LAUSR

This study was conducted to investigate the influence of outer diameter (OD) and length (L) of multiwalled carbon nanotubes (MWCNTs) on biodistribution and the perturbation of endogenous metabolite profiles. Three different‐sized carboxylated MWCNTs (NIEHS‐12‐2: L 0.5–2 μm, OD 10–20 nm, NIEHS‐13‐2: L 0.5–2 μm, OD 30–50 nm, and NIEHS‐14‐2: L 10–30 μm, OD 10–20 nm) in water were administered to female Sprague‐Dawley rats as a single intravenous dose of 1 mg/kg MWCNTs. Biodistribution in liver, lung, spleen, and lymph nodes was evaluated in tissue sections at 1 and 7 days' post‐dosing using enhanced darkfield microscopy and hyperspectral imaging. Nuclear magnetic resonance (NMR) analysis was used for biochemical profiling and pathway mapping of endogenous metabolites in urine collected at 24‐h intervals prior to dosing, at Day 1 and Day 7.