Engineered Nanoparticle Systems to Overcome Biological Barriers for Nanomedicine

Abstract

Biological barriers in the body impede the transport of nanotherapeutics to a target site leading to unfavorable biodistribution profiles and inadequate accumulation of drugs, thus limiting the efficacious responses in diseases. Reimagining nanoparticle-based design strategies to navigate extracellular and intracellular biological barriers is therefore needed for efficient therapeutics. This dissertation focuses on the use of electrohydrodynamic (EHD) co-jetting to engineer novel protein- and biopolymer-based nanoparticle systems to address three major biological transport barriers: the immune system barrier,the blood-brain barrier (BBB), and the oral mucosal barrier. A selection of synthetic protein nanoparticles (SPNPs) prepared from (i) single proteins including human serum albumin (HSA), bovine serum albumin, ovalbumin (OVA), human transferrin (TF), hemoglobin, mucin, insulin, and lysozyme, (ii) blend of different proteins, and (iii) compartmentalization of different proteins in the same nanoparticle are used to target the immune system and BBB. Bicompartmental poly(lactide-co-glycolide) (PLGA)-chitosan nanoparticles as the biopolymer-based system are used to overcome the oral mucosal barrier. Tunable physicochemical properties and biological responses of SPNPs are achieved by altering the protein composition, macromere type, macromer-to-protein ratio, solvent system, and by compartmentalization. A systematic study of SPNPs with various protein compositions led to nanoparticles with low polydispersity indices (0.11-0.19), high circularity (0.82 – 0.90), low anisotropy (< 1.45), and high roundness (0.76 – 0.89). Specific SPNPs are then chosen to overcome each of the biological barriers. To target the immune system interface, antigen-based particles (OVA SPNPs) are fabricated with varying physicochemical properties to improve antigen delivery and immunological responses for cancer immunotherapy. When prepared from a macromer-to-protein ratio of 10%, 266 nm sized particles with an elasticity of 42 kPa showed enhanced uptake by dendritic cells, T cell activation, draining lymph nodes delivery, antibody production and anti-tumor efficacy. To cross the BBB, HSA SPNPs owing to the endogenous property of albumin proteins to mediate endothelium transcytosis are chosen and hitchhiked on RBCs due to their innate vascular mobility and long circulation times. IgG-modified HSA SPNPs showed an average binding of 126 nanoparticles per RBC with no adverse effects on the cells, resulting in a 19-fold and 113-fold increase in brain uptake and in the brain-to-(liver and spleen) ratio, respectively in a mouse model of acute brain inflammation. In another approach, monocytes due to their natural recruitment to the inflamed brain and ability to cross the BBB are used to hitchhike 200 and 500 nm protein-based (HSA and TF) and polymer-based (polystyrene and poly(methyl methacrylate)) nanoparticles to investigate the effect of their physicochemical properties on monocytes. While 500 nm PMMA nanoparticles showed the highest uptake, the migration of 200 nm HSA and TF SPNPs-loaded monocytes were 3.4 and 3.7-fold higher, respectively. These results show that SPNPs delivered by a cell-mediated approach using RBCs or monocytes hold great promise for brain drug delivery. For targeting the oral mucosal barrier, PLGA-chitosan nanoparticles enable different adhesion interactions with mucus layer for oral cancer chemoprevention. The nanoparticles were readily internalized by human oral keratinocytes and penetrated through human oral mucosal explants, with 41% of them reaching the basilar third of the epithelium. PLGA-chitosan nanoparticle-mediated delivery of tocilizumab as a chemopreventive agent resulted in significant oral squamous cell carcinoma tumor-regressive effects. The approaches described in this thesis hence provide new perspectives on transport-driven in vivo mechanisms to enhance the therapeutic efficacy of nanoparticles in the context of biological barriers.