Carotenoporphyrins as selective photodiagnostic agents for tumours

Recent Advances in Photosensitizers as Multifunctional Theranostic Agents for Imaging-Guided Photodynamic Therapy of Cancer

In recent years tremendous effort has been invested in the field of cancer diagnosis and treatment with an overall goal of improving cancer management, therapeutic outcome, patient survival, and quality of life. Photodynamic Therapy (PDT), which works on the principle of light-induced activation of photosensitizers (PS) leading to Reactive Oxygen Species (ROS) mediated cancer cell killing has received increased attention as a promising alternative to overcome several limitations of conventional cancer therapies. Compared to conventional therapies, PDT offers the advantages of selectivity, minimal invasiveness, localized treatment, and spatio-temporal control which minimizes the overall therapeutic side effects and can be repeated as needed without interfering with other treatments and inducing treatment resistance. Overall PDT efficacy requires proper planning of various parameters like localization and concentration of PS at the tumor site, light dose, oxygen concentration and heterogeneity of the tumor microenvironment, which can be achieved with advanced imaging techniques. Consequently, there has been tremendous interest in the rationale design of PS formulations to exploit their theranostic potential to unleash the imperative contribution of medical imaging in the context of successful PDT outcomes. Further, recent advances in PS formulations as activatable phototheranostic agents have shown promising potential for finely controlled imaging-guided PDT due to their propensity to specifically turning on diagnostic signals simultaneously with photodynamic effects in response to the tumor-specific stimuli. In this review, we have summarized the recent progress in the development of PS-based multifunctional theranostic agents for biomedical applications in multimodal imaging combined with PDT. We also present the role of different imaging modalities; magnetic resonance, optical, nuclear, acoustic, and photoacoustic in improving the pre-and post-PDT effects. We anticipate that the information presented in this review will encourage future development and design of PSs for improved image-guided PDT for cancer treatment.

Preparation of monofunctional and phosphorescent palladium(II) and platinum(II) coproporphyrin labeling reagents

A method is described for preparation of monosubstituted derivatives of platinum and palladium coproporphyrin-I. The method is based on chemical differentiation of one of the four alkoxycarbonyl groups of the starting coproporphyrin-I tetraalkyl ester by selective acid hydrolysis. The hydrolysis results after chromatographic purification to pure mono hydroxycarbonyl coproporphyrin, which can be subsequently coupled with a chemical species carrying a functional group of interest. The described method is used for preparation of phosphorescent metalloporphyrin labeling reagents having an isothiocyanato reactive group.

Synthesis of meso-nitrophenylporphyrins covalently linked to a polyphenylene chain bearing methoxy groups

A convenient procedure for the synthesis of polyphenylene porphyrin dyads is described. The dyads consist of a meso-nitrophenylporphyrin covalently linked to a polyphenylene chain by an amide bond. The final phenyl group in the chain bears electron donor methoxy groups. The π-conjugated chain was obtained in excellent yield via a Wittig–Horner reaction, which produces a new double bond (E isomer) incorporating either — COOCH 3 or E isomer) incorporating either — CON ( OCH 3)( CH 3) functional groups. Expansion of the conjugated chain involves the reduction of these groups to aldehydes followed by a second Wittig–Horner reaction. 5-(4-Aminophenyl)-10,15,20-tris(4-nitrophenyl)porphyrin was synthesized from meso-(4-nitrophenyl)dipyrromethane. The E isomer) incorporating either — NO 2 groups in para positions of the peripheral phenyl rings give extra electron-withdrawing character to the porphyrin macrocycles. Coupling of the polyphenylene acids with aminoporphyrin results in the desired dyads. These dyads have moieties with different electron donor–acceptor properties. This present strategy may be easily used for preparation of other similar dyad derivatives. These compounds can be suitable for photodynamic therapy.

