The optical properties of neoplastic and normal tissues have been evaluated in the wavelength region from red to near infrared. The tumor models have been human retinoblastoina and B16 melanotic iuelanoma transplanted in athymic mice and mammary adenocarcinoma in C3H mice. The normal tissue results include in vivo measurements in human and rabbit muscle.

The concentration of Photofrmn II is needed to determine the dose in photodynamic therapy, and in fluorescence diagnosis of tumors. A method based on fluorescence was devised which shows promise. Diffusion theory was applied in slab geometry with closely spaced excitation and emission wavelengths. A function of the measured radiant energy fluences for excitation and emission, and the depth x, was found that canceled the dependence on depth. A function of the diffusion coefficient and attenuation coefficient was derived from the measured diffuse reflectance. This function compensated for differences in absorption and scattering in different tissues, or a calibration phantom and tissue. Comparisons should be made with the concentration derived in other ways, but the fluorescence method shows promise.

Photodynamic therapy (PDT), a relatively new treatment for cancer, has evolved from the investigational stage and is now being evaluated clinically for certain cancer types under FDA-approved protocols. Results obtained to date indicate the treatment to be promising, however, not without limitations. This therapy involves the cooperative action of an injectable tumor-specific sensitizer and light, usually provided by the output of a laser. The general view, supported by a large body of in vitro data, is that the most important agent of tumor destruction is electronically excited oxygen (singlet oxygen) generated by a favored energy transfer from the optically excited sensitizer to ambient ground state oxygen. It is clear, therefore, that to understand the limitations of PDT in cancer treatment one has to fully understand the nature of singlet oxygen (102) interactions in the in vivo environment. This, of course, first requires an appropriate means for 102 detection and measurement. The recent demonstration in this laboratory that in vivo 102 detection during photodynamic treatment of tumors is indeed possible opens up this possibility.

A fiberoptic isotropic probe system has been developed to measure both the Space Irradiance (SI) and Fluorescence (F) within tissue during Photodynamic Therapy (PDT). The probe is 0.8mm in diameter. The system has a SI sensitivity of 0.1 mW/cm2 and a F sensitivity of 0.1 microgram per milliliter of DHE in a tissue phantom solution. It also provides for the time integrated SI and F and a ratio of the F to SI. A biological response study is being undertaken using DHE to determine the correlation of therapeutic response with drug dose, light dose, integrated space irradiance, and integrated fluorescence in a standardized animal tumor model. Description of the device and its performance will be presented along with preliminary results of animal tumor model studies.

An apparatus is designed and realized to detect "early" cancer at the surface of the hollow organs in the human body by endoscopic means. The tumor is localized by the laser induced fluorescence of a dye (HPD) which concentrates selectively in the neoplastic tissue after intravenous injection. Fluorescence contrast between the tumor and its normal surroundings is enhanced by subtracting the background autofluorescence which occurs in both types of tissue. This is done by means of 2-color digital images manipulation in real-time. Preliminary clinical tests of the apparatus demonstrated the detection of carcinoma in situ in the esophagus.

An optical dosimetry model for photodynamic therapy (PDT) is based on the assumption that the tumor-localized photosensitizer must absorb an energy density threshold for tumor necrosis. The relationship between delivered dose and absorbed energy was calculated for idealized geometries with the photon diffusion equation and calibrated by scaling to PDT results for superficial tumors. The predictions of the model are compared with clinical trials on head and neck malignancies.

Since biological response to photodynamic therapy (PDT) depends on the light fluence distribution and photosensitizer concentration in the tissue, these two variables should ideally be measured noninvasively in individual cases. This can be reduced to determining the optical absorption and transport scattering coefficients of the tissue because, if these two parameters are known, the fluence distribution can be calculated and the photosensitizer concentration can be deduced from its characteristic contribution to the absorption spectrum. The temporal spreading of a picosecond laser pulse as it propagates through tissue carries infonnation about both the scattering and absorption properties of the tissue. A mathematical model is presented which allows derivation of the interaction coefficients from the pulse shape, and preliminary experiments are reported which demonstrate the potential of these techniques in PDT dosimetry. Equivalent information can be obtained in the frequency domain by using modulated light sources andmeasuring thephase and modulation of the detected light. Analytical expressions are developed for these observable quantities in terms ofthe optical interaction coefficients. Particular auention is drawn to the potential oflow (less than 200 MHz) frequency measurements as these can be made with relatively simple instrumentation.

