapy PDT as a part of photochemotherapy, is a concerted method where, in addition to light and an administered drug, oxygen is required. PDT represents a concerted action of light, with a sensitizers and an oxygen active specie singlet oxygen which preferentially actions on tumor cells and not on healthy cells.
The administered drug is generally a substance which can efficiently photosensitize the formation of singlet oxygen or other reactive species gastric cancer new treatments from oxygenvermifugo para oxiuros such species react with different biological targets, and cause cellular damage and finally, the cellular death. Activation of the photosensitizers by light is an essential condition for a successful PDT.
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Under such circumstances, this chapter offers the most up—to—date coverage of photodynamic therapy including information on how nanosensitizers, have evolved within the field of cancer therapy and more recently for drugs controlled release in this field, by using personal data correlated with literature reports.
Short history Photodynamic therapy is dating from ancient time, the Indian civilizations reported from the first time the combined action of psoralens with sunlight to treat vitiligo [ 14 ]. Niels Fiensen used UV light to treat small pox, pustular infections eruptions, cutaneous tuberculosis, and for its results he obtained the Nobel Prize in Medicine in Similar results obtained Niels Raab inby using eosin as sensitizer and combining his results with Jesionek and J.
Prime results for skin tumors and epilepsy generated by light induced dermatitis [ 17 ]. Meyer-Betz was the only experimentalist who tested this method on himself, by injecting haematoporphyrin, reporting the observed effects: oedema, erythema and light sensitivity gastric cancer new treatments 18 ].
Photodynamic Nanomedicine Strategies in Cancer Therapy and Drug Delivery
Later, Campbell and Hill studied the PDT effects on microcirculation, reporting the thrombosis and vascular shutdown [ 19 ]. Lipson in went on to treat a patient with a large cancer of the breast following an injection of a derivative of haematoporphyrin HpD. The modern era of photodynamic therapy was established by Dr. Dougherty, at the Division of Radiation Biology at Roswell Park Memorial Institute, Buffalo, USA, who reported that a systematically injected porphyrin on activation with red light caused complete eradication of transplanted experimental tumors [ 20 ].
In the photodynamic therapy occur three types of mechanisms: type I mechanism — electron transfer eT where gastric cancer new treatments photosensitizer excited state generates a radical species, for example by electron transfer from or to a substrate, or by hydrogen atom abstraction from a substrate. The type I mechanism of PDT In type II mechanism - energy transfer ET an energy transfer occurs from the excited photosensitizer to molecular oxygen, to give the sensitizer in its ground state and singlet oxygen.
In this mechanism electronic excitation energy is transferred from the excited triplet T1 of the sensitizer generated by intersystem crossing isc from the ecited singlet S1 to triplet molecular oxygen, to give the sensitizer in its ground state S0 and singlet oxygen 1O2. Sheme 2.
The type II mechanism of PDT Gastric cancer new treatments biological targets are membranes that undergo rupture and the cells are gastric cancer new treatments through the membranes around the mitochondria and the lysosomes.
These organelles induce subsequent cellular destruction by necrosis or apoptosis [ 21 - gastric cancer new treatments ].
Except these two types of mechanisms, there is another one: type III mechanism, which take place when the oxygen is absent in the system. Sheme 3. Photosensitizers 4.
Conventional photosensitizers All the sensitizers could be natural or synthetic compounds, enterobius vermicularis gif proper absorption properties from a light source. They should be pure compounds, soluble in body fluids, with high capacity to be incorporated in malignant cells. Also, they should be fluorescent and able to generate singlet oxygen, which is the excited state of oxygen efficient on malignant gastric cancer new treatments [ 25 ].
Taking into account all these criteria and gastric cancer new treatments the compatibility with human body, the porphyrins are known as ideal sensitizers for photodynamic therapy.
The general chemical structure for some porphyrins and phthalocyanines as PDT agents are represented in Figure 1. Figure 1. The chemical structure of some porphyrins and phthalocyanines First Generation Photosensitizers, includes Photofrin® and HpD and exist as complex mixtures gastric cancer new treatments monomeric, dimeric, and oligomeric structures.
At nm, their gastric cancer new treatments tissue penetration of light is small, 2—3 mm, limiting treatment to surface gastric cancer new treatments. In spite of its safe applications in bladder, esophageal and lung cancers, Photofrin tends to be applied to head human part and thoracic part affected by cancer [ 26 ]. The Second Generation Photosensitizers, includes porphyrins and related compounds porphycenes, chlorins, phthalocyanines, so onmany of them being under clinical tests.
TPPS4 exhibited lower photochemical efficiency than meso-substituted porphyrins containing fewer sulphonated groups [ 28 ]. Except the free-bases, the porphyrins can be chelated with a variety of metals, the diamagnetic ones enhancing the phototoxicity. Paramagnetic metals are shortening the lifetime of the triplet state and as result can make the dyes photoinactive [ 21 ].
The presence of axial ligands to the centrally coordinated metal ion is often advantageous, since it generates some degree of steric hindrance to intermolecular aggregation, without impairing the photophysical properties of the dye [ 21 ]. Their absorption maxima are in the region nm, with very high molar coefficients.
A representative compound is aluminium phthalocyanine tetrasulphonated AlPcS4, commercially known as Photosens, in spite of its skin sensitivity, proper absorption maxima at nm, it is well applied in Russian clinics for stomach, skin, oral and breast cancers [ 33 ]. Another clinical phthalocyanine is silicon phthalocyanine 4 Pc4 which was successful tested in different skin cances pre-malignant - actinic keratosis, Bowen disease or even gastric cancer new treatments malgnant forms of cutaneous cancers [ 343536 ].
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The central metal ions play an important role in gastric cancer new treatments photophysical properties of phthalocyanines. In metallophthalocyanines the central metal M has one or two axial ligands or one or more ring substituents or both.
When a diamagnetic ion is in the center of the ring e. Silicon phthalocyanine allows two appropriate axial ligands, which forbid the ring staking which decrease the clinical efficiency [ 41 - 44 ]. The triplet-state lifetimes of an axially substituted silicon phthalocyanine typically vary from to μs and the yields from 0. Some synthetic silicon phthalocyanine and naphthalocyanine Figure 2 have been used in some laboratory experuiments on K culture gastric cancer new treatments with excellent results [ 4546 ].
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Third generation photosensitizers contains available drugs that are modified them with antibody conjugates, biologic conjugates, etc. These terms are still being used although not accepted unanimously and dividing photosensitizing drugs into such generations may be gastric cancer new treatments confusing. The nanostructures are increasingly being used as carriers for the development of 3rd generation PS, as the most important drug delivery systems used as carriers for PS in the field of anticancer PDT.
Several aspects of the oncological and surgical management are still controversial and so gastric cancer represents a challenge for the surgeon. This book aims to delineate the state of the art in the surgical and oncological treatment of gastric cancer, describing the new TNM staging system, the extent of visceral resection and lymphadenectomy focusing on the different open and minimally invasive surgical techniques and discussing gastric cancer new treatments chemohyperthermia and neoadjuvant and adjuvant treatment.
Figure 2. Nanoparticles have unusual properties that can improve the drug delivery. Hard nanoparticles Inorganic Nanoparticles is the generic term for several nanoparticles including for example metal oxide- and non-oxide ceramics, metals, gold and magnetic nanoparticles.
Ceramic nanoparticles: Ceramic-based nanoparticles have some advantages over organic carriers: particle size, shape, porosity, and mono-dispersibility. They are water-soluble, extremely stable, and known for their compatibility in biological systems without being subjected to microbial attack.