Search PubMed⌕ Search

Biomedical subjects

G Jori

Publications and source records attributed to G Jori.

At least 91 records · Page 5Linked to original sources
PubMed1991

Liposomes as models to study the distribution of porphyrins in cell membranes.

Unilamellar liposomes of dipalmitoylphosphatidylcholine (DPPC) have been chosen as suitable models of cell membranes in studies aimed at defining the influence of specific parameters on the distribution properties of selected hydrophobic photosensitizers, namely hematoporphyrin (HP) and protoporphyrin (PP), in normal and tumour tissues. To better mimic in vivo situations, DPPC liposomes were sometimes mixed with cardiolipin (Card) or cholesterol (Chol). Two techniques were mainly used: the quenching of porphyrin fluorescence by methyl viologen, which can discriminate different dye populations inside the vesicles as well as their degree of accessibility to the external medium, and the polarization of porphyrin fluorescence, which gives information on the dye microenvironment through its degree of rotational freedom. The nature of the porphyrin binding sites in each phospholipid monolayer is found to be a function of the degree of hydrophobicity and the concentration of the dye as well as the chemical composition of the liposomes. In DPPC and DPPC-Chol liposomes, all PP molecules are deeply embedded into very rigid, hydrophobic domains of the inner lipid monolayer. Only in the presence of cardiolipin, for [PP] greater than 2.5 microM, a partial shift of the dye molecules towards the outer lipid monolayer is observed. HP mostly localizes at the inner lipid/water interface in all liposomes: at very low concentrations ([HP] approximately equal to 0.5 microM) the dye is bound to the polar heads of the lipids through its carboxylate groups, leaving the rest of the molecule dissolved in the inner aqueous pool. At higher concentrations, HP molecules change their orientation: the ionized propionic chains still interact with the polar heads while the hydrophobic core lies in the lipid phase in DPPC and DPPC-Card vesicles. HP incorporated into DPPC-Chol mixed liposomes projects from the inner lipid phase into the aqueous compartment in all the concentration range studied by us. A very small fraction of HP population (corresponding to 5-10% of the overall fluorescence) is localized at the water/lipid external interface in DPPC and DPPC-Chol liposomes. This fraction increases in the presence of cardiolipin (up to 30% of the overall fluorescence). The possible implications of these findings for the nature of the targets of photosensitization in cell membranes are discussed.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

Photochemical and photosensitizing properties of monomeric and dimeric Sn(IV)-protoporphyrin.

Sn(IV)-protoporphyrin IX (Sn-Pp) in aqueous media exists as a mixture of monomeric and dimeric species, which can be readily distinguished on the basis of their absorption maxima at around 410 and 386 nm respectively. Sn-Pp dimers prevail as the pH is decreased and are characterized by a lower fluorescence quantum yield, a larger tendency to undergo photobleaching and a reduced photosensitizing efficiency compared with the Sn-Pp monomer. The photosensitizing action of Sn-Pp appears to involve the intermediacy of singlet oxygen (1O2) as shown by photo-oxidation studies with N-acetyl-tryptophanamide in light and deuterated water solutions. Using 1,3-diphenyl-isobenzofuran as a substrate, the quantum yield of 1O2 generation by monomeric Sn-Pp was found to be about 0.6.

Metalloporphyrins↗
PubMed1991

Studies on the mechanism of the hematoporphyrin-sensitized photooxidation of 1,3-diphenylisobenzofuran in ethanol and unilamellar liposomes.

The 5 microM hematoporphyrin-sensitized photooxidation of 1,3-diphenylisobenzofuran (DPBF) was studied in homogeneous ethanolic solutions and in aqueous dispersions of unilamellar liposomes of dipalmitoylphosphatidylcholine; both the porphyrin and DPBF are embedded in the phospholipid bilayer. The rate and quantum yield of DPBF photooxidation were found to increase upon increasing the substrate concentration and were higher in the liposome system, while they were unaffected by the fluidity of the phospholipid bilayer. Time-resolved spectroscopic measurements showed that the photooxidation of DPBF in ethanol solution proceeds by a type II O2(1 delta g)-involving mechanism. In the liposomal vesicles the high local concentration of hematoporphyrin (Hp) and DPBF in the phospholipid bilayer (ca 2000-fold higher than the stoichiometric concentration) enhances the probability of energy transfer from triplet Hp to DPBF with generation of triplet DPBF; hence O2 (1 delta g) formation can be promoted by both triplet Hp and triplet DPBF. A minor fraction of triplet DPBF quenchings appears to generate radical species which propagate DPBF damage by chain reaction.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