We have performed extensive investigations using laser-induced fluorescence in animal as well as human tissue in order to localize diseased tissue and thus discriminate such tissue from normal surrounding areas. In characterizing different tissue types the endogenous fluorescence (autofluorescence) as well as specific fluorescence from different photosensitising substances was utilized. We have investigated different experimental and human malignant tumors in vivo and in vitro as well as atherosclerotic lesions in vitro. A fiber-optic fluorosensor was constructed and used in the experiments and in the clinical examination of patients. Dimensionless spectroscopic functions were formed to ensure that the signals were independent of clinically uncontrollable variables such as distance variations, tissue topography, light source fluctuations and variations in detection efficiency. A multi-color two-dimensional imaging system was constructed for real-time imaging. The system was tested peroperatively and during standard examination patient procedures. Besides utilizing the time-integrated fluorescence signal we have also investigated the possibility of incorporating time-resolved fluorescence characterization.

The therapeutic efficacy of photodynamic therapy (PDT) of malignant tumors utilizing is related to the capability of the photosensitizer to produce excited singlet molecular oxygen(1-0). This work is devoted to the study on detection of 102 molecules produced by two chlorin-type dyes, pheophorbide a (PPa) and chlorin e6Na (Chl) using a highly sensitive near-infrared spectrometer and comparison of their emitted intensity was made with hematoporphyrin derivative (HpD) and Rhordamin 123 (Rd) in water and methanol. By the irradiation of an Ar or Kr laser light, near-infrared emission spectra around 1.27 jim from the 102 molecules were detected in HpD and Chi aqueous solutions, as well as in Chl, PPa, and Rd methanol solutions. The ratio of their emission intensities at 1.27 jim is found to be 1 : 3.7 : 22 : 15 1 for HpD and Chi aqueous solutions and Chl, PPa, and Rd methanol solutions, respectively. These quantitative results support the conclusion that because of greater production of 102 molecules, PPa and Chl provide more effective SPIE Vol. 1203 Photodynamic Therapy: Mechanisms 11(1990) / 97 photosensitized dyes for the PDT following 102 molecule generation than HpD or Rd when used in conjunction with the laser-excitation and endoscopy.

The majority of second generation sensitizers being proposed as possible alternatives to hematoporphyrin derivative, in photodynamic therapy, are hydrophobic in nature. Consequently, specific carrier systems have to be developed for in vivo administration. As an attempt to understand the interactions of these delivery systems in vivo, plasma binding properties of the sensitizer SnET2 complexed with liposomes, emulsions or cyclodextrins have been studied. Additional studies have investigated the effect of the carrier system on the cytotoxicity of SnET2 on transplantable tumors. Preliminary data suggest that tumor response may be mediated by the choice of carrier system. Further studies appear to be necessary before the optimum thug/carrier system complex can be defined.

The silicon naphthalocyanine isoBoSiNc was studied with regard to its photosensitizing properties when carried in the following vehicles: chreinophore, Tween 80 and liposoiaes of various composition. Encapsulation of the sensitizer in liposomes was complicated by the drug's tendency to aggregate, and was successful only at very high lipid: isoBoSiNc ratios. Encapsulation efficiency was low. Liposoinal delivery of the sensitizer in vivo did not seem to significantly improve the biologic response when compared to other vehicles.