Long wavelength absorbing cationic Zn(II)-phthalocyanines as fluorescent contrast agents for B16 pigmented melanoma

Three cationic zinc phthalocyanines ( ZnPcs ), tetrakis-(3-methylpyridyloxy)-, tetrakis-(3-hexyl-pyridyloxy)-, and tetrakis-(3-dodecylpyridyloxy)phthalocyaninezinc ( ZnPc Me, ZnPc He and ZnPc Do) have been studied as advanced fluorescent contrast agents for pigmented melanoma tumor. UV-vis spectroscopic properties of the monomers were investigated. Their photophysical behavior as a substantial part of dye-induced fluorescence was evaluated. The selective accumulation and labeling capacity towards B16F0 pigmented melanoma tumor were determined. Melanin containing cells were isolated and incubated with ZnPcs at several time intervals (1, 1.5 and 6 h) following the kinetics of cellular uptake. The highest accumulation was found for ZnPcHe . A lower uptake was detected for the more lipophilic ZnPcDo and more hydrophilic ZnPcMe . The fluorescence diagnostic potential of ZnPcs towards pigmented melanoma by using an argon-dye laser detection set-up was demonstrated.

Possible in vivo mechanisms involved in photodynamic therapy using tetrapyrrolic macrocycles

Photodynamic therapy (PDT) mediated by oxidative stress causes direct tumor cell damage as well as microvascular injury. To improve this treatment new photosensitizers are being synthesized and tested. We evaluated the effects of PDT with 5,10,15,20-tetrakis(4-methoxyphenyl)-porphyrin (TMPP) and its zinc complex (ZnTMPP) on tumor levels of malondialdehyde (MDA), reduced glutathione (GSH) and cytokines, and on the activity of caspase-3 and metalloproteases (MMP-2 and -9) and attempted to correlate them with the histological alterations of tumors in 3-month-old male Wistar rats, 180 ± 20 g, bearing Walker 256 carcinosarcoma. Rats were randomly divided into five groups: group 1, ZnTMPP+irradiation (IR) 10 mg/kg body weight; group 2, TMPP+IR 10 mg/kg body weight; group 3, 5-aminolevulinic acid (5-ALA+IR) 250 mg/kg body weight; group 4, control, no treatment; group 5, only IR. The tumors were irradiated for 15 min with red light (100 J/cm², 10 kHz, 685 nm) 24 h after drug administration. Tumor tissue levels of MDA (1.1 ± 0.7 in ZnTMPP vs 0.1 ± 0.04 nmol/mg protein in control) and TNF-α (43.5 ± 31.2 in ZnTMPP vs 17.3 ± 1.2 pg/mg protein in control) were significantly higher in treated tumors than in controls. Higher caspase-3 activity (1.9 ± 0.9 in TMPP vs 1.1 ± 0.6 OD/mg protein in control) as well as the activation of MMP-2 (P < 0.05) were also observed in tumors. These parameters were correlated (Spearman correlation, P < 0.05) with the histological alterations. These results suggest that PDT activates the innate immune system and that the effects of PDT with TMPP and ZnTMPP are mediated by reactive oxygen species, which induce cell membrane damage and apoptosis.

Synthesis and photodynamic activity of zinc(II) phthalocyanine derivatives bearing methoxy and trifluoromethylbenzyloxy substituents in homogeneous and biological media

Two zinc(II) phthalocyanines bearing either four methoxy (ZnPc 3) or trifluoromethylbenzyloxy (ZnPc 4) substituents have been synthesized by a two-step procedure starting from 4-nitrophthalonitrile. Absorption and fluorescence spectroscopic studies were analyzed in different media. These compounds are essentially non-aggregated in the organic solvent. Fluorescence quantum yields (phi(F)) of 0.26 for ZnPc 3 and 0.25 for ZnPc 4 were calculated in tetrahydrofuran (THF). The photodynamic activity of these compounds was compared in both THF containing photooxidizable substrates and in vitro on Hep-2 human larynx-carcinoma cell line. The production of singlet molecular oxygen, O(2)((1)Delta(g)), was determined using 9,10-dimethylanthracene yielding values of approximately 0.56 for both sensitizers. Under these conditions, the addition of beta-carotene (Car) suppresses the O(2)((1)Delta(g))-mediated photooxidation. In biological medium, no dark cytotoxicity was found for cells incubated with 0.1 microM of phthalocyanines 3 and 4 for 24 h. However, under similar conditions 0.5 microM of ZnPc 4 was toxic (70% cell survival). The uptake into Hep-2 cells was evaluated using 0.1muM of sensitizer, reaching values of approximately 0.05 nmol/10(6) cells after 3h of incubation at 37 degrees C. The cell survival after irradiation of the cultures with visible light was dependent upon both light exposure level and intracellular sensitizer concentration. A higher photocytotoxic effect was found for ZnPc 3 with respect to 4 (32%/70% cell survival after 15 min of irradiation). Also, these studies were performed treating the cells with 0.5 microM of ZnPc 3. In this case, an increase in the uptake (approximately 0.28 nmol/10(6) cells) was observed, which is accompanied by a higher photocytotoxic activity (20% cell survival). These results show that even though both sensitizer present similar photophysical properties in homogeneous medium, the photodynamic behavior in cellular media can significantly be changed.

