Mjerenje stvaranja singletnog kisika upotrebom fotodegradacijske metode

Fotodinamička terapija (PDT) suvremen je pristup liječenju tumora koji se oslanja na interakciju svjetlosti određene valne duljine s molekulom fotosenzibilizatora koja iz svog pobuđenog tripletnog stanja pobuđuje molekularni kisik na više energetsko stanje. U tom procesu nastaje visoko reaktivni singletni kisik. Terapijski efekt postiže se lokaliziranim citotoksičnim djelovanjem singletnog kisika na tumorsko tkivo. ROS-ovi poput singletnog kisika razaraju proteine, lipide, nukleinske kiseline i ostale stanične komponente na mjestu djelovanja. Učinkovitost fotodinamičke terapije nastoji se poboljšati modifikacijom svojstava fotosenzibilizatora. Porfirini su zbog svojeg karakterističnog apsorpcijskog i emisijskog spektra posebice zanimljivi kandidati za fotosenzibilizatore. Odabir porfirina koji su potencijalni kandidati za PDT zahtijeva razvitak pouzdanih metoda mjerenja produkcije singletnog kisika. U ovom je radu provedeno indirektno mjerenje produkcije singletnog kisika dvaju N-metiliranih i N-oksidiranih porfirina u četiri različita otapala korištenjem fotodegradacijske metode. Fotodegradacijska metoda mjerenja produkcije singletnog kisika oslanja se na mjerenje pada fluorescencije kontrolne boje, u ovom slučaju 1,3-difenilizobenzofurana, u prisutnosti singletnog kisika. Prednost ove metode jest njena praktičnost i komercijalna dostupnost, ali treba imati na umu da rezultat ovisi o uvjetima prilikom mjerenja. Uspoređena je topivost porfirina u otapalima s obzirom na N-supstituent, te je promatran utjecaj topivosti i lipofilnosti N-supstituiranih porfirina na produkciju singletnog kisika. Utvrđeno je da svi ispitivani porfirini imaju značajan kvantni prinos singletnog kisika barem u nekima od ispitivanih otapala, te da produkcija singletnog kisika uvelike ovisi o topivosti porfirina u određenom otapalu.Photodynamic therapy (PDT) is a contemporary approach to cancer treatment that relies on interaction of light of a specified wavelength with a photosensitizer molecule that has the ability to excite molecular oxygen to a higher energy state. During that process, molecular oxygen receives energy from the photosensitizer in its excited triplet state, thus becoming highly reactive singlet oxygen. The therapeutic effect is achieved by cytotoxic activity of singlet oxygen targeted at tumor tissue. Reactive oxygen species such as singlet oxygen are capable of damaging proteins, lipids, nucleic acids and other cellular componets at the site of impact. By modifying the properties of the photosensitizer one can improve the effectiveness of PDT. Due to ther characteristic absorption and emission spectra, porphyrins are particularly interesting candidates for usage as photosensitizer molecules. Choosing a porphyrin that is a potential candidate for PDT requires development of reliable methods for measuring singlet oxygen production. In this work, singlet oxygen production by two N-methylated and two N-oxidated porphyrins in four solvents was measured indirectly using photodegradation method. The aforementioned method relies on measuring the decrease of fluorescence emission by control dye, in this case DPBF, in the presence of singlet oxygen. The advantage of this method is simple application and commercial availability, although it has to be noted that the result vastly depends on conditions during experiment. Solubility of porphyrins in various solvents was compared in regards to their N-substituent as well as the effect of solubility of N-substituted porphyrins on singlet oxygen production. It was found that all of the examined porphyrins have significant singlet oxygen production at least in some of the solvents. Also, it was shown that singlet oxygen production depends on solubility of the porphyrin in a given solvent