Development of pH-Sensitive Hydrogel Nanoparticles for Oral Delivery of High Isoelectric Point Protein Therapeutics

Currently, protein-based therapeutic drugs are only available to patients via injection. This method of drug delivery is uncomfortable to the patient, and thus results in decreased patient compliance. Oral drug delivery of such drugs would be preferable for many patients, but several obstacles in the gastrointestinal tract must be overcome for successful oral protein delivery. Ideally, the protein should be transported across the intestinal epithelium where it can enter the bloodstream. We have developed pH-sensitive polymeric nanoparticle carriers to protect the protein through the acidic upper digestive tract and then swell to release the protein in the higher pH environment of the upper small intestine. For proteins with a low isoelectric point, charge interactions between the protein and the anionic particle facilitate loading and release. However, this is not true for high isoelectric point proteins, as the positively charged protein will remain attracted to the negatively charged particle in neutral conditions, thus hindering release. The present study explores strategies to overcome this attraction between the protein and nanoparticle, and thus, increase bioavailability of the high isoelectric point protein therapeutics.

Hydrogel nanoparticles were synthesized by inverse emulsion polymerization of acrylamide and itaconic acid and crosslinked with N,N’-methylenebisacrylamide. The particles were purified using ethanol precipitation and dialyzed against a gradient of ethanol and water. Particle composition was confirmed with Fourier Transform Infrared Spectroscopy and particle swelling was analyzed with dynamic light scattering to measure particle size at varying pH levels. Electrophoretic light scattering was also used to measure the zeta potential of the particles at varying pH levels. With increasing pH, the particles increase in size, and zeta potential becomes more negative. Protein loading into the particles over time was measured using the Micro BCA protein assay, which showed decreased supernatant protein concentration over time. These pH-sensitive carriers show promise for oral protein delivery. Further studies are in progress to evaluate protein release, cytocompatibility, and transport across the intestinal epithelium.