Hydrophilic Reduction-Resistant Spin Labels of Pyrrolidine and Pyrroline Series from 3,4-Bis-hydroxymethyl-2,2,5,5-tetraethylpyrrolidine-1-oxyl.

Highly resistant to reduction nitroxides open new opportunities for structural studies of biological macromolecules in their native environment inside living cells and for functional imaging of pH and thiols, enzymatic activity and redox status in living animals. 3,4-Disubstituted nitroxides of 2,2,5,5-tetraethylpyrrolidine and pyrroline series with a functional group for binding to biomolecules and a polar moiety for higher solubility in water and for more rigid attachment via additional coordination to polar sites were designed and synthesized. The EPR spectra, lipophilicities, kinetics of the reduction in ascorbate-containing systems and the decay rates in liver homogenates were measured. The EPR spectra of all 3,4-disubstituted pyrrolidine nitroxides showed additional large splitting on methylene hydrogens of the ethyl groups, while the spectra of similar pyrroline nitroxides were represented with a simple triplet with narrow lines and hyperfine structure of the nitrogen manifolds resolved in oxygen-free conditions. Both pyrrolidine and pyrroline nitroxides demonstrated low rates of reduction with ascorbate, pyrrolidines being a bit more stable than similar pyrrolines. The decay of positively charged nitroxides in the rat liver homogenate was faster than that of neutral and negatively charged radicals, with lipophilicity, rate of reduction with ascorbate and the ring type playing minor role. The EPR spectra of N,N-dimethyl-3,4-bis-(aminomethyl)-2,2,5,5-tetraethylpyrrolidine-1-oxyl showed dependence on pH with pKa = 3, ΔaN = 0.055 mT and ΔaH = 0.075 mT.

Aerosol Inhalation Delivery of Ag Nanoparticles in Mice: Pharmacokinetics and Antibacterial Action.

The aerosol inhalation delivery of composite particles consisting of Ag nanoparticles enveloped by polyvinylpyrrolidone was investigated in experiments with mice. An ultrasonic nebulizing system was created for the generation of aerosols with a mean diameter and mass concentration of 700 ± 50 nm and 65 ± 5 mg/m3, respectively. The mass fraction of Ag in the composite particles was α = 0.061. The aerosol delivery was performed in a whole-body chamber with an exposition time of 20 min. Pharmacokinetic measurements were taken and the silver concentrations in the blood and lungs of the mice were measured as a function of time after exposition by means of electrothermal (graphite furnace) atomic absorption spectrometry. The inhalation dose and other pharmacokinetic parameters were determined. The antibacterial effect of aerosolized silver was assessed for mice infected with Klebsiella pneumoniae 82 and Staphylococcus aureus ATCC 25953. The survival rate of the infected mice after the aerosol exposure demonstrated the high antibacterial efficiency of Ag nanoparticles after inhalation delivery.

Studies of the Specific Activity of Aerosolized Isoniazid against Tuberculosis in a Mouse Model.

The aerosol inhalation delivery of isoniazid in mice was investigated, and the specific activity of the aerosol form of isoniazid was studied with the mouse model of tuberculosis infection, the M. tuberculosis H37Rv strain. Aerosol delivery was performed using a laminar-flow horizontal nucleation chamber. The inhalation dose was measured in real-time mode using a diffusion aerosol spectrometer. The mean particle diameter was 0.6 ± 0.03 µm, and the inhalation dose was 5-9 mg/kg. Pharmacokinetic measurements were carried out in nose-only and whole-body chambers. Isoniazid concentration in blood serum and its mass in the lungs were measured as a function of time using high-performance liquid chromatography. Studies of the specific activity of aerosolized isoniazid reveal that treatment with the aerosol lead to the complete recovery of the experimental tuberculosis infection as early as after 28 days after the start of inhalation treatment, while in the animals from the group receiving isoniazid per-orally, sole revivable tuberculosis mycobacteria were detected. Histologic examinations show that only a few macrophagal (nonspecific) granulomas without mycobacteria were detected in the spleen after per-oral and aerosol treatment, the number of granulomas on the 28th day being three times smaller in the latter case. The results show that the developed technique of isoniazid aerosol inhalation may have clinical potential.

