RESUMEN
Two mathematical models describing the accumulation kinetics of hydrophobic sensitizers in the cell membrane and cytoplasm and the influence of intra- and extracellular pH values on intracellular accumulation are suggested. Numerical calculations were done for hematoporphyrin (Hp) as an example. When compared with the experimental data, both models gave satisfactory results describing the accumulation time and level. A biphasic character of the sensitizer accumulation process was obtained as a result of the difference in the accumulation times characteristic for the plasma membrane and cytoplasm. The ratio of characteristic times was determined by the ratio of membrane and cytoplasm volumes and a "water-lipid" partition coefficient reflecting the height of the membrane barrier for the sensitizer penetration through the plasma membrane lipid bilayer. Generally, the enhanced uptake of Hp molecules by cells was obtained when both extracellular and intracellular pH (pHin) values were lower than the physiological ones. A "selectivity" of accumulation was achieved in "tumor" cells for reasonable pHin values (about 6.0). But when compared with the experimental data, the value of selectivity was not high enough, indicating that, though the pH value is an important factor in Hp intracellular accumulation, it might be less important as a factor for selectivity of Hp accumulation in tumors.
Asunto(s)
Modelos Biológicos , Neoplasias/metabolismo , Fármacos Fotosensibilizantes/farmacocinética , Fenómenos Químicos , Química Física , Cómputos Matemáticos , Fotoquimioterapia , Fármacos Fotosensibilizantes/químicaRESUMEN
The interactions between haematoporphyrin (HP) and bilayer lipid membranes (BLM) were studied. A weak effect of HP on BLM conductivity was observed at HP concentrations ranging between 10(-6) and 3 x 10(-5) mol/l. Modulus of elasticity in the direction normal to the membrane plane (E perpendicular) and dynamic viscosity coefficient (eta) were measured, both exhibiting HP-induced decrease by 22-31% in the dark. In this case, membrane potential Vm became negative and reached a value close to -50 mV. Under illumination by low-intensity (1 mW) He-Ne laser (lambda = 632 nm) the values of parameters E perpendicular and eta of the HP-modified membranes increased by 41-66%, and Vm decreased to -20 mV. Upon removing HP from the solution by perfusion, irreversible changes in mechanical properties of the HP-modified membranes induced by the laser light were observed. The reason could be the formation of stable complexes of HP with the lipid molecules. HP binds to membrane noncooperatively, with a binding constant K approximately 10(5) l/mol.
Asunto(s)
Hematoporfirinas/química , Membrana Dobles de Lípidos/química , Sitios de Unión , Fenómenos Biomecánicos , Elasticidad , Técnicas In Vitro , Cinética , Potenciales de la Membrana , ViscosidadRESUMEN
Water-soluble phthalocyanines and phthalocyanines linked to targeting monoclonal antibodies are considered to be one of the most promising photosensitizers in photodynamic therapy. Here the spectrum characteristics of sulphonated aluminium phthalocyanine and its protein conjugate in the pH range 1.8-12.0 in solution have been studied. The pK values are determined.
Asunto(s)
Aluminio/química , Anticuerpos Monoclonales/química , Colorantes Fluorescentes/química , Inmunotoxinas/química , Indoles/química , Compuestos Organometálicos/química , Fármacos Sensibilizantes a Radiaciones/química , Animales , Ratones , Espectrometría de FluorescenciaRESUMEN
The results of a laser picosecond microspectrofluorometric study of the spectral and kinetic characteristics of haematoporphyrin (Hp) fluorescence at various sites in cultured SPEV cells and phosphatidylcholine liposomes are presented. The computer-controlled detection system is based on the single-photon counting method with picosecond time resolution. In aqueous medium, the Hp fluorescence spectrum is characterized by two bands at 615 and 675 nm. In living cells and liposomes, Hp fluorescence is red shifted to 630 and 690 nm. In addition a new band at 665 nm is detected. The dependence of this band on the incubation time and Hp concentration was investigated. The fluorescence decay kinetics of Hp in a culture medium, liposome and a cell nuclear membrane were measured. Possible Hp aggregate formation in the lipid bilayer and its implications are discussed.