pH-responsive hydrogels to protect IgY from gastric conditions: in vitro evaluation

Oral administration of specific egg yolk immunoglobulin (IgY) is effective against a number of gastrointestinal pathogens. However, the activity of orally administered IgY is reduced rapidly, since IgY is sensitive to pepsin and low pH. In this study, hydrogels containing acrylamide and acrylic acid were synthesized and used to encapsulate IgY. The capacity of these structures to load, protect and release IgY and the interaction between IgY and hydrogels by FTIR spectroscopy were studied. The particle size and swelling percentage of hydrogels were highly dependent on the pH of the buffer solution. As expected, pH-sensitive hydrogels had a high IgY loading percentage (99.2 ± 12.9 mg IgY/mg hydrogel) at pH 7.4. It means that each gel piece incorporated approximately 8.4 ± 1.1 mg IgY. The results showed that the hydrogels could efficiently incorporate IgY and retain it inside the polymer network at pH <2.2. However, IgY was slowly released at basic pH and a high percentage remained inside. The IR spectra show that IgY interacts with the hydrogel in its network with extended hydrogen bonds. The present study demonstrates that hydrogels particles can efficiently incorporate the IgY but cannot show a controlled and sustained release of IgY in simulated intestinal fluid probably due to hydrophobic interactions with the polymer network. The stability of IgY in simulated gastric fluid was greatly improved by encapsulation in hydrogels. This approach provides information about a novelty method for delivery of IgY for the prevention and control of enteric diseases.