Spatial distribution of liposome encapsulated tin etiopurpurin dichloride (SnET2) in the canine prostate: implications for computer simulation of photodynamic therapy

Photodynamic therapy (PDT) is a minimally invasive treatment that can be employed in many human diseases including prostate cancer. PDT for prostate cancer depends on the sequestration of a photosensitizing drug within the glandular tissue. The photosensitizer is subsequently activated by light (usually from a laser) and the active drug destroys tissue. Since prostate cancer is a multifocal disease, PDT must ablate the glandular prostate completely. This will depend on the precise placement of light sources in the prostate and delivery of a therapeutic light dose to the entire gland. Also, sources of light and their spatial distribution must be tailored to each individual patient. The uniform, therapeutic light distribution can be achieved by interstitial light irradiation. In this case, the light is delivered by diffusers placed within the substance of the prostate parallel to the urethra at a distance optimized to deliver adequate levels of light and to create the desired photodynamic effect. To help achieve the uniform light distribution throughout the prostate we have developed a computer program that can determine treatment effects. The program predicts the best set of parameters and the position of light diffusers in space, and displays them in graphical or in numerical form assuming a fixed attenuation coefficient. The two parameters of greatest importance in the computer simulation are attenuation coefficient and critical fluence. Both depend on the concentration of active drug within the prostate gland. It is necessary to know the nature of the spatial distribution of photosensitizer within the prostate to execute computer modeling of PDT with high precision. We found that the concentration of SnET2 is heterogeneous in nature, and is higher in the proximity of the glandular capsule. It is clear therefore that any future attempts of computerized modeling of this procedure must take into consideration the uneven sequestration of photosensitizer and the consequential asymmetrical necrosis of the prostate.     

Determination of the tumor tissue optical properties during and after photodynamic therapy using inverse Monte Carlo method and double integrating sphere between 350 and 1000 nm

Photodynamic therapy (PDT) efficacy depends on the amount of light distribution within the tissue. However, conventional PDT does not consider the laser irradiation dose during PDT. The optical properties of biological tissues (absorption coefficient μ(a), reduced scattering coefficient μ's), anisotropy factor g, refractive index, etc.) help us to recognize light propagation through the tissue. The goal of this paper is to acquire the knowledge of the light propagation within tissue during and after PDT with the optical property of PDT-performed mouse tumor tissue. The optical properties of mouse tumor tissues were evaluated using a double integrating sphere setup and the algorithm based on the inverse Monte Carlo method in the wavelength range from 350 to 1000 nm. During PDT, the μ(a) and μ's were not changed after 1 and 5 min of irradiation. After PDT, the μ's in the wavelength range from 600 to 1000 nm increased with the passage of time. For seven days after PDT, the μ's increased by 1.7 to 2.0 times, which results in the optical penetration depth decreased by 1.4 to 1.8 times. To ensure an effective procedure, the adjustment of laser parameters for the decreasing penetration depth is recommended for the re-irradiation of PDT.     

Optical dosimetry for interstitial photodynamic therapy

An approach to photodynamic treatment of tumors is the interstitial implantation of fiber optic light sources. Dosimetry is critical in identifying regions of low light intensity in the tumor which may prevent tumor cure. We describe a numerical technique for calculating light distributions within tumors, from multiple fiber optic sources. The method was tested using four translucent plastic needles, which were placed in a 0.94 X 0.94 cm grid pattern within excised Dunning R3327-AT rat prostate tumors. A cylindrical diffusing fiber tip, illuminated by 630 nm dye laser light was placed within one needle and a miniature light detector was placed within another. The average penetration depth in the tumor region between the two needles was calculated from the optical power measured by the detector, using a modified diffusion theory. Repeating the procedure for each pair of needles revealed significant variations in penetration depth within individual tumors. Average values of penetration depth, absorption coefficient, scattering coefficient, and mean scattering cosine were 0.282 cm, 0.469 cm-1, 250 cm-1 and 0.964, respectively. Calculated light distributions from four cylindrical sources in tumors gave reasonable agreement with direct light measurements using fiber optic probes.     