Synthesis and biological activity of novel platinum(II) complexes of glutamate tethered to hydrophilic hematoporphyrin derivatives

A new series of hematoporphyrin-platinum(II) conjugates was prepared by platination of the glutamate ligand tethered to hydrophilic hematoporphyrin derivatives, in which different numbers of ethylene oxide unit were introduced to modulate the hydrophobic/hydrophilic balance of the conjugates. The antitumor activity of the hematoporphyrin-platinum(II) conjugates was assayed in vitro and in vivo against the leukemia L1210 cell line. Among the complexes, compound 11 exhibited not only higher in vivo activity (T/C% = 192) than cisplatin (T/C% = 184) and carboplatin (T/C% = 168), but also elevated tumor-localizing effect (tumor/muscle ratio > 3).

Photodynamic activity of monocationic and non-charged methoxyphenylporphyrin derivatives in homogeneous and biological media

A novel 5-[4-(trimethylammonium)phenyl]-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin iodide (2) has been synthesized. A positive charge was incorporated at a peripheral position to increase the amphiphilic character of the structure. The photodynamic effect of the cationic porphyrin 2 was compared with that of non-charged 5-(4-aminophenyl)-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin (1), both in a homogeneous medium bearing photooxidizable substrates and in vitro on the Hep-2 human larynx carcinoma cell line. Absorption and fluorescence spectroscopic studies in different media show that 2 is essentially unaggregated in solution, and also in human cells. The singlet molecular oxygen, O2(1delta(g)), production was evaluated using 9,10-dimethylanthracene in N,N-dimethylformamide, yielding phi(delta) values of approximately 0.66 for both porphyrins. The addition of beta-carotene suppresses the O2(1delta(g))-mediated photooxidation. L-Tryptophan and guanosine 5'-monophosphate were used as biological substrate models. Porphyrin 2 sensitizes the decomposition of both compounds faster than does 1. In the biological medium, no dark cytotoxicity was observed, even though a high porphyrin concentration (10 microM) and a long incubation time (24 h) were employed. Cell treatments were performed with 5 microM of porphyrin for 24 h. Under these conditions, the uptake of porphyrin 2 into Hep-2 was about 3 times higher than that of 1. Cell survival after irradiation with visible light was dependent upon both the light exposure level and intracellular sensitizer concentration. Thus, a higher photocytotoxic effect was found for porphyrin 2 in comparison to 1. These results show that the amphiphilic monocationic porphyrin 2 could be a promising model for phototherapeutic agents with potential applications in tumor cell inactivation by photodynamic therapy.

Synthesis, biodistribution and antitumor activity of hematoporphyrin-platinum(II) conjugates

A new series of platinum(II) complexes of pegylated hematoporphyrin derivatives with controlled hydrophobic/hydrophilic balance were synthesized by introducing different kinds of poly(ethylene glycol) and amine ligands to the porphyrin ring. The antitumor activity of the porphyrin-platinum(II) conjugates was assayed in vitro and in vivo against leukemia L1210 cell line and various human tumor cell lines. The present complexes exhibited high antitumor activity and improved water solubility as well as considerable lipophilicity. In particular, complex 16 showed not only higher in vivo activity (T/C%=258) than cisplatin (T/C%=184) and carboplatin (T/C%=168), but also excellent solubility in water and organic solvent. The antitumor activity of complex 20 was superior to that of carboplatin against all human tumor cell lines tested. Moreover, some amphiphilic complexes (7 and 12) exhibited elevated tumor-localizing effect (tumor/muscle ratio>2).

