Distribution and Cellular Uptake of PEGylated Polymeric Particles in the Lung Towards Cell-Specific Targeted Delivery

Abstract

Purpose: We evaluated the role of a poly(ethylene glycol) (PEG) surface coating to increase residence times and alter the cellular fate of nano- and microparticles delivered to the lung.

Methods: Three sizes of PRINT hydrogel particles (80 × 320 nm, 1.5 and 6 μm donuts) with and without a surface PEG coating were instilled in the airways of C57/b6 mice. At time points of 1, 7, and 28 days, BALF and whole lungs were evaluated for the inflammatory cytokine Il-6 and chemokine MIP-2, histopathology, cellular populations of macrophages, dendritic cells (DCs), and granulocytes, and particulate uptake within these cells through flow cytometry, ELISAs, and fluorescent imaging.

Results: Particles of all sizes and surface chemistries were readily observed in the lung with minimal inflammatory response at all time points. Surface modification with PEGylation was found to significantly increase lung residence times and homogeneous lung distribution, delaying macrophage clearance of all sizes, with the largest increase in residence time observed for 80 × 320 nm particles. Additionally, it was observed that DCs were recruited to the airway following administration of unPEGylated particles and preferentially associated with these particles.

Conclusions: Pulmonary drug delivery vehicles designed with a PEG surface coating can be used to delay particle uptake and promote cell-specific targeting of therapeutics.

Keywords: Microparticle; Nanoparticle; PEGylation; Pulmonary drug delivery.

Figure 1

SEM images of PRINT hydrogel particles. (A) 80×320 nm, (B) 1.5 μm donut, (C) 6 μm donut.

Figure 2

Particles dosed to MH-S cells at 25 μg/40 k cells and imaged 4 hours post-dose. Particles (red), Nuclei (blue), Actin (green). Representative images from n=3 independent experiments.

Figure 3

Relative populations of macrophages, dendritic cells (DC) and granulocytes in (A–C) BALF and (D–F) whole lung as determined by flow cytometry analysis (BALF representative gating in Supplemental Figure 1, lung in Supplemental Figure 2). Saline and LPS cell populations analyzed only at 1 and 7 days post-dose. Average values shown (n=4 animals) +/− standard deviation. Analysis by two-way ANOVA with Tukey multiple comparisons test; * p < 0.05, ** p < 0.001, *** p < 0.0001.

Figure 4

H&E stained lung tissue 24 hours after particle dose. (Scale bar = 200 μm, 2x magnification) Representative images from n=4 animals.

Figure 5

IL-6 cytokine and MIP-2 chemokine levels measured from BALF 24 hours post-instillation. Average values shown (n=4 animals) +/− standard deviation.

Figure 6

Flow cytometry analysis of particle uptake, median fluorescence intensity (MFI) of particle positive cells, and total fluorescence. (A–C) BALF macrophage, (D–F) lung macrophage and (G–I) lung DCs at 1, 7 and 28 days post-instillation. Average values shown (n=4 animals) +/− standard deviation. Two-way ANOVA with Tukey multiple comparisons test; * p < 0.05, ** p < 0.001, *** p < 0.0001).

Figure 7

Particle distribution in the lung 1 day post-instillation. Particles (red), Actin (gray), Nuclei (blue), CD11c (green). Representative images from n=4 animals.