In situ supramolecular polymerization-enhanced self-assembly of polymer vesicles for highly efficient photothermal therapy.

Vesicular photothermal therapy agents (PTAs) are highly desirable in photothermal therapy (PTT) for their excellent light-harvesting ability and versatile hollow compartments. However, up to now, the reported vesicular PTAs are generally self-assembled from small molecules like liposomes, and polymer vesicles have seldom been used as PTAs due to the unsatisfactory photothermal conversion efficiency resulting from the irregular packing of chromophores in the vesicle membranes. Here we report a nano-sized polymer vesicle from hyperbranched polyporphyrins with favorable photothermal stability and extraordinarily high photothermal efficiency (44.1%), showing great potential in imaging-guided PTT for tumors through in vitro and in vivo experiments. These excellent properties are attributed to the in situ supramolecular polymerization of porphyrin units inside the vesicle membrane into well-organized 1D monofilaments driven by π-π stacking. We believe the supramolecular polymerization-enhanced self-assembly process reported here will shed a new light on the design of supramolecular materials with new structures and functions.

Integration of a porous coordination network and black phosphorus nanosheets for improved photodynamic therapy of tumor.

Selectively attenuating the protection offered by heat shock protein 90 (HSP90), which is indispensable for the stabilization of the essential regulators of cell survival and works as a cell guardian under oxidative stress conditions, is a potential approach to improve the efficiency of cancer therapy. Here, we designed a biodegradable nanoplatform (APCN/BP-FA) based on a Zr(iv)-based porphyrinic porous coordination network (PCN) and black phosphorus (BP) sheets for efficient photodynamic therapy (PDT) by enhancing the accumulation of the nanoplatforms in the tumor area and attenuating the protection of cancer cells. Owing to the favorable degradability of BP, the nanosystem exhibited accelerated the release of the HSP90 inhibitor tanespimycin (17-AAG) and an apparent promotion in the reactive oxygen species (ROS) yield of PCN as well as expedited the degradation of the PCN-laden BP nanoplatforms. Both in vitro and in vivo results revealed that the elevated amounts of ROS and reduced cytoprotection in tumor cells were caused by the nanoplatforms. This strategy may provide a promising method for attenuating cytoprotection to aid efficient photodynamic therapy.

Photochemical /Photocytotoxicity Studies of New Tetrapyrrolic Structures as Potential Candidates for Cancer Theranostics.

BACKGROUND: Detailed photochemical and photocytotoxicity studies of two new porphyrins: 5,10,15,20-meso-tetrakis-(4-acetoxy-3-methoxyphenyl) porphyrin (P2.1) and 5-(4-hydroxy-3- methoxyphenyl)-10,15,20-tris-(4-acetoxy-3-methoxyphenyl)porphyrin (P2.2) are reported, as potential candidates for theranostics. For powdered samples of P2.1 and P2.2 adsorbed onto a powdered biocompatible substrate, polyethylene glycol (PEG), a concentration study was performed, correlating the fluorescence emission intensity with sample absorption to determine the useful concentration range for photodynamic therapy of cancer (PDT) in which aggregation does not occur. Cytotoxicity studies were performed in dark and illuminated conditions. METHODS: The laser induced luminescence set-up is home-made, a N2 laser is used as the excitation source and a time gated charged-coupled device (ICCD) as the detector. Fluorescence lifetime determinations were made using pulsed light sources from the excitation LEDs and measures of the fluorescence intensities at different time delays after the excitation pulse. The singlet oxygen formation quantum yields ΦΔ measurements were obtained by comparing the total area of the emission spectra for the reference compound and also for the samples under study in the same solvent and with the same optical density at the excitation wavelength (405 nm). An integrating sphere for relative and absolute measurements was used in this work as an alternative methodology to obtain the values for the fluorescence emission quantum yields (ΦF) of the adsorbed porphyrin under study. The cytotoxicity evaluation was made in the dark and under irradiation, using four different human tumor cell lines and one non-tumor primary cell culture. RESULTS: In order to establish the useful range of concentrations of the sensitizer for PDT, and due to the use of powdered samples, a special methodology was needed: the variations of the fluorescence lifetimes and fluorescence quantum yields were evaluated as a function of the concentration of the dye, measured by (1-R)*fdye. Both ΦF and τF are constant in the range from 0.002 to about 0.050 µmol g-1, and only after that a concentration quenching effect becomes visible, decreasing both ΦF and τF. This methodology is based in the correlations established between the Remission Function values and ΦF and τF obtained for increasing values of the sensitizer concentrations. CONCLUSIONS: The study of the aggregation effects of P2.1 and P2.2 porphyrins into a PEG matrix allowed us to determine the usable concentration range for photodynamic therapy use, where the aggregation of porphyrins decreases, therefore reducing the PDT action. The use of an integrating sphere for relative and absolute measurements of fluorescence quantum yields and also the lifetime studies as a function of the dye loading confirms the useful range for the use of P2.1 and P2.2 in PEG as powdered samples. The determination of the GI50, the porphyrin concentration which inhibits 50% of the cell growth, evidences that P2.2, the A3B porphyrin overtakes P2.1 (the A4 porphyrin) in terms of PDT efficiency and both porphyrins are much better PDT agents than the unsubstituted porphyrin, TPP. These data clearly show that porphyrins P2.2 and P2.1 exhibit an excellent behaviour in terms of its photocytotoxicity. These results encourage us to pursuit in the study of this family of porphyrins in which a balance of hydrophobic versus hydrophilic substituents in the phenyl group was achieved.