A comparison of fluorescence methods used in the pharmacokinetic studies of Zn(II)phthalocyanine in mice.

The pharmacokinetics of Zn phthalocyanine (ZnPc) encapsulated in dipalmitoyl-phosphatidylcholine (DPPC) liposomes, injected intravenously in Skh:HR-1 nude mice, was monitored by two in vitro techniques and one in vivo technique, all based on fluorescence spectroscopy. The in vitro methods involve either fluorescence measurements on thin tissue sections or on extracts from these tissues. The in vivo method involves the fluorescence measurement at the skin surface. Both in vitro techniques gave similar results which are consistent with previous findings on the pharmacokinetic behavior of ZnPc. The liver and spleen showed rapid ZnPc concentration increases, reaching a maximum level in 30 min. or less post drug administration. Relatively little ZnPc was detected in the skin, fat or muscle, the maximum concentration occurring at 12 h. In vivo fluorescence reached a maximum intensity approx. 6 h post injection at the mid-chest analysis site and at 12 h in the thigh. The in vivo measurements at two different anatomical sites showed pharmacokinetic behavior that reflects an overall integrated fluorescence originating from several tissue sites.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1990

Photosensitizing activity of water- and lipid-soluble phthalocyanines on Escherichia coli.

Escherichia coli, as most Gram-negative bacteria, is insensitive to the photosensitizing action of both lipid-soluble Zinc-phthalocyanine (Zn-Pc) and water-soluble Zinc-mono/disulfonated phthalocyanine (Zn-PcS). Photosensitivity can be induced by alteration of the outer membrane, as obtained by either induction of competence or treatment with Tris-EDTA. Both phthalocyanines largely bind at the level of the cytoplasmic membrane; however, Zn-PcS shows a superior photosensitizing activity as compared with Zn-Pc. Biochemical analyses performed on irradiated cells suggest that the cytoplasmic membrane is an important target of the photoprocess, while DNA is not involved.

Bacterial Outer Membrane Proteins↗
PubMed1990

Delivery of the tumour photosensitizer zinc(II)-phthalocyanine to serum proteins by different liposomes: studies in vitro and in vivo.

Zn-phthalocyanine (Zn-Pc) incorporated into liposomes of different phospholipids has been incubated in vitro with human serum and administered i.v. to rabbits. In both cases, chromatographic and density gradient ultracentrifugation studies indicate that Zn-Pc is almost exclusively bound by the 3 major lipoprotein components of the plasma (VLDL, LDL and HDL). The amounts of Zn-Pc recovered from the different lipoprotein fractions reflect their relative concentration in the serum. The presence of 20% moles of cholesterol in liposomes of dipalmitoyl phosphatidylcholine (DPPC) optimizes the release of Zn-Pc to LDL. This fact is important for enhancing the selectivity of drug delivery to tumors since LDL display a preferential interaction with neoplastic cells.

Animals↗
PubMed1990

Factors influencing the distribution pattern of porphyrins in cell membranes.