Clinical Application of Photodynamic Therapy

Photodynamic therapy（PDT） is a new medical technology, the study on photodynamic therapy was in full swing in the past two decade. Scientists have made great progress in it. Photosensitizer,oxygen and light source play important role in photodynamic therapy. PDT is a light activated chemotherapy. A photon is adsorbed by a photosensitizer which moves the drug into an excited state. The excited drug can then pass its energy to oxygen to create a chemical radical called “singlet oxygen”. Singlet oxygen attacks cellular structures by oxidation. Such oxidative damage might be oxidation of cell membranes or proteins. When the accumulation of oxidative damage exceeds a threshold level,the cell begins to die. Photodynamic therapy allows selective treatment of localized cancer. PDT involves administration of a photosensitizer to the patients, followed by delivery of light to the cancerous region. The light activates the agent which kills the cancer cells. Without light,the agent is harmless. As a new therapy,photodynamic Therapy has great Advantage in treating cancers. 1. PDT avoids systemic treatment. The treatment occurs only where light is delivered, hence the patient does not undergo go needless systemic treatment when treating localized disease. Side-effects are avoided, from losing hair or suffering nausea to more serious complications. 2. PDT is selective. The photosensitizing agent will selectively accumulate in cancer cells and not in surrounding normal tissues. Hence ,there is selective targeting of the cancer and sparing of surrounding tissues. 3. when surgery is not possible. PDT kills cancer cells but does not damage collagenous tissue structures,and normal cells will repopulate these structures. Hence,if a patient has cancer in a structure that cannot be removed surgicaily（eg. ,the upper bronchi of the lung） ,PDT can still treat the site. 4. PDT is repeatable. Uniike radiation therapy,PDT can be used again and again. Hence,it offers a means of longterm management of cancer even if complete cure is not attainable.     

Updated results of a phase I trial of motexafin lutetium-mediated interstitial photodynamic therapy in patients with locally recurrent prostate cancer.

Locally recurrent prostate cancer after treatment with radiation therapy is a clinical problem with few acceptable treatments. One potential treatment, photodynamic therapy (PDT), is a modality that uses laser light, drug photosensitizer, and oxygen to kill tumor cells through direct cellular cytotoxicity and/or through destruction of tumor vasculature. A Phase I trial of interstitial PDT with the photosensitizer Motexafin lutetium was initiated in men with locally recurrent prostate cancer. In this ongoing trial, the primary objective is to determine the maximally tolerated dose of Motexafin lutetium-mediated PDT. Other objectives include evaluation of Motexafin lutetium uptake from prostate tissue using a spectrofluorometric assay and evaluation of optical properties in the human prostate. Fifteen men with biopsy-proven locally recurrent prostate cancer and no evidence of distant metastatic disease have been enrolled and 14 have been treated. Treatment plans were developed using transrectal ultrasound images. The PDT dose was escalated by increasing the Motexafin lutetium dose, increasing the 732 ran light dose, and decreasing the drug-light interval. Motexafin lutetium doses ranged from 0.5 to 2 mg/kg administered IV 24, 6, or 3 hr prior to 732 ran light delivery. The light dose, measured in real time with in situ spherical detectors was 25-100 J/cm2. Light was delivered via optical fibers inserted through a transperineal brachytherapy template in the operating room. Optical property measurements were made before and after light therapy. Prostate biopsies were obtained before and after light delivery for spectrofluorometric measurements of photosensitizer uptake. Fourteen patients have completed protocol treatment on eight dose levels without dose-limiting toxicity. Grade I genitourinary symptoms that are PDT related have been observed. One patient had Grade II urinary urgency that was urinary catheter related. No rectal or other gastrointestinal PDT-related tox-icities have been observed to date. Measurements of Motexafin lutetium demonstrated the presence of photosensitizer in prostate tissue from all patients. Optical property measurements demonstrated substantial heterogeneity in the optical properties of the human prostate gland which supports the use of individualized treatment planning for prostate PDT.     

Realtime light dosimetry software tools for interstitial photodynamic therapy of the human prostate

