Mucoadhesive poly(ethylene glycol)-based biodegradable polyesters with in-chain model drug

Mucoadhesive polymers have received significant interest in drug delivery due to the prolonged residence time on various mucus gel layers. Not only local effects but also the systemic uptake of active pharmaceutical ingredients can be enhanced by such mucoadhesive excipients. In this study, we design novel poly(ethylene glycol) based mucoadhesive polyesters bearing unsaturated or sulfhydryl functionalities and model drug fluorescein polymerized in the polymeric backbone. The structure of polyesters was confirmed via 1 H NMR and FTIR, while their molar masses, determined by gel permeation chromatography, were found to be between 3.6 and 4.0 kDa. Enzymatic degradation studies showed the ability of lipase to degrade the polymeric chains. Because of the mucoadhesive groups, the viscosity of mucus mixtures with these polymers increased 1.8-fold for the double bond, while 4.3-fold for thiol functional polymers, compared to PEG. Prolonged residence time on porcine intestinal mucosa was detected, as 3 h after application, up to 69 % of the polymers were still on the mucosa, whereas PEG was completely removed within 30 min. Highly pH and enzyme-dependent release of fluorescein was noticed; only pH > 6.8 caused significant drug release. According to the results of this study, PEG-based unsaturated and thiolated polyesters with in-chain model drugs are great mucoadhesive and biodegradable drug carriers with sustained release properties.