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Biomedical subjects

R Cubeddu

Publications and source records attributed to R Cubeddu.

At least 37 records · Page 2Linked to original sources
PubMed1995

delta-Aminolevulinic acid induced fluorescence in tumour-bearing mice.

The potential of protoporphyrin IX fluorescence induced by the systemic administration of delta-aminolevulinic acid (ALA) for the detection of tumours was tested in three different murine models (MS-2 fibrosarcoma, L1210 leukaemia, and Lewis lung carcinoma). Time-gated fluorescence images were acquired up to 4 h after the intraperitoneal injection of ALA (200 mg (kg body mass (BM))-1). For comparison images were acquired also after the administration of 25 mg (kg BM)-1 of haematoporphyrin derivative. The latter drug was characterized by better localization in the tumour area, leading to higher fluorescence contrast between neoplastic mass and surrounding healthy tissue, and consequently was preferable for tumour diagnosis in all the models under study.

Aminolevulinic Acid↗
PubMed1995

Spectroscopic and photoacoustic studies of hypericin embedded in liposomes as a photoreceptor model.

In photoresponsive ciliates, like Blepharisma japonicum and Stentor coeruleus, the photoreceptor pigments responsible for photomotile reactions are hypericin-type chromophores packed in highly osmiophilic subpellicular granules. Lipopsomes loaded with hypericin can constitute a simple model system, appropriate for understanding the primary light-induced molecular events triggering the sensory chain in these microorganisms. Optical absorption, steady-state and time-resolved fluorescence and pulsed photoacoustic calorimetry have been used to measure spectral distributions, fluorescence lifetimes, radiative and radiationless transition quantum yields of hypericin when assembled into egg L-alpha-phosphatidylcholine liposomes. With respect to hypericin ethanol solutions, both absorption and fluorescence maxima are 5 nm red shifted when the pigment is inserted into the lipidic microenvironment, regardless of the hypericin local concentration. Increasing by 100 times the hypericin local concentration decreases the relative fluorescence quantum yield by a factor of around 150 and the fraction of thermally released energy, conversely, increases from 0.6 to 0.9. From the analysis of fluorescence lifetimes and their relative amplitudes it appears that a subnanosecond living component is predominant at the highest hypericin local concentrations.

Acoustics↗
PubMed1994

Antitumor immunity induced by photodynamic therapy with aluminum disulfonated phthalocyanines and laser light.

Photodynamic therapy (PDT) is systemic administration of tumor localizing photosensitizers and subsequent irradiation with light of the appropriate wavelength. The combination of drug uptake in malignant tissues and selective delivery of laser-generated light provides effective therapy, with efficient tumor cytotoxicity and minimal normal tissue damage. There have been few studies of the effects of photoactivated photosensitizers on the host immune response. Since immunity is important in the control of tumor growth and spread, we have examined, in our laboratory, the effects of photoactivated phthalocyanines on the antitumor immune response. Immunosuppressed and normal mice bearing the MS-2 fibrosarcoma treated with 5 mg/kg of aluminum disulfonated phthalocyanine (AIS2Pc) and then the tumor mass exposed to laser light (100 mW/cm2 x 10 min) or treated with surgical excision of the tumor survived indefinitely, with no difference between the different groups. The survivors, tumor-free 100 days after the treatment modalities described above, were rechallenged with the parental MS-2. Some groups of surviving animals were immunosuppressed with cyclophosphamide before the injection of the tumor. Resistance to rechallenge was evidenced only in normal surviving animals cured by PDT, while the immunodepressed surviving animals and animals cured by surgery died of tumor. Finally, mice, cured by PDT and tumor-free, rechallenged with L1210 and P388 murine leukemias did not survive. These results suggest that a potential and specific 'antitumor immunity' is induced by PDT with photoactivated AIS2Pc.

Animals↗
PubMed1994

Absorption spectrum of hematoporphyrin derivative in vivo in a murine tumor model.

Time-resolved reflectance was used to measure the absorption spectrum of hematoporphyrin derivative (HpD) in vivo in a murine tumor model. Reflectance measurements were performed in the 600-640 nm range on mice bearing the L1210 leukemia. Then the animals were administered 25 mg/kg body weight of HpD intraperitoneally. One hour later the reflectance measurements were repeated. Fitting of the data using the diffusion theory allowed assessment of the absorption coefficient before and after the administration. As a difference between the latter and the former data, the in vivo absorption spectrum of HpD was evaluated. Maximum absorption was measured at 620-625 nm. Similar spectral behavior was obtained for HpD in solution in the presence of low-density lipoproteins.