Photodynamic therapy (PDT) for the treatment of prostate cancer has been demonstrated to be a safe treatment option capable of inducing tissue destruction and decreasing prostate specific antigen (PSA) levels. However, prostate-PDT results in large intra- and interpatient variations in treatment response, possibly due to biological variations in tissue composition and short-term response to the therapeutic irradiation. Within our group, an instrument for interstitial PDT on prostate tissue has been developed that combines therapeutic light delivery and monitoring of light transmission via numerous bare-ended optical fibers. Here, we present algorithms that utilize data on the light distribution within the target tissue to provide realtime treatment feedback based on a light dose threshold model for PDT. This realtime dosimetry module is implemented to individualize the light dose and compensate for any treatment-induced variations in light attenuation. More specifically, based on the light transmission signals between treatment fibers, spatially resolved spectroscopy is utilized to assess the effective attenuation coefficient of the tissue. These data constitute input to a block-Cimmino optimization algorithm, employed to calculate individual fiber irradiation times provided the requirement to deliver a predetermined light dose to the target tissue while sparing surrounding sensitive organs. By repeatedly monitoring the light transmission signals during the entire treatment session, optical properties and individual fiber irradiation times are updated in realtime. The functionality of the algorithms is tested on diffuse light distribution data simulated by means of the finite element method (FEM). The feasibility of utilizing spatially resolved spectroscopy within heterogeneous media such as the prostate gland is discussed. Furthermore, we demonstrate the ability of the block-Cimmino algorithm to discriminate between target tissue and organs at risk (OAR). Finally, the realtime dosimetry module is evaluated for treatment scenarios displaying spatially and temporally varying light attenuation levels within the target tissue. We conclude that the realtime dosimetry module makes it possible to deliver a certain light dose to the target tissue despite spatial and temporal variations of the target tissue optical properties at the therapeutic wavelength.     

Optical properties of adenocarcinoma and squamous cell carcinoma of the gastroesophageal junction

Photodynamic therapy (PDT) is an alternative to radical surgical resection for T1a or nonresectable carcinomas of the gastroesophageal junction. Besides the concentration of the photosensitizer, the light distribution in tissue is responsible for tumor destruction. For this reason, knowledge about the behavior of light in healthy and dysplastic tissue is of great interest for careful irradiation scheduling. The aim of this study is to determine the optical parameters (OP) of healthy and carcinomatous tissue of the gastroesophageal junction in vitro to provide reproducible parameters for optimal dosimetry when applying PDT. A total of 36 tissue samples [adenocarcinoma tissue (n=21), squamous cell tissue (n=15)] are obtained from patients with carcinomas of the gastroesophageal junction. The optical parameters are measured in 10-nm steps using new integrating sphere spectrometers in the PDT-relevant wavelength range of 300 to 1140 nm and evaluated by inverse Monte-Carlo simulation. Additional examinations are done in healthy tissue from the surgical safety margin. In the wavelength range of frequently applied photosensitizers at 330, 630, and 650 nm, the absorption coefficient in tumor tissue (adenocarcinoma 1.22, 0.16, and 0.15 mm(-1); squamous cell carcinoma 1.48, 0.13, and 0.11 mm(-1)) is significantly lower than in healthy tissue (stomach 3.34, 0.26, and 0.20 mm(-1); esophagus 2.47, 0.21, and 0.18 mm(-1)). The scattering coefficient of all tissues decreases continuously with increasing wavelength (adenocarcinoma 22.8, 12.99, and 12.52 mm(-1); squamous cell carcinoma 19.44, 9.35, and 8.98 mm(-1); stomach 20.55, 13.96, and 13.94 mm(-1); esophagus 20.34, 12.56, and 12.22 mm(-1). All tissues show an anisotropy factor between 0.80 and 0.94 over the entire spectrum. The maximum optical penetration depth for all tissues is achieved in the range of 800 to 1100 nm. At the wavelength range of 330, 630, and 650 nm, the optical penetration depth is significantly higher in carcinoma tissue (adenocarcinoma 0.27, 1.54, and 1.66 mm; squamous cell carcinoma 0.23, 1.71, and 1.84 mm) than in healthy tissue (stomach 0.16, 1.10, and 1.26 mm; esophagus 0.17, 1.47, and 1.65 mm; p<0.05). Above 1000 nm, a higher absorption coefficient of tumor tissue results in a lower optical penetration depth than in healthy tissue (p<0.05). The higher absorption and scattering of the tumor tissue in the wavelength range of available photosensitizer is associated with a low optical penetration depth. This necessitates higher energy doses and long application times or repeated applications to effectively treat large tumor volumes. Photosensitizers optimized for larger wavelength range need to be developed to increase the efficacy of PDT.     