The mechanism of the sensitizer-membrane interactions has been studied by following the distribution properties of selected porphyrins, including haematoporphyrin (HP) and protoporphyrin (PP), into unilamellar liposomes of dipalmitoyl phosphatidylcholine (DPPC). The endomembrane distribution of HP and PP has been checked as a function of the membrane fluidity and composition by fluorescence polarization and quenching techniques. At porphyrin concentrations below 0.5 microM, HP and PP exclusively localize in the inner phospholipid monolayer; at higher concentrations, the outer monolayer also becomes populated. The porphyrin binding sites in liposomes, however, are different for HP and PP: HP preferentially distributes into water-accessible lipid regions, while PP localizes in the most hydrophobic loci of the lipid matrix. A porphyrin redistribution occurs when the fluidity properties of the liposomes are changed by addition of cholesterol or cardiolipin. In DPPC-cholesterol vesicles, all HP molecules dissolve in DPPC-rich regions while all PP molecules partition in cholesterol-rich environments. In DPPC-cardiolipin vesicles both porphyrins preferentially localize in regions accessible to the external medium. The effect of the nature of the carrier on porphyrin distribution in membranes has been studied by following the uptake and photosensitization properties of free and DPPC-incorporated PP and HP with rat liver mitochondria. The porphyrin photosensitizing efficiency has been checked by following the impairment of the respiratory function of mitochondria upon irradiation. Liposome-bound HP is less active than aqueous HP in determining membrane photodamage in mitochondria. On the contrary, aqueous PP is a very poor sensitizer as compared to a DPPC liposome-entrapped drug.(ABSTRACT TRUNCATED AT 250 WORDS)

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1990

Photothermal sensitizers: possible use in tumor therapy.

Photothermal damage of tissues or endotissular compartments may be induced by pulsed irradiation of either endogenous chromophores (e.g. hemoglobin, melanin) or externally added dyes; the latter should have short triplet lifetimes and mainly decay from electronically excited states by nonradiative pathways. Potential photothermal sensitizers are some metallo derivatives of porphyrins and porphyrinoid compounds, azo dyes and triphenylmethane derivatives. These dyes have the additional property of significant absorbance at wavelengths longer than 600 nm, which can penetrate deep into biological tissues. Spatial confinement of the photothermal process depends on the absorption coefficient of the photoexcited chromophore and its thermal relaxation time. Present evidence indicates that the selective photothermal damage of macromolecules or subcellular organelles requires pulsed excitation at picosecond or nanosecond regimes, while microsecond or millisecond domains are effective in the case of cells or similar structures. The possible use of photothermal sensitization in the treatment of tumors is briefly discussed.

Animals↗
PubMed1990

Zn(II)-phthalocyanine as a photodynamic agent for tumours. II. Studies on the mechanism of photosensitised tumour necrosis.

The mechanism of tumour necrosis photosensitised by liposome-delivered Zn(II) phthalocyanine (Zn-Pc) has been studied in mice bearing a transplanted MS-2 fibrosarcoma. Ultrastructural analyses of tumour specimens obtained at different times after red light-irradiation (300 J cm-2, dose-rate 180 mW cm-2) indicate an early (3 h) photodamage of malignant cells especially at the level of the mitochondria and rough endoplasmic reticulum. The cellular damage becomes more evident between 6 h and 15 h after photodynamic therapy. On the other hand, the capillaries supplying the tumour tissue are modified at a much slower rate and appear to be severely damaged only after 15 h from irradiation, when the whole tissue becomes necrotic. Occasionally, mildly damaged capillaries are observed even at 72 h after irradiation. These findings support the hypothesis that low density lipoproteins (LDL) play a major role in the delivery of Zn-Pc to the tumour tissue; the photosensitiser is released specifically to malignant cells as a consequence of a receptor-mediated endocytosis of LDL.

Animals↗
PubMed1990

Liposome-delivered Si(IV)-naphthalocyanine as a photodynamic sensitiser for experimental tumours: pharmacokinetic and phototherapeutic studies.