An anti-ovarian carcinoma antibody OC125 was conjugated to a derivative of the photosensitizer (PS) chiorin e6 yj polyglutamic acid. Target cells from a human ovarian cancer cell line were treated with this conjugate and laser irradiation at 656 rim (absorption maximum of PS) and fixed 24 h later for electron microscopy. Electron niicrographs showed a high degree of vacoulization, generalized cell necrosis, and extrusion of organelles. No specific damage to the plasma membrane was noted. Untreated control cells, or cells treated with conjugate or light alone exhibited no injury. These data suggest that even though the antibody recognizes a cell surface antigen, the conjugate is internalized under the conditions of the experiment.

Two N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-chlorin es-anti-Thy 1.2 antibody conjugates were synthesized. They differ in the method of antibody binding. in conjugate A, the polyclonal anti-Thy 1 .2 antibody was bound via NEamino groups of lysine residues. Conjugate B contained anti-Thy-I .2 antibodies bound via oxidized carbohydrate groups present near the hinge region of the F part of the antibody molecule. The photodynamic activities of these conjugates (and of appropriate controls) were evaluated on mouse splenocytes in vitro. Both conjugates (A and B) were more biologically active compared to the nontargetable conjugate (without antibody). All polymeric chiorin e6 conjugates were less toxic in the dark compared to free chlorin e6. Conjugate B was the most active; its activity at low concentrations was higher compared to free chlorin e6. The results demonstrate the importance of the chemistry of antibody binding on the biological activity of targetable polymeric drugs.

There are few reports in the literature regarding the effect that photodynamic therapy (PDT) might have on immune function. illumination of skin with light in the long UV range is well known to have immunosuppressive properties mediated by the amplification of a subpopulation of T suppressor cells1. However, PDT effected by light at between 600 and 700 nm and accompanied by an acute inflammatory response has not been studied in depth in terms of its influence on immune function. A few recent reports have documented suppression of immune function in the days immediately following PDTZ3. In one report, the cells responsible for this suppressive effect were characterized as a non-T cell population which were incapable of adoptively transferring the effect2. It is probable that the cells responsible for transient immunosupppression following PDT are activated macrophages, no doubt stimulated by the photodynamic effect and well known for their release ofprostaglandin E2 which is non-specifically immunosuppressive. On the other hand, there is anecdotal evidence from clinical studies attesting to what might be interpreted as immunological enhancement following PDT (infiltration of lymphocytes into inflammatory lesions), as well as reports of elevated levels of interleukin 2 (IL-2) in the urine of patients treated with PDT for bladder cancer'5. Some investigators have reported lymphokine involvement in photodynamically initiated lesions6. Recent work by Gomer and his associates have shown positive correlation with PDT and enhanced natural killer cell activity7 and have suggested that this could play a role in reduction of the metastatic potential of surviving tumor cells8.

The ability of photodynamic therapy (PDT) to activate macrophages and produce cytokines, specifically tumor necrosis factor (TNF), is unknown. Three day thioglycolate elicited macrophages were incubated with 25 ug/mi Photofrin II (P11) for 2 hour, after which they were subjected to 630 nm light with fluences of 0-1800 J/m. The amount of TNF produced in the system as well as macrophage viability was measured 1, 3, 6, and 18 hours after POT. The level of TNF produced by the macrophages was significantly elevated over control levels 6 hours after POT and the absolute level of tumor necrosis factor production was influenced by the treatment energy and the resulting macrophage cytotoxicity. These data suggest that POT therapy induced cytotoxicity in vivo may be amplified by macrophage stimulation to secrete cytokines and these cytokines may also participate in other direct/indirect photodynamic therapy effects, i.e. immunosuppression, vascular effects.