Pulsed diode laser-based monitor for singlet molecular oxygen

Photodynamic therapy (PDT) is a promising cancer treatment. PDT uses the affinity of photosensitizers to be selectively retained in malignant tumors. When tumors, pretreated with the photosensitizer, are irradiated with visible light, a photochemical reaction occurs and tumor cells are destroyed. Oxygen molecules in the metastable singlet delta state O2(1Delta) are believed to be the species that destroys cancerous cells during PDT. Monitoring singlet oxygen produced by PDT may lead to more precise and effective PDT treatments. Our approach uses a pulsed diode laser-based monitor with optical fibers and a fast data acquisition system to monitor singlet oxygen during PDT. We present results of in vitro singlet oxygen detection in solutions and in a rat prostate cancer cell line as well as PDT mechanism modeling.     

Correlation of in vivo photosensitizer fluorescence and photodynamic-therapy-induced depth of necrosis in a murine tumor model

We compared light-induced fluorescence (LIF) to nominal injected drug dose for predicting the depth of necrosis response to photodynamic therapy (PDT) in a murine tumor model. Mice were implanted with radiation-induced fibrosarcoma (RIF) and were injected with 0, 5, or 10 mg/kg Photofrin. 630-nm light (30 J/cm(2), 75 mW/cm(2)) was delivered to the tumor after 24 hours. Fluorescence emission (lambda(excitation)=545 nm, lambda( emission)=628 nm) from the tumor was measured. The LIF data had less scatter than injected drug dose, and was found to be at least as good as an injected drug dose for predicting the depth of necrosis after PDT. Our observations provide further evidence that fluorescence spectroscopy can be used to quantify tissue photosensitizer uptake and to predict PDT tissue damage.     

Spectroscopic measurements of photoinduced processes in human skin after topical application of the hexyl ester of 5-aminolevulinic acid.

Although 5-aminolevulinic acid, ALA, and its derivatives, have been widely studied and applied in clinical photodynamic therapy (PDT), there is still a lack of reliable and non-invasive methods and technologies to evaluate physiological parameters of relevance for the therapy, such as erythema, melanogenesis, and oxygen level. We have investigated the kinetics of these parameters in human skin in vivo during and after PDT with the hexyl ester of ALA, ALA-Hex. Furthermore, the depth of photosensitizer (protoporphyrin IX, PpIX) production after different application times was investigated. It was found that the depth increased with increasing application time of ALA-Hex. We also investigated the depth of PpIX before and after light exposure causing 50% photobleaching at 407 nm. The PpIX localized in superficial layers of the normal tissue was removed during the bleaching. Thus, after bleaching, the remaining PpIX was localized mainly in the deeper layers of normal tissue. We have applied fluorescence emission spectroscopy, fluorescence excitation spectroscopy, and reflectance spectroscopy in the study of the above-mentioned parameters. In conclusion, fluorescence excitation spectroscopy and reflectance spectroscopy are simple, useful, reliable, and noninvasive techniques in the evaluation of the processes taking place in human skin in vivo during and after PDT. Using these methods we were able to quantify melanogenesis, O2 level, erythema, vasoconstriction, and vasodilatation.     

Interstitial Doppler optical coherence tomography monitors microvascular changes during photodynamic therapy in a Dunning prostate model under varying treatment conditions

We measure the tumor vascular response to varying irradiance rates during photodynamic therapy (PDT) in a Dunning rat prostate model with interstitial Doppler optical coherence tomography (IS-DOCT). Rats are given a photosensitizer drug, Photofrin, and the tumors are exposed to light (635 nm) with irradiance rates ranging from 8 to 133 mWcm(2) for 25 min, corresponding to total irradiance of 12 to 200 Jcm(2) (measured at surface). The vascular index computed from IS-DOCT results shows the irradiance rate and total irradiance dependent microvascular shutdown in the tumor tissue during PDT. While faster rates of vascular shutdown were associated with increasing PDT irradiance rate and total irradiance, a threshold effect was observed as irradiance rates above 66 mWcm(2) (surface), where no further increase in vascular shutdown rate was detected. The maximum post-treatment vascular shutdown (81%) without immediate microcirculatory recovery was reached with the PDT condition of 33 mWcm(2) and 50 Jcm(2). Control groups without Photofrin show no significant microvascular changes. Microvascular shutdown occurs at different rates and shows correlation with PDT total irradiance and irradiance rates. These dependencies may play an important role in PDT treatment planning, feedback control for treatment optimization, and post-treatment assessment.     

