Dendrimer nanocarriers for transport modulation across models of the pulmonary epithelium.

The purpose of this study was to determine the effect of PEGylation on the interaction of poly(amidoamine) (PAMAM) dendrimer nanocarriers (DNCs) with in vitro and in vivo models of the pulmonary epithelium. Generation-3 PAMAM dendrimers with varying surface densities of PEG 1000 Da were synthesized and characterized. The results revealed that the apical to basolateral transport of DNCs across polarized Calu-3 monolayers increases with an increase in PEG surface density. DNC having the greatest number of PEG groups (n = 25) on their surface traversed at a rate 10-fold greater than its non-PEGylated counterpart, in spite of their larger size. This behavior was attributed to a significant reduction in charge density upon PEGylation. We also observed that PEGylation can be used to modulate cellular internalization. The total uptake of PEG-free DNC into polarized Calu-3 monolayers was 12% (w/w) vs 2% (w/w) for that with 25 PEGs. Polarization is also shown to be of great relevance in studying this in vitro model of the lung epithelium. The rate of absorption of DNCs administered to mice lungs increased dramatically when conjugated with 25 PEG groups, thus supporting the in vitro results. The exposure obtained for the DNC with 25PEG was determined to be very high, with peak plasma concentrations reaching 5 µg·mL(-1) within 3 h. The combined in vitro and in vivo results shown here demonstrate that PEGylation can be potentially used to modulate the internalization and transport of DNCs across the pulmonary epithelium. Modified dendrimers thereby may serve as a valuable platform that can be tailored to target the lung tissue for treating local diseases, or the circulation, using the lung as pathway to the bloodstream, for systemic delivery.

Quantitative detection of PLGA nanoparticle degradation in tissues following intravenous administration.

The biodegradable polymer poly(lactic-co-glycolic) acid (PLGA) has been extensively utilized and investigated as a drug delivery system. Although in vivo biodegradation (at specific administration sites only) of PLGA-based drug delivery constructs, such as foams and microparticles, has been studied, quantitative in vivo biodegradation of distributed polymer nanoparticles has not been accomplished and is quintessential for designing formulations to achieve desired pharmacokinetic properties of a drug in a target tissue. We determined the in vivo degradation kinetics of PLGA nanoparticles, of two sizes, distributed in liver, spleen, and lungs following intravenous administration. In addition, we simultaneously determined the amount of polymer in tissues. Nanoparticle degradation in vitro and in vivo appears to be a first-order process, and useful correlations were obtained between in vitro and in vivo tissue degradation of the nanoparticles. The ability to detect in vivo degradation and biodistribution of polymer nanoparticles is a significant milestone for the rational design of degradable nanoparticle-based drug delivery systems capable of delivering the therapeutic agent in a closely predictable manner to target tissue.

Rapid lymph accumulation of polystyrene nanoparticles following pulmonary administration.

PURPOSE: Pulmonary administration of polymeric nanoparticle drug delivery systems is of great interest for both systemic and local therapies. However, little is understood about the relationship of particle size and pulmonary absorption. We investigated uptake and biodistribution of polystyrene nanoparticles (PN) of 50 nm, 100 nm, 250 nm, and 900 nm diameters in mice following administration to lungs via pharyngeal aspiration. METHODS: The amount of PN in tissues was analyzed by gel permeation chromatography (GPC). RESULTS: At 1 h, larger diameter PN (250 nm and 900 nm) had the highest total uptake at around 15% of administered dose, whereas the smaller diameter PN (50 nm and 100 nm) had uptake of only 5-6%. However, at 3 h, the 50 nm PN had the highest total uptake at 24.4%. For each size tested, the highest nanoparticle deposition was observed in the lymph nodes (LN) as compared to other tissues accounting for a total of about 35-50% of absorbed nanoparticles. CONCLUSION: PN size impacts the rate and extent of uptake from lungs and, further, the extent of LN deposition. The extent of uptake and lymph distribution of the model, non-degradable PN lends potential to pulmonary administered, biodegradable polymeric nanoparticles for delivery of therapeutics to regional lymph nodes.

Quantitative nanoparticle organ disposition by gel permeation chromatography.

Gel permeation chromatography (GPC) also known as size exclusion chromatography (SEC) is a highly valuable tool for the purification, separation, and characterization of synthetic and natural polymers. In this technique, the analyte (usually a polymer) is dissolved in a suitable solvent and is injected into columns made of porous inert material. The columns separate the analyte based on its hydrodynamic size rather than the molecular weight. GPC systems typically have an RI detector, UV detector, or light scattering unit attached to the columns. With advanced detection systems coupled to the GPC, we can obtain important information about polymers including their molecular weight distribution, average molecular mass, degree of branching in the polymers, etc. In addition to the separation of polymers, GPC allows for the separation of enzymes, nucleic acids, polysaccharides, and hormones. With regards to nanotoxicity, GPC can be used for the quantitative determination of tissue deposition of polymer nanoparticles after in vivo exposure. Understanding the organ specific exposure to a nanomaterial is helpful in choosing appropriate toxicity assays, interpreting data from other toxicity assessments, and in determining potential risk.