Analysis of effective molecular diffusion rates for verteporfin in subcutaneous versus orthotopic Dunning prostate tumors

Photosensitizer biodistribution change inside tissue is one of the dominant factors in photodynamic therapy efficacy. In this study, the pharmacokinetics of a benzoporphyrin derivative (BPD), delivered in verteporfin for injection formulation, have been quantified in the rat Dunning prostate tumor MAT-LyLu model, using both subcutaneous and orthotopic sites. Blood plasma sampling indicated that BPD had a bi-exponential metabolic lifetime in vivo, with the two lifetimes being 9.6 min and 8.3 h. The spatial distributions in the tumor were quantified as a function of distance from the perfused blood vessels, using fluorescence histologic images of the tumor. A fluorescent vascular marker was used to obtain locations and shapes of perfused capillaries at a wavelength of emission different from that of BPD and to allow colocalized images to be acquired of vessel and BPD locations. Using the BPD fluorescence images obtained 15 min after intravenous administration, a forward finite-element solution to the diffusion equation was used to predict the drug distribution by matching the fluorescence intensity images observed microscopically. An inverse solver was used to minimize the root mean square error between the image of simulated diffusion and the experimental image, resulting in estimation of the diffusion coefficient of BPD in the tumor models. Effective diffusion coefficients were 0.88 and 1.59 microm2/s for the subcutaneous and orthotopically grown tumors, respectively, indicating that orthotopic tumors have significantly higher vascular extravasation rates as compared with subcutaneous tumors. This analysis supports the hypothesis that leakage rates of the photosensitizer vary considerably. Thus, although varying the time between injection and optical irradiation may be used to vary the targeting between vascular and less vascular areas, the precise time of treatment will depend on the nature of the permeability of the vasculature in the tissue being treated.     

Electric field-mediated transport of plasmid DNA in tumor interstitium in vivo

Local pulsed electric field application is a method for improving non-viral gene delivery. Mechanisms of the improvement include electroporation and electrophoresis. To understand how electrophoresis affects pDNA delivery in vivo, we quantified the magnitude of electric field-induced interstitial transport of pDNA in 4T1 and B16.F10 tumors implanted in mouse dorsal skin-fold chambers. Four different electric pulse sequences were used in this study, each consisted of 10 identical pulses that were 100 or 400 V/cm in strength and 20 or 50 ms in duration. The interval between consecutive pulses was 1 s. The largest distance of transport was obtained with the 400 V/cm and 50 ms pulse, and was 0.23 and 0.22 microm/pulse in 4T1 and B16.F10 tumors, respectively. There were no significant differences in transport distances between 4T1 and B16.F10 tumors. Results from in vivo mapping and numerical simulations revealed an approximately uniform intratumoral electric field that was predominantly in the direction of the applied field. The data in the study suggested that interstitial transport of pDNA induced by a sequence of ten electric pulses was ineffective for macroscopic delivery of genes in tumors. However, the induced transport was more efficient than passive diffusion.     

Electrically enhanced percutaneous delivery of delta-aminolevulinic acid using electric pulses and a DC potential

Selectivity of photodynamic therapy can be improved with localized photosensitizer delivery, but topical administration is restricted by poor diffusion across the stratum corneum. We used electric pulses to increase transdermal transport of delta-aminolevulinic acid (ALA), a precursor to the photosensitizer protoporphyrin IX (PpIX). ALA-filled electrodes were attached to the surface of excised porcine skin or the dorsal surface of mice. Pulses were administered and, in some in vivo cases, a continuous DC potential (6 V) was concomitantly applied. For in vitro 14C ALA penetration, 10 microm layers parallel to the stratum corneum were assayed by liquid scintillation analysis, and 10 microm cross sections were examined autoradiographically. As the electrical dose (voltage x frequency x pulse width x treatment duration) increased, there was an increase in penetration depth. In vivo delivery was assayed by measuring the fluorescence of PpIX in skin samples. A greater than two-fold enhancement of PpIX production with electroporative delivery was seen versus that obtained with passive delivery. Superimposition of a DC potential resulted in a nearly three-fold enhancement of PpIX production versus passive delivery. Levels were higher than the sum of PpIX detected after pulse-alone and DC-alone delivery. Electroporation and electrophoresis are likely factors in electrically enhanced delivery.     