Photodynamic therapy induces an immune response against a bacterial pathogen

Photodynamic therapy (PDT) employs the triple combination of photosensitizers, visible light and ambient oxygen. When PDT is used for cancer, it has been observed that both arms of the host immune system (innate and adaptive) are activated. When PDT is used for infectious disease, however, it has been assumed that the direct antimicrobial PDT effect dominates. Murine arthritis caused by methicillin-resistant Staphylococcus aureus in the knee failed to respond to PDT with intravenously injected Photofrin(?). PDT with intra-articular Photofrin produced a biphasic dose response that killed bacteria without destroying host neutrophils. Methylene blue was the optimum photosensitizer to kill bacteria while preserving neutrophils. We used bioluminescence imaging to noninvasively monitor murine bacterial arthritis and found that PDT with intra-articular methylene blue was not only effective, but when used before infection, could protect the mice against a subsequent bacterial challenge. The data emphasize the importance of considering the host immune response in PDT for infectious disease.     

Photodynamic inactivation of viruses using upconversion nanoparticles

Photodynamic therapy (PDT) is a promising treatment modality that utilizes light of an appropriate wavelength to excite photosensitive materials called photosensitizers, which upon excitation, generate reactive oxygen species (ROS) that are cytocidal and virucidal. However, problems such as hydrophobicity of photosensitizers and limited tissue penetration ability of the current light sources impeded its promotion as a mainstay in medical technology. Here, by using near-infrared (NIR)-to-visible upconversion nanoparticles (UCNs), we demonstrate UCN-based photodynamic inactivation as a potential antiviral strategy. These UCNs are nanotransducers which not only act as carriers of photosensitizers but also active participants in PDT by transducing NIR radiation to visible emissions appropriate for excitation of the attached photosensitizers. The UCNs effectively reduced the infectious virus titers in vitro with no clear pathogenicity in murine model and increased target specificity to virus-infected cells. Hence, this is a promising antiviral approach with feasible applications in the treatments of virus-associated infections, lesions and cancers.     

A model to estimate the outcome of prostate cancer photodynamic therapy with TOOKAD Soluble WST11

Interstitial photodynamic therapy is becoming an interesting modality to treat some early stage prostate cancers. A light-sensitive drug is injected to the patient and activated by light using optical fibres inserted inside the prostate. In this work, we were interested in the characterization of the light action model for the WST11 (Tookad? Soluble) drug. A retrospective analysis was performed on results from 28 patients enrolled in phase I and II trials with the WST11 drug. A drug dose of 4 mg/kg patient, dose light of 200 J cm(-1) and wavelength of 753 nm were used. Correlation between the illuminated volume and the obtained necrosis, measured at day 7 MR images, was clearly established. This result suggests that photodynamic therapy planning is possible based on this model.     

Near-infrared light induced in vivo photodynamic therapy of cancer based on upconversion nanoparticles

Upconversion nanoparticles (UCNPs) that emit high-energy photons upon excitation by the low-energy near-infrared (NIR) light are emerging as new optical nano-probes useful in biomedicine. Herein, we load Chlorin e6 (Ce6), a photosensitizer, on polymer-coated UCNPs, forming a UCNP-Ce6 supramolecular complex that produces singlet oxygen to kill cancer cells under NIR light. Excellent photodynamic therapy (PDT) efficacy is achieved in tumor-bearing mice upon intratumoral injection of UCNP-Ce6 and the followed NIR light exposure. It is further uncovered that UCNPs after PDT treatment are gradually cleared out from mouse organs, without rendering appreciable toxicity to the treated animals. Moreover, we demonstrate that the NIR-induced PDT based on UCNP-Ce6 exhibits a remarkably increased tissue penetration depth compared to the traditional PDT using visible excitation light, offering significantly improved treatment efficacy for tumors blocked by thick biological tissues. Our work demonstrates NIR light-induced in vivo PDT treatment of cancer in animals, and highlights the promise of UCNPs for multifunctional in vivo cancer treatment and imaging.     

Transperineal in vivo fluence-rate dosimetry in the canine prostate during SnET2-mediated PDT

Advances in photodynamic therapy (PDT) treatment for prostate cancer can be achieved either by improving selectivity of the photosensitizer towards prostate gland tissue or improving the dosimetry by means of individualized treatment planning using currently available photosensitizers. The latter approach requires the ability to measure, among other parameters, the fluence rate at different positions within the prostate and the ability to derive the tissue optical properties. Here fibre optic probes are presented capable of measuring the fluence rate throughout large tissue volumes and a method to derive the tissue optical properties for different volumes of the prostate. The responsivity of the sensors is sufficient to detect a fluence rate of 0.1 mW cm(-2). The effective attenuation coefficient in the canine prostate at 660 nm is higher at the capsule (2.15+/-0.19 cm(-1)) than in proximity of the urethra (1.84+/-0.36 cm(-1)). Significant spatial and temporal intra- and inter-canine variability in the tissue optical properties was noted, highlighting the need for individualized monitoring of the fluence rate for improved dosimetry.     