Pharmacokinetics and pharmacodynamics of liposomal chemophototherapy with short drug-light intervals.

Chemophototherapy (CPT) merges photodynamic therapy with chemotherapy and can substantially enhance drug delivery. Using a singular liposomal formulation for CPT, we describe a semi-mechanistic pharmacokinetic-pharmacodynamic (PK/PD) model to investigate observed antitumor effects. Long-circulating, sterically-stabilized liposomes loaded with doxorubicin (Dox) stably incorporate small amounts of a porphyrin-phospholipid (PoP) photosensitizer in the bilayer. These were administered intravenously to mice bearing low-passage, patient-derived pancreatic cancer xenografts (PDX). Dox PK was described with a two-compartment model and tumor drug disposition kinetics were modeled with first-order influx and efflux rates. Tumor irradiation with 665 nm laser light (200 J/cm2) 1 h after liposome administration increased tumor vascular permeabilization and drug accumulation, which was accounted for in the PK/PD model with increased tumor influx and efflux rates by approximately 12- and 4- fold, respectively. This modeling approach provided an overall 7-fold increase in Dox area under the curve in the tumor, matching experimental data (7.4-fold). A signal transduction model based on nonlinear direct cell killing accounted for observed tumor growth patterns. This PK/PD model adequately describes the CPT anti-PDX tumor response based on enhanced drug delivery at the short drug-light interval used.

Phase-Change Material Packaged within Hollow Copper Sulfide Nanoparticles Carrying Doxorubicin and Chlorin e6 for Fluorescence-Guided Trimodal Therapy of Cancer.

Environmental stimuli, including pH, light, and temperature, have been utilized for activating controlled drug delivery to achieve efficient antitumor therapeutics while minimizing undesirable side effects. In this study, a multifunctional nanoplatform based on hollow mesoporous copper sulfide nanoparticles (H-CuS NPs) was developed by loading the interior cavity of the NPs with a drug-loaded phase-change material (PCM, 1-tetradecanol). Doxorubicin (DOX) and chlorin e6 (Ce6) were selected as the model chemotherapeutic drug and photosensitizer, respectively, which were encapsulated in H-CuS NPs via the PCM to form H-CuS@PCM/DOX/Ce6 (HPDC) NPs. When exposed to near infrared laser irradiation, this nanocomplex could produce a strong photothermic effect and thus induce the controlled release of DOX and Ce6 from the melting PCM. Subsequently, the DOX-mediated chemotherapeutic effect and Ce6-mediated photodynamic effect further contributed to enhanced tumor eradication. The efficacy of this multimodal cancer treatment combining chemo-, photothermal, and photodynamic therapies was systematically evaluated both in vitro and in vivo using a 4T1 mouse mammary tumor cell line and a mouse model bearing breast cancer. Moreover, this nanoplatform exhibited minimal systemic toxicity and good hemocompatibility and may provide an effective strategy for the delivery of multiple therapeutic agents and application of multimodal cancer treatments.