There exists little doubt that profound changes occur to both tumor and normal tissue microvasculature during photodynamic therapy, and that these changes are important in the process of tumor destruction. We hypothesize that singlet oxygen, produced during light activation of photosensitizer, interacts with cellular membranes and induces the release of arachidonic acid metabolites, notably thromboxane, into the intravascular environment. This leads to vasoconstriction, platelet aggregation, and hemostasis. To test this hypothesis, we have measured the release of thromboxane into serum as a function of porphyrin and light doses used in phototherapy. Sprague Dawley rats bearing chondrosarcoma in the right hind limb were injected with 0-25 mg/kg Photofrin IP'. A catheter was implanted in the carotid artery 24 h later, and the hind limb exposed to 0-135 J/cm2 630 nm light. Immediately after treatment, serum was collected and thromboxane levels were measured by radioimmunoassay. We found significant increases in systemic thromboxane concentrations following phototherapy at the highest porphyrin and light doses, compared to drug and light controls. The administration of indomethacin (10 mg/kg i.p.) prior to treatment suppressed the release of thromboxane from tumor and normal tissues and inhibited hemostasis and tumor response to phototherapy. These studies have reinforced the important role of arachidonic acid metabolites in producing vascular damage during phototherapy.

In-vitro sensitivity to porphyrin mediated photodynamic therapy (PDT) has been examined in cell lines resistant to hyperthermia. Parental (HA-i) and heat resistant (3012) Chinese hamster fibroblasts as well as parental (RIF-i) and temperature resistant (TR-4, TR-5 and TR-iO) mouse radiation-induced fibrosarcoma cells were evaluated for thermal and PDT sensitivity. Quantitative survival curves were generated and porphyrin uptake properties were obtained for all cell lines. Significant resistance to hyperthermia (450C for varying exposure periods) was documented for the 3012 and TR cell strains when compared to 'the parent lines. However, normal and heat resistant clones exhibited comparable levels of porphyrin uptake and photosensitivity. Our results indicate that cross resistance between hyperthermia and PDT is not observed and that members of the 70 kD heat shock protein family (which are elevated in the thermal resistant cells and may be associated with the heat resistant phenotype) do not play a significant role in modulating PDT sensitivity. Mechanisms of in-vitro cytotoxicity appear to be different for PDT and hyperthermia even though possible subcellular targets (such as the plasma membrane) and types of damage (protein denaturation) may be similar for the two modalities.

Photodynamic therapy is a treatment technique that utilizes the photoactived species of a drug to destroy tumor tissue. To be successful, the drug must localize in tumor tissue preferentially over normal tissue and must be activated by light of a specific wavelength. Currently the only drug to be approved for clinical use is Heinatoporphyrin Derivative (HpD) although a series of new drugs are being developed for use in the near future. One of the drugs belongs to a class called purpurins which display absorp-' tions between 630-711 nm. Along with several other investigators, we are currently exploring the characteristics of a specific purpurin (SnET2) in normal and tumorous canine tissue. The use of this compound has demonstrated increased tumor control rates in spontaneous dog tumors. Preliminary pharmacokinetic studies have been performed on 6 normal beagle dogs. SnET2 (2 mg/kg) was injected intravenously over 10 minutes and blood was collected at 5, 15, 30, 45 minutes and at 1, 2, 4, 8, 12 and 24 hours following administration for determination of drug concentration and calculation of pharinacokinetic parameters. Skin biopsies were collected at 1, 4, 8, 12 and 24 hours. Dogs were euthanized at 24 hours and tissues (liver, kidney muscle, esophagus, stomach, duodenum, jejunum, ileura, colon, adrenal gland, thyroid, heart, lung, urinary bladder, prostate, pancreas, eye, brain) were collected for drug raeasurement. Drug was shown to persist in liver and kidney for a prolonged period of time coiapared to other tissues. Knowledge of the pharmacokinetic properties of the drug will greatly add to the ability to treat patients with effective protocols.

The photochemotherapeutic properties of several novel benzophenothiazines were evaluated zn-vzvo in three distinct tumor types consisting of a murine sarcoma, human carcinoma, and a rat glioma. Subcutaneous or intravenous administration of dyes to tumor bearing animals coupled with irradiation of the tumor area with 640 nm light resulted in substantial tumor necrosis 24h post photodynamic therapy as determined by histological evaluation. Significantly, there was minimal concurrent damage to the surrounding normal tissue. These results offer further evidence for the potential usefulness of benzophenothiazines in the photodynamic therapy of neoplasms.

