Joint persistence and organ accumulation of IA-injected PEG-SWCNTs. Two groups (N = 5) of healthy 3-month-old female C57BL/6J (B6) mice were unilaterally IA-injected in the knee with 5 μg of PEG-SWCNT-750 in 10 μL of PBS or equivalent doses (~0.4 μmol) of free Seta750. PEG-SWCNT-750 were also IA-injected in the arthritic knees of a group (N = 5) of 3-month-old female B6 mice with OA (1 month post-DMM surgery). NIR fluorescence images of animals were taken through the IVIS Spectrum system during the following 14 days, and the fluorescence intensity of the treated knees was measured (A). After 14 days, PEG-SWCNT-treated mice were sacrificed, the major organs (spleen, liver, kidneys, and lungs) extracted, and their NIR-emission measured. NIR signals from these organs were undetectable. Legs were also collected, the skin removed, and their NIR-emission measured. Bright NIR signals arose from treated knees (right), whereas NIR signals from untreated knees were undetectable (left) (B).