Rheological properties of dextrin-riboflavin solutions under thermal and UV radiation effects

The combination of saccharides and UV sensitive chemical molecules in the solution form has been in the interest of medicine for treating medical complications and imaging techniques due to their remarkable properties under UV radiation. Therefore, two samples of dextrin based riboflavin solutions containing 10 wt% of dextrin content and 0.1 wt% of UV sensitive riboflavin content were prepared at the room temperature. In order to understand how UV radiation affects the viscosity of prepared solutions at various temperatures, one of the prepared samples was protected from light while another sample was radiated to UV at a biologically harmless wavelength where the absorbance peaks are obtained by UV/visible spectroscopy. Dynamic viscosity measurements of UV-radiated and un-radiated solutions for different temperatures were performed with constant velocity where the most reliable torque is shown. It was understood that application of UV radiation increased the viscosity value of radiated sample at the room temperature, however; it did not alter the fluid types of test samples. Fluid type of all test solutions was found to be non-Newtonian dilatant fluids as the shear stress vs. shear rate curves of solutions reliably obeyed Ostwald-de-Waele equation. Flow type of all solutions was classified as shear thickening fluids (STF) since power law consistency coefficient (n) of Ostwald-de-Waele equation was found to be > 1 (n > 1). Based on this experimental outcome, the effect of UV radiation on shear thickening behavior of the solutions which include low viscous biocompatible solutions was studied for the first time. Thermal behavior of all test solutions was mathematically modeled via Arrhenius viscosity equation. The degree of STF increased and viscosity of dextrin based riboflavin solutions was found to be slightly greater than other test samples at increasing temperature values after UV radiation. As expected, viscosity values of all test samples decreased at elevated temperatures.