Comparison of photosensitizer (AIPcS2) quantification techniques: in situ fluorescence microsampling versus tissue chemical extraction

A noninvasive in situ fluorescence-based method for the quantification of the photosensitizer chloroaluminum disulfonated phthalocyanine was compared to the highly accurate but nonreal time ex vivo spectrofluorometry method. Our in vivo fluorescence technique is designed to allow real-time assessment of photosensitizer in tumor and normal tissues and therefore temporally optimal light delivery. Laser-induced fluorescence was used to measure photosensitizer concentration from multiple microscopic regions of tissue. Ex vivo chemical extraction was used to quantify photosensitizer concentration in the same volume of tissue. The amount of photosensitizer in the vascular and/or parenchymal compartments of skeletal muscle and liver was determined by quantifying fluorescent signal in vivo, ex vivo and after blood removal. Confocal microscopy was used to spatially document photosensitizer localization 30 min and 24 h after delivery. While a linear correlation can exist between the fluorescence intensity measured by our fiber-optic bundle system and actual tissue concentration, temporal changes to this calibration line exist as the photosensitizer changes its partitioning fraction between the blood (vasculature) and the tissue parenchyma. In situ photosensitizer fluorescence microsampling (dosimetry) systems can be performed in real time and linearly correlated to actual tissue concentration with minimal intertissue variance. Tissue-specific differences may require temporal alterations in the calibration.     

Tuning the In Vivo Transport of Anticancer Drugs Using Renal‐Clearable Gold Nanoparticles

Precise control of in vivo transport of anticancer drugs in normal and cancerous tissues with engineered nanoparticles is key to the future success of cancer nanomedicines in clinics. This requires a fundamental understanding of how engineered nanoparticles impact the targeting‐clearance and permeation‐retention paradoxes in the anticancer‐drug delivery. Herein, we systematically investigated how renal‐clearable gold nanoparticles (AuNPs) affect the permeation, distribution, and retention of the anticancer drug doxorubicin in both cancerous and normal tissues. Renal‐clearable AuNPs retain the advantages of the free drug, including rapid tumor targeting and high tumor vascular permeability. The renal‐clearable AuNPs also accelerated body clearance of off‐target drug via renal elimination. These results clearly indicate that diverse in vivo transport behaviors of engineered nanoparticles can be used to reconcile long‐standing paradoxes in the anticancer drug delivery.     

Analysis of the heterogeneity of pO2 dynamics during photodynamic therapy with verteporfin.

Photodynamic therapy (PDT) with verteporfin provides a reliable way to destroy malignant tissues. Changes in the blood flow and oxygen partial pressure (pO2) during verteporfin-PDT were studied here in the tumor tissue of the rat mammary R3230Ac carcinoma model. Oxygen microelectrodes (6-12 microns tip diameter) were used to measure the transients locally within tumors during intravenous injection of 1.0 mg/kg verteporfin followed by irradiation 15 min later with 690 nm light at 200 mW/cm2, for a cumulative dose of 144 J/cm2. The observed changes in pO2 were heterogeneous and there was a difference in the response of low-pO2 regions relative to higher-pO2 regions. The change in pO2 in hypoxic tissue regions (pO2 < 8 mmHg) had acute pO2 loss after treatment, whereas the response in regions of higher pO2 (> 8 mm Hg) was more heterogeneous with some areas maintaining their pO2 value after treatment was completed. Blood flow measurements taken on a subset of the animals indicated a significant loss in flow during the initial light delivery that remained low after treatment, indicating some vascular stasis. The results suggest that hypoxic or poorly perfused vessels may be more susceptible to acute stasis than normoxic vessels in this treatment protocol.     