In vivo wireless photonic photodynamic therapy.

An emerging class of targeted therapy relies on light as a spatially and temporally precise stimulus. Photodynamic therapy (PDT) is a clinical example in which optical illumination selectively activates light-sensitive drugs, termed photosensitizers, destroying malignant cells without the side effects associated with systemic treatments such as chemotherapy. Effective clinical application of PDT and other light-based therapies, however, is hindered by challenges in light delivery across biological tissue, which is optically opaque. To target deep regions, current clinical PDT uses optical fibers, but their incompatibility with chronic implantation allows only a single dose of light to be delivered per surgery. Here we report a wireless photonic approach to PDT using a miniaturized (30 mg, 15 mm3) implantable device and wireless powering system for light delivery. We demonstrate the therapeutic efficacy of this approach by activating photosensitizers (chlorin e6) through thick (>3 cm) tissues inaccessible by direct illumination, and by delivering multiple controlled doses of light to suppress tumor growth in vivo in animal cancer models. This versatility in light delivery overcomes key clinical limitations in PDT, and may afford further opportunities for light-based therapies.

A Tumor-Activatable Theranostic Nanomedicine Platform for NIR Fluorescence-Guided Surgery and Combinatorial Phototherapy.

Fluorescence image-guided surgery combined with intraoperative therapeutic modalities has great potential for intraoperative detection of oncologic targets and eradication of unresectable cancer residues. Therefore, we have developed an activatable theranostic nanoplatform that can be used concurrently for two purposes: (1) tumor delineation with real-time near infrared (NIR) fluorescence signal during surgery, and (2) intraoperative targeted treatment to further eliminate unresected disease sites by non-toxic phototherapy. Methods: The developed nanoplatform is based on a single agent, silicon naphthalocyanine (SiNc), encapsulated in biodegradable PEG-PCL (poly (ethylene glycol)-b-poly(ɛ-caprolactone)) nanoparticles. It is engineered to be non-fluorescent initially via dense SiNc packing within the nanoparticle's hydrophobic core, with NIR fluorescence activation after accumulation at the tumor site. The activatable nanoplatform was evaluated in vitro and in two different murine cancer models, including an ovarian intraperitoneal metastasis-mimicking model. Furthermore, fluorescence image-guided surgery mediated by this nanoplatform was performed on the employed animal models using a Fluobeam® 800 imaging system. Finally, the phototherapeutic efficacy of the developed nanoplatform was demonstrated in vivo. Results: Our in vitro data suggest that the intracellular environment of cancer cells is capable of compromising the integrity of self-assembled nanoparticles and thus causes disruption of the tight dye packing inside the hydrophobic cores and activation of the NIR fluorescence. Animal studies demonstrated accumulation of activatable nanoparticles at the tumor site following systemic administration, as well as release and fluorescence recovery of SiNc from the polymeric carrier. It was also validated that the developed nanoparticles are compatible with the intraoperative imaging system Fluobeam® 800, and nanoparticle-mediated image-guided surgery provides successful resection of cancer tumors. Finally, in vivo studies revealed that combinatorial phototherapy mediated by the nanoparticles could efficiently eradicate chemoresistant ovarian cancer tumors. Conclusion: The revealed properties of the activatable nanoplatform make it highly promising for further application in clinical image-guided surgery and combined phototherapy, facilitating a potential translation to clinical studies.

Multifunctional theranostic Pluronic mixed micelles improve targeted photoactivity of Verteporfin in cancer cells.

