2.7. In Vivo Pharmacokinetic Study

All procedures in the in vivo pharmacokinetic study were carried out according to the Guidelines for Animal Experimentation of Shenyang Pharmaceutical University (Shenyang, China) and with the approval of the Animal Ethics Committee of the institute. Male Sprague-Dawley rats (body weight 200 ± 20 g) were randomly divided into three groups (n = 3 for each studied group). Prior to the experiments, the rats were fasted overnight with free access to water. Aqueous suspensions of IMC-MSNRs, IMC-MSNSs, or IMC at 40 mg/kg were orally administered, respectively, and blood samples (0.5 mL) were collected at predetermined time points (0.5, 1, 2, 3, 4, 6, 8, 12, 24, and 32 h) in microcentrifuge tubes containing heparin by retro-orbital venipuncture technique. The blood samples were immediately centrifuged (10 min, 5000× g) and the supernatant was collected for the HPLC analysis of IMC.

Plasma samples were processed as follows: each plasma sample (200 μL) was mixed with 20 μL of an internal standard solution (0.5 mg/mL naproxen), 90 μL 10% K₂HPO₄, and 1 mL dichloromethane, and then vortexed for 3 min. After centrifugation at 10,000 rpm (6900× g) for 4 min, the upper water layer was removed, and the organic layer was then evaporated in a gentle stream of nitrogen at room temperature. The residue was resuspended in 100 μL of the mobile phase. After vortex mixing and centrifugation, a 20 μL aliquot was analyzed by using HPLC.