Antivascular treatment of solid melanoma tumors with bacteriochlorophyll-serine-based photodynamic therapy

We describe here a strategy for photodynamic eradication of solid melanoma tumors that is based on photo-induced vascular destruction. The suggested protocol relies on synchronizing illumination with maximal circulating drug concentration in the tumor vasculature attained within the first minute after administrating the sensitizer. This differs from conventional photodynamic therapy (PDT) of tumors where illumination coincides with a maximal concentration differential of sensitizer in favor of the tumor, relative to the normal surrounding tissue. This time window is often achieved after a delay (3-48 h) following sensitizer administration. We used a novel photosensitizer, bacteriochlorophyll-serine (Bchl-Ser), which is water soluble, highly toxic upon illumination in the near-infrared (lambda max 765-780 nm) and clears from the circulation in less than 24 h. Nude CD1 mice bearing malignant M2R melanotic melanoma xenografts (76-212 mm3) received a single complete treatment session. Massive vascular damage was already apparent 1 h after treatment. Changes in vascular permeability were observed in vivo using contrast-enhanced magnetic resonance imaging (MRI), with the contrast reagent Gd-DTPA, by shortening spin-spin relaxation time because of hemorrhage formation and by determination of vascular macromolecular leakage. Twenty-four hours after treatment a complete arrest of vascular perfusion was observed by Gd-DTPA-enhanced MRI. Histopathology performed at the same time confirmed primary vascular damage with occlusive thrombi, hemorrhage and tumor necrosis. The success rate of cure of over 80% with Bchl-Ser indicates the benefits of the short and effective treatment protocol. Combining the sensitizer administration and illumination steps into one treatment session (30 min) suggests a clear advantage for future PDT of solid tumors.     

Correlating Anticancer Drug Delivery Efficiency with Vascular Permeability of Renal Clearable Versus Non‐renal Clearable Nanocarriers

Enhancing tumor targeting of nanocarriers has been a major strategy for advancing clinical translation of cancer nanomedicines. Herein, we report a head‐to‐head comparison between 5 nm renal clearable and 30 nm non‐renal clearable gold nanoparticle (AuNP)‐based drug delivery systems (DDSs) in the delivery of doxorubicin (DOX). While the two DDSs themselves had comparable tumor targeting, we found their different vascular permeability played an even more important role than blood retention in the delivery and intratumoral transport of DOX, of which tumor accumulation, efficacy, and therapeutic index were enhanced 2, 7, and 10‐fold, respectively, for the 5 nm DDS over 30 nm one. These findings indicate that ultrahigh vascular permeability of renal clearable nanocarriers can be utilized to further improve anticancer drug delivery without the need for prolonged blood retention.     

Magnetic Mesoporous Silica Nanoparticles Cloaked by Red Blood Cell Membranes: Applications in Cancer Therapy

Targeted drug delivery is an emerging technological strategy that enables nanoparticle systems to be responsive for tumor therapy. Magnetic mesoporous silica nanoparticles (MMSNs) were cloaked with red blood cell membrane (RBC). This integrates long circulation, photosensitizer delivery, and magnetic targeting for cancer therapy. In vivo experiments demonstrate that RBC@MMSNs can avoid immune clearance and achieve magnetic field (MF)‐induced high accumulation in a tumor. When light irradiation is applied, singlet oxygen rapidly generates from hypocrellin B (HB)‐loaded RBC@MMSN and leads to the necrosis of tumor tissue. Such a RBC‐cloaked magnetic nanocarrier effectively integrates immunological adjuvant, photosensitizer delivery, MF‐assisted targeting photodynamic therapy, which provides an innovative strategy for cancer therapy.     

PHOTODYNAMIC THERAPY OF HEAD and NECK SQUAMOUS CELL CARCINOMA: OPTICAL DOSIMETRY and CLINICAL TRIAL

Abstract This paper reports the retrospective comparison of a PDT dosimetry model with the current results of an ongoing clinical trial on photodynamic therapy (PDT) for head and neck squamous cell carcinoma (HNSCC). The model is based on the assumption that tumor eradication requires a minimum absorption of radiant energy by the tumor-localized porphyrins. The diffusion approximation was employed to calculate the incident light dose required to attain the minimum absorbed energy density at tumor boundaries most distant from the light source. Dosimetry tables for HNSCC were calculated with estimated tissue parameters, giving the PDT light dose for front surface exposure (FS) and illumination by interstitial cylindrical diffuser fibers (CI) in terms of the tumor dimensions. The model includes a correction for the photobleaching of the localized photosensitizer by the therapeutic light. The PDT trial was carried out on nine patients with previously untreated or recurrent early stage tumors and one patient with a recurrent advanced stage tumor. A complete response was obtained in 83% (10/12) of the sites treated. The calculated doses for FS and CI exposures vary from comparable with to three-fold lower than the actual doses for each complete response tumor site.     

