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Photosensitizer - Essay Example

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In this modern era of industrialization and modified lifestyles, human beings come across various agents that could turn out to be hazardous for health. These agents could be carcinogenic, teratogenic or may damage tissues. Carcinogenic agents promote the formation of tumors…
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Download file to see previous pages The most imperative aspect of this therapy is nontoxic nature of photosensitizers. Production of singlet oxygen is of paramount significance therefore, agents promoting the formation of singlet oxygen as well as two photons absorption are considered to be highly efficient in the therapy. Numerous receptor molecules are over-expressed in tumor cells which are of considerable importance. Peptides recognizing these receptors are conjugated with photosensitizers to reach the target cells. However, after a certain interval when photosensitizers in normal cells degenerate, the tumor cells are exposed to a particular wavelength of light which cause the excitation of the photosensitizer resulting in the formation of cytotoxic singlet oxygen. This oxygen is very reactive and cause cytotoxicity of the diseased or cancerous cells. The phenomenon is exploited in photodynamic therapy to eliminate the side-effects imposed by other cancer therapeutic measures.
Photosensitizer or photosensitizing agent is a molecule or a drug that is capable of producing a chemical alteration in another molecule or cell during the photochemical process. Photosensitizers, when exposed to a particular wavelength of light. Photosensitizers generate a form of cytotoxic oxygen that can kill the adjoining cells in the living organism. This property of photosensitizers is exploited to treat numerous superficial and localized cancers together with certain noncancerous conditions (Lau et al, 2014).
Photosensitizers are involved in medical science under the name photodynamic therapy or phototherapy, as the therapy involves insertion of certain light sensitive non-toxic chemical agents called photosensitizers, it is also known as photochemotherapy. As long as photosensitizers are not exposed to light they remain non-toxic, in the presence of certain wavelength of light they generate cytotoxic oxygen which can destroy, cancerous cells as well as other contaminated cells including ...Download file to see next pagesRead More
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...oxygen with the assist of photosensitizers, like Rose Bengal. Such compounds use light to convert triplet into singlet oxygen. Due to low activation energy and its electron configuration singlet oxygen is a highly reactive molecule and can readily form bonds with a number of organic molecules. It is less stable than the normal form of oxygen. However, depending on the environment singlet oxygen has the possibility to exist for more than one hour at room temperature. (Schweitzer, et al., 2003) One of the reactions that singlet oxygen can take part in, is the oxidation of amino acid residues of proteins. Cysteine and methionine residues are particularly susceptible to such forms of oxidation. In contrast to oxidation of...
12 Pages(3000 words)Essay


...? Table of Contents Table of Contents 2 Introduction 3 Singlet and triplet oxygen 4 Formation of singlet oxygen 6 Type I and Type II oxidation pathways 8 Photosensitizers 10 Aromatic hydrocarbons and organic dyes 10 Phthalocyanines, porphyrins and other tetrapyroles 14 Transition metal complexes as photosensitizers 16 Semiconductors 17 Immobilized photosensitizers 17 Methionine oxidation 18 Determination of singlet oxygen 21 Aims 24 Materials and methods 25 General Information 25 Oxygen measurements 25 Singlet oxygen consumption at different methionine concentrations 26 Singlet oxygen consumption induced by laser. 27 Results and discussion 27 Conclusions 46 References: 48 Abstract The...
41 Pages(10250 words)Essay

ESBL positive Escherichia coli and Klebsiella interaction with human urothelial cells

...which also damage the healthy cells can be avoided. A promising and effective alternative treatment that has been used for many years is photosensitizing porphyrin derivatives in combination with laser light in the treatment of tumours (reviewed in Wainwright, 1998). This therapy arose from the observation that porphyrins fluoresce during surgery. The porphyrin-laser light combination results in the production of reactive oxygen species that attack the tumour cells, resulting in death of the cells. This approach is known as photodynamic therapy (PDT). This therapy is target specific, because the porphyrin derivatives used are tumour-specific and the laser light can be directed to the tumour mass itself. Therefore, if...
22 Pages(5500 words)Literature review

The use of free radicals in the treatment of disease

...radical by enzymes. In healthy cells the produced free radical reacts with oxygen and breaks down into inactive molecules. In contrast to oxygen rich normal cells, in hypoxic tumour cells the free radical collapses to form an active drug and the “trigger” residue. As an example of the drug that uses this mechanism tirapazamine can be mentioned (Harrison, 2002). It has the ability to selectively kill tumour cells leaving normal cells unharmed. The effectiveness of this drug can be elevated if used in conjunction with radiotherapy or chemotherapy (Hayakawa, 2001). Another perspective method to treat cancer using free radicals is to use a photodynamic therapy. In this kind of treatment initially a photosensitizer drug is...
8 Pages(2000 words)Literature review

