Autori: R.M.Ion, M.Grigorescu, F.Scarlat, V.I.R.Niculescu, Fl.Scarlat

Editorial: Editurea Academiei Romane, Romanian Journal of Physics, 46 (9-10), p.637-646, 2001.

Rezumat:

Imensul potential al porfirinelor pentru aplicatii medicale si biologice, implica metode sintetice de dezvoltare a elaborarii porfirinelor cu proprietati fotofizice si fotochimice extinse si versatile.
Porfirinele sintetice solubile in apa apar ca bune modele pentru crearea de noi medicamente eficiente pentru terapia fotodinamica a cancerului (PDT). La iradiere, porfirinele utilizate ca medicamente induc clivajul ADN in principal prin mecanism de tip II (mediat de oxigen singlet)
si mai rar prin mecanism de tip I (mediat de radicali).Cei mai
utilizati sensibilizatori sunt cei anionici, care nu se pot lega puternic de ADN si care se utilizeaza pentru studiul distrugerii sensibilizate a ADN-ului. Actiunea fotodinamica a porfirinelor asupra ADN conduce la o varietate de schimbari a proprietatilor lor incluzand scaderea puunctelor de topire a temperaturii si a proprietatilor de absorbtie si emisie.
In prezenta lucrare se estimeaza interactiile dintre ADN si doua porfirine sulfonate (solubile in apa) 5,10,15,20-tetra-p-sulfonato-fenil porfirina (TSPP) si 5,10,15,20-tetra-para sulfonato-naftil -porfirina (TSNP)] prinintermediul unor tehnici adecvate : Spectrofotometria UV-Vis, tehnica punctului de topire, tehnici de fluorescenta si fluorescenta cu polarizare. Influenta speciilor agregate a porfirinelor in timpul complexarii cu ADN, este de asemenea evaluata in aceasta lucrare, fiind mult mai pronuntata pentru TSPP decat pentru TSNP. De asemenea, reactia de fotodegradare a porfirinelor implicate in aceste studii care joaca un rol important in timpul procesului PDT, este evaluata adecvat.
The great potential of porphyrins for medical and biological applications, involve widely developed synthetic methods for porphyrin elaboration with extensive and versatile photophysical and photochemical properties. Synthetic water-soluble porphyrins appear to be good models in order to create new efficient drugs for photodynamic therapy of cancer (PDT).
Under irradiation, the porphyrins used as drugs induce DNA cleavage mainly via a Type II (singlet oxygen mediated) mechanism, and more rarely a Type I (radicals mediated) mechanism. The comonly used sensitizers are anionic dyes and even they do not strongly bind with DNA, they have been extensively used to study the photosensitized damage of DNA.
The photodynamic action of porphyrins on DNA leads to a variety of changes in their properties including a decrease in the melting point temperature or in viscosity due to chain breaks, and also, changes in the absorption and emission properties.
In the present paper it is estimated the distinct interactions between DNA and two sulfonated porphyrins (water-soluble) [5,10,15,20-tetra-sulphonated-phenyl-porphyrin (TSPP) and 5,10,15,20-tetra-sulphonated-naphthyl-porphyrin (TSNP)] by means of adequate techniques: UV-Vis spectrophotometry, melting point technique, fluorescence and polarization fluorescence techniques. The influence of the aggregated forms of porphyrins during the complexation with DNA, is evaluated in this paper, being more pronounced for TSPP than for TSNP. Also, the photodegradation reaction of porphyrins involved in such studies, which play an important role during PDT process, is properly evaluated.

Cuvinte cheie: porfirine, sensbilizare, ADN // porphyrins, photosensitization, DNA