DH-I-180-3-mediated photodynamic therapy: biodistribution and tumor vascular damage

An important goal of photodynamic therapy (PDT) for treatment of various cancers is to shorten PDT-performing time and simultaneously enhance PDT efficacy. Here, we investigated the nontumor tissue distribution of and the tumor vascular damage caused by a new photosensitizer, DH-I-180-3, in mice with implanted EMT6 mammary tumor cells. In addition, we performed cell-based assays to evaluate the basic antitumor effect of DH-I-180-3/PDT in EMT6 cells. After administration of PDT, the type of cell death was characterized to be apoptosis, and a change in the mitochondrial membrane potential was also observed within minutes. On the other hand, tumor growth was remarkably retarded in vivo in mice that received DH-I-180-3/PDT, compared with mice in the control group, which were exposed to light irradiation alone. Finally, tumors in some mice nearly healed. The antitumor drug reached a maximum concentration approximately 3 h after administration. However, PDT was most effective when there was substantial accumulation of DH-I-180-3 in the tumor vasculature and in healthy tissue. The histological demonstration provided further evidence of tumor vascular damage. On the basis of these findings, we suggest that PDT with the photosensitizer DH-I-180-3 induces vascular damage with blood vessel shutdown, in addition to direct killing of tumor cells, in mice.     

OXYGEN LIMITATION OF DIRECT TUMOR CELL KILL DURING PHOTODYNAMIC TREATMENT OF A MURINE TUMOR MODEL

The relationship between levels of in vivo accumulated photosensitizer (Photofrin II), photodynamic cell inactivation upon in vitro or in vivo illumination, and changing tumor oxygenation was studied in the radiation-induced fibrosarcoma (RIF) mouse tumor model. In vivo porphyrin uptake by tumor cells was assessed by using 14C-labeled photosensitizer, and found to be linear with injected photosensitizer dose over a range of 10 to 100 mg/kg. Cellular photosensitivity upon exposure in vitro to 630 nm light also varied linearly with in vivo accumulated photosensitizer levels in the range of 25 to 100 mg/kg injected Photofrin II, but was reduced at 10 mg/kg. Insignificant increases in direct photodynamic cell inactivation were observed following in vivo light exposure (135 J/cm2, 630 nm) with increasing cellular porphyrin levels. These data were inconsistent with expected results based on in vitro studies. Assessment of vascular occlusion and hypoxic cell fractions following photodynamic tumor treatment showed the development of significant tumor hypoxia, particularly at 50 and 100 mg/kg of Photofrin II, following very brief light exposures (1 min, 4.5 J/cm2). The mean hyupoxic cell fractions of 25 to 30% in these tumors corresponded closely with the surviving cell fractions found after tumor treatment in vivo, indicating that these hypoxic cells had been protected from PDT damage. Inoculation of tumor cells, isolated from tumors after porphyrin exposure, into porphyrin-free hosts, followed by in vivo external light treatment, resulted in tumor control in the absence of vascular tumor bed effects at high photosensitizer doses only.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intracrystalline diffusivities and surface permeabilities deduced from transient concentration profiles: methanol in MOF manganese formate

The intracrystalline concentration profiles during molecular uptake of methanol by an initially empty, single crystal of microporous manganese(II) formate (Mn(HCO2)2), representing an ionic inorganic-organic hybrid within the MOF family, are monitored by interference microscopy. Within these profiles, a crystal section could be detected where over the total of its extension ( approximately 2 microm x 50 microm x 30 microm) molecular uptake ideally followed the pattern of one-dimensional diffusion. Analysis of the evolution of intracrystalline concentration in this section directly yields the permeability of the crystal surface and the intracrystalline diffusivity as a function of the concentration of the total range of 0 相似文献   

UNUSUALLY HIGH AFFINITY OF Zn(II)-TETRADIBENZOBARRELENOOCTABUTOXY- PHTHALOCYANINE FOR LOW-DENSITY LIPOPROTEINS IN A TUMOR-BEARING MOUSE

Abstract— An important factor in determining the efficacy of photosensitizing compounds in photodynamic therapy of tumors is the level to which tumors take up the photosensitizers after systemic injection. This parameter seems to be related to the transport modalities of the photosensitizer in the bloodstream. In this work the photosensitizer Zn(II)-tetradibenzobarreleno-octabutoxyphthalocyanine was shown to have an unprecedentedly high association with low-density lipoproteins (71% of the phthalocyanine in the plasma) when delivered in Cremophor micelles to tumor-bearing mice. This was accompanied by a particularly high tumor uptake at 24 h post-injection.     

