Reactive oxygen species (ROS) produced by photodynamic therapy (PDT) is recorded in vivo using a chemiluminescence (CL)-based gated optical system. A novel approach is developed to utilize the fluorescence (FL) of the CL probe as an internal fluorescence to calibrate the observed CL on pharmacokinetics of the probe in situ. The results show that during an in vivo PDT session, the intensity of CL decreases significantly and the decaying of CL is governed by fast and slow time components. By comparing the temporal profile of FL to that of the corresponding CL, it is found that the slow component is mainly attributed to the probe pharmacokinetics, whereas the fast component is likely due to rapid oxygen consumption as a result of PDT treatment. With carefully selected criteria, it is possible to minimize the effect of probe pharmacokinetics. This significantly improves the monitoring method for practical applications.
KEYWORDS: Photodynamic therapy, Skin, Oxygen, Luminescence, In vivo imaging, Chemiluminescence, Tissue optics, In situ metrology, Signal detection, Light scattering
Singlet oxygen (1O2) is an important factor mediating cell killing in photodynamic therapy (PDT). We previously reported that chemiluminescence (CL) can be used to detect 1O2 production in PDT and linked the signal to the PDT-induced cytotoxicity in vitro. We develop a new CL detection apparatus to achieve in vivo measurements. The system utilizes a time-delayed CL signal to overcome the interference from scattered excitation light, thus greatly improving the accuracy of the detection. The system is tested on healthy skin of BALB/ca mouse for its feasibility and reliability. The CL measurement is made during a synchronized gating period of the irradiation light. After each PDT treatment and in situ CL measurement, the skin response is scored over a period of 2 weeks. A remarkable relationship is observed between the score and the CL, regardless of the PDT treatment protocol. Although there are many issues yet to be addressed, our results clearly demonstrate the feasibility of CL measurement during PDT and its potential for in vivo PDT dosimetry. This requires further investigations.
Photodynamic therapy (PDT) is a cancer therapy that utilizes optical energy to activate a photosensitizer drug in a target
tissue. Always, the curative effect is dependent on the light fluence, the concentration of the photosensitizer and the
concentration of the oxygen. To date, Protophorphyrin IX (PpIX) as the only one endogenous photosensitizer is widely
used in PDT of brain tumors. Since PpIX is synthesized in intracellular structure, and is likely dependent on the phase of
the cell cycle. The cell cycle dependence of PpIX production is thus investigated in the current work in 9L gliosarcoma
cells.
Photodynamic therapy (PDT) utilizes light energy of a proper wavelength to activate a pre-administered photosensitizer
in a target tissue to achieve a localized treatment effect. Current treatment protocol of photodynamic therapy (PDT) is
defined by empirical values such as irradiation light fluence, fluence rate and the amount of administered photosensitizer.
It is well known that Singlet oxygen is the most important cytotoxic agent responsible for PDT biological effects. An in
situ monitoring of singlet oxygen production during PDT would provide a more accurate dosimeter for PDT. The
presented study has investigated the feasibility of using Fhioresceinyl Cypridina Luciferin Analog (FCLA), a singlet
oxygen specific chemiluminescence (CL) probe, as a dosimetric tool for PDT. Raji lymphoma cell suspensions were
sensitized with Photofrin(R) of various concentrations and irradiated with 635 nm laser light at different fluence rates.
FCLA-CL from singlet oxygen produced by the treatment was measured, in real time, with a photon multiplier tube
(PMT) system, and linked to the cytotoxicity resulting from the treatment. We have observed that the CL intensity of
FCLA is dependent on the PDT treatment parameters. After each PDT treatment and CL measurement, the irradiated
cells were evaluated by MIT assay for their Viability. The results show that the cell viability is highly related to the
accumulated CL. With 102 quencher, we confirmed that the CL was mainly related to PDT produced 102 The results
suggest that the FCLA-CL system can be an effective means in measuring PDT 1O2 production and may provide an
alternative dosimetry technique for PDT.
