Effect of the Route of Administration and PEGylation of Poly(amidoamine) Dendrimers on Their Systemic and Lung Cellular Biodistribution.

There are many opportunities in the development of oral inhalation (oi) formulations for the delivery of small molecule therapeutics and biologics to and through the lungs. Nanocarriers have the potential to play a key role in advancing oi technologies and pushing the boundary of the pulmonary delivery market. In this work we investigate the effect of the route of administration and PEGylation on the systemic and lung cellular biodistribution of generation 3, amino-terminated poly(amidoamine) (PAMAM) dendrimers (G3NH2). Pharmacokinetic profiles show that the dendrimers reach their peak concentration in systemic circulation within a few hours after pulmonary delivery, independent of their chemistry (PEGylated or not), charge (+24 mV for G3NH2 vs -3.7 mV for G3NH2-24PEG1000), or size (5.1 nm for G3NH2 and 9.9 nm for G3NH2-24PEG1000). However, high density of surface modification with PEG enhances pulmonary absorption and the peak plasma concentration upon pulmonary delivery. The route of administration and PEGylation also significantly impact the whole body and local (lung cellular) distribution of the dendrimers. While ca. 83% of G3NH2 is found in the lungs upon pulmonary delivery at 6.5 h post administration, only 2% reached the lungs upon intravenous (iv) delivery. Moreover, no measurable concentration of either G3NH2 or G3NH2-24PEG1000 is found in the lymph nodes upon iv administration, while these are the tissues with the second highest mass distribution of dendrimers post pulmonary delivery. Dendrimer chemistry also significantly impacts the (cellular) distribution of the nanocarriers in the lung tissue. Upon pulmonary delivery, approximately 20% of the lung endothelial cells are seen to internalize G3NH2-24PEG1000, compared to only 6% for G3NH2. Conversely, G3NH2 is more readily taken up by lung epithelial cells (35%) when compared to its PEGylated counterpart (24%). The results shown here suggest that both the pulmonary route of administration and dendrimer chemistry combined can be used to passively target tissues and cell populations of great interest, and can thus be used as guiding principles in the development of dendrimer-based drug delivery strategies in the treatment of medically relevant diseases including lung ailments as well as systemic disorders.