Animals↗
PubMed1993

Time-gated fluorescence imaging for the diagnosis of tumors in a murine model.

A system for time-gated fluorescence imaging was used to perform measurements on tumor-bearing mice treated with hematoporphyrin derivative (HpD). The aim of the study was to define the potential of this technique in the diagnosis of tumors by taking advantage of the long fluorescence lifetime of the exogenous dye with respect to the decay times of the natural fluorescence. After the administration of three different drug doses (5, 10 and 25 mg/kg body weight), fluorescence images were acquired at various uptake times (from 2 h to 10 d), to determine the best instrumental conditions and experimental procedure for the detection of tumors in the murine model considered. The optimal fluorescence contrast between the tumor area and the surrounding healthy tissue was found at 12 h after the administration of either 5 or 10 mg/kg HpD and was anticipated at 8 h for the highest drug dose. In this optimum condition, the tumor region could be identified even after the injection of 5 mg/kg HpD. A better fluorescence contrast was always obtained in 15 ns-delayed images with respect to synchronous ones.

Animals↗
PubMed1992

Steady state and time-resolved spectroscopic studies on zinc(II) phthalocyanine in liposomes.

Zinc(II) phthalocyanine (ZnPc), a potential second-generation phototherapeutic agent for tumours, has been incorporated into small unilamellar vesicles (SUVs) (diameter, 52 nm) and large unilamellar vesicles (LUVs) (diameter, 84 nm) of dipalmitoyl-phosphatidylcholine (DPPC). Absorption spectroscopy, as well as steady state and time-resolved fluorescence emission studies, indicate that ZnPc is monomeric in SUVs at a stoichiometric concentration below 0.25 microM (corresponding to an actual endoliposomal concentration of about 0.5 mM), while in LUVs it is monomeric below 2 microM. The fluorescence lifetime of the monomer is 3-3.5 ns. Upon increasing the ZnPc concentration, aggregated derivatives are formed, which are characterized by shorter fluorescence lifetimes (1.2-1.5 ns; 0.4-0.6 ns). The possible implications of these observations for the phototherapeutic efficiency of ZnPc are briefly discussed.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

Action spectrum of photoactivated phthalocyanine AIS2Pc in tumor bearing mice.

The action spectrum of disulfonated aluminum phthalocyanine (AIS2-Pc) as a photosensitizer for photodynamic therapy (PDT) was evaluated in vivo from 640 to 710 nm on two murine tumors with different biological properties. Mice bearing MS-2 fibrosarcoma and mice bearing the pigmented tumor B16 melanoma were injected with 5 mg/kg of AIS2Pc and irradiated with a light dose of 50 mW for 10 min for the MS-2 fibrosarcoma and of 100 mW for 10 min for the B16 melanoma. The action spectrum for both tumors presents a red shift with respect to the absorption spectrum of AIS2Pc in saline. The effectiveness is limited for short wavelengths (less than or equal to 655 nm for MS-2 and less than or equal to 660 for B16), whereas it increases at longer wavelengths and reaches its maximum at a peak (672 nm). For wavelengths beyond 672 nm the photodynamic activity remains up to 710 nm despite the significant decrease in absorption. The results obtained for both murine tumors seem therefore to indicate that an appreciable modification of the absorption spectrum takes place when AIS2Pc is incorporated into tissues following systematic administration.

Animals↗
PubMed1991

Time-gated fluorescence spectroscopy of porphyrin derivatives and aluminium phthalocyanine incorporated in vivo in a murine ascitic tumour model.

The effect of systemic administration on drug uptake at cellular level was evaluated using time-gated fluorescence spectroscopy performed on a murine ascitic tumour model. Mice bearing L1210 leukaemia were injected intraperitoneally or intravenously with 25 mg per kg body weight hematoporphyrin derivative (HpD), 12.5 mg per kg body weight photofrin II (PII), 25 or 5 mg per kg body weight disulphonated aluminium phthalocyanine (AlS2Pc). Every 2 h and for up to 22 or 30 h, mice were sacrificed, leukaemic cells extracted from the peritoneum, washed, and resuspended in buffer for fluorescence measurements. HpD and PII emission spectra were almost identical 12 h after intraperitoneal injection with main peaks at 630 nm and no appreciable changes afterwards. In the first 12 h, the PII fluorescence spectrum was constant, while in the case of HpD a shoulder at 615 nm was detectable. Similar fluorescence behaviour was observed after intravenous administration of porphyrin derivatives. These results seem to confirm that the tumour localizing fraction is the part actually retained by the cells. The AlS2Pc spectrum peaked at 685 nm and did not change in any of our experiments. AlS2Pc is incorporated more rapidly with respect to porphyrins, as was clearly observed in the case of intravenous administration, where the AlS2Pc fluorescence was readily detectable after 2 h, whereas the PII emission became apparent only after 4-6 h.

