Increasing Single Wall Carbon Nanotube Delivery to Macrophages by Independent Modifications of the Material and Cellular Activity

Single wall carbon nanotubes (SWCNTs) are a class of nanomaterials with unique physical and optical properties which make SWCNTs well-suited for biomedical applications. Recent studies have shown the potential for SWCNT use as drug and gene delivery vectors, imaging probes for cellular labeling and tracking, molecular sensors, and for thermal ablation of cells in situ. SWCNTs are routinely dispersed in aqueous solution using polyethylene glycol (PEG) copolymers, lipids, and proteins. Yet, there remains a limited mechanistic understanding of how different molecular SWCNT surface coatings interact with a complex, dynamic cellular state, such as those found in immune cells. Nanomaterial interactions with cells of the immune system, such as macrophages, are particularly important for determining mechanisms of toxicity and developing specific medical therapeutics for inflammation and cancer detection. We investigated the differential effects of SWNCT dispersion with bioinert Pluronic F-127 (PF127) polymer and bioactive bovine serum albumin (BSA) protein on SWCNT uptake and localization in J774A.1 macrophages and NIH-3T3 fibroblasts. We also examined stimulation of macrophages with lipopolysaccharide (LPS) to measure effects of cell state on SWCNT uptake.

We quantified cellular uptake of SWCNTs over three orders of magnitude (1-100 μg/ml) using Raman spectroscopy. Macrophages exhibited a steady dose dependent increase in cell associated SWCNTs with approximately double the effect for BSA-SWCNTs compared to PF127-SWCNTs. Cells treated with BSA-SWCNTs showed gross changes in size, morphology, proliferation capability and other phenotypic changes. In contrast, these cellular changes were not observed for macrophages with PF127-SWCNTs or fibroblasts with either PF127-SWCNTs or BSA-SWCNTs.  Cellular stimulation with LPS increased uptake, and an additive effect was observed for pre-stimulated macrophages with increasing SWCNTs, but the uptake of BSA-SWCNTs plateaued at higher exposure concentrations.  Taken together, these results indicate the sensitivity of macrophage uptake to bioactive SWCNT coatings and cellular stimulation, as well as the ability of macrophages to adapt for increased uptake of bioactive coated SWCNTs.