The pharmacokinetic behaviour and phototherapeutic effectiveness of bis(di-isobutyloctadecylsil-oxy)-2,3-naphthalocyanatosilicon (iso-BOSiNc) incorporated into dipalmitoyl-phosphatidylcholine (DPPC) liposomes have been studied in Balb/c mice bearing an MS-2 fibrosarcoma. We found that iso-BOSiNc i.v.-injected at a dose of 0.5 mg kg-1 b.w. is preferentially transported by serum lipoproteins; in particular, the photosensitiser is associated with LDL (57.8% of total recovery in the serum) and HDL (35.7%) while minor amounts are associated to VLDL (2.63%) and other serum proteins (3.89%), Iso-BOSiNc concentrations greater than 1 microgram g-1 of tissue are recovered from the tumour at 12-48 h after administration while the ratio of iso-BOSiNc concentration in tumour and peritumoral tissue is greater than 10. Upon increasing the injected dose, the additional iso-BOSiNc is almost exclusively bound by HDL, which leads to large uptake of the photosensitiser by liver and spleen. The efficiency of iso-BOSiNc as a photodynamic agent was measured upon irradiation with a different dose-rate for a total light dose of 450 J cm-2. The extent of tumour necrotic area increases as a function of the time after the end of PDT treatment and reaches a maximum level after about 24 h. Moreover, the necrotic area is linearly dependent on the irradiation dose-rate up to 100 mW cm-2. In all there is substantial evidence that iso-BOSiNc delivered in a liposomal dispersion is a highly effective photosensitizer for PDT of tumours.

Animals↗
PubMed1990

Liposome- or LDL-administered Zn (II)-phthalocyanine as a photodynamic agent for tumours. I. Pharmacokinetic properties and phototherapeutic efficiency.

The pharmacokinetics of Zn-phthalocyanine (Zn-Pc) in mice bearing a transplanted MS-2 fibrosarcoma has been studied using dipalmitoyl-phosphatidylcholine (DPPC) liposomes and low density lipoproteins (LDL) as drug delivery systems. LDL induce a higher Zn-Pc uptake by the tumour and improve the selectivity of tumour targeting as compared to DPPC liposomes. Experimental photodynamic therapy (PDT) of the MS-2 fibrosarcoma has been performed using liposome-delivered Zn-Pc and the efficiency of tumour necrosis has been measured following four different irradiation protocols. We found that Zn-Pc doses as low as 0.07-0.35 mg kg-1 are sufficient for inducing an efficient tumour response that is linearly dependent on the injected dose. The amount of Zn-Pc in the tumour decreases very slowly as a function of time, hence PDT gives satisfactory results even if performed at relatively long time intervals after administration.

Animals↗
PubMed1990

Photosensitized processes in vivo: proposed phototherapeutic applications.

The use of photosensitizing dyes having intense absorption bands in the 600-900 nm spectral interval opens up new prospects in the field of photochemotherapy, because it allows the illumination of relatively large tissue volumes with no significant damage to photosensitizer-free tissues. Special interest is currently focused on the photodynamic therapy of solid tumors, because of the property of several dyes with a macrocyclic chemical structure (porphyrins, chlorins, phthalocyanines, xanthenes) to accumulate in significant amounts and be retained for prolonged periods of time by neoplastic lesions. Strategies are being developed for enhancing the selectivity of tumor targeting by photosensitizers through the exploitation of functional or biochemical differences between normal and malignant cells.

Humans↗
PubMed1990

Bronze baby syndrome: an animal model.

We evaluated the appropriateness of an animal model for the bronze baby syndrome. Ligation of the common bile duct in adult Wistar rats induces an accumulation of porphyrins and copper in the liver and a 20% conversion of protoporphyrin IX into (Cu(II)-protoporphyrin IX. Upon irradiation of these animals with super-blue lamps, the plasma content of Cu(II)-protoporphyrin increases by about 30%. Cholestasis also increases the recovery of porphyrins in the urine, although light treatment of ligated rats further increases urinary porphyrin excretion. The spectroscopic changes induced by irradiation of sera of ligated rats are consistent with the formation of products that have the typical spectrum found in bronze baby syndrome patients, i.e. a reduced absorbance in the visible region and an increased absorption in near-UV and red spectral regions. The products responsible for the brown discoloration found in bronze baby syndrome seem to result from phototransformation of copper-porphyrins subsequent to an electron transfer between photoexcited bilirubin and the copper ion.

Animals↗
PubMed1989

In vivo transport and pharmacokinetic behavior of tumour photosensitizers.