Photodynamic therapy induces an immune response against a bacterial pathogen

Photodynamic therapy (PDT) employs the triple combination of photosensitizers, visible light and ambient oxygen. When PDT is used for cancer, it has been observed that both arms of the host immune system (innate and adaptive) are activated. When PDT is used for infectious disease, however, it has been assumed that the direct antimicrobial PDT effect dominates. Murine arthritis caused by methicillin-resistant Staphylococcus aureus in the knee failed to respond to PDT with intravenously injected Photofrin^®. PDT with intra-articular Photofrin produced a biphasic dose response that killed bacteria without destroying host neutrophils. Methylene blue was the optimum photosensitizer to kill bacteria while preserving neutrophils. We used bioluminescence imaging to noninvasively monitor murine bacterial arthritis and found that PDT with intra-articular methylene blue was not only effective, but when used before infection, could protect the mice against a subsequent bacterial challenge. The data emphasize the importance of considering the host immune response in PDT for infectious disease.     

System for interstitial photodynamic therapy with online dosimetry: first clinical experiences of prostate cancer

The first results from a clinical study for Temoporfin-mediated photodynamic therapy (PDT) of low-grade (T1c) primary prostate cancer using online dosimetry are presented. Dosimetric feedback in real time was applied, for the first time to our knowledge, in interstitial photodynamic therapy. The dosimetry software IDOSE provided dose plans, including optical fiber positions and light doses based on 3-D tissue models generated from ultrasound images. Tissue optical property measurements were obtained using the same fibers used for light delivery. Measurements were taken before, during, and after the treatment session. On the basis of these real-time measured optical properties, the light-dose plan was recalculated. The aim of the treatment was to ablate the entire prostate while minimizing exposure to surrounding organs. The results indicate that online dosimetry based on real-time tissue optical property measurements enabled the light dose to be adapted and optimized. However, histopathological analysis of tissue biopsies taken six months post-PDT treatment showed there were still residual viable cancer cells present in the prostate tissue sections. The authors propose that the incomplete treatment of the prostate tissue could be due to a too low light threshold dose, which was set to 5 J∕cm2.     

Carbogen breathing significantly enhances the penetration of red light in murine tumours in vivo

We report results of experiments that evaluated the influence of oxygenation on the penetration of red light in tissue, with particular emphasis on 630 and 650 nm laser wavelengths commonly used in photodynamic therapy (PDT) of solid tumours. Direct measurements in tissue-simulating phantoms comprised of intact human erythrocytes suspended in a scattering emulsion demonstrated significant enhancements in fluence rate at depths of 0.5-2 cm from the irradiated surface when the cells were fully oxygenated versus fully deoxygenated. The 630 and 650 nm fluence rates at depth in the homogeneous phantoms continued to increase when examined over a continuous range of oxygen partial pressures from 0 to 160 Torr. When considered as a function of haemoglobin oxygen saturation, the largest increases in fluence rate were observed as the saturation increased beyond 70%. Dramatic increases in optical fluence rate were measured at the base of 1-cm-thick subcutaneous EMT6 mammary carcinomas in vivo when the tumour-bearing mouse was subjected to carbogen through a nose cone. These results indicate that improved tumour oxygenation is important in PDT not only for the maintenance of the oxygen-dependent photochemistry but, through the effects reported here, may also enable more efficient treatment of thicker lesions.     

光动力疗法的抗肿瘤机制及光敏剂的研究进展

光动力疗法（PDT）是利用光动力效应对疾病进行诊断与治疗的一种非侵袭性技术,已被用于临床头颈部、乳腺、肺、前列腺及皮肤等部位肿瘤的治疗.与传统治疗方法相比,PDT具有创伤小、毒性低、选择性好、适用范围广及不易产生耐药等优势,因而受到肿瘤治疗领域的广泛关注.PDT的抗肿瘤机制复杂,光敏剂是发挥其光动力学效应的关键因素之一,提高光敏剂的靶向输送和携氧能力是改善光动力疗效的重要途径.对PDT的抗肿瘤机制及光敏剂的研究进展进行综述.