Millex gs filter

Ciprofloxacin was obtained via the hospital pharmacy from Bayer Austria (400 mg/200 mL infusion solution). [¹⁴C]Ciprofloxacin (labeled in the 2-position of the quinoline ring, molar activity: 2.2 GBq/mmol, radiochemical purity: 98.2%) was obtained from Hartmann Analytic GmbH (Braunschweig, Germany). For the i.v. injection, [¹⁴C]ciprofloxacin (7 kBq, 1.1 µg) was dissolved in 10 mL of physiological saline solution and filtered through a sterile Millex-GS filter (0.22 µm; Millipore Corporation, Bedford, MA, USA).
No formal dosimetry calculation was performed for [¹⁴C]ciprofloxacin. Because of the very high sensitivity of AMS, the administration of only very low ¹⁴C amounts is required (7 kBq in the current study). In addition, as the energy of the β⁻ particles emitted in the decay of ¹⁴C is relatively low (0.156476 MeV), AMS microdosing studies usually fall within risk category I (trivial risk, total effective dose < 0.1 mSv) according to the International Commission on Radiological Protection Publication 62 “Radiological Protection in Biomedical Research” [30 ]. However, an intravenously injected ¹⁸F-labeled radiotracer for PET (400 MBq) typically gives a total effective dose in the range of 5–10 mSv, corresponding to risk category IIb (minor to intermediate risk) in the International Commission on Radiological Protection publication 62 [30 ].

Animals were randomly divided into three groups; each group received CPZEN-45 at a dose of 1 mg/kg in solution by the IV (n = 7) or SC (n = 6) routes or CPZEN-45 powders (1 mg/kg) by the pulmonary route (INS; n = 6) (Table 1). CPZEN-45 solutions were prepared by dissolving a weighed amount of CPZEN-45 hydrochloride salt in water for injection and filtering the solution through a 0.22-μm Millex GS filter (Millipore, Cork, Ireland). To administer the CPZEN-45 powders by INS, each animal was first anesthetized, and the trachea was visualized with the help of a laryngoscope. The tube of a small-animal insufflator (Penn Century Inc., Wyndmoor, PA, USA) was inserted into the trachea, and the CPZEN-45 powder was aerosolized into the airways of the animal with the help of air from an empty 10 mL syringe [19 (link)]. Blood samples (0.3 mL) were collected from each animal into heparinized micro-centrifuge tubes at 0 (prior to dosing), 0.08, 0.25, 0.50, 1, 1.5, 2, 3, 4, and 5 h after administration of the single dose CPZEN-45 by the different routes. Warm sterile saline solution was used to replace the volume of blood drawn after each sample collection to maintain the volume of distribution constant in each animal.

Fish powder samples were incubated with 6 mL of aqueous nitric acid (6.9% v/v) in a Thermomixer comfort (Eppendorf Japan, Tokyo, Japan). Collected supernatants were filtered through a Millex GS filter (0.22 mm, EMD Millipore, Billerica, MA) using SPS5510 (Hitachi High-Tech Science Corporation, Tokyo, Japan). The sediment samples were freeze-dried, and 10 mg of the powder was incubated with 1 mL of methanol at 50 °C for 15 min. After centrifugation (14000 rpm, 5 min), the supernatants were removed and 2 mL of aqueous nitric acid (6.9% v/v) was added, and the sample incubated at 50 °C for 15 min. The supernatants were collected after centrifugation (14000 rpm, 5 min), and the extraction using 2 mL of aqueous nitric acid (6.9% v/v) was repeated three times. The water samples were diluted to ten times using milli-Q water, and then used for ICP-OES analyzes. The ICP-OES analysis was conducted using an SPS5510 instrument, with a range of wavelengths from 167 to 785 nm and 74 applicable elements. The ICP-OES data is available in Table S5.