MICROSTRUCTURED CHITOSAN/CARBOXYMETHYLCELLULOSE POLYELECTROLYTE COMPLEXES AS A VEHICLE FOR NIACINAMIDE

The use of controlled release systems has attracted the attention of academic and industrial researchers, aiming at improving the stability and efficiency of formulations, mainly at the nanometric scale. Charged biopolymers, such as chitosan (CHS, polycationic) and carboxymethylcellulose (CMC, polyanionic), are promising candidates for applications in supramolecular structures to be used as carrier systems. In addition, these two biopolymers are biocompatible, easily biodegradable, and present manufacturing costs. The coacervation between oppositely charged biopolymers presents in its primary stage, micro-coacervation, the formation of fine particulate coacervates, which gives turbidity to the reagent dispersion. Then, the macro-coacervation stage can be reached, in which the microparticles coalesce, originating larger particles. This study proposed developing an easy and efficient strategy for encapsulating the bioactive compound niacinamide (vitamin B3), using the complex coacervation technique between chitosan and carboxymethylcellulose with the inclusion of this vitamin. This bioactive compound was chosen because of its low stability under processing conditions, so its microencapsulation may improve its bioavailability in formulated products. A Box-Behnken design was set to study the effects of three independent variables – processing time, X1 (60, 120, and 180 min), pH, X2 (3, 4, and 5), and niacinamide concentration, that is, X3 (0.02, 0.04 and 0.06, g·L-1), on the encapsulation efficiency (Y1) and the binding capacity (Y2) of CMC/CHS micro-PECs to niacinamide. The nanocarriers were synthesized from the simultaneous drop-by-drop addition of biopolymer dispersions (0.5% m/v) under stirring. The final mixture was centrifuged at 20,000 g for 2 hours to separate the micro-PECs containing or not a vitamin. The supernatant was used in the calculation of encapsulation efficiency. Niacinamide was quantified by UV-vis spectrophotometry at wavelength = 228 nm. Depending on the experimental conditions, the encapsulation efficiency (Y1) and loading capacity (Y2) presented significant variations, between 0.86 and 80.78% and 0.03 and 3.89%, respectively. Both responses studied (Y1 and Y2) were affected mainly by the pH of the medium. The in vitro digestibility of CMC/CHS micro-PECs containing niacinamide was evaluated using a static gastrointestinal model. Four kinetic models were fitted to the niacinamide release kinetics data: Zero Order, First Order, Higuchi, and Korsemeyer-Peppas. The zero-order model showed the best (for both gastric and enteric digestion), with low zero-order constants (K0) (0.002 - 0.003), and similar for all systems studied, demonstrating a low release rate. Overall, we showed that a relatively simple process could encapsulate niacinamide, with better bioavailability and slow release of this bioactive in a simulated gastrointestinal environment. This result opens the doors for this research's next steps, which consist of assessing the practical viability of including the niacinamide-loaded CMC/CHS complexes in a formulated food.