The photodynarnic effects of bacteriochlorophyll-a (bchl-a) , a sensitizer of high light absorption at long wavelengths, are greatly influenced by its rapid degradation in vivo to also photodynamically active pheophytins and chlorophylls. This can result in overall tumor destruction and direct tumor cell kill over a wide range of different wavelengths, although tumor curability is restricted to the bchl-a wavelength of 780 nm. Tumor cures are also limited to treatment conditions where light follows drug injection after a brief interval (2 hours) . The major mechanism of tumor destruction appears to be vascular. Normal tissue photosensitivity induced by 780 nm light declines rapidly with time after sensitizer injection.

Methods for the preparation of the naphthalocyanines SiNc(OSi(n-C6H13)3)2, SiNc(OSi(i-C4H9)2n-C18H37)2, GeNc(OSi(n-C6H13)3)2, SnNc(OSi(n-C6H13)3)2, AlNcOSi(n-C6H13)3 ' and GaNcOSi(n-C6H13)3 the halonaphthalocyanine isomer mixtures SiMc(Cl)4(OSi(n-C6H13)3)2 and SiNc(Br)4(OSi(n-C6H13)3)2; and the butoxyphthalocyanines GePc(0-n-C4H9)g(OSi(C2H5)3)2 , SnPc(O-n-C4H9)8(OSi(C2H5)3)2, Al(O-n- C4H9)8OSi(C2H5)3 , Ga(O-n-C4H9)8OSi(C2H5)3 , PdPc(O-n-C4H9)8, and Ru(O-n- C4H9)8(C6H5N)2 are outlined. Ultraviolet-visible spectra and other properties of these compounds are described, and their potential as sensitizers is touched upon.

The in vitro photodynamic inactivation ofherpes simplex virus (HSV-1), an enveloped virus with a membranous coat, was studied using the decaalky sapphyrin 2. This new sensitizer, an unusual 22 icelectron "expanded porphyrin" with an absorption maximum at roughly 680 nm, generates singlet oxygen in roughly 25% quantum yield in its non-aggregated monomeric form and is very efficient for the photo-inactivation of HSV- 1 . It is as active as dihematoporphyrin derivative (DHE) on a per macrocycle basis and, because of light absorption by oxyhemoglobin, considerably more so in blood on a per mcident light intensity basis. Supporting fluorescence studies indicate that compound 2 has a high affinity for nonpolar environments, where it exists in its most active monomeric form, suggesting a mechanism of action that depends both on selective localization in the HSV- 1 viral membrane and accompanying efficient singlet oxygen production. In preliminary experiments with cell-free HIV-1 (also an enveloped virus), it was found that compound 2 effects a ca. 50% photo-killing with little dark toxicity at 4 jiM concentration and an essentially complete photo-eradication at 16 jiM concentration, as judged by standard reverse transcriptase assay. At this latter concentration, however, the light-induced viral inactivation is accompanied by considerable dark toxicity, which, on the basis of control experiments with uninfected cells, is ascribed to a high sensitivity of the H9 cell line employed and not to an overall, or inherent, cytotoxicity of the sapphyrin nucleus.

Among the water-soluble sulfonated metallo phthalocyanine (M-PcS), the monoand disulfonated derivatives exhibit the highest photodynamic activity. The effect of two further modifications of the M-PcS2 structure was studied using V-79 Chinese hamster cells. The addition of axial ligands onto the central metal ion of Si-PcS12 did not interfere with cell uptake and appeared to reduce intracellularaggregation. Combined with diminished in vitro phototoxicity these data suggest that the tendency to form aggregates promotes targeting of the dye with vital cell constituent. Addition of benzyl rings onto the mäcrocycle was evaluated as a second structural modification. The resulting sulfonated metallo naphthalocyanines (Zn-NcS) were 1-2 orders of magnitude less photoactive in vitro as the corresponding phthalocyanine dyes.