Nanotechnology development provides new strategies to treat cancer by integration of different treatment modalities in a single multifunctional nanoparticle. In this scenario, we applied the multifunctional Pluronic P123/F127 mixed micelles for Verteporfin-mediated photodynamic therapy in PC3 and MCF-7 cancer cells. Micelles functionalization aimed the targeted delivery by the insertion of biotin moiety on micelle surface and fluorescence image-based through rhodamine-B dye conjugation in the polymer chains. Multifunctional Pluronics formed spherical nanoparticulated micelles that efficiently encapsulated the photosensitizer Verteporfin maintaining its favorable photophysical properties. Lyophilized formulations were stable at least for 6months and readily reconstituted in aqueous media. The multifunctional micelles were stable in protein-rich media due to the dual Pluronic mixed micelles characteristic: high drug loading capacity provided by its micellar core and high kinetic stability due its biocompatible shell. Biotin surface functionalized micelles showed higher internalization rates due biotin-mediated endocytosis, as demonstrated by competitive cellular uptake studies. Rhodamine B-tagged micelles allowed monitoring cellular uptake and intracellular distribution of the formulations. Confocal microscopy studies demonstrated a larger intracellular distribution of the formulation and photosensitizer, which could drive Verteporfin to act on multiple cell sites. Formulations were not toxic in the dark condition, but showed high Verteporfin-induced phototoxicity against both cancer cell lines at low drug and light doses. These results point Verteporfin-loaded multifunctional micelles as a promising tool to further developments in photodynamic therapy of cancer.

Biodegradable nanocomplex from hyaluronic acid and arginine based poly(ester amide)s as the delivery vehicles for improved photodynamic therapy of multidrug resistant tumor cells: An in vitro study of the performance of chlorin e6 photosensitizer.

Photodynamic therapy (PDT), which enables the localized therapeutic effect by light irradiation, provides an alternative and complementary modality for the treatment of tumor. However, the aggregation of photosensitizers in acidic microenvironment of tumor and the non-targeted distribution of photosensitizers in normal tissues significantly affect the PDT efficiency. In this study, we developed a biodegradable nanocomplex HA-Arg-PEA from hyaluronic acid (HA) and arginine based poly(ester amide)s (Arg-PEA) as the nanocarrier for chlorin e6 (Ce6). HA enhanced the tumor-specific endocytosis mediated by the overexpression of CD44 receptor. Arg-PEA not only provide electrostatic interaction with HA to form self-assembled nanostructure, but also improve the monomerization of Ce6 at physiological pH as well as mildly acidic pH. The biodegradable characteristic of HA-Arg-PEA nanocomplex enabled the intracellular delivery of Ce6, in which its release and generation of singlet oxygen can be accelerated by enzymatic degradation of the carrier. The in vitro PDT efficiency of Ce6-loaded HA-Arg-PEA nanocomplex was examined in CD44 positive MDA-MB-435/MDR multidrug resistant melanoma cells. CD44-mediated uptake of Ce6-loaded HA-Arg-PEA nanocomplex significantly improved Ce6 level in MDA-MB-435/MDR cells within short incubation time, and the PDT efficiency in inhibiting multidrug resistant tumor cells was also enhanced at higher Ce6 concentrations. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1487-1499, 2017.

A safety study of a novel photosensitizer, sinoporphyrin sodium, for photodynamic therapy in Beagle dogs.

