Effect of differently sized nanoparticles' accumulation on the optical properties of ex vivo normal and adenomatous human colon tissue with OCT imaging and diffuse reflectance spectra

Using optical coherence tomography (OCT) and diffuse reflectance spectra, we investigated the dynamics of titanium dioxide (TiO₂) nanoparticles, of different sizes, when penetrating and accumulating in human normal colon tissue (NC) and adenomatous colon tissue (AC). The process of nanoparticle penetration and accumulation in biotissue is accompanied by changes in the optical properties of tissue. Continuous OCT monitoring showed that, after application of TiO₂ nanoparticles, the OCT signal intensities of NC and ac both increase with time, and the larger nanoparticles tend to produce a greater signal enhancement in the same type of tissue. The average attenuation coefficient decreased from 4.03 ± 0.36 to 2.68 ± 0.24 mm⁻¹ at approximately 127 min for NC with 60 nm TiO₂, from 4.14 ± 0.38 to 2.91 ± 0.27 mm⁻¹ at about 148 min for NC with 100 nm TiO₂, from 8.49 ± 0.77 to 3.54 ± 0.34 mm⁻¹ at about 110 min for AC with 60 nm TiO₂, and from 8.61 ± 0.79 to 3.89 ± 0.41 mm⁻¹ at about 128 min for AC with 100 nm TiO₂, respectively. Spectral measurements confirm that the nanoparticles penetrate and accumulate in NC and AC. The results suggest that the penetration and accumulation of TiO₂ nanoparticles have significant effects on the optical properties of NC and AC. (letter)