Physiological parameters and biodistribution of 5,10,15,20-tetra (4-methoxyphenyl) porphyrin in rats

Physiological parameters on hepatic and renal functionality and biodistribution, accumulation and elimination, in different organs of the 5,10,15,20-tetra (4-methoxyphenyl) porphyrin (TMP) were determined in Wistar rats. The transport of TMP by low-density (LDL) and high-density lipoproteins (HDL) was also investigated. The photosensitizer is accumulated in the spleen, where its concentration is significantly increased 21 d post-injection; it also accumulates in the liver and in a lower proportion, in the duodenum, and poorly in brain and muscle. The urine and serum biochemical parameters reached normal values both in control and treated groups. The glomerular filtrate rate was not affected by the TMP treatment in any of the studied times. These results would indicate that the sensitizer does not modify the renal glomerular function. TMP is mainly eliminated from the organism via the bile-gut pathway. Considering the total amount of porphyrin bound to both lipoproteins (LDL and HDL) in comparison with the total value of the TMP in serum, it can be inferred that a large amount of the agent is transported by lipoproteins in the plasma. This study proves information about the behavior of TMP in vivo under dark conditions. The results can be used to design photodynamic treatments using this porphyrin model as the sensitizer.

Synthesis and selective tumor targeting properties of water soluble porphyrin-Pt(II) conjugates

We have designed and synthesized a series of novel water soluble porphyrins and their platinum(II) conjugates, cis-[(Por)Pt(dmso)X], where Por=5-(4-pyridyl)-10,15,20-tris(4-sulfonatophenyl)porphyrin) (PyTPPS) or 5-[4-(3-aminopropyl)pyridiniumyl]-10,15,20-tris(4-sulphonatophenyl)porphyrin (PyTPPS-NPn), X=2Cl, 1,1-cyclobutanedicarboxylic acid, oxalate, or malonate. Their biodistribution in tumor bearing mouse was examined along with their antitumor activity against murine leukemia L1210 cell line. The representative complex 1 exhibited a significant accumulation in tumor tissue with a tumor/muscle ratio of 7 after 24 h post injection. The antitumor activity of the title compounds was marginal (T/C: 95-117%), but it was found that platinum(II) coordination to the porphyrin periphery did not affect the tumor accumulating properties of the porphyrin permitting further derivatization for efficient delivery of the Pt(II) antitumor agent.

Synthesis and biological evaluation of methoxyphenyl porphyrin derivatives as potential photodynamic agents

A new meso-2,4,6-trimethoxyphenyl porphyrin covalently linked to a 2',6'-dinitro-4'-trifluoromethylphenyl group by an amine bond 5 and its metal complex with Cd(II) 6 was prepared. The photodynamic activities of 5 and 6 were evaluated in vitro on Hep-2 cells. A considerable increase in the photocytotoxic effect was found for 6, which has higher singlet molecular oxygen, O(2)((1)Delta(g)), production.

Developments toward diagnostic breast cancer imaging using near-infrared optical measurements and fluorescent contrast agents

The use of near-infrared (NIR) light to interrogate deep tissues has enormous potential for molecular-based imaging when coupled with NIR excitable dyes. More than a decade has now passed since the initial proposals for NIR optical tomography for breast cancer screening using time-dependent measurements of light propagation in the breast. Much accomplishment in the development of optical mammography has been demonstrated, most recently in the application of time-domain, frequency-domain, and continuous-wave measurements that depend on endogenous contrast owing to angiogenesis and increased hemoglobin absorbance for contrast. Although exciting and promising, the necessity of angiogenesis-mediated absorption contrast for diagnostic optical mammography minimizes the potential for using NIR techniques to assess sentinel lymph node staging, metastatic spread, and multifocality of breast disease, among other applications. In this review, we summarize the progress made in the development of optical mammography, and focus on the emerging work underway in the use of diagnostic contrast agents for the molecular-based, diagnostic imaging of breast.

