A UHPLC-MS/MS method coupled with simple and efficient alkaline hydrolysis for free and total determination of conjugate nanomedicine: Pharmacokinetic and biodistribution study of poly (l-glutamic acid)-graft-methoxy poly (ethylene glycol)/combretastatin A4.

Poly (l-glutamic acid)-Combretastatin A4 conjugate (PLG-CA4) is a novel nano-anticancer drug. For macromolecule conjugate nanomedicine, its pharmacology mechanism is closely related to the pharmacokinetic profiles in vivo. It is a great significance that evaluates this polymer drug combined by covalently bound via studying the pharmacokinetics and distribution characteristics. Therefore, it is urgent to develop a simple, accurate and practical analytical method for such conjugated polymers combined by covalently bound. In this study, a simple and complete alkali hydrolysis was designed and optimized for the total CA4 concentrations obtained from PLG-CA4. Ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method with multiple-reaction monitoring (MRM) mode and the internal standard (IS) were adopted to develop a sensitive and accurate method satisfied both free and total determination of PLG-CA4 in biosamples. The method was validated which showed good linearity over a wide concentration range (R2 > 0.99), and the intra- and inter-day assay variability was less than 15% for CA4. The mean extraction recoveries of CA4 from plasma were all more than 80.0%. Furthermore, the method was applied to the study of pharmacokinetics (PK) and tissue distribution of PLG-CA4 in tumor-bearing nude mice. PLG-CA4 significantly prolonged retention time and enhanced distribution of CA4 in tumor.