Functionalization is believed to have a considerable impact on the biodistribution of fullerene in vivo. However, a direct comparison of differently functionalized fullerenes is required to prove the hypothesis. The purpose of this study was to investigate the influences of surface modification on the biodistribution of fullerene following its exposure via several routs of administration. ¹³C skeleton-labeled fullerene C₆₀ (¹³C-C₆₀) was functionalized with carboxyl groups (¹³C-C₆₀-COOH) or hydroxyl groups (¹³C-C₆₀-OH). Male ICR mice (~25 g) were exposed to a single dose of 400 μg of ¹³C-C₆₀-COOH or ¹³C-C₆₀-OH in 200 μL of aqueous 0.9% NaCl solution by three different exposure pathways, including tail vein injection, gavage and intraperitoneal exposure. Tissue samples, including blood, heart, liver, spleen, stomach, kidneys, lungs, brain, large intestine, small intestine, muscle, bone and skin were subsequently collected, dissected, homogenized, lyophilized, and analyzed by isotope ratio mass spectrometry. The liver, bone, muscle and skin were found to be the major target organs for C₆₀-COOH and C₆₀-OH after their intravenous injection, whereas unmodified C₆₀ was mainly found in the liver, spleen and lung. The total uptakes in liver and spleen followed the order: C₆₀ > > C₆₀-COOH > C₆₀-OH. The distribution rate over 24 h followed the order: C₆₀ > C₆₀-OH > C₆₀-COOH. C₆₀-COOH and C₆₀-OH were both cleared from the body at 7 d post exposure. C₆₀-COOH was absorbed in the gastrointestinal tract following gavage exposure and distributed into the heart, liver, spleen, stomach, lungs, intestine and bone tissues. The translocation of C₆₀-OH was more widespread than that of C₆₀-COOH after intraperitoneal injection. The surface modification of fullerene C₆₀ led to a decreased in its accumulation level and distribution rate, as well as altering its target organs. These results therefore demonstrate that the chemical functionalization of fullerene had a significant impact on its translocation and biodistribution properties. Further surface modifications could therefore be used to reduce the toxicity of C₆₀ and improve its biocompatibility, which would be beneficial for biomedical applications.

To understand the sources and migration pattern of PM_2.5 in the Yangtze River Delta (YRD), China, the total carbon (TC) and total nitrogen (TN) concentrations and the corresponding stable isotope ratios (δ¹³C_TC and δ¹⁵N_TN) were determined in aerosol samples simultaneously collected from August 2014 to April 2015 at three different locations (Shanghai, Ningbo, Nanjing). Ningbo and Shanghai are geographically closer, the research results precisely divide Nanjing and the other two cities into two categories. Nanjing has a higher proportion of nitrogen in PM_2.5 (13.2–15.3%) than Shanghai and Ningbo (8.6–12.6%), and the correlation analysis shows that nitrogen components (mainly ammonium nitrogen) might be the main driving force for the formation of PM_2.5. The isotopes were proven to be sensitive sensors to reflect the impact of special events on PM_2.5. For example, compared to other seasons, δ¹³C_TC in autumn in the three cities are relatively depleted, indicating an input from biomass combustion to PM_2.5 at this time. On New Year’s Eve, three cities simultaneously observed enriched δ¹³C_TC due to the burning of fireworks. During the Qingming Festival, abnormally depleted nitrogen isotope ratios were observed, reflecting the vehicle exhaust pollution caused by people’s short travel. Isotopes are also used to trace the transport process of PM_2.5. Postponing the sampling date in Nanjing by one day increased the linear fit (r²) of δ¹³C_TC between Nanjing and Ningbo from 0.03 to 0.75, while that of δ¹⁵N_TN improved from 0.16 to 0.63, which means PM_2.5 might transport from Nanjing to Shanghai and Ningbo, and the transfer time takes one day.