Site-specific prodrug release using visible light

Using a photosensitization-singlet oxygenation-dioxetane cleavage strategy, a photodynamic prodrug system has been developed, whereby drugs bearing carbonyl groups can first be attached to a photosensitizer to give a photosensitizer-drug complex and then released from the complex upon visible light irradiation. Visible light, which has good penetration through tissue, generates singlet oxygen via the photosensitizer, which then releases the prodrug when and where required. With this system, drug mimics and methyl esters of NSAIDs have been successfully incorporated with photosensitizers related to verteporfin and then released by visible light illumination in high to quantitative yields within minutes.     

PHOTOFRIN ACCUMULATION IN MALIGNANT AND HOST CELL POPULATIONS OF A MURINE FIBROSARCOMA

Abstract— Photofrin (25 mg/kg) was administered to the FsaR fibrosarcoma-bearing mice (either syngeneic or severe combined immunodeficient [SOD]) and the tumors were excised 24 h later. The photosensitizer content in the cells dissociated from tumor tissue was analyzed using flow cytometry. Staining the cell suspensions with the monoclonal antibodies against specific membrane markers served to identify the malignant cells and various types of host immune cells infiltrating the tumor. Photofrin content was also examined in the cells from normal tissues of the tumor-bearing mice (spleen, heart muscle, peritoneal macrophages). The results show a marked heterogeneity in the Photofrin cellular content of FsaR tumor, particularly within the population of tumor-associated macrophages (TAM). The Photofrin levels in some TAM were lower or similar to those in the malignant cells. In contrast, a subpopulation of TAM accumulated very high levels of the photosensitizer, which exceeded by far the levels found in the other tumor cell populations. This TAM fraction was characterized by particularly high expression of interleukin-2 receptors and increased cell size and granularity when compared to the other TAM, which suggests that these macrophages are in the activated state. Their average Photofrin content was almost 13 times higher than in the malignant cells. The lowest photosensitizer levels in the tumor were found in tumor-infiltrating leukocytes other than TAM. In FsaR tumors growing in SCID mice, the pattern of Photofrin distribution in TAM and other cellular populations was similar to that found in tumors growing in syngeneic mice. Due to a presumably better perfusion, these tumors accumulated higher levels of Photofrin in all cellular populations. The findings of this study suggest that the tumor-localizing effect of Photofrin can be attributed to the accumulation of extremely high levels of the photosensitizer in a subpopulation of TAM.     

Modeling of oxygen transport and cell killing in type-II photodynamic therapy

Photodynamic therapy (PDT) provides an effective option for treatment of tumors and other diseases in superficial tissues and attracts attention for in vitro study with cells. In this study, we present a significantly improved model of in vitro cell killing through Type-II PDT for simulation of the molecular interactions and cell killing in time domain in the presence of oxygen transport within a spherical cell. The self-consistency of the approach is examined by determination of conditions for obtaining positive definitive solutions of molecular concentrations. Decay constants of photosensitizers and unoxidized receptors are extracted as the key indices of molecular kinetics with different oxygen diffusion constants and permeability at the cell membrane. By coupling the molecular kinetics to cell killing, we develop a modeling method of PDT cytotoxicity caused by singlet oxygen and obtain the cell survival ratio as a function of light fluence or initial photosensitizer concentration with different photon density or irradiance of incident light and other parameters of oxygen transport. The results show that the present model of Type-II PDT yields a powerful tool to quantitate various events underlying PDT at the molecular and cellular levels and to interpret experimental results of in vitro cell studies.     