Aluminum↗
PubMed1991

Age-related changes in the fluorescence of melanin and lipofuscin granules of the retinal pigment epithelium: a time-resolved fluorescence spectroscopy study.

The photophysical properties of purified populations of melanin and lipofuscin granules from human retinal pigment epithelium, and their changes with donor age, have been investigated using high-sensitivity time-resolved fluorescence spectroscopy techniques with picosecond gating capabilities. The overall fluorescence intensity of both melanin and lipofuscin granules clearly increased with increasing donor age, the increase being most marked for melanin. In all granule populations the fluorescence decays were multiexponential with subnanosecond and nanosecond decay components. The resultant time-integrated and time-gated spectra also exhibited marked age-variations for each type of granule. Young melanin showed spectral patterns similar to those of bovine melanin, while a yellow-orange fluorescence band appeared in melanin samples from older age groups. Lipofuscin granules exhibited a blue, a yellow and an orange band whose relative amounts were age-related. The results demonstrate the potential of time-resolved techniques for discriminating fluorophores in vitro and in situ, and have confirmed results previously obtained using extraction techniques. Furthermore, the ability of this technique to identify and quantify individual fluorophores within granules may provide an important insight into the origin and development of lipofuscin within the retinal pigment epithelium and ultimately into the mechanisms of age-related retinal diseases.

Adolescent↗
PubMed1990

Age-related changes in the morphology, absorption and fluorescence of melanosomes and lipofuscin granules of the retinal pigment epithelium.

The morphological and spectral characteristics of purified populations of melanosomes and lipofuscin granules from the human retinal pigment epithelium (RPE) were studied with respect to donor age. All melanosome and lipofuscin fractions exhibited the typical ultrastructural appearance associated with these granules. Absorption profiles of both melanin and lipofuscin granules demonstrated an increased optical density of the granules with increasing age. The former was associated with an overall increase of melanin within the granules. Melanosomes were weakly fluorescent; emission in the blue decreased with increasing age while emission in the red increased. The fluorescent intensity of lipofuscin granules increased with age. These results provide support for the concept that melanogenesis is occurring within the human RPE throughout life and that pigment granules within the RPE undergo age-related modifications during life.

Adolescent↗
PubMed1990

Comparative study of the therapeutic effect of photoactivated hematoporphyrin derivative and aluminum disulfonated phthalocyanines on tumor bearing mice.

Although the hematoporphyrin derivative (Hpd) is one of the most studied photosensitisers for photodynamic therapy (PDT), it is far from ideal. Therefore, many laboratories have been investigating a new group of sensitisers, the phthalocyanines. Particularly, in our laboratory we decided to study the aluminum disulfonated phthalocyanines (AlS2PC). They are chemically stable, readily soluble in water and have a strong absorption in the red part of the spectrum at 675 nm. Mice bearing the MS-2 fibrosarcoma treated with 5 mg/kg of AlS2PC survived indefinitely also using a low laser power of 100 mW/cm2 X 10' of exposure time, in contrast to experiments carried out with Hpd where the optical therapeutic laser power was 400 mW/cm2 X 10' and the dose of Hpd was 25 mg/kg. Furthermore, treatment of mice bearing the highly metastatic tumor, B16 melanoma, with 5 mg/kg of AlS2PC and laser light (100 mW/cm2 X 10'), significantly prolonged the survival time in respect to mice treated with 25 mg/kg of Hpd and laser light (400 mW/cm2 X 10').

Animals↗
PubMed1990

Time-gated fluorescence spectroscopy of porphyrin derivatives incorporated into cells.

