RHEOLOGICAL STUDY OF BILE SALT/LECITHIN AND NANOCELLULOSE AGGREGATES

Bile salts are biosurfactants that have a polar and a nonpolar face, produced in the liver and responsible for fat solubilization ^[1]. Lecithin is a natural zwitterionic surfactant, formed by two nonpolar tails and a polar head, found in soybeans and egg yolks^[2]. Combining these two surfactants with nanocellulose particles (nanocrystals (CNC) and nanofibrils (CNF)) can produce self-aggregated systems, which can be used as a platform for encapsulation and release of medicines. The systems were prepared from stock solutions of lecithin and sodium taurodeoxycholate (NaTDC) solubilized in methanol in the proportion of 0.8 (mol/mol) NaTDC/Lecithin, stirring for 1 h and placed in an oven at 35 °C for approximately 48 h to evaporate the methanol. Then, 3.4 mL of 1.4 % (m/v) CNF or CNC and 6.6 mL deionized water were added and systems were stirred at 100 rpm for 24 h. All systems remained at rest for at least 48 hours before analysis. Aggregates with 350 nm average diameter size and zeta potential of -30 mV were obtained, indicating a good stability of the systems. Rheological analyses showed that NaTDC/lecithin and CNF particles presented the highest zero shear viscosity value (h₀) (165 Pa.s) and the storage (G') and loss (G'') moduli presented typical curves of gel-like systems, with G’ and G’’ independent of frequency with values of 30 and 1.1 Pa.s, respectively. NaTDC/lecithin systems with CNC particles exhibited lower viscoelasticity, indicating low density of entanglement among the aggregates. In this scenario, NaTDC/lecithin with CNF can be a good candidate to be used as a platform for drug delivery.