Quantification of glucose diffusion in human lung tissues by using Fourier domain optical coherence tomography

In this study, we report permeability coefficients of 30% glucose diffusion by the optical coherence tomography signal slope (OCTSS) method in four kinds of human lung tissue in vitro: normal lung tissue, benign granulomatosis lung tissue, squamous cell carcinoma and adenocarcinoma tumor. To quantify the permeability coefficient of the agent, the monitored region was 80 μm thickness at a tissue depth of ca 230 μm from the surface. The permeability coefficients of 30% glucose from 10 independent experiments were averaged and found to be (1.35 ± 0.13) × 10(-5) cm s(-1) from the normal lung tissue, (1.78 ± 0.21) × 10(-5) cm s(-1) from the benign granulomatosis lung tissue, (2.88 ± 0.19) × 10(-5) cm s(-1) from the adenocarcinoma tumor and (3.53 ± 0.25) × 10(-5) cm s(-1) from the squamous cell carcinoma, respectively. It could be clearly seen that the permeability coefficients of 30% glucose increase ca 32%, 113% and 162% in the benign granulomatosis, adenocarcinoma tumor and squamous cell carcinoma of human lung tissue compared with that from the normal lung tissue, respectively. Therefore, we inferred from this pilot study that the OCT imaging is a feasible method to distinguish normal and cancer lung tissue.     

Delivery of Benzoporphyrin Derivative, a Photosensitizer, into Atherosclerotic Plaque of Watanabe Heritable Hyperlipidemic Rabbits and Balloon-Injured New Zealand Rabbits

Abstract— In this study we compared the plasma distribution and arterial accumulation of a photosensitizer, benzoporphyrin derivative (BPD), in two models of atherosclerosis: the spontaneous lesions of the Watanabe heritable hyperlipidemic (WHHL) rabbit and induced lesions of the balloon-injured, cholesterol-fed New Zealand white (NZW) rabbit. Selective uptake and retention of a photosensitizer by the abnormal portion of a vessel is a necessity in order for photodynamic therapy to become a successful modality for inhibition of intimal hyperplasia, selective removal of atherosclerotic tissue or imaging of diseased arteries. Liposome-based formulations were compared to freshly isolated native low density lipoprotein (LDL) and acetylated-LDL (Ac-LDL) as delivery vehicles for BPD. Plasma distribution of the photosensitizer was analyzed by KBr density gradient ultracentrifuga-tion. Although the delivery vehicle influenced plasma distribution immediately postinjection, BPD subsequently partitioned according to the plasma concentration of the lipoproteins. Photosensitizer level in plaque and normal artery specimens was determined by ethyl acetate extraction and spectrofluorometric measurement. The measurement of BPD in normal and atherosclerotic arterial tissue demonstrated a selective accumulation in atherosclerotic tissue. Preassociation with LDL and Ac-LDL enhanced accumulation of BPD in atherosclerotic tissue when compared with normal artery (mean ratios of 2.8 and 4.1 were achieved, respectively). These results indicate that the preferential uptake of BPD by atherosclerotic plaque can be enhanced by preassociation with plasma lipoproteins, suggesting that light activation could lead to a highly selective destruction of diseased vascular tissue.     

Temporally and spatially heterogeneous distribution of mTHPC in a murine tumor observed by two-color confocal fluorescence imaging and spectroscopy in a whole-mount model

Efficient intratumor delivery of anticancer drugs and photosensitizers is an important factor in the success of chemotherapy and photodynamic therapy, respectively. Unfortunately, their adequate and uniform intratumor distribution is impeded by several physiological barriers and by binding to tissue components. Measurement of gross tumor drug accumulation is a routine method of investigating the uptake and clearance of chemotherapy agents and photosensitizers but tells little about their extravascular spatial distribution. We use whole-mount two-color confocal fluorescence imaging and imaging spectroscopy of unprocessed excised murine tumor fragments to investigate the intratumor distribution of the photosensitizer meso-tetrahydroxyphenyl chlorin (mTHPC) as a function of distance from blood vessels perfused with 0.2 mum diameter fluorescent microspheres. Significant mismatches between drug and perfused vasculature are caused by heterogeneities in tumor blood supply. We describe complex microscopic mTHPC gradients that reverse dramatically relative to the perfused vasculature with time after injection. This imaging technique can be applied to screen the dynamic intratumor distribution of other fluorescent photosensitizers and anticancer drugs.