Time-gated fluorescence spectroscopy was performed on the tumour-localizing fraction (TLF) of haematoporphyrin derivative (HPD) incorporated into cells. Three different cell lines were incubated with 20 and 5 micrograms ml-1 of TLF for various time periods; they were then washed and resuspended in buffer. Fluorescence decay measurements and time-integrated and time-gated spectra were then obtained from the cell suspensions. Similar experiments were repeated using HPD containing 60% of the active material. The experimental results show a modification of the emission spectra for both drugs depending on the incubation time; this modification is more significant for the TLF. In particular, the emission peak observed in aqueous solution at 615 nm is shifted to 630 nm as a consequence of incorporation into cells, and the gated spectra indicate that the fluorescence emission is mainly related to monomers and unfolded polymeric chains. The ratio between the intensities of the two peaks depends on the relative amount of the TLF; the peak at 615 nm is more pronounced for HPD. The results obtained seem to indicate that both the composition of the drug and the metabolic properties of the biological environment strongly influence the uptake process and the fluorescence behaviour of the incorporated sensitizer.

Animals↗
PubMed1989

Time-gated fluorescence spectroscopy of the tumor localizing fraction of HpD in the presence of cationic surfactant.

Time-gated fluorescence spectroscopy was performed on the tumor localizing fraction (TLF) of HpD in buffer at different concentrations of cationic surfactant. This technique obtains emission spectra with programmable delay relative to the excitation pulse. According to the measured fluorescence decay-time constants (approximately 0.7, approximately 3 and approximately 15 ns) three gates were considered, delayed by 0, 5 and 18 ns, respectively, to evaluate the contribution of the emitting molecular species to the spectra. Simultaneous to these measurements, fluorescence decay waveforms and time-integrated spectra were also detected. In buffer and in detergent micelles the fluorescence spectra are given by the superposition of the emission of the different molecular species present in the solution, and no appreciable interaction among the chromophores is observed. On the contrary, in the pre-micellar range of the surfactant, evidence for the existence of an energy transfer mechanism was found. This effect seems to be related to the configurational state of the TLF polymeric chains and depends on the relative TLF/surfactant concentration.

Cetrimonium↗
PubMed1987

Laser irradiation and balloon dilatation in experimental transluminal angioplasty.

Percutaneous transluminal balloon angioplasty (PTA) is being currently used in patients with coronary artery disease. Laser irradiation (LI) has been effective in vaporizing atherosclerotic plaques. The purpose of this work was twofold: to compare PTA and LI techniques in the recanalization of experimental obstructive arterial lesions, and to evaluate the possibility of reducing the failures and local complications and increasing the success rate of PTA by the combined use of LI. Atherosclerotic iliac stenoses were induced in 27 rabbits; lesions were evaluated angiographically before and after intervention and were studied histologically and by electron microscopy. Argon-ion LI delivered through microlens-tip optic fibers reduced the stenotic area from 64.2 +/- 21.8% to 40.3 +/- 10.7% (n = 10, P less than .01) and PTA from 60.7 +/- 15.9% to 30.4 +/- 7.7% (n = 9, P less than .01). However, percentage reduction was higher in PTA-treated stenoses (48.4 +/- 10.1% vs 34.5 +/- 13.5%, P less than .0125). In eight more rabbits, low power LI (4.55 +/- 1.25 J) was delivered after PTA in dilated segments. Post-PTA LI further decreased stenoses (from 31.2 +/- 7.8% to 29.1 +/- 8.1%, P less than .0125); laser-irradiated segments showed diffuse carbonization of the disrupted intimal layer. The normalized transtenotic pressure gradient decreased significantly in all groups: LI reduced the gradient from .40 +/- .25 to .17 +/- .07 (P = .005); PTA from .37 +/- .14 to .11 +/- .04 (P = .001); LI after PTA from .40 +/- .16 to .12 +/- .06 (P = .001). Thus, LI is effective (less than PTA) in relieving experimental atherosclerotic stenoses and seems useful when combined with PTA.

Angioplasty, Balloon↗
PubMed1987

Photodynamic therapy of spontaneous animal tumors using the active component of hematoporphyrin derivative (DHE) as photosensitizing drug: clinical results.

Photodynamic therapy was performed on 25 primary spontaneous tumors in dogs and cats. The animals were injected with 2.5 mg/kg body wt. of tumor localizing fraction of hematoporphyrin derivative and treated 48 h later with laser light at 631 nm. In 5 cases the treatment was performed on the tumor bed after surgical excision of the tumor mass. An evaluation of clinical results is presented and discussed. Complete remission was obtained in 19 cases and partial remission in 6 cases.

Animals↗