Quasiaromatic heterocycles (QAM) such as substituted 1 , 3 , 5 , 7 , 8-pentamethylpyrromethene boron difluorides (PMP-BF2) and - (dimethoxyphosphinylmethyl, methyl) bimane have been evaluated for their abilities to produce cellular toxicities when used in photodynamic therapy (PDT) for ovarian cancer. The most active QAH tested to date has been the disodiuxn salt of PMP-2,6-disulfonate--BF2 (PMPDS-BF2). Human ovarian cancer cells from fifteen different patients have been grown in culture. Cells were obtained from biopsy material and grown in RPMI medium with 10% FBA plus penicillin and streptomycin. Cells were harvested and as single cell suspensions exposed to PMP-BF2 complexes or bimanes in concentrations of 0.004-0.4 ug/106 cells/ml of medium. Initially the cells were exposed to the chemicals for 30 minutes in a 5% CO2 incubator (37°C) with gentle shaking. The cells were washed with plain RPMI medium, then resuspended in the enriched RPMI medium and exposed to a sunlamp for 10-20 minutes. Cells were then allowed to grow in an soft agar culture media at 37°C (5% C02) for 14 days. When compared to controls (only light or only chemicals) there was 100% inhibition of all cellular growth for PMPDSBF2 at the 0.4 ug/mi concentrations. There was variations in concentrations of the chemical needed to produce 100% inhibition when the 15 different ovarian cancer cell specimens were compared at all concentrations. PMP-BF2 complexes are characterized by extremely high extinction coefficients, superior laser activity and little if any triplet-triplet absorption. The biamanes share these properties however are less active in ovarian cancer cell The lasing properties of PMP-BF2, and bimanes will be compared to their PDT effectiveness.

We wish to report on PDT simulation studies of a class of compounds, which because of their commercial nonavailability, had hitherto been overlooked: the tetrabenzoporphyrins (TBP5) . We have studied absorption and fluorescence of these compounds in homogeneous solutions and in liposome vesicles. Each substance was examined for its photodynamic effects on 9,lO-dimethylanthracene (DMA, an effective probe for singlet oxygen in PDT simulation) . Since TBPs display absorption in the 630 nm region, a 15 mW He-Ne laser proved convenient for these studies. All our data were intercorrelated and compared with standard HPD and Photofrin samples, as well as studies of self-destruction of these chromophores under similar light irradiation conditions. Despite the fact that some TBPs such as MgTBP and ZnTBP have strong absorption bands in the 630 nixt region (orders of magnitude greater than HPD) , we found that other physical factors may play a dominant role in PDT effectiveness. We followed the photosensitization of DMA in real time by monitoring its fluorescence decrease at 457 nra and found that DMA undergoes an oxygen-mediated (type II) photosensitization reaction. ZnTBP was found to be the most efficient photosensitizer followed by PF-II, MgTBP, HPD and ZnPC. The partition coefficients of the sensitizers to lecithin liposomes are also reported.

There has been considerable interest in the development of photosensitizers having increased absorption in the red or near infrared region for PDT applications. It is known that porphyrin absorptions can be shifted to longer wavelengths by expanding the n-conjugation of the macrocycle and by introducing electron-withdrawing groups at the ring. This principle has been applied to a number of porphyrinone (oxochlorin), porphyrintriones (dioxobacteriochlorins and dioxoisobacteriochlorins), as well as a porphyrintrione. The oxo group in this class of compounds has been transformed into sulfido-, imino, and methide derivatives, i.e., the ring system contains at least one exocyclic double bond connected to S, N-CN, and C(CN)2 using suitable reaction conditions. Many of these compounds exhibit absorption maxima longer than 700 nm, some even in the 800 nm region. Since the porphyrinones are generally photodynamically active to in vitro cells, they are attractive for PDT drug use.

