Calcium triggered self-assembly of alginate-graft-POEGMA via RAFT for the encapsulation of lipophillic actives

Alginate based comb copolymers were synthesized by reversible addition-fragmentation chain transfer (RAFT). Alginate was used both in its supplied (213 kDa) and depolymerized (73 kDa) forms and prepared into a macroRAFT agent by solubility modification with tetrabutyl ammonium ions and functionalization with a RAFT agent on its hydroxyl moieties. Poly(oligo ethylene glycol methacrylate) (POEGMA) was then polymerized from the macroRAFT agents in organic solvent demonstrating pseudo first-order kinetics. The copolymers dissolved well in a range of organic solvents and demonstrated self-assembly into nanoparticles upon the introduction of calcium chloride in both aqueous and methanolic solutions with particle sizes ranging between 100 and 500 nm. Remarkable encapsulation efficiencies of 4-n-butylresorcinol, a lipophillic active pharmaceutical ingredient, were demonstrated in methanol, and a sustained release profile was observed over 6 hours in aqueous acidic media. These new materials complement a growing library of biodegradable and sustainable polymers that show notable potential for the use in encapsulation and drug delivery.