Determining the Rates of Biosynthesis of Porphyrin in Relation to -Aminolaevulic Acid Dehydrate

...determining step of the reaction pathway. Consequently, ALAS over expression in eukaryotic and prokaryotic cells usually results into accumulation of photosensitizing heme precursor photoporphyrin IX. Therefore, it is worth determining whether these properties can potentially lead to the application of the ALAS variants or ALAS within the photodynamic therapy of tumors among other dysplasia. Porphyrin biosynthesis rate in mammals is usually controlled the pyridoxal 5?-phosphate-dependent enzyme 5-aminolevulinate synthase activities. Therefore, it is assumed that the turnover of this enzyme is controlled by the application conformational dynamics site loop and is highly conserved as have been reported in other research...
6 Pages(1500 words)Essay

Differences between chronic periodontitis, aggressive periodontitis and developmental or acquired deformities and conditions spe

...that when paramecia were exposed to certain chemicals and certain light wavelengths would then be negatively affected. This new process works under similar principles. The process involves a photosensitizer or a photoactivable compound, which targets specific bacterial cells and once activated by light, on a particular wavelength, causes a formation of free radicals, which, ultimately, leads to a toxic reaction within the targeted cells. This process is showing great results, however, only upon the bacteria studied. Further research is needed to determine its efficiency in relation to a broader use.(Novaes, Schwartz-Filho,, de Oliveira, Feres, Sato & Figueiredo, 2012) Chronic periodontitis is seldom cured. In most cases...
7 Pages(1750 words)Research Paper


.... For instance, UVB is often administered with topical corticosteroids (Meola et al., 1991), or with short-contact dithranol therapy or with calcipotriene (Hecker and Lebwohl, 1997). However, caution must be exercised when combining phototherapy with other agents because the possibility of increased photosensitivity and burning or shortened duration of remission (Honigsmann, 2001). A major breakthrough in the treatment of psoriasis was made with the introduction of Psoralen plus UVA (PUVA). PUVA was developed in the 1970's and involves the ingestion of 8-methoxypsoralen (8-MOP), a classical photosensitizer, followed by irradiation with UVA. UVA consists of radiation wavelengths of 320 - 400 nm. Some...
20 Pages(5000 words)Essay

Photochemistry of Ruthenium Complexes

.... Energy transfer involves the transfer of energy from a higher excitation state to a lower excitation state. Ru(bpy)3+2 has been studied as a photosensitizer for both the oxidation and reduction of water. Upon absorbing a photon, Ru(bpy)3+2converts to the triplet state, Ru(bpy)3+2* which transfers an electron from a ligand, to an oxidant in solution. Ru(bpy)3+2* which has high reducing power can reduce many compounds including methylviologen, a renewable electron carrier (Ohtani, Kobayashi and Ohno). This reaction has been utilized in photocatalysis. The transfer of electrons oxidizes Ru(bpy)3+2 to Ru(bpy)3+3 while producing an anion in the solution. Free energy is produced by the electron transfer which is used to...
7 Pages(1750 words)Essay

Exam papers

...Section A a) Explain, with examples, why singlet oxygen is important in the degradation of organic molecules in the environment. Unlike the oxidative properties of the ground-state oxygen, singlet oxygen which by nature works in its excited state is capable of degrading molecules through photosensitization. A singlet oxygen is typically produced by a photosensitizer pigment with which such element facilitates the sun’s detrimental impact upon organic matters in significant number. Concrete instances would be the study conducted on the selective oxidative degradation of organic pollutants by singlet oxygen-mediated photosensitization as well as the eradication of cancer cells by singlet oxygen during photodynamic therapy. (b) Give... ...
7 Pages(1750 words)Essay

Cancer Spotting Googles by Dr. Samuel Achilefu

...., Ohulchansky, T., Potter, W., Zhong, T. & Pandey, R. K. (2005). A novel approach to a bifunctional photosensitizer for tumor imaging and phototherapy. Bioconjugate chemistry, 16(5), 1264-1274. EurekAlert (2014). Samuel Achilefu, WUSTL scientists develop high-tech glasses that detect cancer cells during surgery, Newsroom (2014). Special glasses help surgeons ‘see’ cancer​​​​​​​​​, Washington University in St.Louis, retrieved from Preidt, R. (2014). Experimental Eyewear Helps Surgeons See Cancer, Study Says, Health US News Store. Retrieved from Sharon, R. (2011) profiles in Cancer research, National cancer Institute....
10 Pages(2500 words)Essay
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