Phenoxazine dyes, including several Nile blue analogs, are known to localize selectively in animal tumors. In general, oxazine dyes have low photo-reactivity due to inefficient singlet4riplet crossover of excited states. Structural modifications have yielded a series of halogenated, thia- or phenyl-substituted analogs with different pKa's, hydrophobicities and singlet oxygen yields. In this study, possible correlations of these properties to the uptake, retention and photosensitization activity of these oxazines were examined in a human bladder tumor cell line (MGH..Ul) in culture. The effectiveness of these derivatives in causing photo-killing of tumor cells in vitro, as determined by colony forming assay, correlated well with their singlet oxygen yields indicating that this is likely to be the main mechanism for the photocytotoxicity. Using the derivative with the highest singlet oxygen quantum yield (0.821), over 90% cell kill was achieved at a dye concentration of 5x108 M, which is about 3 orders of magnitude more effective than HPD, indicating that some of these dyes can be potentially effective photosensitizers for tumor therapy. The rates of uptake and efflux do not correlate directly with the pKa's or partition coefficients. Yet the rapid influx and slow efflux of these dyes suggests that dye retention is not dictated by simple rule of diffusion but perhaps related to affinity of the dye with certain cellular components. Experiments with agents which alter cellular membrane potentials indicate that these dyes may have a different uptake mechanism than other cationic dyes in which membrane potentials play a significant role.

In continuation of the effort to search for an ideal photosensitizer, two groups of potential new photosensitizers were synthesized and investigated for their photodynamic actions against tumors in mice. These were derivatives of methyl pheophorbide-a and of silicon naphthalocyanine. Of the former group, the 2 (1-0--hexyl) ethyl-desvinyl--methyl pheophorbide-a, or }IEDP, was the most active sensitizer. HEDP could be readily produced in large quantities and showed an optimum photodynamic action at 665 mu where it absorbs strongly. Also HEDP was cleared from the mouse skin within 4 days after administration, thus possibly alleviating the long-term phototoxic side-effects observed in Photofrin-based therapy. Of the second group of photosensitizers, the bis (dimethyl hydroxypropylsiloxy) silicon naphthalocyanine (HPSiNc) , and the corresponding acetoxy derivative (APSiNc) were of particular interest. At a drug-light dose of 1.0 mg/kg-135 J/cm2 (delivered by a laser at 772 nm), they showed antitumor activities comparable to that of PhotofrinTM. Further studies on these photosensitizers are warranted.

A new fiber optic detector to measure optical radiant energy fluence rates in tissue has been developed by incorporating a fluorescent dye into the rounded tip of a polymethylmethacrylate cylindrical extension on a quartz optical fiber. Model probes were built to test the concept. Nile Blue A free base was used as the fluorescent dye with the absorption maximum blue-shifted to 495 nm, giving an emission maximum at 580 nm. Fluorescence (>570 nm) was monitored using a photodiode. The response was linear with modest fluence rates in the I mW/cm to 700 mW/cm range. The angular response of the probe was investigated using a 3 mm diameter scaled-up model. The influence of dye concentration, geometrical shape and distance between fluorescence tip and fiber were evaluated. A 3 mm long rounded tip, separated by 7 mm from the distal end ofthe fiber, was isotropic in angular response to within 1 0% between OO and 1 50° ofthe forward direction.

Previous biophysical investigations1 demonstrated photosensitive propertieB of EPIRUBICIN with sufficient photochemical stability significant radical production and sufficient maintanance of pharmacological properties like intercalation potency Previous in-vitro investigations2 (human bladder cancer line ATCC 5637) demonstrated after drug treatment an enhancement of cytotoxic activity with continoüs irradiation (100 mW/cm2, 20 mm) performed at the wavelength of maximal absorption of the drug Because of a high tissue absorption of this short wavelength combined with decreasing photochemical reactions in deeper tissue, we investigated whether the reaction rate can be increased using pulsed irradiation with an averaged light power of also 100 mW/cm2. As light sources we used an Ar2-laser and an Excimer dye laser system. To simulate different tissue depths we exposed monolayer cells in a first step with different averaged intensities (100, 10, 1 mW/cm2 ) and in a second step we additionally varied drug concentrations (50, 5 ug/ml). 24 h after EPIRUBICIN treatment using a concentration of 50 ug/ml, viability of pulsed irradiated cells was 2 fold less compared to irradiated cells.