Double emulsion-based encapsulation of iron in amphiphilic block copolymer nanocarriers for controlled release

Abstract

In this study, we explored the design of polymeric nanocapsules as vehicles for controlled release of iron. Amphiphilic block copolymers (ABCs) composed of polyethylene glycol (PEG) and poly (ε-caprolactone) (PCL) segments were synthesized via ring-opening polymerization (ROP), using PEG and methoxy-PEG (mPEG) with varying molecular weights as macroinitiators. Structural and molecular characterizations using infrared spectroscopy, proton nuclear magnetic resonance and gel permeation chromatography confirmed successful copolymerization and narrow dispersity indices (Ð <1.5). Iron-loaded nanocapsules were formulated using the double emulsion solvent evaporation (DESE) technique with synthesized PEG-b-PCL copolymers as polymeric precursors. The impact of the copolymer composition on the particle size, morphology, and encapsulation efficiency (EE%) was evaluated. Spherical nanocapsules with diameters below 500 nm were obtained, and a positive correlation was observed between copolymer molecular weight and EE%, with the highest value (74.4%) achieved for the Fe@COP5-96 formulation. Differential scanning calorimetry (DSC) analysis revealed that iron incorporation altered the thermal behavior of the copolymers, resulting in a shift of the melting peaks toward lower temperatures and a decrease in melting enthalpy, consistent with reduced crystallinity arising from ion–polymer interactions. The iron release kinetics exhibited a sustained release behavior. These results demonstrate the potential of PEG-b-PCL nanocapsules as effective carriers for ionic species with promising applications in nutrient delivery and medical therapies.