The mechanisms by which photodynamic sensitizers are transported in the bloodstream influence their distribution among normal and tumour tissues, as well as their partitioning among the various compartments of tumour tissues. Column chromatographic analysis and density gradient ultracentrifugation of sera obtained from both patients and experimental animals show that hydrophilic photosensitizers (e.g. haematoporphyrin, and tetrasulphonated porphyrins and phthalocyanines) are largely transported by albumin and globulins and mainly deposited in the vascular stroma of tumours. More hydrophobic photosensitizers (haematoporphyrin oligomers, porphyrin esters, monosulphonated or unsubstituted phthalocyanines) are preferentially incorporated in the lipid core of lipoproteins. Tightly aggregated dyes partly circulate as unbound pseudomicellar structures which can be entrapped in the interstitial regions of the tumour, localize in macrophages, or enter neoplastic cells via pinocytotic processes. Low density lipoproteins (LDL), which are endocytosed by neoplastic cells through a specific receptor-mediated pathway, display the most selective release of photosensitizers to tumours. The binding of the injected photosensitizer to LDL can be enhanced by preincorporation of the dye in liposomal vesicles which are in a quasi-solid state at the body temperature.

Animals↗
PubMed1989

Tetra-n-propylporphycene as a tumour localizer: pharmacokinetic and phototherapeutic studies in mice.

The porphin isomer tetra-n-propyl-porphycene (TPP) was incorporated into unilamellar liposomes of dipalmitoylphosphatidylcholine and intravenously injected at a dose of 2 mg/kg to BALB/c mice bearing a MS-2 fibrosarcoma. Pharmacokinetic studies show that TPP is selectively transported by serum lipoproteins and delivered to the tumour tissue with good efficiency (approx. 1 microgram of the TPP per g of tissue at 24 h after injection) and selectivity (ratio of TPP concentration in the tumour to the peritumoural tissue 16.7 at 24 h). Large doses of TPP are also accumulated by the liver, in agreement with the elimination of the drug via the biliary route, while no TPP is recovered from the brain. Red light-irradiation (300 J/cm2) of the tumour area caused extensive necrosis, while only little cutaneous photosensitivity was observed. Since TPP has a large absorbance in the 630-640 nm region, can be synthesized with a high degree of purity and is an efficient generator of singlet oxygen, this drug represents a potential candidate as a phototherapeutic agent for tumours.

Animals↗
PubMed1989

Photokinetic and ultrastructural studies on porphyrin photosensitization of HeLa cells.

Liposome-bound haematoporphyrin or haematoporphyrin dimethylester, as well as haematoporphyrin dissolved in phosphate-buffered saline, were added to HeLa cell monolayers at a dose of 1 microgram of porphyrin per 10(5) cells. After 2 min or 20 min incubation liposome-bound porphyrins were accumulated by cells in an about two-fold larger amount than the water-dissolved haematoporphyrin. This caused a more efficient photosensitization of HeLa cells by liposome-delivered porphyrins upon illumination with 366 nm light. Ultrastructural studies of HeLa cells, which had been incubated in a physiological medium for 24h after the end of irradiation, showed that liposomal porphyrins induce an early and extensive endocytoplasmic damage, leading to swelling of the mitochondria and vesiculation; changes of the permeability of the cytoplasmic membrane are also evident, especially in the case of haematoporphyrin dimethylester. On the other hand, water-dissolved haematoporphyrin predominantly photosensitizes damage of the plasma membrane. The different pattern of cell photodamage probably reflects a different subcellular distribution of the photosensitizing drugs.

Cell Survival↗
PubMed1989

Factors influencing the haematoporphyrin-sensitized photoinactivation of Candida albicans.

Photosensitizing activity of haematoporphyrin (Hp) on Candida albicans cells is mainly promoted by unbound dye molecules in the bulk aqueous medium. Moreover, the death of photosensitized cells is dependent on the dye concentration, irradiation time, irradiation temperature, and the composition of the growth media. Morphological and biochemical studies indicate that the photoprocess involves an initial limited alteration of the cytoplasmic membrane, which allows the penetration of the dye into the cell with consequent photodamage of intracellular targets. In this respect, the Hp-sensitized photoinactivation of eukaryotic microbial cells differs from that in prokaryotic cells.

Candida albicans↗