Lab-on-valve automated and miniaturized assessment of nanoparticle concentration based on light-scattering

Abstract

Nanoparticles (NPs) concentration directly impacts the dose delivered to target tissues by nanocarriers. The evaluation of this parameter is required during NPs developmental and quality control stages, for setting dose--response correlations and for evaluating the reproducibility of the manufacturing process. Still, faster and simpler procedures, dismissing skilled operators and post-analysis conversions are needed to quantify NPs for research and quality control operations, and to support result validation. Herein, a miniaturized automated ensemble method to measure NPs concentration was established under the lab-on-valve (LOV) mesofluidic platform. Automatic NPs sampling and delivery to the LOV detection unit were set by flow programming. NPs concentration measurements were based on the decrease in the light transmitted to the detector due to the light scattered by NPs when passing through the optical path. Each analysis was accomplished in 2 min, rendering a determination throughput of 30 h--1 (6 samples h--1 for n=5) and only requiring 30 $\mu$L (0.03 g) of NPs suspension. Measurements were performed on polymeric NPs, as these represent one of the major classes of NPs under development for drug-delivery aims. Determinations for polystyrene NPs (of 100, 200, and 500 nm) and for NPs made of PEGylated poly-d,l-lactide-co-glycolide (PEG--PLGA, a biocompatible FDA-approved polymer) were accomplished within 108--1012 particles mL--1 range, depending on the NPs size and composition. NPs size and concentration were maintained during analysis, as verified for NPs eluted from the LOV by particle tracking analysis (PTA). Moreover, concentration measurements for PEG--PLGA NPs loaded with an anti-inflammatory drug, methotrexate (MTX), after their incubation in simulated gastric and intestinal fluids were successfully achieved (recovery values of 102--115\\%, as confirmed by PTA), showing the suitability of the proposed method to support the development of polymeric NPs targeting intestinal delivery.