Potentiometric detection of apomorphine in human plasma using a 3D printed sensor.

Apomorphine is a dopamine agonist that is used for the management of Parkinson's disease and has been proven to effectively decrease the off-time duration, where the symptoms recur, in Parkinson's disease patients. This paper describes the design and fabrication of the first potentiometric sensor for the determination of apomorphine in bulk and human plasma samples. The fabrication protocol involves stereolithographic 3D printing, which is a unique tool for the rapid fabrication of low-cost sensors. The solid-contact apomorphine ion-selective electrode combines a carbon-mesh/thermoplastic composite as the ion-to-electron transducer and a 3D printed ion-selective membrane, doped with the ionophore calix[6]arene. The sensor selectively measures apomorphine in the presence of other biologically present cations - sodium, potassium, magnesium, and calcium - as well as the commonly prescribed Parkinson's pharmaceutical, levodopa (L-Dopa). The sensor demonstrated a linear, Nernstian response, with a slope of 58.8 mV/decade over the range of 5.0 mM-9.8 µM, which covers the biologically (and pharmaceutically) relevant ranges, with a limit of detection of 2.51 µM. Moreover, the apomorphine sensor exhibited good stability (minimal drift of just 188 µV/hour over 10 h) and a shelf-life of almost 4 weeks. Experiments performed in the presence of albumin, the main plasma protein to which apomorphine binds, demonstrate that the sensor responds selectively to free-apomorphine (i.e., not bound or complexed forms). The utility of the sensor was confirmed through the successful determination of apomorphine in spiked human plasma samples.

Univariate and Multivariate Determination of Dapagliflozin and Saxagliptin in Bulk and Dosage Form.

BACKGROUND: Dapagliflozin is a sodium glucose cotransporter-II inhibitor while saxagliptin is a dipeptidyl peptidase-4 inhibitor. Both are used to manage type 2 diabetes mellitus. OBJECTIVE: The aim of this work is to develop four simple, accurate, and precise UV-spectrophotometric methods, three univariate and one multivariate, for the estimation of dapagliflozin and saxagliptin in their pure and marketed dosage forms. METHODS: Method (A) is based on the ratio difference method; Method (B) is ratio subtraction with constant multiplication; while Method (C) is a second derivative method and Method (D) is a partial least-squares method. RESULTS: The calibration curves for dapagliflozin and saxagliptin were linear within the concentration range of 2.50-50.0 µg/mL and 5.0-60.0 µg/mL, respectively. The specificity of the proposed methods was studied by analyzing different laboratory-prepared mixtures and their combined pharmaceutical dosage form. According to the International Council for Harmonisation guidelines, the three proposed methods were validated regarding the accuracy, precision, and specificity. Method (D), partial least-squares, was employed for the determination of the same mixture over a wavelength range of 205-300 nm. A statistical comparison was performed between the results of the proposed methods and those of a reported spectrophotometric method and no statistically significant difference was detected at 95% confidence limit regarding both precision and accuracy. CONCLUSION: Four accurate, specific, and precise UV-spectrophotometric methods for dapagliflozin and saxagliptin testing and estimation were successfully utilized and validated. HIGHLIGHTS: The examined methods are simple and do not involve sophisticated and expensive instruments. They could be effectively employed in quality control laboratories for routine examination of the investigated drugs in their pure powdered or combined pharmaceutical formulations.