It has been proved that singlet oxygen is the major cytotoxic agent in Photodynamic therapy (PDT). Chemiluminescence(CL) mediated with Cyp- ridina luciferin analog (FCLA) was recently reported to successfully detect singlet oxygen in chemical and biological systems. The present study has focused on establishing the experiment conditions of FCLA-assisted CL method and tested the validity of the system as a dosimetric tool for PDT in vitro. HL-60 leukemia cell suspensions were sensitized with varying dose of Photofrin and irradiated with 635nm laser light at different rate. The FCLA-CL associated with singlet oxygen was measured with a band-pass filtered photon multiplier tube (PMT) system. We have observed that the CL intensity of FCLA is dependent on PDT treatment parameters. In addition, Cell survival corresponded strongly with peak CL intensity. These results suggest that the FCLA-assisted CL system can be an effective means in in vitro PDT study as an indicator of reactive oxygen species. The system may as well, with additional investigations, provide an alternative dosimetry technique for PDT.
Photodynamic therapy (PDT) is a cancer therapy that utilizes optical energy to activate a photosensitizer drug in a target tissue. Reactive oxygen species (ROS), such as 1O2 and superoxide, are believed to be the major cytotoxic agents involved in PDT. Although current PDT dosimetry mostly involves measurements of light and photosensitizer doses delivered to a patient, the quantification of ROS production during a treatment would be the ultimate dosimetry of PDT. Technically, it is very difficult and expensive to directly measure the fluorescence from 1O2, due to its extreme short lifetime and weak signal strength. In this paper, Photofrin(R) and 635nm laser were used to generate 1O2 and superoxide in a PDT in solution. Compound 3,7- dihydro-6-{4-[2-(N’-(5-fluoresceinyl) thioureido) ethoxy] phenyl}-2- methylimidazo{1,2-a} pyrazin-3-one sodium salt,an Cyp- ridina luciferin analog commonly referred as FCLA, was used as a chemical reporter of ROS. The 532nm chemiluminescence (CL) from the reaction of the FCLA and ROS was detected with a photon multiplier tube (PMT) system operating at single photon counting mode. With the setup, we have made detections of ROS generated by PDT in real time. By varying the amount of conventional PDT dosage (photosensitizer concentration, light irradiation fluence and its delivery rate) and the amount of FCLA, the intensity of CL and its consumption rate were investigated. The results show that the intensity and temporal profile of CL are highly related to the PDT treatment parameters. This suggests that FCLA CL may provide a highly potential alternative for ROS detection during PDT.
In photodynamic therapy (PDT), a target tissue with pre-administered photosensitizer is exposed to laser light. The photochemical process produces reaction oxygen species (ROS), such as singlet oxygen and superoxide, and leads to ultimate cell death. A direct monitoring of ROS production during PDT, thus, may provide important information in both basic science and clinical practice. A cypridina luciferin analogue (FCLA) is a chemiluminescence (CL) probe that selectively detects singlet oxygen and superoxide. In this study, FCLA was used as an optical reporter of ROS produced by photosensitization reaction of Photofrin in Hanks solution and the CL was measured by a photomultiplier system operated at single photon counting mode. By varying the amount of PDT dosage (photosensitizer dose, light irradiation fluence rate) and the amount of FCLA, the intensity of CL were investigated. The results showed the FCLA concentration affects the ratio of the signal to background CL. The decay time of the photosensitized CL was approximately 10 sec., after the excitation source was turned off. In addition, the intensity of the CL-FCLA increased with increasing concentration of Photofrin and fluence rate. The work supported the potential application of FCLA-chemiluminescence probe as a dosimetric tool for PDT.
Photodynamic therapy (PDT) utilizes photon energy to activate a pre-administered photosensitizer drug in tissue to achieve a localized tumor control. PDT cell killing mechanism is directly related to the reactive oxygen species (ROS) produced during the photochemical reactions. Conventional PDT dosimetry evaluates distributions of the photosensitizer drug, photon propagation and absorption, and availability of molecular oxygen in the target tissue. Yet, the ultimate bullet for the damaging effect is ROS. An evaluation of ROS production during PDT should provide a more direct marker for PDT. Fluoresceinyl Cypridina Luciferin Analog (FCLA) is a chemiluminescence probe that specifically interacts with ROS (singlet oxygen and/or superoxide). The work is a preliminary investigation of the feasibility using FCLA as a means to evaluate ROS production in PDT.
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