Sinoporphyrin sodium (DVDMS) is a novel hematoporphyrin-like photosensitizer developed for photodynamic therapy (PDT), an effective therapeutic modality for tumor treatment; however, the safety of photosensitizer-based PDT is always of great concern. The purpose of the current study was to investigate the potential repeated-dose toxicity and describe the toxicokinetic process of DVDMS-based PDT in Beagle dogs. The dogs were randomly allocated to six groups, and then were administrated a DVDMS preparation intravenously at dose levels of 0, 1, 3, 9, 1 and 9 mg per kg body weight, respectively; then, the latter two groups were illuminated 24 h later with a 630 nm laser for 10 min, once every seven days for 5 weeks. During the study period, clinical signs, mortality, body weight, food consumption, body temperature, ophthalmoscopy, hematology, serum biochemistry, urinalysis, electrocardiograms, toxicokinetics, organ weights, gross anatomy and histopathology were examined. After the administration, no deaths were observed; however, the dogs that received PDT showed skin swelling and ulceration, indicating that DVDMS-PDT induced a phototoxic effect. DVDMS led to an increase in blood coagulation in dogs in the 9 mg kg(-1) group and in the two PDT groups on Day 35, whereas it induced a decrease in dogs in the 3 mg kg(-1) group and in the two PDT groups on Day 49. The toxicokinetic study showed that the systematic exposure of DVDMS in dogs occurred in a dose-dependent manner, and DVDMS did not accumulate in blood plasma. The DVDMS-based PDT group showed no obvious treatment-related pathological changes; however, slight or mild brown-and-yellow pigmentation of DVDMS (or its metabolite) was observed to deposit in the liver, spleen, local lymph nodes and marrow of dogs in the mid- and high-dose groups, as well as the high-dose PDT group. In females, the absolute and relative spleen weights increased in dogs in the 9 mg kg(-1) DVDMS groups with and without PDT during the treatment and recovery period, respectively. The target organs are presumed to be the liver and immune organs (spleen, bone marrow and lymph nodes), while all of the responses were slight. Based on the results above, the no-observed-adverse-effect level (NOAEL) was considered to be 1 mg kg(-1), and DVDMS-PDT appeared to be a safe and promising anti-tumor therapy in the clinic.

In vitro and in vivo antitumor activity of a novel porphyrin-based photosensitizer for photodynamic therapy.

PURPOSE: Photodynamic therapy (PDT) is a promising treatment in cancer therapy, based on the use of a photosensitizer activated by visible light in the presence of oxygen. Nowadays significant research efforts have been focused on finding a new photosensitizer. In the present paper, the antitumor effects of a novel porphyrin-based photosensitizer, {Carboxymethyl-[2-(carboxymethyl-{[4-(10,15,20-triphenylporphyrin-5-yl)-phenylcarbamoyl]-methyl}-amino)-ethyl]-amino}-acetic acid (ATPP-EDTA) on two types of human malignant tumor cells in vitro and a gastric cancer model in nude mice, were evaluated. METHODS: The PDT efficacy with ATPP-EDTA in vitro was assessed by MTT assay. The intracellular accumulation was detected with fluorescence spectrometer, and the intracellular distribution was determined by laser scanning confocal microscopy. The mode of cell death was investigated by Hoechst 33342 staining and flow cytometer. BGC823-derived xenograft tumor model was established to explore the in vivo antitumor effects of ATPP-EDTA. RESULTS: ATPP-EDTA exhibited intense phototoxicity on both cell lines in vitro in concentration- and light dose-dependent manners meanwhile imposing minimal dark cytotoxicity. The accumulation of ATPP-EDTA in two malignant cell lines was time-dependent and prior compared to normal cells. It was mainly localized at lysosomes, but induced cell death by apoptotic pathway. ATPP-EDTA significantly inhibited the growth of BGC823 tumors in nude mice (160 mW/cm(2), 100 J/cm(2)). CONCLUSIONS: Present studies suggest that ATPP-EDTA is an effective photosensitizer for PDT to tumors. It distributed in lysosomes and caused cell apoptosis. ATPP-EDTA, as a novel photosensitizer, has a great potential for human gastric cancer treatment in PDT and deserves further investigations.

Lead structures for applications in photodynamic therapy. 5. Synthesis and biological evaluation of water soluble phosphorus(V) 5,10,15,20-tetraalkylporphyrins for PDT.

Improved photosensitizers for use in photomedicine must possess good water-solubility and optimal photophysical properties. Phosphorus(V) porphyrins fulfill these criteria and are a class of porphyrins with significant potential applications in phototherapy. Five phosphorus(V) porphyrins bearing alkyl substituents have been synthesized. Reasonable to good yields were obtained for all P(V) insertions and all compounds underwent biological evaluation for their PDT activity on two esophageal cancer cell lines, OE33 and SKGT-4. Their cellular uptake was investigated using a high content screening method. Notably, three compounds displayed good uptake and using the MTS cell proliferation assay, two were shown to have photocytotoxicity comparable to mTHPC (Temoporfin(®)) with IC50 values of 6.5 and 5.5 µM.

