Encapsulation of folic acid in copper-alginate hydrogels and it's slow in vitro release in physiological pH condition

Folic acid (FA) is an essential micronutrient but its delivery and bioavailability is a problem due to its inherent instability at various conditions. A robust protective encapsulation system for folic acid is highly desirable. This work reports the use of the divalent copper in complex with alginate as a strong encapsulation system for folic acid. Using gel spherification technique, hydrogels were formed upon dropwise addition of sodium alginate solution in a copper bath. In the presence of folic acid, encapsulation was achieved as evidenced by the yellow coloration, intact surface morphology (SEM), the presence of nitrogen (23.08% N; EDX), and thermal gravimetric degradation for folic acid (28% FA; TGA). The spherical hydrogels do not burst upon 2 m-drop test and remain intact at pH 1.2 with no evident release of folic acid indicating stability of the encapsulation system at the abdominal gastric condition. The copper alginate acted as gastro-resistant material and slow release of folic acid occurs only at pH > 5 especially at simulated intestinal conditions (pH 8.2). The study indicates the potential of copper alginates as a protective encapsulant to ensure stability and slow release of FA in simulated physiological pH conditions.