Real-Time Analysis of Tenofovir Release Kinetics Using Quantitative Phosphorus (31P) Nuclear Magnetic Resonance Spectroscopy

Abstract

The dialysis method is classically used for drug separation before analysis, but, does not provide direct and real-time drug quantification and has limitations affecting the dialysis rate. In this study, a phosphorus nuclear magnetic resonance (31P-qNMR) method is developed for the real-time quantification of therapeutic molecules in vitro. The release kinetics of model drug tenofovir (TFV: anti-HIV microbicide) was analyzed in vaginal fluid simulant (VFS), semen fluid simulant (SFS), and human plasma (HP) from chitosan nanofibers (size ~100–200nm) using the NMR (direct) method and compared with dialysis/UV-Vis (indirect) method. The assay was linear in VFS/SFS (0.20–5.0mM), HP (0.30–5.0mM) and specific (no drug 31P-qNMR chemical shift (~15ppm) interference with formulation/media components). LOD values were 0.075/0.10/0.20mM, whereas, LOQ values were 0.20/0.20/0.30mM in VFS/SFS/HP, respectively. The method was robust, precise (%RSE <2%), and accurate (%mean recovery: 90-110%). After 12h, ~75%/72%/70%w/w of TFV release was observed with 31P-qNMR, compared to ~47%/52%/52%w/w by dialysis method in VFS/SFS/HP, respectively. Approximately 20% decrease in %drug release observed with dialysis method suggested an interference with drug transport process due to the dialysis membrane and the Gibbs-Donnan effect. Overall, 31P-qNMR provides more accurate, real-time and direct drug quantification for effective in vitro/in vivo correlation.

Direct and Real-Time Quantification Of Bortezomib Release From Alginate Microparticles Using Boron (11B) Nuclear Magnetic Resonance Spectroscopy

“…Therefore, it is expected that the integrated peak for a polymeric formulation of BTZ will be very broad in comparison to free BTZ (in solution), due to slow tumbling . Shimming was applied to each sample to maintain the same line width in each spectrum.…”

“…Excess material was removed using a paintbrush, and the sample was sputter-coated with a thin layer of gold. Images were acquired at an accelerating voltage of 5 kV …”

“…Nowadays, qNMR is routinely used in the identification of drugs, the determination of multicomponent drugs composition, isomeric composition determination, drug degradation studies, impurities level determination and elucidation of their structure, quality assessment, as well as counterfeit drugs determination. − Commonly qNMR nuclei used in pharmaceutical applications are 1 H and 13 C. , This is partly due to the high proportion of carbon and hydrogen atoms in natural and synthetic compounds, compared to other NMR active atoms. Other studies have investigated NMR active heteroatoms, such as 19 F, 31 P, and 15 N, in the quantification and characterization of therapeutic molecules. − …”

Determining chemical exchange rate constants in nanoemulsions using nuclear magnetic resonance

“…A variety of techniques have been used to study the exchange dynamics in eqn (1) , such as dialysis and related methods, 12 electrochemical techniques, 13 and flow cytometry. 14 NMR has also been used 15 to study the kinetics in eqn (1) . Since most NMR studies are performed under equilibrium conditions, differences between an A and A Emul molecule's physical properties, such as self-diffusion coefficients, 16,17 and/or NMR spectral parameters, such as chemical shifts, spin–spin couplings, and transverse ( T 2 ) and longitudinal ( T 1 ) spin relaxation times, 18,19 are required in order to determine k F and k B in eqn (1) .…”

Unique Usage of a Classical Selective Homodecoupling Sequence for High-Resolution Quantitative 1H NMR

“…Comparing the 1 H signal area of an analyte with that of an internal standard different from the analyte allows the purity or concentration of the analyte to be determined accurately. This method is particularly useful to accurately quantify analytes for which reliable reference materials are not available. − However, the chemical shift range for the 1 H NMR spectra is narrower than those for the NMR spectra of other nuclei (e.g., 13 C, − 19 F, − and 31 P − ), which have been used for quantitative analysis of organic molecules. Broadening of 1 H signals also occurs due to 1 H– 1 H spin couplings.…”