Drug delivery with PEGylated MoS2 nano-sheets for combined photothermal and chemotherapy of cancer.

MoS2 nanosheets functionalized with poly-ethylene glycol are for the first time used as a multifunctional drug delivery system with high drug loading capacities. Using doxorubicin as the model drug and taking advantages of the strong near-infrared absorbance of MoS2, combined photothermal and chemotherapy of cancer is realized in animal experiments, achieving excellent synergistic anti-tumor effect upon systemic administration.

Complementary strategies for developing Gd-free high-field T1 MRI contrast agents based on Mn(III) porphyrins.

Mn(III) porphyrin (MnP) holds the promise of addressing the emerging challenges associated with Gd-based clinical MRI contrast agents (CAs), namely, Gd-related adverse effect and decreasing sensitivity at high clinical magnetic fields. Two complementary strategies for developing new MnPs as Gd-free CAs with optimized biocompatibility were established to improve relaxivity or clearance rate. MnPs with distinct and tunable pharmacokinetic properties can consequently be constructed for different in vivo applications at clinical field of 3 T.

Myocardial electrical conduction block induced by photosensitization reaction in exposed porcine hearts in vivo.

BACKGROUND AND OBJECTIVE: This study proposes photosensitization reaction for non-thermal cardiac ablation in arrhythmia therapy. Acute and chronic phase experiments were conducted in exposed porcine hearts to demonstrate the photosensitization reaction-induced myocardial electrical conduction block in vivo. STUDY DESIGN/MATERIALS AND METHODS: The porcine left atrial appendage was exposed under an open-chest procedure. Then, a water-soluble chlorin photosensitizer, NPe6, was injected into the pigs intravenously at 5 or 10 mg/kg. About 15 or 30 minutes after the injection, a 663-nm continuous-wave diode laser was irradiated on the surface of the atrial appendage through a silica optical fiber. The laser energy was delivered to the tissue point by point at an energy density of 50-208 J/cm(2). RESULTS: Acute and chronic tissue damages as a result of the photosensitization reaction were determined by electrophysiology and histology, respectively. The change in the myocardial conduction time between two electrodes was measured immediately after the completion of the 35-mm irradiation line between the electrodes. The conduction delay of 35.5 milliseconds might be due to the change in the conduction pathway induced by transmural acute conduction block with the photosensitization reaction. The tissue temperature increase in the irradiated area was approximately 12.8°C. Azan-staining revealed about 1-mm transmural fibrosis of the atrial appendage at 2 weeks after the irradiation (50 J/cm(2)). CONCLUSIONS: The results suggest that the photosensitization reaction might induce acute and chronic myocardial electrical conduction block. Cardiac ablation with the photosensitization reaction might be a non-temperature-mediated methodology for arrhythmia therapy.

Pharmacokinetic study of a novel sonosensitizer chlorin-e6 and its sonodynamic anti-cancer activity in hepatoma-22 tumor-bearing mice.

PURPOSE: The sonodynamically induced anti-tumor effect of chlorin-e6 (Ce6) was studied in mice bearing hepatoma-22 solid tumors. METHODS: In order to determine the optimum timing of ultrasound exposure after administration of Ce6, the Ce6 concentrations in plasma, skin, muscle and tumor were estimated by measuring the fluorescence intensity of tissue extractions with a fluorescence photometer based on the standard curve. A three-dimensional optical imaging system (IVIS spectrum) was used further to characterize the distribution of Ce6 in H-22 tumor. The anti-tumor effects were estimated by measuring tumor size after sonodynamic therapy. RESULTS: Similar pharmacokinetic trends of Ce6 in mice were observed either by fluorescence spectrophotometry or by bio-optical imaging. The results also demonstrated that Ce6 has a preferential localization in tumors, but low accumulation and rapid clearance in normal tissues. The results of anti-tumor effects revealed that at an ultrasound intensity of 4 W/cm(2) and a Ce6 dose of ≥10 mg/kg, a significant synergistic effect of ultrasound combined with Ce6 was observed, reducing the tumor volume significantly. CONCLUSION: Chlorin-e6 is a potential sonosensitizer for fluorescence imaging as well as for sonodynamic therapy for cancer. The anti-tumor effect of ultrasound could be enhanced in the presence of Ce6, which might be involved in a sonochemical mechanism.

