(38a) Nanoparticle Delivery Vehicle to Mimic Bacterial Invasion of Lung Epithelium

A variety of phylogenetically distinct bacterial pathogens, such as non-typeable Haemophilus influenzae (NTHi), invade host cells in the upper airways by binding the platelet-activating factor (PAF) receptor. Lipooligosaccharide (LOS) glycoforms naturally expressed on the bacterial cell surface facilitate bacteria-epithelial interactions. We are utilizing LOS ligands isolated from the bacteria surface to coat the surface of nanosized delivery vehicles to mimic the invasion characteristics of NTHi, enabling targeting of drug molecules to the respiratory epithelium. We have observed that modification of the surface of nanoparticles with absorbed LOS glycoforms from the 2019 NTHi strain increased cellular adherence and penetration when applied to bronchial epithelial cell cultures in vitro. However, when LOS modified nanoparticles were applied to a more physiologically relevant model of the respiratory system their diffusion through the respiratory fluid barrier is hindered. Therefore, the goal of our research is to minimize nanoparticle interactions with respiratory fluids while retaining the improved cellular adherence and penetration afforded by the LOS coating.

Commercially available fluorescent nanoparticles were modified with various NTHi LOS glycoforms, polyethylene glycol (PEG; 5-40 kDa), and combinations thereof. Upon coating, the modified nanoparticles exhibited an increase in size proportional to the molecular weight of the coating material and more neutral surface charge. Calu-3 bronchial epithelial cells were grown to confluent monolayers under air-interfaced culture conditions on semi-permeable Transwell membranes. The adherence and uptake of nanoparticles into the epithelial cells was determined under three apical fluid conditions: no apical fluid, natural secretions produced by the cells and synthetically prepared mucus mimetic. Laser scanning confocal microscopy was used to differentiate the nanoparticles associated with the cell monolayer from those that remained in the apical fluid. Our results show that transport through mucosal fluids and uptake into lung epithelium is improved through optimization of: PEG molecular weight, PEG surface coverage and choice of LOS bacterial strain.