DEVELOPING NOVEL PHOTODYNAMIC THERAPY PROTOCOLS WITH ASSISTANCE OF OPTICAL MONITORING
In this paper we report on a comparative analysis of different photodynamic therapy (PDT) regimes employing chlorin-based photosensitizers. Owing to two pronounced peaks in the absorption spectrum of chlorine e6 located in the blue and the red ranges of the visible spectrum, the PDT procedure can be performed either with blue or with red light. Due to significant difference of biotissue optical properties in these ranges, one can control the impact depth of a PDT procedure by proper choice of the irradiation wavelength. The way of photosensitizer (PS) administration provides an additional opportunity for tuning the treatment protocol: topical administration ensures accumulation of PS in superficial tissue layers, while intravenous injection provides PS transport through the organism vascular system. We compare the effect of single- and dual-wavelength protocols with intravenous or topical PS administration to model CT-26 tumors in Balb/c mice. The study also included control groups with irradiation-only regimes. PDT procedure monitoring involved noninvasive optical imaging modalities: fluorescence imaging allowing for tracing PS accumulation and photobleaching in the course of a PDT procedure and optical coherence angiography allowing to detect function response to treatment manifested by interruption in microcirculatory activity. Histology study in 7 days after the procedure was employed for morphological analysis of the procedure outcome.
The PS intravenous injection regimes with red light only and dual-wavelength exposure demonstrated the full tumor response, while for topical administration and irradiation only regimes the most pronounces response was observed for blue light regimes.
The study is supported by the Russian Science Foundation (project 17-15-01264).
Institute of Applied Physics RAS
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