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.
Photodynamic Therapy (PDT) is one of the tumor-targeting therapeutics, and has been an established medical
practice in recent years. PDT mediates tumor destruction mainly by killing tumor cells directly and damaging the
tumor-associated vasculature, also inducing an immune response against tumor cells. For the Photofrin-mediated PDT,
Vascular system injury is the predominant destruction that results in vascular collapse and blood plasma leakage, then
leading to tumor infarction. However, thrombus formation during PDT may influence the light transmission and oxygen
supply. Also some tumor cells not killed by PDT may irritate angiogenesis, causing the tumor recurrence under the
condition of hypoxia after PDT. In our work, to prolong coagulation and formation of thrombus, an anticoagulant heparin
was employed before the Photofrin-mediated PDT. After being administrated both Photofrin and anticoagulant heparin,
the BALB/c mice with the subcutaneous EMT6 mammary carcinomas model were exposed to laser (635nm). And then
an enhanced effect was received. Our experiments indicated that its antitumor effect may be attributed to the
improvement of the light delivery to the deep part of tumor and oxygen supply for PDT. The results suggested that
heparin can be used to enhance the effect of PDT in a solid tumor treatment.
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