PEGylated insulin loaded complexation hydrogels for protected oral delivery.

While a number of enteric coatings and pH-sensitive oral delivery vehicles have been developed, they lack the ability to sufficiently protect proteins from proteolytic degradation once released from the carrier. In this work, we show that H-bonded, pH-sensitive poly(methacrylic acid-grafted ethylene glycol) glycol (henceforth designated as P(MAA-g-EG) gels) exhibit great promise as protein carriers, as they utilize poly(ethylene glycol) (PEG) chains to promote mucoadhesion in the small intestine, increasing the chances that the drug is released within the villus of the absorptive intestinal wall. Importantly, PEG was also conjugated to the B29-lysine (LysB29) position of insulin in order to protect the drug from proteolytic degradation once released in the small intestine and adhere the drug to the intestinal epithelium through improved mucoadhesion. PEG-conjugated (PEGylated) molecules were found to actively participate in the carrier loading and release mechanism, with the drug conjugate hydrogen bonding to the MAA while in the collapsed state and subsequently repulse the drug above the polymer's isoelectric point. This effect was enhanced through the evaluation of PEG graft density within the carrier. Cellular transport and changes in transepithelial resistance caused by the PEGylated insulin (PI) in the presence of P(MAA-g-EG) microparticles were analyzed using a 1:1 co-culture of human colon adenocarcinoma (Caco-2) and: the mucus-secreting human colon carcinoma cell(HT-29-MTX). Finally, the in vivo absorption of insulin was measured in Sprague-Dawley rats to ensure that the PEGylated insulin conjugates are biologically active, as well as to compare the bioavailability to control insulin. Collectively, these results lead toward the development of a novel system for improved insulin delivery, with improved stability of insulin through PEGylation.