Synthesis and properties of novel (oxido)pyridyl porphyrins for use in photodynamic therapy

Fotodinamička terapija (PDT) predstavlja jedan od suvremenijih pristupa liječenju tumora. Komponente fotodinamičke terapije su fotosenzibilizator (PS), kisik i svjetlo, tri zasebno netoksične kompone, koje zajedno stvaraju toksičan učinak na stanice. Za uspješnu fotodinamičku terapiju bitan je odabir fotosenzibilizatora kao i njegova lokalizacija u stanicama. Porfirini, tetrapirolni makrociklički spojevi, zbog svojeg karakterističnog apsorpcijskog i emisijskog spektra, kao i visokog prinosa singlet kisika, predstavljaju vrlo učinkovite fotosenzibilizatore za PDT. Amfifilni porfirini su vrsta porfirina koji se sastoje od hidrofilnog dijela koji omogućuje bolju topljivost u vodi, te hidrofobnog dijela koji služi lakšem prolasku kroz staničnu membranu. Sinteze amfifilnih porfirina su relativno jednostavne, no problem predstavlja pročišćavanje dobivenih spojeva. U sintezi (oksido)piridilporfirina konjugiranih lancima masnih kiselina, kao glavni problem se pokazala N-oksidacija piridilnih dušikovih atoma, odnosno pročišćavanje produkata. U ovom radu optimizirane su reakcije N-oksidacije različitih 3-piridilporfirina te ispitani alternativni putevi sinteze novih (oksido)piridilporfirina. Sintetiziranim porfirinima su ispitana fotofizikalna svojstva, te je utvrđeno da svi sintetizirani piridilporfirini imaju visok prinos singletnog kisika. Testom internalizacije (oksido)piridilporfirina primijećen je problem netopljivosti dobivenih spojeva u vodi i puferima, te je došlo do agregacije spoja na staničnoj membrani i spoj nije internalizirao u stanicu. Također, pokazalo se da je spoj vrlo toksičan i pri malom intezitetu svjetla zbog nevijabilnog izgleda stanica tijekom testa.Photodynamic Therapy (PDT) is one of the most recent approaches to treating tumors. Components of the PDT are photosensitizer (PS), oxygen and light, three non-toxic components that together can produce a toxic effect on the cells. For successful photodynamic therapy, it is essential to select a photosensitizer with good localization in cells. Porphyrins, tetrapyrrole macrocyclic compounds, due to their specific absorption and emission spectra, as well as the high yield of singlet oxygen, represent a highly efficient photosensitizers for PDT. Amphiphilic porphyrins are type of porphyrins that consist of hydrophilic part that allows better water solubility and hydrophobic part of the molecule that facilitates passing through the cell membrane. The synthesis of amphiphilic porphyrins is relatively simple, however purification of the compounds is often very difficult. In the synthesis of (oxidopyridyl)porphyrins conjugated with fatty acid chains, the main problem that occured was N-oxidation of the pyridyl nitrogens, and purification of the products. In this work, attempts for optimization of N-oxidation reactions of various 3-pyridylporphyrins and alternative pathways of synthesis of new (oxidopyridyl)porphyrin are described. Photophysical properties of the synthesized porphyrins were tested, and it was found that all synthesized pyridyporphyrins produce singlet oxygen in high yields. In the internalization test it was found that synthesized (oxido)pyridylporphyrin was not sufficiently soluble in water and buffers, and did not internalize into the cell probably due to the aggregation of the compound on the cell membrane. Also, it was shown that the compound is very toxic even with low intensity of light used for photoactivation, as shown by appearance of non-viable cells during the test