Localisation and accumulation of a new carotenoporphyrin in two primary tumour models

We have investigated the tumour-localising properties and in vivo fluorescence kinetics of a hexamethoxylated carotenqporphyrin (CP6) in two primary tumour models: UV-B-induced early skin cancer in hairless mice and chemically induced mucosal dysplasia in the rat palate. CP6 fluorescence kinetics are investigated by measuring in vivo fluorescence spectra and images of the mouse skin and the rat palate at different time points after injection. For the tumour-localising properties, microscopic phase-contrast and fluorescence images are recorded. The in vivo fluorescence kinetics in the mouse skin show localization of CP6 in the tumours. However, fluorescence microscopy images show that CP6 localises in the dermis and structures that are not related to the malignant transformation of the mouse skin. The fluorescence kinetics in the rat palate show a significant correlation between the degree of malignancy and the CP6 fluorescence build-up time in the palate. The microscopic images show that CP6 fluorescence localises in the connective tissue and not in the dysplastic epithelium. In conclusion, CP6 does not localise preferentially in (pre-) cancerous tissue in the two primary tumour models studied here, in contrast to reports about localisation of carotenoporphyrins in transplanted tumours. However, the CP6 build-up time in rat palates correlates with the degree of malignancy and this might possibly be a useful parameter in tumour detection.

Photochemical and pharmacokinetic properties of selected flavins

Some photochemical and pharmacokinetic properties of riboflavin, lumiflavin and the 2',3',4',5' tetraacetyl, tetrapropionyl, tetrabutiryl and tetrapalmitoyl esters of riboflavin have been studied. The esters are considerably more photostable than riboflavin but less so than lumiflavin, and appear to be photosensitizers with a behaviour similar to that of riboflavin, promoting photoreactions of biological targets even in the absence of molecular oxygen. The various flavins display important differences in their pharmacokinetic behaviour. Riboflavin, lumiflavin and the short-chain esters (the acetyl and propionyl esters) are rapidly cleared from serum, and recovered in comparable amounts from the liver and kidneys. These results are in agreement with their hydrophilic or moderately hydrophobic character. In contrast, the longer-chain butiryl and palmitoyl esters exhibit a prolonged retention in serum and undergo a significantly larger accumulation in the liver as compared with the kidneys; they are also found in the spleen. In all cases the tissue uptake of these esters becomes appreciable only after 24 h. These results are coherent with the highly hydrophobic character of these esters, which induce a slow release from serum lipoproteins and have a preferential clearance via the bile-gut pathway, showing affinity for the components of the reticuloendothelial system. These long-chain riboflavin esters will probably have a greater and more persistent risk of photoinduced hepatotoxicity than riboflavin, lumiflavin and the short-chain esters.

Localization of Luminescent Inhomogeneities in Turbid Media with Spatially Resolved Measurements of cw Diffuse Luminescence Emittance

We present a steady-state method for localizing a source ofluminescence (i.e., fluorescence or phosphorescence) buried in asemi-infinite turbid medium with unknown optical properties. Adiffusion theory expression describing the emittance of an isotropicpoint source is fit to spatially resolved surface measurements of thediffuse emittance from the luminescent source. The techniquereports the location of the center of a 6.0-mm-diameter, fluorophore-containing spherical bulb embedded in a liquid phantom withan accuracy of 1.0 mm or better for source depths as great as 40.0mm. Monte Carlo data are analyzed to investigate the range and thepossible sources of error in the reconstructed source depth.

Physiological and pathological factors of human breast disease that can influence optical diagnosis

The 'normal' human female breast is a very complex organ that changes considerably during development, pregnancy and menopause. In addition, it is an excretory organ that, during lactation, discharges various metabolites and certain drugs that can be optically active. Optical diagnosis of breast cancers requires detection of differential concentrations of 1) various absorbers and scatterers or 2) native or exogenous fluorophores to distinguish cancers from surrounding 'normal' and benign breast tissues. The differential concentrations are due to the biology of the cancer cells and the host responses to the cancer growth. For most patients, the cancer will be intermixed with a complex 3-dimensional array of 'normal' breast tissue and benign breast lesions. This complexity will challenge the optical biopsy investigator but, with the recent advances in our understanding of light transport, optical diagnostic techniques and devices can be developed to complement and supplement current breast cancer screening techniques.

