Evaluation of Mass Spectrometry Compatible Reagents for Determining Small Molecule Loading in Poly(lactic acid)...

The objective was to understand if sufficient base hydrolysis and subsequent small molecule quantitation within poly(lactic acid) nanoparticles (PLA-NPs) could be achieved using a mass spectrometry friendly volatile base, such as ammonium hydroxide. Additionally, we sought to evaluate the impact of NP formulation parameters on drug loading as assessed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) quantitation.

A microfluidics approach was used to create a library of NPs by systematically varying flow rate ratio (FRR; 1 or 3) and surfactant composition (poly(vinyl alcohol) or poly(glutamic acid)). NPs were characterized using dynamic light scattering to determine their size, polydispersity index, and zeta potential. Several hydrophobic drugs (NRX204647 and 7C, RARγ agonists; SF-7-044, p38α modulator) were tested for NP encapsulation. Base-catalyzed hydrolysis of PLA-NPs using either sodium hydroxide or ammonium hydroxide was employed to release encapsulated drug, which was then quantified using LC-MS/MS.

Comparison of sodium hydroxide- and ammonium hydroxide-mediated base hydrolysis of PLA-NPs demonstrated that ammonium hydroxide was as effective for releasing encapsulated hydrophobic drugs for LC-MS/MS-based quantitative analysis. NP formulation parameters (FRR and surfactant chemistry) and drug physicochemical properties influenced NP characteristics and drug loading.

Using a mass spectrometry friendly base for release of hydrophobic drugs encapsulated within PLA-NP is effective, enabling a simplified quantitative method to evaluate drug loading.