Development of a P((MAA‐co‐NVP)‐g‐EG) Hydrogel Platform for Oral Protein Delivery: Effects of Hydrogel Composition on Environmental Response and Protein Partitioning

Abstract

Hydrogels based upon terpolymers of methacrylic acid, N-vinyl pyrrolidone, and poly(ethylene glycol) are developed and characterized for their ability to respond to changes in environmental pH and to partition protein therapeutics of varying molecular weights and isoelectric points. P((MAA-co-NVP)-g-EG) hydrogels are synthesized with PEG-based cross-linking agents of varying length and incorporation densities. The composition is confirmed using FT-IR spectroscopy and shows peak shifts indicating hydrogen bonding. Scanning electron microscopy reveals microparticles with an irregular, planar morphology. The pH-responsive behavior of the hydrogels is confirmed under equilibrium and dynamic conditions, with the hydrogel collapsed at acidic pH and swollen at neutral pH. The ability of the hydrogels to partition model protein therapeutics at varying pH and ionic strength is evaluated using three model proteins: insulin, porcine growth hormone, and ovalbumin. Finally, the microparticles are evaluated for adverse interactions with two model intestinal cell lines and show minimal cytotoxicity at concentrations below 5 mg mL .

Student Award for Outstanding Research Winner in the Undergraduate Category for the 2017 Society for Biomaterials Annual Meeting and Exposition, April 5–8, 2017, Minneapolis, Minnesota: Development and characterization of stimuli‐responsive hydrogel microcarriers for oral protein delivery

“…At the equivalence point during the titration, the number of moles of titrant is equal to the number of moles of ionizable groups in the terpolymer; thus, the composition of MAA in the gels can be determined . In P((MAA‐co‐NVP)‐ g ‐EG) hydrogels, neither NVP nor PEGMMA has any cationic or anionic activity, and the only ionizable group is contributed from the pendant carboxylic acid group on the MAA . The P((MAA‐co‐NVP)‐ g ‐EG) hydrogels with PEG1000 were determined to have MAA contents between 47 and 48%, as shown in Table , whereas the P((MAA‐co‐NVP)‐ g ‐EG) hydrogels with PEG5000 were determined to have MAA contents at ∼62%.…”

“…In gastric conditions of pH 1.2, all hydrogel formulations showed minimal to no volume swelling, indicated by volume swelling ratios, Q , of approximately 1–2. The hydrogel maintained a collapsed state when below the p K a of MAA, 4.8–4.9, due to the hydrogen bonding complexes between the protonated carboxylic acid on MAA, the carbonyl on the lactam ring on NVP, and the etheric oxygen in the PEG chain . Previous work had determined the hydrogen bonding group ratio chosen for MAA:NVP in P(MAA‐co‐NVP) hydrogel formulations maintained the most favorable hydrogel network at pH values less than MAA p K a, thus minimizing protein release at gastric conditions .…”

“…All cells were cultured in T‐75 flasks (Corning Inc.) while sustained in a humidified incubator at 37°C and 5% CO 2 with frequent media changes every 72 hours. Upon reaching 80–90% confluence, cells were passaged and plated into T‐75 flasks at a 1:2–1:6 sub‐cultivation ratio and then appropriately diluted with modified DMEM as described previously . In all in vitro experiments, Caco‐2 cells were used during passages 65–80 and HT29‐MTX cells were used during passages 10–20.…”

“…When the pendant groups are protonated, hydrogen bonding causes the polymer complex to remain in a collapsed state, able to protect and keep the therapeutic payload within the system. However, when the pendant groups are ionized, electrostatic repulsive forces are generated between the surrounding solution and negative charged polymer backbone allowing for water imbibition and creating a pH‐mediated driving force for the hydrogel to swell . Previous work has shown that pH‐responsive hydrogels incorporated with methacrylic acid exhibit substantial promise in the oral delivery of protein therapeutics.…”

“…Previous work developed terpolymers based on MAA, NVP, and PEGMMA, denoted as P((MAA‐co‐NVP)‐ g ‐EG), to harness the functionality of each of the individual monomer species. These systems have shown the desired pH‐responsive swelling behavior and successful partitioning of model therapeutics, including insulin, porcine growth hormone, and ovalbumin . While previous work studied the effect of varied PEG‐based cross‐linker density and length in the terpolymer system, modulating the length and incorporation density of the PEGMMA tethers has not been explored.…”