Liquid lecithin crystals as carriers of biologically active substances and nanoparticles

Lecithin liquid crystals are promising carriers for transdermal drug delivery. They are able to include both lipophilic and hydrophilic substances, as well as solid particles. In this work, liquid crystals in a system comprising lecithin, avocado oil, tea tree oil, and water, containing biologically active substances and nanoparticles, were studied.
It was shown that in the range of shear rates from 0.01 to 1.0 s^-1, the introduction of 1.0 and 3.0 mol/L NaCl aqueous solutions increased the viscosity of liquid crystals, on average, by 4 and 9.1 times in comparison with the control sample. The introduction of potassium chloride glucosamine sulfate solutions with mass concentrations of 50, 100, and 150 g/l increased viscosity by 1.3, 2.2, and 3.3 times, while the introduction of 1 wt.% albumin in a citrate buffer solution into the liquid crystalline sample increased its viscosity by 1.5 times.
The addition of 0.3 wt.% of CuO nanoparticles (92±3 nm) increased the viscosity by 2.0 times, and that of CuSO₄ aqueous solution by 2,5 times compared with the control sample. When 0.3 wt.% of CuO microparticles (31,2±3,5 mm) was added, the viscosity decreased by 1.3 times. The kinetics of the release of copper ions from liquid crystals (copper content 2.4 mg/g) by dialysis were studied at T = 37 °C. The release rate of Cu²⁺ for liquid crystals with the CuSO₄ solution was 7,6 · 10^-4 g/(m² · h); for CuO nanoparticles, it was 5,86 · 10^-4 g/(m² · h); and for microparticles, it was 2,36 · 10^-4 g/(m² · h). Therefore, a dimensional effect was observed. This difference can be explained by the fact that copper ions in liquid crystals with CuSO₄ are already in the solution, but for samples with CuO particles, their dissolution is required.
The results obtained will help in the development of medical products based on lecithin liquid crystals.