Swelling and drug delivery kinetics of click-synthesized hydrogels based on various combinations of PEG and star-shaped PCL: influence of network parameters on swelling and release behavior

Polyethylene glycol (PEG)- and polyethylene glycol-polycaprolactone (PEG-PCL)-based hydrogels were synthesized with various compositions of prepolymers by using ROP and click chemistry methods. Relevant prepolymers were characterized by(1)H NMR and FTIR spectroscopy. In order to study the influence of network parameters on swelling and release kinetics, experimental data were approximated by several mathematical models including zero order, first order, Higuchi and Korsmeyer-Peppas to determine the kinetics of swelling and diclofenac sodium release from hydrogels. The obtained results showed that the swelling and release data were best fitted to Korsmeyer-Peppas model. The results of the swelling study showed that the swelling properties of the hydrogels varied with the changes in the PEG molecular weights, as well as concentration of PCL. All of the hydrogels showed non-Fickian diffusion, but when PCL concentration increased and PEG molecular weights decreased, the n values were decreased and reachedn = 0.5 (Fickian diffusion). The kinetics of diclofenac sodium release from hydrogels showed similar behavior so that in F hydrogels with the highest PCL concentration, the release mechanism fully changed from non-Fickian to Fickian diffusion. In other words, with increasing cross-link density and PCL concentration, the swelling degree and flexibility of networks decreased. Therefore, the swelling and release mechanism changed from non-Fickian to Fickian diffusion.