Surface Coating Approach to Overcome Mucosal Entrapment of DNA Nanoparticles for Oral Gene Delivery of Glucagon-like Peptide 1

Oral delivery of nucleic acid therapy is a promising strategy in treating various diseases because of its higher patient compliance and therapeutic efficiency compared to parenteral routes of administration. However, its success has been limited by the low transfection efficiency resulting from nucleic acid entrapment in the mucus layer and epithelial barrier of the gastrointestinal (GI) tract. Herein, we describe an approach to overcome this phenomenon and improve oral DNA delivery in the context of treating type II diabetes (T2D). Linear PEI (lPEI) was used as a carrier to form complexes with plasmid DNA encoding glucagon-like peptide 1 (GLP-1), a common target in T2D treatments. These nanoparticles were then coated with a mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dimyristoyl-rac-glycero-3-methoxy poly(ethylene glycol)-2000 (DMG-PEG) to render the nanoparticle surface hydrophilic and electrostatically neutral. The surface-modified lPEI/DNA nanoparticles showed higher diffusivity and transport in the mucus layer of the GI tract and mediated high levels of transfection efficiency in vitro and in vivo. Moreover, these modified nanoparticles demonstrated high levels of GLP-1 expression for more than 24 h in the liver, lungs, and intestine in a T2D murine model after a single dose, as well as controlled blood glucose levels within a normal range for at least 18 h with repeatable therapeutic effects upon multiple dosages. Taken together, this work demonstrates the feasibility of an oral plasmid DNA delivery approach in the treatment of T2D through a facile surface modification to improve the mucus permeability and delivery efficiency of the nanoparticles.