Encapsulation of A, B/C and P riboflavin into calcium-alginate particles for controlled release and antibacterial applications

Objective — to investigate the possibility of encapsulating hydrophilic B/C and P forms of riboflavin in calcium alginate particles, to study the release of riboflavin from particles and its antibacterial properties. Materials and methods. Alginate particles were obtained by cross-linking of sodium alginate with calcium ions and loaded in situ with B/C and P types of riboflavin. The strains of Pseudomonas aeruginosa bacteria were used to evaluate antibacterial activity. Results. Two polymorphic modifications and the salt form of riboflavin (types A, B/C and P) were successfully encapsulated into calcium alginate particles of about 600 μm in size. Optical and electron microscopy methods show that types A and B/C retain the shape of crystals and crystalline junctions, while riboflavin type P is uniformly distributed in the gel matrix. X-ray phase analysis confirmed the retention of the crystalline form of riboflavin type A, but showed that B/C type crystalline aggregates amorphise upon encapsulation. It was demonstrated that alginate particles containing B/C type riboflavin are characterised by a prolonged release of the active ingredient into deionised water, while for P type the equilibrium concentration is reached after 30 minutes. It was found that particles loaded with B/C and P types exhibit pronounced antibacterial activity against Gram-negative bacteria. Conclusion. Encapsulation of riboflavin types B/C and P in alginate particles allows preserving the antibacterial activity of the substance and ensuring its controlled release.