(F-229) Design of a Self-assembled Oral Delivery Carrier for Therapeutic Proteins to Treat Autoimmune Diseases

Introduction:: Autoimmune diseases are characterized by the failure of an organism to tolerate its own cells and tissues which can lead to pathological changes and tissue dysfunction. Biologics, specifically monoclonal antibodies, are considered highly significant in the treatment of these diseases due to their remarkable specificity and effectiveness. As a result of their high molecular weight, low bioavailability, and susceptibility to degradation, their administration is limited to parenteral routes. Out of the numerous alternative administration routes that have been proposed, oral delivery offers the most advantages regarding costs, accessibility, and reduced discomfort, which increases patient compliance. Nevertheless, the oral route has significant biological and physicochemical challenges such as the presence of proteolytic enzymes, drastic changes in pH, as well as the mucus and the epithelial cell layer. These challenges must be overcome to successfully deliver monoclonal antibodies across the intestinal epithelium into the bloodstream. One approach to protecting them from these barriers is to use polymeric nanocarriers. Thus, this project aims to develop pH-responsive self-assembled polymersomes based on block copolymers to deliver monoclonal antibodies via the oral route to treat autoimmune diseases.


Materials and Methods:: All reagents were purchased from Sigma Aldrich, Laysan Bio, or Fisher Scientific and used as received. Di- and triblock copolymers containing poly(methacrylic acid) (PMAA) and poly(ethylene glycol) (PEG) were synthesized using reversible addition−fragmentation chain-transfer polymerization and carbodiimide-mediated coupling reactions. Different degrees of polymerization and number of blocks were examined to see the effect of the hydrophilic weight fraction on the micellar polymorphism. The nanoprecipitation technique was used to prepare the nanoparticles, 1X phosphate-buffered saline (PBS) at pH 7.4 as the solvent and 1X PBS at pH 2 as the non-solvent. The block copolymers were analyzed by Fourier-transformed infrared spectroscopy (FTIR) to examine the varying ratios of PMAA in the block copolymers, and ¹H nuclear magnetic resonance (NMR) spectroscopy to verify the successful addition of the PEG chain and to calculate the degree of polymerization of both PEG and PMAA through end group analysis. The effect of the polymer concentration and the degree of polymerization in nanoparticle size was determined using dynamic light scattering (DLS). Lastly, the block copolymers were studied by transmission electron microscopy (TEM) to examine the nanostructures formed.

Results, Conclusions, and Discussions:: Analysis by FTIR and ¹H NMR confirmed the polymerization of PMAA and the successful addition of the PEG chain. Diverse hydrophilic weight fractions for the di- and triblock copolymers were obtained. DLS studies showed hydrodynamic diameters ranging from 201 nm to 591 nm. By using TEM, the effect of the hydrophilic weight fraction and the number of blocks on the micellar polymorphism was analyzed and both polymersomes and micelles were obtained.
By varying the hydrophilic weight fraction of the block copolymers composed of PMAA and PEG, we were able to prepare pH-responsive nanoparticles with diverse micellar polymorphisms. In future studies, further optimization of the nanoparticle system will be implemented including strategies to increase the pKa of the block copolymer and exploring alternatives to PEG. The loading and release capacity of the polymersomes, as well as their abilities to cross the mucus and the epithelial cell layer, will be analyzed using Caco-2 and HT-29/MTX co-culture. The development of these nanocarriers will help us achieve the oral delivery of monoclonal antibodies for the treatment of autoimmune diseases.


Acknowledgements (Optional): : NIH grant number R01-EB022025, the Cockrell Family Chair Foundation, the Office of the Dean of the Cockrell School of Engineering at the University of Texas at Austin (UT) for the Institute for Biomaterials, Drug Delivery, and Regenerative Medicine, and the UT-Portugal Collaborative Research Program. FAC-V acknowledges support from the CONACYT/ConTex Fellowship (Mexico).


References (Optional): :