Water-soluble porphyrin-polyethylene glycol conjugates with enhanced cellular uptake for photodynamic therapy.

Water soluble porphyrins were designed and prepared by Williamson ether synthesis reaction between tetrakis(p-bromomethylphenyl)porphyrin and polyethylene glycol (PEG) for photodynamic therapy. The quantum yields for the generation of singlet oxygen of tetra-polyethylene glycol branched porphyrin shows above 80% in D2O. Luminescence of singlet state oxygen was observed from D2O solution under the single-photon excitation at 514 nm. In vitro test, cellular uptake efficiency has been enhanced by simple modification of molecular structure through changing the number of PEG unit without any support such as polymer-encapsulated inorganic nanoparticles.

Physiological and pharmacological roles of ABCG2 (BCRP): recent findings in Abcg2 knockout mice.

The multidrug transporter ABCG2 (BCRP/MXR/ABCP) can actively extrude a broad range of endogenous and exogenous substrates across biological membranes. ABCG2 limits oral availability and mediates hepatobiliary and renal excretion of its substrates, and thus influences the pharmacokinetics of many drugs. Recent work, relying mainly on the use of Abcg2(-/-) mice, has revealed important contributions of ABCG2 to the blood-brain, blood-testis and blood-fetal barriers. Together, these functions indicate a primary biological role of ABCG2 in protecting the organism from a range of xenobiotics. In addition, several other physiological functions of ABCG2 have been observed, including extrusion of porphyrins and/or porphyrin conjugates from hematopoietic cells, liver and harderian gland, as well as secretion of vitamin B(2) (riboflavin) and possibly other vitamins (biotin, vitamin K) into breast milk. However, the physiological significance of these processes has been difficult to establish, indicating that there is still a lot to learn about this intriguing protein.

Photodynamic therapy using talaporfin sodium for synovial membrane from rheumatoid arthritis patients and collagen-induced arthritis rats.

We investigated the efficacy of photodynamic therapy (PDT) using talaporfin sodium as a new method of synovectomy for rheumatoid arthritis (RA). We first used RA synovial membrane (RASM) for in vitro and in vivo study. The RASM was obtained from patients with RA during total knee replacement. In the in vitro study, RA fibroblast-like synoviocytes (RASCs) obtained from the RASM were examined by fluorescent microscopy to measure the intracellular localization of talaporfin sodium. The cells were then subjected to PDT, and their viability was examined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-tetrazolium inner salt assay. In the in vivo assay, RASM was obtained as described above, grafted onto severe combined immunodeficiency (SCID) mice and subjected to PDT. The damaged area of RASM was evaluated histologically at 1 day after PDT. Next, we performed a separate experiment using rats with collagen-induced arthritis (CIA). After intra-articular injection of talaporfin sodium, the concentration of talaporfin sodium accumulated in the CIA synovial membrane (CIASM) was compared with that in cartilage, periarticular muscle, and skin. We then performed PDT with intra-articular injection of talaporfin sodium and intra-articular irradiation. The damaged area of the CIASM was measured at 1 day after the PDT, and the articular histological and radiological changes of the ankle were observed at 56 days after the PDT. In RASM, talaporfin sodium accumulated in lysosomes in vitro, and the phototoxicity to RASCs in vitro and to RASM grafted onto SCID mice in vivo depended on the concentration of talaporfin sodium and the laser energy. In CIA rats, there was a greater accumulation of talaporfin sodium in the CIASM than in normal tissue. The CIASM was selectively damaged at 1 day after the PDT, and the bone and cartilage destruction were ameliorated at 56 days after the PDT. In conclusion, PDT using talaporfin sodium might be a new method for synovectomy in patients with RA.