Laser-induced fluorescence studies of the biodistribution of carotenoporphyrins in mice

The biodistribution of two recently developed tumour markers, trimethylated (CP(Me)3) and trimethoxylated (CP(OMe)3) carotenoporphyrin, was investigated by means of laser-induced fluorescence (LIF) after i.v. injection into 38 tumour-bearing (MS-2 fibrosarcoma) female Balb/c mice. At 3, 24, 48 or 96 h after administration, the carotenoporphyrin fluorescence was measured in tumoral and peritumoral tissue, as well as in the abdominal, thoracic and cranial cavities. The fluorescence was induced by a nitrogen laser-pumped dye laser, emitting light at 425 nm, and analysed by a polychromator equipped with an image-intensified CCD camera. The fluorescence was evaluated at 490, 655 and 720 nm: the second and third wavelengths represent the carotenoporphyrin (CP)-related peaks, whereas the first one is close to the peak of the tissue autofluorescence. The tumour and the liver were the two tissue types showing the strongest carotenoporphyrin-related fluorescence, whereas the cerebral cortex and muscle consistently exhibited weak substance-related fluorescence. In most tissue types, the fluorescence intensities decreased over time. A few exceptions were observed, notably the liver, in which the intensity remained remarkably constant over the time period investigated.

Structure and biodistribution relationships of photodynamic sensitizers

Photodynamic therapy (PDT) has, during the last quarter century, developed into a fully fledged biomedical field with its own association, the International Photodynamic Association (IPA) and regular conferences devoted solely to this topic. Recent approval of the first PDT sensitizer, Photofrin (porfimer sodium), by health boards in Canada, Japan, the Netherlands and United States for use against certain types of solid tumors represents, perhaps, the single most significant-indicator of the progress of PDT from a laboratory research concept to clinical reality. The approval of Photofrin will undoubtedly encourage the accelerated development of second-generation photosensitizers, which have recently been the subject of intense study. Many of these second-generation drugs show significant differences, when compared to Photofrin, in terms of treatment times postinjection, light doses and drug doses required for optimal results. These differences can ultimately be attributed to variations in either the quantum efficiency of the photosensitizer in situ, which is in turn affected by aggregation state, localized concentration of endogenous quenchers and primary photophysics of the dye, or the intratumoral and intracellular localization of the photosensitizer at the time of activation with light. The purpose of this review is to bring together data relating to the biodistribution and pharmacokinetics of second-generation sensitizers and attempt to correlate this with structural and electronic features of these molecules. As this requires a clear knowledge of photosensitizer structure, only chemically well-characterized compounds are included, e.g. Photofrin and crude sulfonated phthalocyanines have been excluded as they are known to be complex mixtures. Nonporphyrin-based photosensitizers, e.g. rose bengal and the hypericins, have also been omitted to allow meaningful comparisons to be made between different compounds. As the intracellular distribution of photosensitizers to organelles and other subcellular structures can have a large effect on PDT efficacy, a section will be devoted to this topic.

Photodynamic imaging of a rat pancreatic cancer with pheophorbide a

Laser-induced fluorescence of pheophorbide a (Ph-a) was used for in vitro photodynamic imaging (PDI) of a rat pancreatic acinar tumor. A 400 nm excitation induced a 470 nm autofluorescence and a 678 nm dye fluorescence in tumors and their surrounding pancreas 24 h after a 9 mg kg-1 body weight Ph-a intravenous administration. With lower intensities in these blood-rich tumors than in pancreas, Ph-a fluorescence signals are unable to provide tumor images. A dimensionless function (the ratio of Ph-a fluorescence by autofluorescence, called Rt for the tumor and Rp for the pancreas) was used for fluorescence contrast calculation (C = Rt/Rp) between six tumors and their paired pancreas. Among five available laser excitation wave-lengths, only the 355 nm excitation gave a distinctive contrast (C = 1.5). The PDI of six intrapancreatic tumors and their intraperitoneal metastasis and of two control normal pancreas was thus performed ex vivo using a 355 nm excitation source delivered by a tripled Nd:YAG laser and a charged-coupled device camera. Fluorescence images were recorded at 680 nm (dye), 640 nm (background) and 470 nm (autofluorescence) through three corresponding 10 nm width bandpass filters. Computed division for each pixel of Ph-a fluorescence values by autofluorescence generated false color image. In this way, contrasted tumor images were obtained. But in five out of six animals false-positive images were present due to an autofluorescence decrease in some normal pancreatic areas. A 470 nm autofluorescence imaging on the same tumors gave in all cases false-positive image and false-negative in half of the cases. These observations suggest that autofluorescence alone is unable to achieve accurate PDI of pancreatic carcinoma and that using Ph-a as a PDI dye needs strong improvements.