Aerosol Inhalation Delivery of Ceftriaxone in Mice: Generation Procedure, Pharmacokinetics, and Therapeutic Outcome.

Aerosol inhalation delivery of ceftriaxone in mice was investigated. An ultrasonic nebulizer within the ranges of mean particle diameter 0.5-1.5 µm and mass concentration 0.01-0.6 µg/cm3 was used in inhalation experiments. Pharmacokinetic measurements were carried out using a nose-only chamber. Ceftriaxone concentration in blood serum and its mass in the lungs of mice were measured as a function of time using high-performance liquid chromatography. The body-delivered dose was within the range 3-5 mg/kg. The antibacterial effect of aerosolized ceftriaxone was investigated for mice infected with Klebsiella pneumoniae 82 and Staphylococcus aureus ATCC 25 953. The survival rate for infected mice after the treatment with ceftriaxone aerosol revealed the high antibacterial efficiency of this kind of treatment.

Aerosol Inhalation Delivery of Triazavirin in Mice: Outlooks for Advanced Therapy Against Novel Viral Infections.

Under pandemic-caused emergency, evaluation of the potential of existing antiviral drugs for the treatment of COVID-19 is relevant. Triazavirin, an antiviral drug developed in Russia for per-oral administration, is involved in clinical trials against SARS-CoV-2 coronavirus. This virus has affinity to epithelial cells in respiratory tract, so drug delivery directly in lungs may enhance therapeutic effect and reduce side effects for stomach, liver, kidneys. We elaborated ultrasonic method of triazavirin aerosol generation and investigated the inhalation delivery of this drug in mice. Mean particle size and number concentration of aerosol used in inhalation experiments are 560 nm and 4 × 105 cm-3, respectively. Aerosol mass concentration is 1.6 × 10-4 mg/cm3. Inhalation for 20 min in a nose-only chamber resulted in 2 mg/kg body delivered dose and 2.6 µg/mL triazavirin concentration in blood plasma. Elimination rate constant determined in aerosol administration experiments was ke = 0.077 min-1, which agrees with the value measured after intravenous delivery, but per-oral administration resulted in considerably lower apparent elimination rate constant of pseudo-first order, probably due to non-linear dependence of absorption rate on triazavirin concentration in gastrointestinal tract. The bioavailability of triazavirin aerosol is found to be 85%, which is about four times higher than for per-oral administration.

Supramolecular Complex of Ibuprofen with Larch Polysaccharide Arabinogalactan: Studies on Bioavailability and Pharmacokinetics.

BACKGROUND AND OBJECTIVES: In the present work, pharmacological and pharmacokinetic properties of the supramolecular complex of non-steroid anti-inflammatory drug ibuprofen (IBU) with natural polysaccharide arabinogalactan (AG) were studied. The main goals of such complexation were the increase of ibuprofen's bioavailability and decrease its effective dose after oral administration. METHODS: The complex with mass ratio as IBU:AG 1:10 was obtained by mechanochemical synthesis and characterized by water solubility, electron microscopy, differential scanning calorimetry, X-ray powder diffraction analysis and 1H-nuclear magnetic resonance spectroscopy. Different animal models of pain and inflammation was used to investigate IBU:AG biological effects. Plasma concentration of IBU and its pharmacokinetic parameters were evaluated after oral introduction. RESULTS: It was found that ibuprofen's effective analgesic and anti-inflammatory dose decreased twofold after its introduction as a complex with AG. The reason of this difference is due to the increase of ibuprofen concentration in rats' plasma: C max of IBU at doses of 20 and 40 mg/kg was found as 0.088 and 0.132 µg/ml, whereas C max of IBU in the complex form was 0.103 and 0.160 µg/ml, respectively. CONCLUSIONS: Thus, we have shown that complexation of the IBU with AG results in its bioavailability increase, reduction of the effective dose and should decrease toxic side effects.