The Extracellular Matrix Limits Nanoparticle Diffusion and Cellular Uptake in a Tissue-Specific Manner.

Overexpression and remodeling of the extracellular matrix (ECM) in cancer and other diseases may significantly reduce the ability of nanoparticles to reach target sites, preventing effective delivery of therapeutic cargo. Here, we evaluate how tissue-specific properties of the ECM affect nanoparticle diffusion using fluorescence video microscopy and cellular uptake via flow cytometry. In addition, we determined how PEGylation chain size and branching influence the ability of nanoparticles to overcome the ECM barrier from different tissues. We found that purified collagen, in the absence of other ECM proteins and polysaccharides, presented a greater barrier to nanoparticle diffusion as compared to decellularized ECM from the liver, lung, and small intestine submucosa. Nanoparticles with dense PEG coatings achieved up to ~2000-fold enhancements in diffusion rate and cellular uptake up to ~5-fold greater than non-PEGylated nanoparticles in the presence of ECM. We also found nanoparticle mobility in the ECM varied significantly between tissue types and the optimal nanoparticle PEGylation strategy to enhance ECM penetration was strongly dependent on ECM concentration. Overall, our data supports the use of low molecular weight PEG coatings which provides an optimal balance of nanoparticle penetration through ECM and uptake in target cells. However, tissue-specific enhancements in ECM penetration and cellular uptake were observed for nanoparticles bearing a branched PEG coating. These studies provide new insight into tissue specific ECM barrier functions which can facilitate the design of nanoparticles that effectively transport through target tissues, improving their therapeutic efficacy.