Tumor labeling in vivo using cyanine-conjugated monoclonal antibodies

Far-red-emitting cyanine fluorochromes have many properties desirable for in vivo imaging: absorption and emission at wavelengths where blood and tissue are relatively transparent, high quantum yields, and good solubility even at high molar ratios of fluorochrome to antibody. Potentially, conjugation by multiple linkages should minimize hydrolysis in vivo. We conjugated two tumor-targeting monoclonal antibodies: anti-SSEA-1 (IgM, kappa) at ratios of 1.2-35 mol dye/mol antibody and 9.2.27 (IgG2a, kappa) at 0.6-6 mol dye/mol antibody, using the cyanine fluorochromes Cy3.18, Cy5.18, and Cy5.5.18. Nude mice were inoculated using the SSEA-1-expressing MH-15 teratocarcinoma or the 9.2.27 antigen-expressing SK-MEL-2 melanoma to give tumors at several sites. Conjugated antibody was injected, and mice were imaged immediately after injection and at appropriate intervals thereafter using a standard camera lens, dissecting microscope, or endoscopes. Images were acquired using either an image-intensified video camera or cooled CCD cameras. Immediately after injection, major blood vessels and the heart, liver, and kidneys were readily visualized. After 1 day, tumor-targeting antibody conjugates were concentrated in tumors and there was little circulating conjugate; however, the bladder and kidneys were still visible. Tumors labeled by specific antibody were the most fluorescent tissues at 2 days after injection, but non-specific antibody conjugates did not concentrate in the tumors. The small intestine was weakly visualized by both specific and non-specific antibody conjugates. These data support the possibility of visualizing tumor metastasis by optical means, including currently available endoscopes.

Interaction of phthalocyanines with lipid membranes: a spectroscopic and functional study on isolated rat liver mitochondria

Absorption and emission spectroscopic studies on Zn(II)-phthalocyanine (ZnPc) incorporated into unilamellar liposomes of dipalmitoylphosphatidylcholine, sometimes added with cholesterol or cardiolipin, and released to rat liver mitochondria via the three types of liposomal vesicles indicated that: (a) ZnPc predominantly dissolves in all lipid domains of biological membranes with the exception of cardiolipin-containing regions; a partial localization of ZnPc in protein binding sites is also postulated; (b) the spectroscopic properties of ZnPc, although mainly determined by the aggregation state of the dye, are somewhat influenced by the physico-chemical characteristics of the lipid environment; (c) ZnPc-binding lipid domains in mitochondria are mainly localized in the outer membrane; this conclusion is clearly deduced from the trends of Arrhenius plots of the ZnPc fluorescence quantum yield in whole mitochondria and isolated inner or outer membrane in the temperature range -10 degrees C-(+)45 degrees C; (d) the nature of the ZnPc-binding site in mitochondria is not dependent on the chemical composition of the liposome carrier, contrary to what observed for other hydrophobic dyes, such as porphyrins. This has been also confirmed by photosensitization experiments. Actually, illumination of ZnPc-loaded mitochondria by 600-700 nm light causes a decline of the respiratory control ratio, which is essentially dependent on the amount of incorporated photosensitizer, irrespective of the composition of the carrier.

Laser-induced fluorescence in malignant and normal tissue in mice injected with two different carotenoporphyrins

Laser-induced fluorescence (LIF) was used to characterise the localisation of an intravenously administered trimethylated carotenoporphyrin [CP(Me)3] and a trimethoxylated carotenoporphyrin [CP(OMe)3] in an intramuscularly transplanted malignant tumour (MS-2 fibrosarcoma) and healthy muscle in female Balb/c mice, 3, 24, 48 and 96 h post injection. The fluorescence was induced with a dye laser pumped by a nitrogen laser, emitting light at 425 nm. The fluorescence spectra were recorded in the region 455-760 nm using a polychromator equipped with an image-intensified CCD camera. The tumour/peritumoral muscle ratio was about 5:1 for CP(Me)3 and about 6:1 for CP(OMe)3 in terms of the background-free fluorescence intensity, which peaked at about 655 nm. By including the endogenous tissue fluorescence, the contrast was further enhanced by a factor of approximately 2.