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 ( 31 P-qNMR) method is developed for the real-time quantification of therapeutic molecules in vitro . The release kinetics of model drug, tenofovir (anti-HIV microbicide), was analyzed in vaginal fluid simulant (VFS), seminal fluid simulant (SFS), and human plasma (HP) from chitosan nanofibers (size ∼100-200 nm) using the NMR (direct) method and compared with dialysis/UV-Vis (indirect) method. The assay was linear in VFS/SFS (0.20-5.0 mM), HP (0.30-5.0 mM of drug concentration range) and specific no drug 31 P-qNMR chemical shift [∼15 ppm] interference with formulation/media components. Limit of detection values were 0.075/0.10/0.20 mM, whereas limit of quantification values were 0.20/0.20/0.30 mM in VFS/SFS/HP, respectively. The method was robust, precise (%RSE 31 P-qNMR provides more accurate, real-time, and direct drug quantification for effective in vitro–in vivo correlation.