1. Daria K. Tuchina, Alexey N. Bashkatov, Elina A. Genina, Valery V. Tuchin Department of Optics and Biophotonics of Saratov State University, Saratov, Russia Saratov Fall Meeting 2012

2. For the last two decades the optical method as a tool for clinical functional imaging of physiological conditions, cancer diagnostics and therapies is of great interest due to its unique informative features, simplicity, safety and low cost in contrast to conventional X-ray computed tomography, magnetic resonance imaging and ultrasound. However, the main limitations of the optical imaging techniques are connected with strong light scattering in tissue. Optical clearing is perspective technique for solution of the problem. However, in spite of numerous investigations, optical clearing of skin tissue has not be studied in detail. Goal of the study is to investigate of optical clearing of skin by PEG-300 Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2012

3. Twelve samples of intact rat skin were used in the in vitro experiments. Before experiments hairs and hypodermic fatty layer were removed. The area of the samples was about 10 × 20 mm. Collimated transmittance spectra of the skin samples were measured by USB4000-Vis-NIR spectrometer (Ocean Optics, USA) concurrently with administration of PEG-300 in the spectral range 400-1000 nm. All measurements were performed at room temperature (about 20°C). Refractive index of PEG-300 was measured as 1.465. Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2012

4. Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2012

5. Dynamic of collimated transmittance of the rat skin sample placed in PEG-300 Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2012

6. Spectra of collimated transmittance of the rat skin sample placed in PEG-300 measured at different time intervals concurrently with administration of PEG-300 Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2012

7. The time dependence of attenuation coefficient during optical clearing of the rat skin sample placed in PEG-300 Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2012

8. Spectra of light attenuation coefficient during optical clearing of the rat skin sample placed in PEG-300 measured at different time intervals Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2012

9. Degree of optical clearing of skin tissue was estimated as: µ t (t=0) is attenuation coefficient at t = 0 µ t (t) is the time-dependent attenuation coefficient Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2012

10. The equation was used to calculate parameter A, which characterizes maximum of degree of optical clearing of skin tissue, and parameter τ, which characterizes time of optical clearing of skin tissue: The solution of the problem is minimization of the target function: N t is the number of time points obtained at registration of the time dependence of collimated transmittance, µ t is experimental values of the time-dependent attenuation coefficient Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2012

11. A0.381 τ, min8.691 Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2012

12. Acknowledgements Saratov Fall Meeting 2012 Saratov State University Department of Optics and Biophotonics Grants # 11-02-00560 and 12-02-92610-КО of Russian Foundation of Basis Research Russian Federation governmental contacts 02.740.11.0770, 02.740.11.0879, 11.519.11.2035, and 14.B37.21.0728 Grant #224014 Network of Excellence for Biophotonics (PHOTONICS4LIFE) of the Seventh Framework Programme of Commission of the European Communities